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Oracle JMP-1 removes the need for a battery in the Marshall JMP-1

I've been toiling with the idea of replacing the static 8k x 8 RAM in our favourite MIDI valve pre-amp with a non-volatile SRAM (nvSRAM) for long time, now and I'm delighted to report that after a lot of work, including testing over recent weeks, my Oracle battery eliminator for the Marshall JMP-1 is finally here.

I understand why batteries were used to back up machine memory in say the late seventies and eighties and even in the nineties but now-a-days, it all seems totally unnecessary. Could it possible to integrate modern nvSRAM technology into a machine that's more than thirty years old, though?

Modern machines don't have batteries. Many will be familiar with my love of the Behringer DEQ2496 Ultracurve Pro, which is an example off the top of my head, of a machine that doesn't have battery backed-up memory. Indeed, when I say 'modern', please consider that at the time of writing this, the DEQ2496 is more than fifteen years old!

Behringer DEQ2496 has no memory back-up battery
This fifteen year old Behringer DEQ2496 UltraCurve Pro doesn't have battery backed up memory.

CPU control in the JMP-1 is typical of the time. Although I know this machine inside-out, it was still worth double-checking, just to make sure I hadn't missed anything. Indeed it was obvious that other than removing the battery, no other modifications were necessary to implement Oracle.

Marshall JMP-1 SRAM and battery
The CPU controller side of things in the JMP-1 is very typical of the time.

Look, no battery means that you'll never have to  worry about losing your pre-sets and more importantly (perhaps) is that a battery won't leak if it's not there! Oh wow... peace of mind all around. That's exactly what my Oracle battery eliminator for the Marshall JMP-1 was intended to achieve.

Oracle Battery Eliminator for the Marshall JMP-1

Well anyway, a few months ago, I decided to just do it and so I've developed a little kit which involves replacing the Hyundai Hy6264 SRAM chip inside the JMP-1, with a snap-in PCB which has few components on it and which means that you can pull out your battery and lose it. "Seriously?" Yes, SERIOSULY!!!!

So the real challenge wasn't finding a nvSRAM chip. Oh no, there are loads out there. Unfortunately, many of them still rely on batteries but instead of an external battery, the battery is built into the chip, which... kind of just moves the problem from one place to another. Those that don't however, are either much larger than 64k or simply aren't pin-for-pin compatible with the SRAMs of yesteryear, or both. Hey, I got there in the end! 🙂

Lots of nvSRAM chips to chose from

The Oracle JMP-1 kit includes a 28-way turned-pin IC socket, so once the original device is removed, all you have to do is solder in the socket and drop in Oracle. This is a great option because it allows you to return your JMP-1 to factory hardware at any time, by simply pulling out Oracle and installing a Hyundai Hy6264 or equivalent SRAM IC.

SO HOW DOES ORACLE JMP-1 WORK?

Inside the heart of Oracle battery eliminator for the Marshall JMP-1Okay, so it's not magic. At the heart of my Oracle battery eliminator for the Marshall JMP-1, is an IC that uses something called quantum trap technology (well, perhaps it is magic). Fundamentally there are two parts to the IC; a conventional static RAM (SRAM) like the original Hyundai Hy6264) and an Electrically Erasable Programable Random Access Memory (EEPROM). When switched on, the SRAM fires up and reads and writes data as one would expect, like nothing's really changed. The data that's in the SRAM however, can be written into the EEPROM. This is done by one of two methods; either in software or by specific hardware configuration, the latter of which has a two or three options. Well, I wasn't going to try rewriting the JMP-1's firmware so the autosave hardware configuration seemed to be the obvious way to go. Oracle JMP-1 is set up to retain memory when your JMP-1 is switched off. Isn't that just so cool?!?!?

Oracle battery eliminator for the Mrshall JMP-1 retains memory for 100 years

Of course, Oracle won't retain your JMP-1's memory indefinitely. Nothing lasts forever, right? It will however, keep your pre-sets safe for a very long time. Opposite is an extract from the nvSRAM device's datasheet and amongst the features, the manufacturer quotes a 100 year memory retention. 

Just above that specification, you'll also notice that the datasheet quotes a million save cycles. What that means is that if you switch your JMP-1 off twenty-seven times a day, the nvSRAM chip will work fine for a hundred years!

I'm not quite sure how we're going to check those specifications. I'm definitely not going to be around that long. On the other hand, if they're correct, Oracle JMP-1 will last a lot longer than several CR2032s!

Oracle JMP-1 battery eliminator for the Marshall JMP-1

As I've already said, I checked out a whole bunch of devices that would be suitable for my Oracle battery eliminator for the Marshall JMP-1. With very specific technical criteria in mind, price was also going to be an important factor, especially if I was intending to release Oracle as a commercial product, . Trying to satisfy all requirements, I actually settled on two versions of the same device. Technically they're identical but one has a physical form factor of a 300 mil (7.62mm row spacing) 28-pin DIP IC and the other is packed into a 600 mil (15.24mm row spacing) 28-pin DIP IC. Yes, you guessed it, the 'slim' version is much more expensive. Not being sure whether or not using the higher-cost IC would be sustainable, I ended up designing two PCBs hence, V. 1.0 and V. 2.0.

Oracle 300 mil and 600 mil versions
Oracle V. 2.0 uses a 600 mil 28-pin DIP IC but the PCB is only 2mm wider than Oracle V. 1.0.

For the time-being, both versions will be available but I have a feeling that I'll have to phase out V. 1.0, due to cost.

