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Marshall JMP-1 Full Service

I’ve seen a few Marshall JMP-1s in my time and as some will know, I really do like this simple and straight-forward MIDI valve pre-amp. As such, I love working on them and enjoy testing the results even more! Having a Marshall JMP-1 in that needs a little attention is never tiring.

Anyway, last week a customer who had just bought one of these off eBay, took the initiative and sent it to me for a full service.

Although dated 1992 making it an original production example, you just wouldn’t guess it from the condition of the unit, it’s pristine. What a find!

Marshall JMP-1 Full Service

Stuart said that he’d like the valves checked as well as the back-up battery. He also commented that the data encoder was skipping. This latter issue is quite common. Marshall didn’t incorporate a hardware bounce eliminator into the JMP-1 and the outputs of the encoder, go straight into the processor. I therefore, took this opportunity to design something that would sort this problem out once and for all. In fact, Stuart's JMP-1 became the first unit to have my 'Eclipse' bounce eliminator for the Marshall JMP-1 data encoder installed and you can read more about that  here soon.

The valves were original and electronically, they will probably last another thirty years. Without modification, we know that the valves don’t really contribute too much to the tone of the JMP-1 but on this occasion, I decided to change them anyway, just so that everything’s nice and clean and so I dropped in a pair of cryogenically treated premium valves sourced from my good friend Derek at Watford Valves.

The two ECC83 in the Marshall JMP-1.

The most disturbing observation when I took the lid off, was the back-up battery. It was obviously swollen and although still backing up the memory, was in desperate need of changing. This point is of particular importance. I leaking battery could render your JMP-1 useless! Please do check out my post of Battery Acid Damage.

Soldered CR2032 in Marshall JMP-1
Just about to pop, the CR2032 as fitted in the Marshall factory twenty-eight years ago.

I explained my Live Forever memory back-up battery mod’ to Stuart and he loved the idea so we went ahead with that.

I cleaned the volume pot on the front as well as the sockets which although looked okay, hadn’t been touched for almost thirty years.

Since the unit had just been bought, there were no user patches of significance so I initialised the memory. If you need to initialise your unit, follow my guide here.

I put the lid back on, plugged it in and WOW! This machine looks, feels and sounds like it was made last week. FANTASTIC!!!!

Marshall JMP-1 looking, feeling and sounding like new
Marshall JMP-1 looking, feeling and sounding like new.

People love their Marshall JMP-1s and I often get asked to supply more than a service. As an example, I recently had a JMP-1 in, that had a data encoder knob which looked like it had spent half-an-hour in boiling water! The rest of the unit was pristine.

Of course, being discontinued for well over twenty years, Marshall don’t really hold a lot of spares for the JMP-1 and sourcing alternatives isn’t easy.

There are two knobs on the front panel and although they look the same, the fittings are quite different. The knob for the volume pot has a 6mm spline shaft and the knob for the data encoder has a ¼” D-shaft. Finding a knob with the correct base diameter, height, ergonomics and colour is hard enough. To find a knob that satisfies all of that and is available in two versions, one with a 6mm spline shaft fitting and another with a ¼” D-shaft fitting is well, kinda impossible. So, while my hunt continues, I am forced to improvise. Having said that, customers seem well chuffed with the results.

Marshall JMP-1 replacement knobs, nuts, bezels
Replacement nuts and bezels for front panel sockets, knob to fit 6mm shaft of volume pot and the same but modified knob to fit the 1/4" D-shaft of the data encoder.

The other items which often gets lost or damaged, are the black nuts on the front input and headphone jacks. Well you’ll be pleased to know that I have managed to track down this rare beast including the black bezel for these particular jacks.

As mentioned, I don’t tire of working on these machines, so if you’ve got a Marshall JMP-1 that you feel could benefit from some attention, just contact me.


Super Nova switched-mode power supply for the Roland Juno-106
Super Nova, the world's first switched-mode power supply for the Roland Juno-106.

Following on from last summer’s Aurora project (read more about that here), I thought I’d have another look inside one of my favourite keyboard synths and see if I could do something similar. Well, it took me about a week to design the basics of what was very quickly to become the Super Nova switched-mode power supply for the Roland Juno-106.

Being a guitarist, my selection of keyboard synthesisers is quite modest but I consistently find it amusing that many musicians walking into my studio, inevitably make a bee-line for my humble Juno-106.

My Roland Juno-106
My favourite keyboard synthesiser; the Roland Juno-106.

I have always loved this machine! It’s just so easy to ‘draw’ a sound using the top-panel controls and it always delivers. Lush, phase coherent and warm with no mistaking that classic Roland chorus, the Juno-106 has played a big part in my own musical history.

Intended as a budget synthesiser, the Juno-106 was released in 1984, the same year as the MKS-80 and the JX-8P. It’s lack of velocity sensitivity and simple voice architecture didn’t seem to inhibit this monster-sounding machine’s popularity. Indeed, the Juno-106 is probably one of the best-selling synthesisers of all time.

My Roland Juno-106

Today many named artists still use this fab synth and variations like the Juno-106S and HS-60 (or Synth Plus 60) both with built-in speakers, still sit in many a lounge or music room. After more than three decades however, time is taking its toll. Many will be familiar with the failing 80017A VCA / VCO devices, for example. Fortunately, Analogue Renaissance offers a replacement, the AR80017A. My Juno-106 is doing alright at the moment so I haven’t had the opportunity to try these yet. Having said that, I’ve only heard good things about the AR chips and I salute Jeroen Allaert of Cask Strength Electronics for such excellent work. On top of that, they look really, really cool!

