I sold the last kit from the latest build six months back. I do not market it aggressively so sales are slow.
My current issue is that I ran out of circuit boards and have to order more, along with sourcing components. Covid and sanctions on China disrupted the supply chain (also made my last 2 component orders difficult and expensive).
I can’t get the quality of circuit boards I need and the price has gone up 5x plus we have to pay a 25% tariff on top of this for orders from China.
The worldwide shortage of chips/components is serious for all makers and for me has got to the point where critical items like the DAC used are no longer available.
I created a board design using newer components but those components are also in short supply. It is going to take a while to resolve this as I can’t source the quality and price I need to make it viable at the current price.
Roland Juno-106 restoration/repair, nice update parts are now available
When quoting restoration/repair of the Juno-106 I often describe it as a money pit because of the amount of work it requires, and high parts price. If it is in physically nice condition and you want to keep it then it is worth investing in as it is a nice sounding synth. I just want folks to know what they are getting into up front and that it is not a quick and cheap fix as if the voice modules have not been dealt with then they need to be.
We all know about the voice module issues on the Juno-106. If the module has not failed the chances are it will so I recommend changing all 6 80017a modules. If you have the original 80017 modules then you need to change them as a set as Roland warns your in the Service Notes that the timbre is different on the “a” variant. A common belief is that it is the epoxy coating becoming conductive over the years that is causing the failures (dead, crackling, failing the various tests in Test Mode) and that the acetone strip method was a cure. Long term the acetone strip method was not holding up and I had a couple of units in for rework that had been to the xxxxSpa. Looking at these with a microscope I 
saw incomplete material removal between the pins of the chips, and pins on the chips and the chips pins going cold-soldered. This leads to the belief that it is not the epoxy becoming conductive, but more it is the that the epoxy was pushing against the chips and as the temperature fluctuates, it expands and contracts which eventually lifts legs off the pads on the PCB. I re-flow the solder on all the pins on my re-work solder station under a microscope, then coat the module with silicone conformal coating to seal the moisture out and protect them. This will not cure a bad chip but has recovered a far greater percentage of modules with far less fallout. I also see failures of the Wave modules but the acetone strip (if the epoxy comes off with this method) does not seem to help as there is a red coating of “other stuff” over the actual chips that I have not tried to remove so cannot re-flow the soldering. This coating is much softer than epoxy so the epoxy is not applying any leverage on the chips.
I still do some acetone strips but prefer folks to order the complete package of 6 voice and
3 wave modules from Analog Renaissance in Belgium (Analogue Renaissance voice and wave module package ) and bring/send them with the synth. They have a buy 5, get 6 pricing on the voice modules. These are really nice and a much better solution than acetone stripping. Shipping is a bit slow and the price is something like $350 depending on the exchange rate but I so much prefer installing them as I know I can just put them in and they set-up easily and work. Syntaur also carries the modules but do not offer a complete package price.
I change the battery and reload the factory patches on a service, plus clean the unit inside and out. There is a factory FCO for early battery fail that was later incorporated. Check that pins 4&5 of IC4 which is near the battery.
On the modulation panel it is common for the mod lever and/or 
LFO bend plate to be broken. Syntaur carries these. I also see failures of the sliders. When I service a mod panel with the old crumbling gaskets still in place I remove the old gasket and fit a new new laser cut gaskets (foam or fiber) which I have had made.
Th
e final area of concern, and one which many initially come in for is the front panel. Bad sliders cause it to constantly drop into edit mode 
(you can see bad ones wittering on the MIDI Out stream). The gaskets over the sliders crumble and fall into the slider impacting its smooth travel so things get worse and worse with the shaft breaking when you move a tight one. The switches behind the buttons become sticky and intermittent (they can’t be cleaned).
For a front panel service we:
- Clean the panel removing all the old gasket material
- Clean (or replace the sliders… I’m recommending these really nice ones from
- LASynth that the slider caps are a correct fit on. These work and feel perfect: LA Synth Juno-106 Slider set )
- Fit new laser cut gaskets (foam or fiber) which I glue to the front
panel. This looks - really nice and works well
- Replace all of the button switches if they are original/any are failing.
One final item folks like is to have the original 2 pin power connector replaced with a standard IEC grounded cable connector
As you can see there is a lot of work to do in order to get a tired Juno-106 back to a nice operating condition. Contact me if you would like yours restored.