I'm a stickler for detail and I also believe in preventative action so apart from  Oracle JMP-1 being supplied with a high-quality turned-pin 28-pin IC socket, it also comes with a small 4mm rubber pad with double-sided tape on one side. This gets stuck on the bottom your JMP-1 PCB, underneath Oracle, or rather the supplied IC socket. Why? Well, I'm just a bit worried that in all the excitement, it would be quite easy to just press Oracle into place a little too hard! The rubber pad will supply some support and prevent damage to the JMP-1 PCB. 🙂

Oracle Battery Eliminator for the Marshall JMP-1

There's another slightly less obvious benefit to Oracle; since your JMP-1's memory, i.e. your pre-sets, MIDI mapping, etc are stored in a device that doesn't need a battery, guess what? You can pull Oracle and drop it into another JMP-1 and all your stuff will be as it was but in the new box! Coolamundo, dudes! 😮

My Oracle battery eliminator for the Marshall JMP-1 joins my growing arsenal of bits 'n' pieces that I make for one of the best guitar pre-amps ever and having a Marshall JMP-1 with no battery, well it's just seriously cool! 😀 You can check out all my Marshall JMP-1 stuff here.

After a lot of testing over several weeks, I'm delighted to announce that my conclusions confirm that Oracle JMP-1 works just great. The only problem I have now, is that I've got to write an installation manual. Hmm... not my favourite part of a project, LOL.

Oracle JMP-1 battery eliminator for the Marshall JMP-1 is available to buy here:


CR2032 BATTERY ADAPTER FOR THE MARSHALL JMP-1

Back in July 2023 (like only nine months ago), I released a CR2032 battery adapter for the JMP-1. I had to find it slightly amusing, that I decided to follow up on my idea of Oracle so soon after I'd launched this adapter. Typical!

The image below is of my 'lab' JMP-1. It's used to test stuff I make for the JMP-1 before I send it out to customers. As you can see, Oracle JMP-1 is installed as is my CR2032 battery adapter... less the battery, of course.

Oracle was developed shortly after I launched my CR2032 adapter for the Marshall JMP-1
My lab JMP-1 with both my CR2032 battery adapter and Oracle. Of course, the former is now empty. Who needs a battery when you have an Oracle?

My CR2032 battery adapter will remain available as I fully accept that swapping out that big SRAM IC for Oracle JMP-1, isn't going to be everyone's cup of tea. You can read more about it here.

Okay so, I'm sure folks are thinking "Why Oracle JMP-1? Why not just Oracle?" Well, I'm currently developing similar devices to eliminate the necessity for battery backed up memory for other machines. Some of those machines for example, don't even have 64k RAM and therefore use a 24-pin nvSRAM device. Also, component layout and PCB size may vary so as to fit.

And finally... I'm continually reviewing and sometimes tweaking the design of my products. More often than not, this is necessary due to the fact that component availability and prices can be annoyingly flaky. The pictures of Oracle, both V. 1.0 and V. 2.0, featured in this article are of my first pre-production prototypes so if you buy Oracle, it may look a little different.

Roland MKS-70 with full upgrades

Yes, you read correctly. A lovely customer in Miami, who I've got to know rather well over the past couple of years, sent me his beautiful synth module asking me to put everything into it. I have a few of these come in on a regular basis from the US but on this occasion, I can't think of anything that the customer didn't ask for so ended up doing a Roland MKS-70 full upgrade. Of course I couldn't help myself and while I had it, Brent's MKS-70 got referred to as 'The Miami Sound Machine'. 😀

DHL Express LogoBrent couldn't find a good deal on shipping so I arranged for his instrument to be collected on my DHL Express (import) account. Yes, it's a little extra work for me but I know that the package will be looked after, I won't pay import duty and Brent would only pay duty on the work done (and not the MKS-70 itself), when it's returned to him. 🙂 Above all, it was considerably cheaper than anything he could find locally.

Yeah, I know so if you're in the US or Canada, then you're busting to know, right? Well, the cost of shipping The Miami Sound Machine from Florida to Hemel Hempstead, UK was less than 180 GBP and the package was here in three days. Brent couldn't guarantee he'd be in when DHL was scheduled to collect so he took it to a DHL depot. Be warned however. If you do that, DHL will most likely open the package for security reasons (fair enough).

Brent had already bought some bits 'n' pieces and packaged with his MKS-70 were Fred Vecoven's Super-JX Flash module, Fred's latest digital PWM kit and four Xvive MN3009 replacement chorus chips.

Vecoven Flash Module Installed In Roland MKS-70
Fred Vecoven's Super-JX Flash Module is part of my Roland MKS-70 full upgrade package.

Knowing that this Roland MKS-70 full upgrade was coming in, I bought a GU-280 VFD replacement display kit off my friend, Guy Wilkinson and had ordered parts to build a Nebula balanced outputs jack-board and a P0004 modular switched-mode power supply. Is there a Super-JX (MKS-70 or JX-10) on the planet that's not powered by a P0004?!?!?

Nebula is part of my Roland MKS-70 Full Upgrade
Delivering superior phase coherency, Nebula uses dedicated balanced line driver ICs to produce balanced outputs of each channel, as opposed to a dual op-amp configuration. Each output line on Nebula has a full compliment of diode protection and inductive and capacitive filtering which considerably improves the signal quality. Nebula is also now available with optional screened internal audio cables which reduce the noise picked up from within the MKS-70.

Brent figured that while the machine was here, it would be prudent to also change the front panel switches... so I ordered them, too.

Okay, so Brent told me that his MKS-70 was displaying random behaviour like freezing, intermittent booting, bad sound and so on. I immediately suspected the power supply so when I got, I was NOT going to switch it on!

Instead, I ripped out the power supply as a P0004 modular switched-mode power supply was already on the upgrade list.

I could immediately tell the power supply was quite fatigued. The filtering capacitors were starting to swell and there was some mild scorching around the rectifier joints.

Then, on removing the power supply, I was shocked to find that the 2SD1406 responsible for regulating -15V was so dry-jointed, that none of its pins were making contact with the tracks on the underside of the PCB.