AR80017A by  Analogue Renaissance
In my humble opinion, one of the most significant developments for the Juno-106, the Analogue Renaissance AR80017A replacement VCA / VCO modules.

KiwiTechnics has always been a name you can trust when it comes to synth repairs and upgrades and after a couple of years in development, the guys recently launched a seriously powerful hardware / firmware combination for the Juno-106. Known as the Kiwi-106, this is a significant upgrade offering a huge array of fantastic and modern features that well, change everything! In fact one of the reasons Super Nova is red is to match the Kiwi-106 so I strongly suggest that you check out to find out more!

All these people doing this great stuff for the Roland Juno-106 and I couldn’t find anyone making a replacement power supply. Perhaps it's because we all know that Roland power supplies are really quite robust and have stood the test of time.

Roland Juno-106 power supply
In my humble opinion, Roland has always made really good power supplies.

An interesting feature and unlike many synthesisers of that era, the transformer in the Juno-106 is multi-tapped meaning that by moving a wire from one post to another (and changing the fuse), you can use the synth on virtually any domestic voltage supply across the world. 

Juno-106 power transformer
Multi-tapped power transformer of the Roland Juno-106 makes international usage a little easier.

The thing is, power supplies do fail. If the transformer packs up for example or starts humming, then that’s it. That’s why I designed Super Nova. Not just a replacement power supply, Super Nova is a modern, switched-mode power supply for the Roland Juno-106, meaning that for a start, it generates considerably less heat than the original linear power supply. There’s NO mains hum either and since Super Nova's filters are based on my good friend, Guy Wilkinson's design, Super Nova is also super quiet. And of course, being a switched-mode design, you can still plug your Juno-106 into any electricity supply around the world but this time... without having to open it up and change the transformer tap!

Super Nova installed and powered up
Super Nova installed, powered up and showing status LEDs.

Individually coloured LEDs for each supply including the 5V reference voltage, means that you can very quickly check line status with a glance. If you really want to know what's going on, conveniently located test points make measurements a breeze.

Super Nova status LEDs and test points
Super Nova also has conveniently placed test points.

The 5V reference voltage is set when each Super Nova is made, using regularly calibrated test equipment. A multi-turn pre-set however, allows for fine adjustment which may be necessary after several years, due to component value drift.

Super Nova allows for fine adjustment of 5V reference
Although set up when built, Super Nova allows for fine adjustment of the 5V reference. Also pictured is Q2 which is a power-on-reset device to ensure that the processor in the Juno-106's doesn't start running code before everything is powered up.

One of my most popular upgrades to many machines I receive from customers, is my Live Forever battery mod’ and so like Aurora, Super Nova includes a provision to replace the memory back-up battery in the Juno-106 and take it off the CPU board. This has several advantages:

  • A much larger back-up battery can be installed meaning that you probably won’t have to change it in your lifetime!
  • In the unlikely event that the battery leaks, your precious CPU board is safe and won’t be damaged by battery fluids.
  • Battery voltage can be easily checked without fuffing around with the CPU board.
  • Just in case you do have to change the battery, it’s so much easier and doesn't require any soldering.
Super Nova has on-board back-up battery for Juno-106 memory back-up
Super Nova has on-board back-up battery for Juno-106 memory back-up.

The battery connects directly to the original battery points on the CPU board so all components associated with the back-up battery continue to function as as normal.

Like several synthesisers of its day, the Roland Juno-106 is built on a plywood base. Heavy items like the keyboard assembly and power transformer, are attached to the base using machine-type screws that secure into corresponding steel lugs which are sunk into the plywood. The much lighter PCBs however, simply use wood screws to secure them (via spacers) to the wooden base. When you consider that the plywood base in less than 10mm thick, that sounds a little risky. On the other hand, there's no history of 'stuff' coming lose!

I wanted Super Nova to be super secure so although the PCB could have actually been smaller, I chose to extend it, thereby taking advantage of the otherwise redundant M4 lugs that were previously used to hold down the transformer. Mounted on an aluminium plate, both PCB and plate are very securely anchored to the base of the Juno-106. The plate is further held in place with four wood screws.

Super Nova is anchored to redundant transformer mounting lugs
Much more secure than just screwing to the plywood base, Super Nova is anchored to the redundant transformer mounting lugs.

Super Nova fits perfectly into the Juno-106 and is relatively easy to install by anyone with some technical competence.

Super Nova wiring
Super Nova is even easy to wire-up.

It's very efficient, can be plugged into just about any power outlet in the world and has on-board Live-Forever battery mod.

Super Nova fits perfectly into the Juno-106
A perfect fit and there's no messing about!

UPDATE - 6th January 2021

Super Nova has now been fully tested and I'm lovin' it! I've completed detailed and fully illustrated, step-by-step installation instructions so, if you have a Roland Juno-106 with a bad power supply and are considering a replacement or if you have any questions, please just contact me.

Or you could just...

Plasma Music Limited -

I'm deeply concerned about the environment and the exploitation of labour and so  I always use local manufacturers in preference to the Far East, with the following in mind:

  1. I can be confident that workers are treated fairly and earn a proper wage.
  2. I can be confident of the standard of quality of each item that is delivered to me.
  3. Communication is important and using local manufacturers, all correspondence is quick and understandable.
  4. I believe in supporting the local economy.
  5. I can be confident that the disposal of manufacturing waste is managed properly and in accordance with national and EU law. 