Dry joints underneath MKS-70 Power Supply PCB
Here's the underside of the power supply PCB showing Q4 (a 2SD1406, highlighted in red ) which is part of the -15V regulator circuit. As you can see, it's had enough! Dry-joints are a common source of problems on these old PCBs, especially under components that get hot.

This Roland MKS-70 full upgrade isn't cheap but if you're a Super-JX owner, please  at least consider replacing your synth's power supply with a P0004.

Having the right equipment and using a couple of very well seasoned techniques (which might not be in the book, incidentally), I'm able to remove components without marking, let alone damaging the PCB or the components themselves.

MKS-70 Module-Board prepd for Digital PWM upgrade
This is one of Brent's MKS-70 module-boards which is being prep'd for Fred Vecoven's digital PWM upgrade.

As original components for this generation of electronics are becoming scarce and increasingly more difficult to procure, with the customer's approval, salvaging them off jobs like this is a godsend and will inevitably help another Roland MKS-70 owner some time down the line. It's a true privilege being part of this kind of community! 😀

Here's the underside of the PCB after the four 82C54Ps have been taken off. You simply can't achieve this level of clean removal with a manual hand pump type desoldering tool.

Of course, after doing all of that, you gotta test it all but a Roland MKS-70 full upgrade is so worth it and gives this legendary synth module a whole new lease of life.

Vecoven Digital PWM is part of this Roland MKS-70 Full Upgrade
And here is one of the Vecoven digital PWM boards installed on to a module-board.

A few weeks ago, I decided to take an idea I've had for a long time, to the next level; I made a pair of screened audio cables for the Roland MKS-70 to replace the original 'wires' that connect the outputs from the module-boards to the jack-board.

Screened audio cables are part of this Roland MKS-70 full upgrade
Accepting the insane cost of the tool that crimps the wires to the terminals that are inside the Molex connector was the hard part! Also visible, is the insulating boot over the IEC C14 power connector and of course, the chassis is securely connected to mains earth.

Before I started work on The Miami Sound Machine and while everything was still factory, I used Brent's instrument to test my new screened audio cables for the Roland MKS-70. A plug 'n' play installation, this is a simple but very worthwhile upgrade. You can read the whole story here. 🙂 Indeed, Brent's instrument was the first to receive my new screened audio cables for the Roland MKS-70 installed.

Screened audio cables for Roland MKS-70 fit perfectly on to Nebula
Here are my new screened cables for the Roland MKS-70, fitting snuggly to Nebula's audio board.

If you don't want to buy Nebula, then these screened cables will work equally well with the stock Roland jack-board.

Part of the work I do, includes keeping the customer updated on progress. I'm not sure what's happened in the past year or so but things have just got rather busy. Maintaining regular communications with customers however, remains paramount.

Okay, so you want to know just exactly what the customer got on this occasion. What does this Roland MKS-70 full upgrade include? Well, here ya' go:

  • Guy Wilkinson's P0004 power supply for Super-JX.
  • Earth bonding kit with IEC C14 power inlet connector.
  • Guy Wilkinson's VFD Super-JX display module.
  • Nebula balanced outputs / upgraded MIDI jack-board.
  • Replacement of wires connecting module-boards to Nebula with screened audio cables.
  • Fred Vecoven's Super-JX Flash module.
  • Fred Vecoven’s digital PWM upgrade.
  • Live-forever battery mod.
  • Replacement of all front-panel switches.
  • Chorus chip replacement with 4 x Xvive MN3009.
  • Rerouting of internal cables to reduce noise.
  • RE-MKS-70 rack-ears.
  • MCK-70 memory checker ROM.
  • Check all functions and calibrate module-boards.
  • 15% discount over purchasing items individually.

Sub-assemblies like the P0004 power supply and Nebula are tested prior to installation. The MKS-70 is then tested after every single upgrade. If something isn't right, I'll know straight-away.

Some of the Roland MKS-70 Full Upgrade Options
I've highlighted some of the options included in this Roland MKS-70 full upgrade. Note the severe lack of the original Roland cable looms!

A lot of the upgrades are not apparent from the outside of the MKS-70 but Guy Wilkinson's GU280 based VFD definitely is and looks absolutely fabulous!

Guy Wilkinson's VFD is part of this Roland MKS-70 Full Upgrade
Visually one of the most impressive upgrades for the MKS-70, is Guy Wilkinson's VFD kit.

Making life a lot easier and in my humble opinion, being much more secure, the controller PCB for the VFD is mounted on my unique V02b bracket and not to the back of the front-panel chassis, as per Guy Wilkinson's installation instructions. Guy popped over while I was doing work on this baby and couldn't help notice the mounting solution. He loved it!

Guy Wilkinson's VFD controller PCB on my V02b bracket
Guy Wilkinson's VFD controller PCB on my 1mm thick, mild steel, V02b bracket.

You may have noticed a couple of perhaps unexpected items in the inclusion list above. Well, Brent's MKS-70 didn't have rack-ears so he asked me to include my RE-MKS-70 rack-ear kit. He also asked for a copy of Guy's MCK-70 memory checker and so The Miami Sound Machine was accompanied by a few extra bits on its return to, well... Miami.

A few extra bits for Brent
Included with the return shipping to the sunshine state, was my RE-MKS-70 rack-ears kit and a copy of Guy Wilkinson's MCK-70 memory checker.

A big T H A N K  Y O U to Guy Wilkinson and Fred Vecoven for developing some awesome kit for the Roland Super-JX. 😀

When it comes to packaging, I don't take any chances. Touch wood, I've never had anything damaged, let alone lost but I still believe in good, sometimes excessive packaging. Apart from protecting equipment, it helps the courier, too.

Well packaging items, greatly reduce the risk of damage
The Miami Sound Machine packed and ready to go home.

The shipment is marked up as 'Return after repair' so as to ensure that worst-case scenario, the customer will be charged on the cost of the repair and not the value of the item and the cost of the repair.