Super Nova was designed by me and every Super Nova is hand-built and tested by me, here in Hemel Hempstead, Hertfordshire. The aluminium mounting plate is made by Lenton Engineering which is based just up the road in Watford and the printed circuit boards are manufactured by Minnitron Limited in Ramsgate, Kent.

Plasma Music uses local manufacturers

At the heart of Super Nova are four high-performance Vigortronix AC / DC converters which are made in Witney, Oxfordshire.

Super Nova uses Vigortronix AC DC converters made in the UK
Super Nova uses Vigortronix AC DC converters made in the UK.

Using local manufacturers isn’t always the cheapest option but the above points are important to me. I hope that they’re important to you too.

This week I've had two machines come in; a Marshall JMP-1 and a Sequential Circuits Prophet 5 (yes, you read correctly). One was just in time and prior to battery leakage. Unfortunately the other arrived too late and had suffered considerable battery acid damage.

Last week I received a call from someone who had just bought a Marshall JMP-1 and, after stumbling across my article on Marshall JMP-1 Service while doing a little research on-line, decided to send me his new purchase for a once-over.

I got a shock, when I opened it as the battery was right on the point of popping. This was incredibly lucky. With a date of manufacture of 1992, the battery was the original, as fitted in Marshall factory, twenty-eight years ago!

Soldered CR2032 in Marshall JMP-1
Just about to pop, this CR2032 was fitted on to the main PCB of this JMP-1 at the Marshall factory in 1992.

After quickly removing the battery, I tried to take some macro pictures to show  swelling. If you look closely, you might be able to see what I'm talking about. The top of the battery should be flat.

Swollen CR2032 from Marshall JMP-1 (2020.12.15)
Look carefully and you'll notice the slight 'hump' on the top of the battery indicating that although this battery is still holding memory, it's also about to start leaking.

I analogise battery check-up with home security; most of us consider investing in CCTV or an alarm system after an incident! Stuart took the initiative and sent me his JMP-1 shortly after he bought it.

Unfortunately the owner of the Sequential Circuits Prophet 5 wasn't so lucky. Apparently this machine had been stored in a case since it was used with Roxy Music over thirty years ago.

A Sequential Circuits Prophet 5 last used over thirty years ago.
Last used over thirty years ago with Roxy Music, this Sequential Circuits Prophet 5 looks amazing.

It's incredibly sad to see horrendous battery acid damage on the inside of such a beautiful example of this legendary machine.

Battery Acid Damage in Prophet 5 2 (2020.12.16)
Inside the Prophet 5, what a mess!

Many components and quite a bit of PCB tracking are damaged but I'm going to try my best to fix this. Having said that, I've already informed the customer that things aren't looking good.

Battery Acid Damage in Prophet 5 (2020.12.15)
Components in the battery acid affected area have just rotted away. Some components just fell out of the machine as soon as I took off the bottom case.

So, I urge anyone who's buying vintage gear to get the memory back-up battery checked. I also strongly advise all, to regularly check the memory back-up battery in your equipment. Battery acid damage is a terrible thing and can cost a fortune to put right, if at all even possible.

My Live Forever battery mod which is available for most synthesisers, keyboards, effects processors, etc, doesn't just replace the factory fitted battery with something more substantial but if possible, I also move the battery off the main PCB.

Live Forever battery mod at Plasma Music
Large capacity CR123A battery mounted off-board.

Aurora (for the Roland MKS-80) and Super Nova (for the Roland Juno-106), are a couple of switched-mode power supplies that I make and that are either available ready assembled or can be installed by me. I recently released Aurora Board Bx, an option that includes a remote memory back-battery and Super Nova was designed with fully integrated remote memory back-battery facility.

Aurora Bx and Super Nova with on-board Live Forever
Both Aurora and Super Nova have an on-board Live Forever memory back-up battery facility.

I'm currently designing power supplies for several other machines and I'm including the same remote memory back-up battery facility on all of them.


Back-up batteries aren't just wired to memory chips. There's always associated circuitry which depending on the age of the machine, the manufacturer and so on, can do several jobs such as switch between battery and PSU power when the unit is switched on and off, provide current limiting and reverse polarity protection.

Memory back-up battery in the Marshall JMP-1 showing associated components.
As an example, here's a part of the Marshall JMP-1 schematic showing the memory back-up battery and associated circuitry.

Since my Live Forever battery mod connects directly to the original back-up battery connection points, any components or circuitry associated with the memory back-up function remain untouched and fully active. As far as your machine's concerned, nothing's changed!

I've had my old serial EPROM programmer for years, well... decades and last week, I bit the bullet and replaced it with something a little newer. Instead of having to hunt down old 'windowed' EPROMs, I can now offer a firmware update service providing the latest devices.

Firmware update service

I don't often get asked for firmware but when I do, I'm usually able to oblige as over the years, I've built up a small repository of firmwares for various machines.

EPROM blower hardware

99% of the time, I'll use EEPROMs (electrically erasable programable read only memory) for my firmware update service. These devices don't have the window associated with older EPROMs and don't need exposure to ultra-violet light, to be erased. They're also considerably cheaper and from a programmer's point of view, a lot more reliable.

EPROM programming software

I guess the hard part for end-users, is identifying the firmware version inside their machines. Some machines display the version when they boot but many don't and the only way to find out, is to open up the box! I understand that can be a bit daunting for some, so for a small fee, I'm happy to do that for you, if you can get to me.