UPDATE - 10th April 2024

I'm always dead curious if and how much customers get charged import duty. It helps me advise customers in the future and is just really helpful for everyone. Brent kindly informed me of the following duties breakdown:

  • MERCHANDISE PROCESSING 31.67 USD
  • IMPORT EXPORT DUTIES 167.78 USD
  • DUTY TAX PROCESSING 17.00 USD
  • TOTAL CHARGES 216.45 USD

Unfortunately on this occasion, US Customs got a bit funny and asked for 'additional information'. Annoyingly, the additional information was in fact included in amongst the documentation that I included with the shipment but at stupid O'clock in the morning, I sent Brent everything that Customs had asked for, in a letterheaded document. A couple of days later, Brent received his baby.

ParcelForce or ParelFarce

Here's yet another example of why Worst Courier Ever Award goes To ParcelFarce.

I’ve been desperately waiting for a shipment of my PML-TX01 replacement transformers for the Marshall JMP-1, to arrive. I have customers who are also waiting!

PML-TX01 back in stock

The transformers are made in the very same factory that made the original Dagnall TXMA-00014 transformer. The factory is in Europe which means I need to import them into the UK. Unfortunately, the UK leg of the shipment is handled by ParcelForce, a UK courier who I only hear bad things about and which fills me with dread every time I have anything to do with them.

Last week I received the expected letter informing me of customs duty charges and appreciating the urgency of the shipment, I paid this straight-away (including the 12 GBP handling fee), on Tuesday 20th February 2024. I was of the understanding that the parcel would be delivered within twenty-four hours.

Not having heard, let alone received anything by Thursday, I thought I’d see what was going on. Using the ParcelForce portal, I checked the status of the shipment using the tracking number and was promptly informed that the parcel was waiting for customs duty payment. Okay, so perhaps my payment didn’t go through and so I went to pay (again) using the ParcelForce reference number. Oh! “Payment for this item has been made” I’m told.

I then tried to get in contact with someone (human) at ParcelForce and I have to say that I’ve never known a company to make it more difficult to talk to someone.

Anyway, I eventually got to talk to a person. After a whole load of security, I was again informed that the parcel was waiting for customs duty to be paid. I explained that I had paid. I gave the gentleman the date of payment and told him that I was looking at my bank account on my phone and that the payment is showing as having cleared.

The shipment would now be delivered on Monday, not tomorrow, which would have been Friday. I couldn't help myself and politely expressed my dissatisfaction. Apparently, my 'complaint' was noted.

So, today is Tuesday and at about 4:15 in the afternoon, the parcel finally arrived. That’s a week since I paid the customs duty and even longer since it entered the UK.

It’s of no surprise that this courier is often referred to ParcelFarce. It’s the only courier I’ve ever had dealings with, which has received a damages claim from me. I won’t go into that one as you’ll die laughing. I almost died out of shear frustration.

CONGRATULATIONS!!!! Worst courier ever award goes To ParcelFarce.

In response to a question I get asked a lot, "where can I get screws for my JMP-1?", I've decided to release a complete screw kit for the Marshall JMP-1.

Screw kit for the Marshall JMP-1

Yeah, I know... it's not a big deal but it's just one of those things in life that niggles us, especially if you have a JMP-1 with err... missing screws!

The JMP-1 was produced with some interesting hardware:

  • All the screws are black... err, except for one of the big earthing screws that secures to the chassis. The other earthing screw is err... black!
  • Some screws are Phillips cross-head and some are hex-head… oh and at least two are flat-head (seriously?).
  • Most are M3.
  • Most are machine screws but three are self-tap.

Surely it would have been cheaper for Marshall to at least use all the same type of screws but hey, it was Bletchley, 1992.

Marshall JMP-1 screws
Perhaps Marshall ran a competition for the staff: "How many different types of screws can we get into the JMP-1, guys?"

Another conundrum is why did Marshall use ordinary washers and spring washers on the earthing points, when they used nylon locking nuts. They didn't do that with the locking nuts that secure the IEC C14 power connector. My screw kit for the Marshall JMP-1 omits those superfluous spring washers and since the holes in the rear chassis for the IEC C9 aren't threaded, my kit replaces the weird flat-head screws here, with standard metric cross-head types.

Another tweak in my screw kit, is that the three screws that secure the top-case (lid) to the bottom-case at the rear of the unit, look quite different. The screws in this kit replace the original wide-head screws that Marshall used, with more elegant, standard-headed screws. They fit perfectly and are considerably less obtrusive.

More elegant rear screws for Marshall JMP-1
Perhaps slightly more elegant standard-headed rear screws for Marshall JMP-1.

With only cross-head screws in my screw kit for the Marshall JMP-1, you only need one screwdriver! 🙂 Yeah, okay... two then (a medium cross head and a smaller cross head).

I would have liked to keep everything the same but unfortunately, those three screws at the rear of the unit, that secure the lid to the bottom-case as mentioned earlier, have to be self-tapping.

There's no manual supplied supplied with this kit but there is a pretty comprehensive hardware guide that's available after purchase, just to make sure that you put the right screws in the right places. 🙂

Here's a list of the contents of my screw kit for the Marshall JMP-1 (total number of items = 29)

  • 3 screws for rack-ear left
  • 3 screws for rack-ear right
  • 2 screws for IEC C14 power inlet connector
  • 2 screws for internal front panel PCB bracket
  • 2 locknuts for IEC C14 power inlet connector
  • 3 screws for rear chassis
  • 2 screws for front facia top
  • 3 screws for front facia bottom
  • 1 screw for top-case front
  • 1 screw for earthing point left side of case
  • 1 screw for earthing point in front of transformer (bottom case right)
  • 1 washer for earthing point left side of case
  • 1 washer for earthing point in front of transformer (bottom case right)
  • 1 lock nut for earthing point left side of case
  • 1 locknut for earthing point in front of transformer (bottom case right)
  • 2 screws for footswitch port on rear

A complete set of screws for the Marshall JMP-1

One thing I really must emphasise is that unless your Marshall JMP-1 is going on a deep-space mission, please (PLEASE) don't over-tighten the screws!!!!

If you do over-tighten, you might end up threading a screw hole or two and if you ever have to open up your JMP-1, having to undo tightened screws, increases the risk of screwdriver slippage and hence, damaging something. You could also mess up the odd screwhead and if that happens, you might have to drill out a screw and that's not good.

Something else I get asked a lot for, are the rack-ear reinforcement brackets and so I decided to have a go at designing some replacements. In fact, at the time of writing, I'm waiting for some protypes to be made by my friends at Lenton Engineering. I'll keep you all posted about them.

And in case you've missed some of my stuff, here's a bunch of other bits 'n' pieces that I make for the Marshall JMP-1:

Fix the skipping encoder

Spare knobs, bezels and power button kit

PML-TX01 replacement transformer for the Marshall JMP-1

CR2032 battery adapter for the Marshall JMP1

RE-JMP-1 replacement rack-ears for the Marshall JMP-1


Check out all of my Marshall JMP-1 stuff in my on-line store...

Marshall JMP-1 stuff at Plasma Music

Introducing Plasma Music UnlimitedOver the years, I’ve been very fortunate to have got to know some truly lovely people. Spread over two quite discrete customer bases (UK and non-UK) however, and as things have become increasingly busier recently, I’ve been considering streamlining my business with a view to ensure that I’m able to continue to deliver the best and most cost-effective service, to everyone.

Hence, as of 1st April 2024, I’ll be running two set-ups; Plasma Music Limited and Plasma Music Unlimited.

Amongst other administrative changes, the new trading body, will not be VAT registered, thereby reducing the time I spend on book-keeping for example. I’m also aiming to offer simpler payment options. It’s all about reducing overheads, keeping down costs and ensuring that I can deliver a level of service that I would expect for myself.

Plasma Music Unlimited is already card payment ready
Ready for (the new) business.

Of course, nothing’s going to change for regular Plasma Music Limited customers. 😊

 

 

 

I have a lot of requests for parts and information for the Marshall JMP-1. To keep things simple and straight-forward, I've therefore decided to make dedicated Marshall JMP-1 category in my on-line store.

Marshall JMP-1 stuff at Plasma Music

I don't offer original Marshall spares as they're obsolete and therefore impossible to procure. My new Marshall JMP-1 category in my on-line store however, does comprise some goodies which are either very close to the original items or 'smarter', if you know what I mean. My performance knob and bezel set which bears a close resemblance to the originals, is for example, offered alongside a 'studio' knob and bezel set which looks very cool.

Marshall JMP-1 Knobs Nuts and Bezels
From the bottom (why didn't I stack them the other way around) we have original knobs, my performance knobs and then, my studio knobs.

I've developed things like Eclipse which fixes the annoying skipping of the data encoder as these things are getting rather old now. What am I saying? Marshall didn't do this properly in the first place! 🙁

Eclipse Bounce Eliminator for the Marshall JMP-1
Eclipse bounce eliminator for the Marshall JMP-1.

And then there's my PML-TX01 replacement transformer for the Marshall JMP-1. Comprising laminates that are made from a different (more expensive) material than was used in the original, my transformer runs cooler and will theoretically live a lot longer. I even managed to get this made in the same factory that made the original Dagnall TXMA-00014.

A replacement transformer for the Marshall JMP-1, my very quiet PML-TX01
My PML-TX01 replacement transformer for the Marshall JMP-1 fits like a glove and runs cooler and quieter than the original.

Recently, I finished designed my RE-JMP-1 replacement rack-ears for the Marshall JMP-1 and my first batch have just been delivered. I'm really happy with these.

RE-JMP-1 Rack-Ears for the Marshall JMP-1
Supplied with six black crosshead screws, my new RE-JMP-1 replacement rack-ears for the Marshall JMP-1 look amazing and fit perfectly.

I've also got together a screw kit for the Marshall JMP-1 which I hope, will help out a few JMP-1 die-hards.

A complete set of screws for the Marshall JMP-1
A collection of black, crosshead external screws for the Marshall JMP-1.

There's also a top-secret JMP-1 project under development which I'm busting to share with but... well, just check in regularly!


I often get asked to modify equipment with a view to changing the sound and indeed the Marshall JMP-1 is no exception, with requests to do so, being received on a semi-regular basis. My response is always the same...

"If you don't like the sound, buy something you do like the sound of."

Yes, I know what you're thinking...

"How can you say that Alex, when you make so much stuff?"

Well, take a closer look, guys. All the peripherals I design and manufacture, have two objectives in mind:

  • To improve reliability
  • To increase longevity

It's that simple and nothing I offer, changes the sound of the equipment we all love.

Yes, there are exceptions. My modular switched-mode power supplies like Aurora, Supernova and Galaxy for example,  inadvertently remove transformer generated hum and power supply induced noise. Nebula was designed to give the Roland MKS-70, balanced outputs but it also (and inadvertently)  improves fidelity. Hey but they're all good things, right? 🙂


UPDATE - 10th April 2024

So when I posted this article, I mentioned a 'top secret' project. Well here it is, everyone!

Oracle JMP-1 battery eliminator for the Marshall JMP-1

Oracle JMP-1 is my latest upgrade for our favourite MIDI valve pre-amp. It eliminates the requirement for a battery to back up the memory. You can read all about here.