If you want to try this yourself, then you're looking for a chip which which will be in a socket. It may have the firmware version just written on a label that's stuck on top of the chip and covering a little window. Some companies Roland used a coded label as shown below right.

Firmware EPROMs in Sound Lab SST-19 (left) and on Roland MKS-80 voice-board (right)
Firmware EPROMs in Sound Lab SST-19 (left) and on Roland MKS-80 voice-board (right).

The EPROM label on the left shows the date (4th November 1987), followed by a 'M' which I'm guessing to be the actual version. The EPROM on the right is on the voice-board of a Roland MKS-80 Rev 4 and the label indicates that the firmware version is 1.1.

Both images show older devices which have windows under the labels through which exposure to ultra-violet light is used to erase the device. So don't peel the label off!

To take advantage of my firmware update service, please just message me with your requirements and I'll see what I can do.

New Aurora Bx board with large capacity back-up battery

Over the past few of months, I've installed several Aurora systems into customers' MKS-80s and my Live Forever battery mod gets asked for a lot so that got me thinking...

The layout of the Aurora Board B which hosts mains protection and filtering, has been tweaked so as to allow for a couple of additional components. The new Aurora Board Bx now has a CR123 / CR123a battery holder and SMD pads which, after removing the original CR-1/3N memory back-up battery, can be connected to the battery points on your MKS-80's CPU board.

Back-up battery in Roland MKS-80
The original CR-1/3N isn't just on the (bottom) CPU board but it's also right at the back. While Roland thought of nice, large SMD pads so as to measure the battery voltage, they're still really awkward to get to and, well... you could just stick your probes on the side of the battery!

Live Forever battery mod on MKS-80 - CPU board connection
Here's a view after the battery has been removed. Terminal pins have been inserted into the original battery contacts on the CPU board and flying leads added.

As with the original Aurora Board B, the new Aurora Board Bx sits on a steel plate just like the one that supported the original MKS-80 transformer, making upgrading easy.

Aurora Bx Secured Battery Holder
The CR123a battery holder is screwed to the PCB.

With a capacity of 1.5 Ah, a CR123a will last almost nine times longer than the original CR-1/3N. The battery voltage can be easily checked without having to lift the MKS-80's two voice boards (oh boy). On top of those benefits, if (seriously, if) the battery ever leaked, your precious CPU board will be well out of harms way.

Aurora Bx Battery Connection Points
Conveniently located SMD pads that wire to the original battery points on your MKS-80's CPU board. These also make measuring the battery's voltage a breeze.

Since the enhanced back-up battery mod connects directly to the points on the CPU board where the original battery was, there are no other components to add and circuitry around the original battery remains untouched. There is for example, a protection diode that's in series between the battery and pin 24 of IC5 (memory). This is not bypassed and remains totally functional.


  • Don't forget to back up your MKS-80's memory before disconnecting the back-up battery.
  • Switch off AND unplug your MKS-80 from the mains, whenever checking the battery voltage.

Of course not everyone will want to take advantage of the enhanced back-up battery option that the new Aurora Bx board has to offer. That's why the original Aurora Board B will still be available. Check out my store or contact me for further information.

Aurora Board B and new Board Bx 2
The original Aurora Board B will still be available.

Here's the official Aurora post and here's a post detailing the development of Aurora.

Oh just one more thing; batteries are NOT included! I've always wanted to put that somewhere. 🙂 No seriously, shipping stuff with batteries is a little difficult. Our postal service really doesn't like it.

UPDATE - 24th December 2020

Aurora installation instructions are now available in German.

Die Installationsanleitung für Aurora und Aurora Board Bx ist jetzt in deutscher Sprache verfügbar.

Plasma Music Limited -

I'm deeply concerned about the environment and the exploitation of labour and so  I always use local manufacturers in preference to the Far East, with the following in mind:

  1. I can be confident that workers are treated fairly and earn a proper wage.
  2. I can be confident of the standard of quality of each item that is delivered to me.
  3. Communication is important and using local manufacturers, all correspondence is quick and understandable.
  4. I believe in supporting the local economy.
  5. I can be confident that the disposal of manufacturing waste is managed properly and in accordance with national and EU law.

Plasma Music uses local manufacturersUsing local manufacturers isn’t the cheapest option but the above points are important to me. I hope that they’re important to you too.

After thirty-something years, many instruments that use the famous Panasonic designed MN3007 or MN3009 bucket brigade delay lines are now displaying symptoms of noise and it may be time to consider a chorus chip transplant.

Matsushita MN3007 BBD chips inside the Roland SBF-325
Original Matsushita MN3007 bucket brigade delay lines inside the Roland SBF-325. Note the factory-fitted IC sockets.

Initially, the sound when passing through the chorus, seems to contain artefacts. As the degradation of the substrate worsens, the chorus becomes increasingly noisy and can even have a kind of crunch to it (distortion). Do not however, confuse noise generated within the chip with LFO leakage into the audio path. This is quite different and can usually be tuned out via pre-set potentiometers in processors like the SBF-325.

Fortunately the MN3007 is still available and Xvive has released a design of the MN3009 which I think sounds amazing.

Xvive MN3007 and MN3009 bucket brigade delay-lines
Xvive MN3007 and MN3009 bucket brigade delay-lines.