RE-JMP-1 Rack-Ears for the Marshall JMP-1

I got an e-mail from Lenton Engineering this morning, informing me that a whole bunch of stuff I asked them to do for me, was now done and ready to collect. Amongst all the bits 'n' pieces were a pair my RE-JMP-1 replacement rack-ears for the Marshall JMP-1. Oh, I was so excited!!!! 😀

Lenton Engineering is in Watford so only ten miles away but did I race there or what?!?!? Then... I raced back to the lab!

I have three Marshall JMP-1s in at the moment but decided to try these on my own test JMP-1 first, the one I use to test Eclipses before they get sent out.

RE-JMP-1 replacement rack-ears for the Marshall JMP-1 fit perfectly
RE-JMP-1 replacement rack-ears for the Marshall JMP-1 fit perfectly.

Oh man, these things fitted like a glove. Why was I so excited about a couple of bits of metal? Well, these have been in the making for a couple of years, that's why. In fact, looking at my very first drawing, I see that it's dated 5th February 2021. That's three years ago, almost to the day!

I only had original rack-ear reinforcements to work from and measuring, remeasuring and remeasuring again, I wasn't even sure if they were designed with metric or Imperial units. Anyway, now I don't give a damn because the Lenton boys have have done it again. What a great job, guys!

RE-JMP-1 Rack-Ears for the Marshall JMP-1 includes screws
My RE-JMP-1 rack-ears for the Marshall JMP-1 includes screws.

The Marshall JMP-1 is an awesome early MIDI controllable valve pre-amp. Now accredited with 'vintage' status' and adorning a 'classic' badge, the humble Marshall JMP-1 continues to be used by many named artists like Phil Collen (Def Leppard), Billy Gibbons (ZZ Top) and Trent Reznor (Nine Inch Nails), to name but a few.

One thing that makes the JMP-1 unique amongst guitar pre-amps of the time, is the fact that it's analogue. Yeah, I know what you're thinking; "How can that be when it's got MIDI and presets?" Well, just like many early MIDI synthesisers, the audio is all analogue. In the JMP-1 specifically, the audio signal (the output from your guitar) passes through analogue circuitry only but some of it is digitally controlled, thanks to the use of voltage controlled amplifiers (VCAs). A preset comprises a whole load of noughts and ones which are converted to analogue control voltages which in turn, are used to set the gain of those VCAs, hence provide variable gain, volume, tone controls, etc.

Toshiba TC9176L VCA in Marshall JMP-1
Highlighted in red is half of one of the Toshiba TC9176L VCAs that's used to control parameters (such as volume) in the Marshall JMP-1.

Anyway, I digress. So... finding a really nice JMP-1 is becoming increasingly more challenging and buyers are often forced to compromise. Joining my arsenal of JMP-1 peripherals, I'm rather hoping that my RE-JMP-1 replacement rack-ears for the Marshall JMP-1 will help out a few users. I currently have three JMP-1s in for service. Pictured below, the bottom unit which belongs to a lovely gentleman called Tim, doesn't have rack-ear reinforcement brackets so I know there's going to be at least one happy JMP-1 owner very soon! 😀

Marshall JMP-1s in for service at Plasma Music Limited
Hmm... I tend to regularly have a small collection of customer JMP-1s in now-a-days.

Supplied with six black Phillips crosshead screws, my RE-JMP-1 replacement rack-ears for the Marshall JMP-1 can be installed in a few minutes. Yes, you read correctly; Phillips crosshead. I often replace the original hex heads, which in my humble opinion, are crap anyway, with Philips crosshead screws. In fact, all the screws in my screw kit for the Marshall JMP-1 are crosshead types, which makes maintenance of your Marshall JMP-1 a little easier and reduces the risk of messing up a screw head.

Please, please, please don't just have a go! Things may work out really expensive for you if you screw it up. I'm a nice guy and I often don't charge for the time that it actually may take to perform a rescue operation.

A few weeks ago, I received a module-board from a Roland JX-10. It had a couple of faults on it which the customer was unable to fix so after a couple of failed DIY repair attempts, he decided to send me... just the board! 

I pretty quickly tracked down a duff 82C54P timer IC. I always try to replace ICs in vintage gear with the same devices and on this occasion, I didn't have any of these in stock. That meant I had to wait some time for an order to come in.

Roland JX-10 Module Board with Replaced 82C54
Roland JX-10 Module Board with Replaced 82C54.

It was quite apparent that all of the 4051s had been replaced. 🙁 Note how the turned-pin IC sockets are extended and cover up the PCB component reference. Seriously?!?!?

Customer Replaced 4051s on Roland JX-10 Module Board
Notice how the sockets that the customer used for the 4051s inconveniently obscure the PCB component references. Grr...

So knowing that things wouldn't be as simple as changing a duff 82C54P, I proceeded to check connections and discovered three that weren't... connected, I mean.

Incidentally, buzzing out one of these boards requires a lot of time, patience and coffee!

Roland JX-10 Module Board with Repaired tracks
Broken tracks that had to be repaired. Sorry but these didn't happen by themselves!

Final testing and at last, everything seems to be working. Of course I'll need to go through a whole bunch of routines to be sure. 🙁

Roland JX-10 Module Board
A now repaired and fully functional Roland JX-10 Module Board.

Eighties synthesisers are just beautiful but they're also incredibly complicated and being thirty-something years old, they're also a little fragile. Today there's a wealth of information out there on the www but you still need to know what you're doing. Service notes are often riddled with mistakes for example and following them as if they were written in stone, is a common mistake in itself. So unless you have the right equipment, knowledge and experience, please don't just have a go!

Please don't just have go. Fixing a bad DIY attempt includes final testing which takes a lot time
Even final testing takes time. After going through a couple of routines several times, I left the MKS-70 with the repaired board, on soak for a day... or two.