Here's a list of some Roland instruments, processors and amps and the chorus chips that they contain:

  • SDD-320 Dimension-D (2 x MN3007)
  • SBF-325 (2 x MN3007)
  • MKS-10 (2 x MN3007)
  • MKS-20 (2 x MN3007)
  • JC series guitar amps, like the JC-120 (1 x MN3007)
  • VP-330 (2 x MN3009)
  • SA-0 (2 x MN3009)
  • Juno-6 (2 x MN3009)
  • Juno-60 (2 x MN3009)
  • Juno-106 (2 x MN3009)
  • Juno-106s (2 x MN3009)
  • HS-60 (2 x MN3009)
  • Alpha Juno 1 (2 x MN3009)
  • Alpha Juno 2 (2 x MN3009)
  • JX-3P (2 x MN3009)
  • JX-8P (2 x MN3009)
  • JX-10 (4 x MN3009)
  • MKS-30 (2 x MN3009)
  • MKS-50 (2 x MN3009)
  • MKS-70 (4 x MN3009)

I charge a standard £100 plus VAT (£120) to change the chips in all of the above machines with the exception of the Super-JX (JX-10 and MKS-70) which will cost £130 plus VAT (£156).

Two Xvive MN3009s on top voice-board of Roland MKS070
Here are two of the four Xvive MN3009s sitting in the top voice-board of a Roland MKS-70.

High-quality turned-pin sockets are fitted before the chips are installed and the new replacement devices then simply plug into the sockets. This means that they can easily be removed without desoldering, anytime in the future,

In my humble opinion, the new devices from Xvive sound very solid and not airy like the original chips. With definition and detail, you'll defiantly hear a substantial difference in your tone. If you'd like to book in your machine, please just contact me or check out the Chorus Chip Transplant item in my store.

My first stand-alone sequencer was the Alesis MMT-8, so when I recently got one of these in for a full repair and refurbishment, it brought back a lot of great memories.

Alesis MMT-8
The Alesis MMT-8. My first stand-alone sequencer.

In the late eighties, I had a couple of Roland S-550 samplers. If you remember this machine, you might also remember the monochrome (green) screen, the mouse and the sequencer software. All quite superb but even back then, I didn't always want to 'boot up' my 'sequencer' S-550, just to get down an idea.

Rear of Alesis MMT-8
Mirroring the simplicity of the top panel, the back of the MMT-8 has ports for MIDI (obviously), tape in and out for back-up, START / STOP and CLICK OUT.

Stand-alone sequencers at the time, like the Roland MC-500 for example, were quite expensive until that is, Alesis released the 'MIDI Multi-Track 8' or MMT-8. Small, easy to use, no fuff and above all, very cost-effective, the MMT-8 soon became a big hit and I find it's popularity today not just amusing but a testament to it's design. A quick look around Google reveals that many named artists, specifically DJs, are using this machine even today!

Others soon tried to bite back and in 1990 for example, Roland brought out the MC-50 (shortly followed by the MC-50 Mk II). Although hugely powerful, machines like the MC-50 were still considerably more expensive than the humble MMT-8. In fact, the MC-50 was my second stand-alone sequencer and I recall not regretting hanging on to my humble MMT-8.

Sure it's got a couple of drawbacks; limited memory (100 songs, 100 parts, 10,000 notes), external storage via MIDI or tape only (no on-board floppy disk drive) and a small 16 x 2 screen. The thing was, the MMT-8 was instantly familiar to many as it kind of felt like a multi-track recorder so once you accepted its limitations, you realised that you had a tight little sequencer which actually contributed to a healthy workflow.

So this MMT-8 was definitely looking worse for wear and things just weren't working like they used to. In fact on power-up, although it came on, it was just all locked up. Seeing as it didn't have any knocks, dents or scratches though, the first thing to do was to completely take it apart and give the casing and the switch contact membrane, a good wash. At least it's going to look the business so if nothing else, I could turn this classic into a bit of modern art! 🙂

After several decades, even a well kept MMT-8 will suffer badly from intermittent and / or none functional keys. The problem is that while the switches on the back of the rubber contact membrane use small carbon-coated pads similar to those used in keyboards, the complimentary contact PCB just had metal track, like the track side of an old PCB.

So the next thing to do was to make sure that this aspect of the machine was fixable. Well, having had one of these myself, you guessed it, of course I knew it was fixable!

Alesis MMT-8 Mk I switch contacts on rubber
Here's a view of the carbon switch contacts on the inside of the contact membrane.

Alesis MMT-8 Mk I switch contacts on PCB
And here's the other side. The switch contacts on the contact PCB are just ordinary metal track.

Cleaning and treating the switch contacts on both the contact membrane and the contact PCB, is well worth it, making an old MMT-8 respond like it did when it was taken out of its box for the very first time but... it's got to be done properly.

The MMT-8's casing is plastic, which is now old plastic, the point being that it's become quite brittle. Hence, care should be taken when disassembling this box and removing the contact PCB in particular. It's not difficult to break the screw pillars and they really aren't easy to repair if at all. When reassembled, if the contact PCB is not tight to the contact membrane due to a missing or badly fitting screw, then you might have cleaned and treated the switch contacts but you'll have some play when depressing the switches and you'll kind of be back to square one. It's equally important when replacing the contact PCB that the screws are NOT overtightened.

I then checked the battery which had years of capacity left on it. Next, the dreaded freeze. As previously mentioned, when you switch on, a bunch of LEDs light up, there's nothing on the screen and the machine is quite unresponsive. Let's try a factory reset first; hold down <ERASE>, <PAGE UP> and <PAGE DOWN> simultaneously, while powering up. Hmm... well that didn't fix anything. Probably cleared the memory, though. 🙁

This is actually a fairly well-known issue and one of several components that comprise the processor reset circuitry, is usually the problem so that's where I looked and low-and-behold...

Alesis MMT-8 main pcb
Close-up of the main PCB inside the Alesis MMT-8. How simple is that?

After ensuring that the contacts were good, both on the rubber contact membrane and the contact PCB, it would appear that I still had a couple of 'switching' issues.

You'll notice on the first image at the top of this post, that track LEDs 4,5 and 6 are out. That's not because they're switched off. In fact the buttons actually work. It's the LEDs that aren't working. Also, a couple of other buttons were still faulty and not doing anything however hard I pressed.

I quickly traced the problems back to U7 and U8; two HC754E 8-way flip-flops. It would appear that five flip-flops were stuck and not flipping or flopping!

3 x HC754s 8-way flip-flops in Alesis MMT-8 used for controlling switches and LEDs
3 x HC754s 8-way flip-flops in Alesis MMT-8 used for controlling switches and LEDs.

So now this MMT-8 looks like new and more importantly, it actually works like new!

Well... not quite.

One thing I remember about this machine was the questionable viewing angle of the display. The MMT-8 isn't a square or any other regularly shaped unit. It's all kinda slanted and just says "you need to be sitting down to program me". Well indeed, that's very true and after three decades, even sitting down, the LCD has become pretty unreadable with a low-level backlight and low contrast.

Actually, the contrast and hence the viewing angle is adjustable, via a pre-set pot that's inside the machine (R67). In fact I have a theory as to why the viewing angle is so poor; when these units were inspected and set up at the factory, the technicians were probably err... sitting down! Hence, the contrast was adjusted accordingly.

Alesis MMT-8 contrast adjustment is via R67 inside the unit
Alesis MMT-8 contrast adjustment is via R67 inside the unit.

So my Alesis MMT-8 repair and refurbishment continued with hunting down a suitable LCD.  I soon came across circuitbenders and bought the perfect module for this machine. The brightness, clarity and viewing angle of modern LCDs is obviously very different to those early devices from the eighties.

Now we're done and will you take a look at that... A blast from the past in stunning, fully working condition.

An Alesis MMT-8 from the late eighties. Fully refurbished in 2020
An Alesis MMT-8 from the late eighties. Fully refurbished in 2020.

The Alesis MMT-8 has got to be one of the few machines with a copy of the user-manual built in!

The unique Alesis MMT-8 built-in user manual
The unique Alesis MMT-8 built-in user manual. Now you definitely have to be sitting down to read that!

A final few words; I've already mentioned that one limitation of the Alesis MMT-8 is it's memory so it'll come as no surprise that someone out there has developed a simple way to expand the machine's event capacity. You can find details here.

While very cleaver, on this occasion, I advised the customer to consider keeping his machine as original as possible and to avoid drilling holes to fit switches, etc. I'm glad he listened to me.

The operating system on this example is version 1.08. To the best of my knowledge, the last version issued by Alesis was 1.11. Changing the firmware isn't difficult and only involves opening up the case (four screws), pulling out the EPROM and inserting the new one (the right way around, of course). I'd advise checking the revision history before doing that however, as the whole exercise might not be something that's relevant to the way that you use the machine.

I'm aware that an OLED module suitable for use in other Alesis equipment of the same era, was made by Winstar.  I'm uncertain however, as to whether this unit is still available. Another Winstar product code I've seen around, is WEH001602DBPP5N00000 and at the time of writing, this unit is available. If you're interested, then it might be worth checking out. Any display you consider, should have a 14-way connector, be 16 x 2 character and measure 85mm x 30mm.

Winstar WEH001602DBPP5N00000
The Winstar WEH001602DBPP5N00000 looks like it might be compatible with the Alesis MMT-8. This stock image is actually upside-down (connector strip should be on the right) relative to the orientation inside the MMT-8!

Alesis released a second version of the MMT-8 but it's really quite difficult to find any info' on it. Some suggest that it was a limited edition version, others believe that it was a Mk II and addressed some of the issues in the well-known grey version. If you know anything about the infamous black Alesis MMT-8, please do let me know.

Technically, this this refurb cost more than the unit is probably worth and quite honestly, I would have dissuaded the customer from proceeding if the machine wasn't in such pristine cosmetic condition. The customer absolutely loves his MMT-8 and like many refurbishments, it's not a case of monitory value. On the other hand, it's something you need to balance up.

So, if you're in a similar situation and considering either an Alesis MMT-8 repair and refurbishment or giving a little TLC to any other bit of gear that you really love, then just message me.

UPDATE - 24th November 2020

Okay so I couldn't help myself and, at my own expense, I bought a Winstar WEH001602DBPP5N00000  from Rapid Electronics, SKU is 60-9686 and it arrived this morning.

After checking the pin assignments, I soldered a 14-way connector on to the module, plugged it into the MMT-8 and hey, it worked!

It looks great! I mean it seriously looks good but being lower than the original (and the replacement I bought from circuitbenders), it doesn't butt up against the inside of the display window. Ironically, the viewing angle is therefore slightly reduced, LOL.

Alesis MMT-8 with Winstar WEH001602DBPP5N00000 OLED module
Alesis MMT-8 with Winstar WEH001602DBPP5N00000 OLED module.

At more than two-and-a-half times the price of the circuitbenders' LCD module, you need to think carefully if considering the Winstar WEH001602DBPP5N00000 as an option.

A couple of things to mention; on the original LCD module, the contrast voltage is delivered to pin 3. This is not connected to anything on the Winstar OLED as OLEDs don't have a contrast control.