Screened audio cables for the Roland MKS-70With voice generation on two boards that were separate to the audio output board and with so much electromagnetic radiation within the box, one wonders why Roland didn't use screened cables to connect the audio signals from the module-boards to the jack-board. Well, thirty-something years later, some idiot's decided to address the issue and make screened audio cables for the Roland MKS-70... ME! 😀

Screened audio cables for the Roland MKS-70 can be installed in minutes
Screened audio cables for the Roland MKS-70 can be installed in minutes.

Weird isn't it; The audio connections between the module-boards and the jack-board in the JX-10 are screened but they aren't in the MKS-70. Of course the distance they need to cover is much greater in the JX-10, with one cable running from near the PSU (hint, hint) on the right of the keyboard, all the way to the jack-board which in on the left.

Roland JX-10 module-boards to jack-board cable route
Highlighted in yellow, you can clearly see that the audio cables from the module-boards to the jack-board in the JX-10, are very long and are tied up in the same loom that carries power and digital signals.

In comparison, the distance that the audio cables cover in the MKS-70 is only about 30cm.

Audio routing in MKS-70
Highlighted in yellow is the route of the standard wires that make the audio connection between the top module-board in the MKS-70 and the jack-board. Obviously a lot shorter than in the JX-10 but in my humble opinion, still unnecessarily long.

The potential for noise inside these old synths is considerable and the wires that Roland used act like aerials and can pick up a lot of internally generated noise.

Replacing the original power supply in the MKS-70 (or indeed the JX-10) with Guy Wilkinson's P0004 modular switched-mode power supply, will go a long way to reducing electromagnetic radiation as for a start, that big transformer gets wasted. Unfortunately, there are still a lot of wires distributing DC power voltages, digital signals, etc, all over the place and these do generate stuff that really isn't good for our audio. Unlike it's Super-JX cousin, the audio cables in the MKS-70 aren't tied up in a long loom together with other cables, so that's at least one consolation.

Guy Wilkinson's P0004 modular switched-mode power supply for the Roland MKS-70
Guy Wilkinson's P0004 modular switched-mode power supply for the Roland MKS-70 means no transformer.

Nebula, my balanced outputs jack-board for the MKS-70, improves noise immunity between the MKS-70 and the destination device like a mixing desk, for example. Nebula however, cannot get rid of noise that arrives at its inputs. Any noise at the inputs of Nebula will be passed on to its outputs, albeit with pristine quality!

Nebula balanced outputs jack board for the Roland MKS-70
Nebula gives the MKS-70 balanced outputs and a revised MIDI circuit but it can't filter out noise picked up from within the box and is present at its inputs.

My screened audio cables for the Roland MKS-70 have been extracted from multi-core cables. These selected, high-quality, low-mass and flexible cables have an internal metal foil screen which, unlike the mesh screen in say, a microphone cable, provides 100% coverage of the audio signal carrying conductors. That's a big deal as this makes it really difficult for noise to get to our audio in the first place.

Screened audio cables for the Roland Super-JX have 100% screening
Overlapping metal foil inside the screened audio cables for the Roland MKS-70, ensures 100% coverage of the audio signal conductors.

Now then, you'll notice a slight difference between the wires going into the connectors I'm using and the wires going into the stock Roland connectors; I have three wires (left, right, earth) and Roland has four. Well, the additional wire on the Roland version is another earth wire giving you left audio / left earth, right audio / right earth.

One of the connectors of my screened audio cables for the Roland Super-JX
Luckily, you can still buy the connectors that Roland used in machines like the Super-JX. Only problem is that the crimp tool is horrendously expensive.

But hang on a minute; those earth wires are connected (shorted) at the module-board end but also at the jack-board end. So why on earth (pardon the pun), did Roland do this? An excellent question.

Separate earths for left and right audio channels is a method employed by designers to reduce crosstalk, often when high source impedances or low destination impedances are present or when there's the potential for ground (earth) not to be exactly zero volts!

As can be seen in the image below, the outputs from the module-boards come off a pair of op-amp stages and so the output-impedance of the module-boards is (very) low. The passive mixing / switching on the jack-board which combines respective module-board channels and also automatically gives the Super-JX either stereo or individual outputs depending on which output sockets are used however, comprises relatively low value resistors. Okay, no big deal because the input-impedance of each channel of the headphone amp is about 100kΩ. Effectively strapped across each input, we can consider the input-impedance of the jack-board to be very close to that and hence; high. This configuration is the same on both the MKS-70 and the JX-10. Great! So that's all good.

Roland MKS-70 audio earths between module-board output and jack-board input.
On the left is the output of a MKS-70 module-board. On the right are the inputs of a MKS-70 jack-board. I've highlighted the earth connections in green. Left and right earths are connected on each module-board and ALL earths are connected on the jack-board.

So crosstalk isn't an issue in the MKS-70 as it is in the JX-10.

Incidentally, if you're interested, you can read more about Super-JX crosstalk here.

It's also worth mentioning that if the system has an absolute earth, then crosstalk would be greatly reduced. The reason for that, is discussed in the post link above.

As we know however, many Roland instruments from the time of the Super-JX, were supplied with IEC 2-pin C9 power sockets and were therefore not directly connected to mains earth. Could this be the reason why Roland used two earth wires between each module-board and the jack-board? It certainly sounds like it.

If you're Super-JX has an IEC 2-pin C9 power input socket, then you really should consider my IEC C14 earth bonding kit.

One small point of convenience with my screened audio cables for the Roland MKS-70, is that since they're extracted form multi-core cables, the cores are numbered. This means that confusion between upper, lower, module board A, module board B, EPROM B, EPROM C, is now a thing of the past.

Numbered multi-cores
Numbered cables cuts down confusion.

The module-board assignment is as follows:

  • module board A is the upper voice-board and has ROM B installed.
  • module board B is the lower voice-board and has ROM C installed.

NOTE: Module board A with ROM B installed should have a black wire in position 10 on CN2. Module board B with ROM C does not have this wire and position 10 on CN2 is empty.