Also worth noting is that Winstar makes several different coloured versions of the WEH001602D, so if you don't want blue, you might find a colour that does appeal to you. 🙂

The Roland SBF-325 stereo analogue flanger / chorus
Released just in time for Christmas 1979, you may notice an intriguing correlation between the date of the service notes (in the background) and the date of this post!

Recently, one of my customers brought in a Roland MKS-80 for repair. Well, no surprise there but... Tom also brought me a poorly sounding Roland SBF-325, one of the best ever flanger / chorus units ever made.... in my humble opinion.

Roland brought out the SBF-325 in 1979 and before things were designed with built-in obsolesce, this machine was on the market for seven years, just before I joined Roland (UK) Limited as Group Technical Manager in fact (oh, those were the days).

The SBF-325 reeks analogue. So much so, that if not tuned properly, you'll easily  hear the LFO leaking into the audio via the Matsushita MN3007 bucket-brigade-delay-lines (BBDs). When set up correctly however and in accordance with Roland's service notes, this thing just sounds sweet.

Matsushita MN3007 BBD chips inside the Roland SBF-325
Matsushita MN3007 BBD chips inside the Roland SBF-325.

The Roland SBF-325 is of course, a stereo flanger with three modes; mono (only Channel A is actually active but is split later on down the line to the two outputs), stereo and stereo with cross-mixing which outputs an extra wide stereo flanging effect by incorporating panning between the two delays.

The chorus was obviously designed to deliver Roland's famous, tried and tested chorus sound of the time and I guess there just wasn't a need to mess with it. The Juno-106, the JX-3P, the Boss CE-1 and so many more machines, used the very distinctive, smooth but rich Roland chorus effect.

In chorus mode, the modulation section works as it should but the feedback control doesn't do anything. Why would it?

Roland SBF-325 at Plasma Music

The modulation section is very comprehensive with all the usual controls you'd want on a unit like this; centre frequency, rate (speed) and depth. For flanging in particular, 'feedback' is also important.

Now-a-days manufacturers seem to have the need to bung on a load of stuff that only they know what it does and that 'we' don't even want. The simplicity of machines like the SBF-325 reminds us of a time when things were just simpler but sounded new and cool!

Roland SBF-325 - simple but powerful modulation

The input and output levels are switchable between -16dBm and +4dBm. Unfortunately none are balanced, something that we take for granted, now-a-days. Actually, the sockets aren't PCB mounted which means that you might be able to make balanced inputs and outputs. Hmm... I have to think about that.

With input and output sockets on both the front and rear of the unit, there are also various options to invert one output with respect to the other and even invert the modulation on Channel B. Best of all however, is the provision for CV. Pre-MIDI, the front panel 'Ext CV In' jack, allows the LFO on the SBF-325 to be clocked from another machine including an external LFO. Even today, using a MIDI-to-CV converter, it's easily possible to link the SBF-325 to your DAW. How cool is that?

So, Tom has quite a lot of American gear and indeed this unit was a 117V example, as was the MKS-80 he brought me.

He told me that the unit was distorting and to be honest, I kind of had an idea what might be causing this.

From a service perspective, the problem with this early Roland stuff is that while the service notes go into as much detail as ever, the PCB is really quite difficult to navigate. Roland had this weird finish on the components side of their PCBs which after several minutes, can make you a little dizzy and trying to read component references is almost impossible. Having said that, the tracking on the underside of the board was graphically copied to the components side so once you got used to the bloody thing, this aspect of the board design could work in your favour.

A classic example of unreadable PCBs from the seventies
Inside the Roland SBF-325 - a classic example of psychedelic PCB styling from the seventies that's totally unreadable. What were they on?!?!?

So it took me a while to switch into 'Seventies' mode but it soon became apparent that one of the BBDs wasn't biased properly. Okay, not a problem, I thought. Let's go through the process. Ah! I couldn't actually bias it and soon found out why; a little resistor had gone way out of spec'. Ten minutes to change that and let's try again. Wow! We have no distortion in any of the flanger modes but... there were artefacts still present on channel B when in chorus mode. On top of that, it was obvious that there was excessive LFO clock leakage into the audio on the same channel.

The age of this machine made it a perfect candidate for a BBD swap-out and so I dropped in a pair of new Xvive MN3007s.

Tuning out the LFO noise is a little tricky on these machines as the pre-sets are so incredibly sensitive but I got there in the end.

Once the machine was distortion and LFO leak free, I cleaned all of the pots and switches. It seemed that they'd never been touched since the machine was made and I have to say, dialling in parameters suddenly felt and sounded very smooth, indeed.

Ah, that's more like it. Be warned however. If you're used to plug-ins or even digital processors, you might hear things in this old analogue gear that you don't like! There's a lot more interaction between harmonics and so the sound is more 'organic' than that of a digital processor or a bit of software. At some frequencies, things happen which might seem a little unexpected. This gives machines like the SBF-325 a certain character and it's not everyone's cup of tea. On the other hand, this is proper analogue flanging and chorusing as they were meant to be.

The Roland SBF-325

I love this stuff. I really do. In fact I'm actually thinking of designing a modern version of this classic analogue processor, perhaps using MIDI for external control instead of CV and give it some memory, too. Now there's a couple of ideas...

In the meantime, if you have a vintage effects processor like the Roland SBF-325 that needs a little TLC, give me a shout. Like I said, I just love this stuff.

IR3R03 VCO in Roland MKS-80
Roland's own IR3R03 VCO chip as found in the MKS-80.

There are several differences between the Roland MKS-80 Rev 4 and the Rev 5, undoubtedly the most significant being that the former used the Curtis CEM3340 VCO while the latter used Roland's own IR3R03. Perhaps the other differences are as a result of this change.

Curtis Electromusic re-released their CEM3340 in 2016. The new device is known as the CEM3340 Rev G and information on it is readily available. Here's the data-sheet available on the Curtis Electromusic website. Unfortunately, the same can't be said of Roland's replacement and I was only able to find a single resource, on-line. Being the size of a postage stamp, I decided to knock up this version (pictured below) for anyone who might need a little help with a faulty MKS-80 Rev 5 or who just wants to know how this thing works.

Inside the Roland IR3R03 VCO.
Inside the Roland IR3R03 VCO.

From my own experience, the Roland IR3R03 seems to be a little more robust than the Curtis device and I find it quite frustrating that people assume a duff chip when fault-finding a problem on a Rev 5. Before you do that, please check out other stuff like capacitors (hint, hint).

You can download a pdf of the above image here.

Over the years, I've heard several theories as to why Roland developed its own VCO but it should be noted that the IR3R03 wasn't just a replacement for the CEM3340. It also removed the need for Roland's infamous EHM-S226W83S; the so-called hybrid chip which was used to synchronise the Curtis VCOs. The IR3R03 also reduced the number of components that comprise the cross-modulation circuit.

Doing all that, you'd be forgiven for thinking that the voice-boards in a Rev 5 should look a little sparse compared to its predecessor. NOPE! The insides of both versions bear an uncanny resemblance to what was under the bonnet of my first couple of Jags!

The famous CEM3340 and Roland EHM-S226W83S partnership in the MKS-80 Rev 4
The famous Curtis 3340 VCO and Roland EHM-S226W83S  sync' buffer partnership in the MKS-80 Rev 4.

If you're not technical or simply don't want to open up your MKS-80 to find out which revision it is, then it's pretty easy to suss things out from the serial number. According to the second edition service notes of April 1985, the revision changed after serial number 511800 (inclusive). So, if your serial number is higher than that, you've got a Rev 5.

Okay, so the whole point of this post was to host the IR3R03 spec' sheet that I knocked up but... ya' just know that people researching the CEM3340 are going to have this page pop up somewhere in their search results.

I've already mentioned that Curtis re-released this very famous chip so there's actually a lot of information already out there but it might not tell you the answer to this question: What's with the white dot? Just about every MKS-80 Rev 4 I've ever opened up has 'white-dot' CEM3340 inside. Each chip has literally a white mark on it.

Well, Roland actually graded a lot the chips as they came in from various manufacturers and the CEM3340 was definitely no exception.

According to Roland's service bulletin 100248 and without going into too much detail, the white dot CEM3340s had better low frequency response and linearity than the CEM3340s that were marked with a red dot and I bet you didn't even know that there were red dot CEM3340s.

Mind you, I don't think I've ever seen red Tipp-Ex, LOL. 🙂

Roland white-dot and new Rev G CEM3340
Roland white-dot and new Rev G CEM3340. The former was recently pulled from a MKS-80.

So the next question would be;

If I need CEM3340s replaced in my MKS-80 Rev 4, is okay to use the re-released version? Do they sound the same as the Roland white-dot chips?

That’s actually two questions but…

You know I previously used the term “without going into too much detail”? Well perhaps there’s a couple of points which I should mention;

Roland did NOT actually specify white-dot CEM3340s for the MKS-80! The specially graded chips were destined for machines like the SH-101 and Jupiter-6.

The other point I need to make is that chips weren’t graded to make certain models sounds better but for the following reasons:

  • Testing devices supplied from other manufacturers prior to fitting reduced the number of faulty units that came off the production line. You have to remember that this was the beginning of the eighties. When I was at Simmons, we had horrendous problems because we didn’t do that!
  • The use of graded devices meant that the set-up time of machines after production was greatly reduced.

Both of those reasons meant that Roland could keep costs down.

Now then, comparing the CEM3340 Rev G with the original white-dot Roland graded chips isn’t something I’ve gone out of my way to do, suffice to say however, that I have refitted many MKS-80s with Curtis’ newer version and I’ll be damned if I can tell the difference! Others have done comparisons. Check out Gregory Cox’s video on the Synthtopia website.

So there you have it. I started writing a post about the Roland IR3R03 and half of it is about the Curtis CEM3340! I think I need to focus more...

Eddie Van Halen On Stage1978 and I remember vividly putting Van Halen (self-titled first album) on to the turntable. The expression 'Blew my mind' has never been so apt and indeed, Eruption changed the sound of guitar forever. Suddenly everything before was just two-dimensional and mediocre. Finger tapping, shredding, a very articulate and defined sound with oodles of sustain (the brown sound), it all started here.

A Strat with humbuckers, a Marshall 1959, a little MXR phaser pedal and a whole lotta talent. Van Halen was the talk of the town… for many, many years. He influenced a whole generation of guitarists and the very sound of rock for an entire decade.

If there was one thing absolutely annoying about Eddie, it was that he made it all look so effortless!

A true natural, many didn’t know that he actually started playing drums with his brother Alex on guitar. One imagines divine intervention that made them swap!

Iconic, people like Eddie Van Halen were supposed to be immortal, live forever but of course we’re all just human.

From a humble Dutch immigrant background, Eddie’s life was inspirational, not just his guitar playing.

6th October 2020
You will be missed