NOTE 2: It doesn't matter which module-board is physically the top one or the bottom one although it would make sense to have the 'upper' module-board on top. 🙂 'Upper' doesn't mean top and 'lower' doesn't mean bottom. Upper and lower refer to the voice groups.

Quite simply, the lowest numbered core goes to CN3 on module-board A (with EPROM B) and the highest numbered core goes to CN3 on module-board B (with EPROM C).

My screened audio cables for the Roland MKS-70 are about 30% shorter than the originals
My screened audio cables for the Roland MKS-70 are about 30% shorter than the originals.

Okay, let's be honest; all that explanation is meaningless if there's no difference between using the original cable and my new screened cable, right? Well, this wasn't just something I did because I felt like it and in my usual manner, I conducted several tests.

Below is an image which shows the result of one of the tests. As can be clearly seen, one of the wires used in the original connection between module-board and jack-board picks up a lot of 50Hz (I'm in the UK) mains hum. The screened equivalent doesn't!

Mains hum on original Roland cable Vs screened cable
Measured simultaneously, the original wire as used by Roland, picks up a lot of mains hum (yellow). In contrast, the induced hum in the screened cable is barely measurable (blue). NOTE: Apart from the oscilloscope, neither cables are connected to anything but the screen on the screened cable is earthed to the MKS-70 earth.

The reason that my audio cables for the Roland MKS-70 took a while to get out was because I had to buy a special crimping tool to attach the metal terminals that are in the connector housing, to the wires inside the cores. So what's the big deal? Well, it cost 345 GBP plus tax and with respect to all my Roland MKS-70 friends, this was a big commitment and it took me a while to make the decision to do this. As ever, Julie my wife was really helpful and reminded me of just how much I love what I do.

I don't like being taken for granted but my customers demand the best and delivering the best is something they can take for granted.

Molex crimp tool
Yes, there are budget alternatives but if you're going to do something, do it properly. 

With no soldering required, all you need to do is open up your MKS-70 and replace the existing aerials, sorry, I mean wires, with my screened audio cables for the Roland Super-JX. It's a simple ten minute job and will reduce the noise that's picked up from internal electromagnetic fields that's generated by components and wires carrying DC power and other stuff.

If you want to improve the quality of the signal that comes out of your Roland MKS-70, you can buy my screened audio cables for the Roland Super-JX here:

This kit will now also be available at a reduced price, to those who buy Nebula.

NOTE: My screened audio cables for Roland MKS-70 will not fit into the JX-10 as they're way too short. On top of that, the internal audio cables in the JX-10 are already screened!

EVEN MORE NOISE REDUCTION

As I've already mentioned, my Nebula balanced outputs jack-board increases noise immunity between your MKS-70 and the destination device, like a mixing desk. My screened audio cables for the Roland MKS-70 will considerably reduce noise picked up between the outputs of the MKS-70 module-boards and the jack-board. BUT... remember that this is an analogue machine! There's a lot of 'analogue' stuff happening on those module-boards and yet they've got a whole bunch of power and data cables running all over them.

Realising that the beautifully loomed Roland cabling could be a source of noise for the module-boards, Guy Wilkinson addressed the issue by rerouted it. What he did is definitely worth checking out. Here Guy goes into great depth, explaining a lot of theory and how to perform a simple cable modification that'll reduce the noise picked up by the module-boards. HEY, AND NO SOLDERING INVOLVED!!! 🙂

 

Old valves still showing red ink

Essential test equipment, the valve tester is a must have bit of kit when you service / repair as many valve amps as I do! Not everything is what it seems and a really good valve tester ensures that the valves in my customers’ amps are good and healthy. A valve tester quickly highlights any issues and does so with the valves removed from the amp.

A regular customer recently dropped off a Mesa Boogie Mark 2 C Plus Combo. There wasn't anything specifically wrong with the amp but with seven years since its last service, Keith just wanted me to give it the once over.

Mesa Boogie Mark 2 C Plus Combo
Keith's gorgeous Mesa Boogie Mark 2 C Plus combo in for a regular service.

While we chatted, I explained that the legend on JJ Tesla valves should be a bright red, thus indicating that the devices are healthy. When the writing turns white, then you really need to change the valves. This characteristic is not common to all manufacturers' valves. The legend on the valves in this amp were indeed a nice shade of red.

Well, regular customers will know that I don’t take anything for granted and I tested the valves anyway.

Different valves have different specifications (of course) and the 6L6s inside this amp, should have a plate current somewhere between 12 mA and 40 mA. One of the valves is slightly out. In fact, after about half-an-hour, the reading fell to 10.1 mA.

Essential test equipment, the valve tester shows that the plate current on one of the 6L6s is less than the recommended 12 mA
The valve tester clearly indicated that one of the valves had a plate current slightly under spec'.

Another important valve parameter is transconductance and for 6L6s this should be than 2.0 mMhos. As you can see, my digital valve tester is showing that the suspect valve falls short. Just like the plate current reading above, after about half-an-hour, the transconductance fell to 1.7 mMhos.

The transconductance for 6L6s should be greater than 2.0mMHos
Indeed, the transconductance for the suspect valve was out of range, too.

Essential test equipment, the valve tester in this example isn't cheap. My Maxi Matcher 2 cost about 900 USD several years ago and took a couple of months to be delivered. On the other hand, customers like Keith; discerning musicians who look after their gear and get it serviced regularly, make it all worthwhile. Remember, there wasn't anything particularly wrong with Keith's amp. He just wanted a service. 🙂

On this occasion, Keith's lovely little Mesa Boogie combo (which weighs a ton, incidentally), gets a late Christmas present; a brand new matched quad of burnt-in, premium Harma 6L6s. 🙂

Matched quad Harma 6L6s in Mesa Boogie Mk2 C Plus Combo
A happy amp and don't those valves look lovely!