Still very much in Business
I can’t believe how long it has been since I updated the blog, need more time to keep up with such things. Opto-key is available to ship in both MIDI and Non-MIDI versions.
Check out the newly manufactured and restored original MiniMoog cases that are exclusively available through This Old Synth. This work is carried out in a small US woodworking shop with all work done by the owner for consistent quality. I also have solid MDF replacement case bottoms to replace the crumbling originals.
It is a great time for analog synths with all of the re-issues going on, and thankfully for me there is still great interest in the vintage ones that I’m focused on.
I have been struggling here with a lack of space and sore back so I have had to stop doing large synths. MiniMoog’s are the main focus here and always welcome!
If you are in the bay area you should check out Lance’s Synth Museum in Emeryville (near Oakland), lots of cool stuff you can see and play for a very low fee. http://www.vintagesynthmuseum.com/Info_%26_Rates.html
I decided to turn off comments to older posts today as I’m getting bombarded by spammers who have nothing better to do than bombard me. Oh well, welcome to the world of blogging!
Opto-Key Project is here, and the builds started
Kevin’s Opto-Key build environment has transferred from Synthfool to This Old Synth. The components, software, circuit boards etc. arrived on Wednesday afternoon. Two days of work later I have 
partially completed 5 units. Time to get a components order submitted so I can complete them! I did purchase the very last of unit built by Kevin and have begun testing using it in my MiniMoog; exciting times!
CHD MIDI Upgrade for the Roland TR-808
When writing about the MTG TurboCPU upgrade I promised to put a blog entry up for a really nice and non-intrusive MIDI mod for the Roland TR-808, and here it is. The thing I really like about this implementation is the degree to which they went to make in non-intrusive (i.e. drilling holes!).
It comes complete with a printed manual of step-by-step instructions, and supporting CD.
For the MIDI connector the existing Din-Sync connector is removed, along with its In/Out switch. A new connector that includes MIDI In/Out is fitted (a special adapter cable is supplied. The switch is replaced by a 3 way one, In/MIDI/Out.
The “umbilical cord” for triggers and power is socketed at the controller end, so for service it can be unplugged and the TR-808 will still work (so this is not a CPU upgrade/replacement like TurboCPU).
Only one hole needs to be drilled, and it is for a MIDI active Led and sits in the Start/Stop switch, under the yellow label. Awkwardness here is that they specify a metric drill, and for accuracy a 
woodworking one is probably best. I’m sure you could get by with a slightly larger US drill and use a band of shrink-wrap tubing or some-such to tighten the fit. Of course you could ignore this step and just know that center switch is MIDI on!
Be sure to keep the parts removed such that the TR-808 can be put back to standard if need be. Here is a link to the CHD TR-808 MIDI kit. I may well contact CHD and offer to distribute this in the USA.
E-Mu SP-1200 Noritake Display
My customer Aaron, was fed up with the poorly back-lit display on his black re-release SP-1200, and wanted to have the Noritake CU16025-UW6J display from Digi-Key fitted. They are expensive, and being glass, fragile; but they are bright and clear so a good upgrade.
Unfortunately the display is smaller than the aperture in the circuit board, and an attempt at notching out mountings was made to no avail. The display is also thicker than the original and spacers are 
needed to move it down. After several attempts I decided to make 3mm deep adapters on the 3D printer, and this gave me a stable mounting that I could squarely align the display on. You also have to make an adapter cable as the pins are reversed.
The next issue was that the display character area was smaller than the original, and it did not have a bezel. This looked bad, and
the glass was exposed. Thankfully I had an 80×2 line lcd filter lens in my parts bin and could cut that to size. It covered the ugliness nicely, and protected the display. Aaron was happy! Final job was to open all switches and drum pads to clean them and restore playability.
ARP Soloist meets 3D Printing
This is a 
rare original ARP Soloist (before the ProSoloist or DGX). A lot or restoration work was done on it, but one issue remained; the slider shafts were all broken at the point where they exited the case, and the slider caps were long gone.
The sliders are the same type as fitted to the ARP 2600 and moog SonicSix, amongst others. This is a hard to find part, and here we have 4 sliders with 3 different values. 
Sometimes you can find replacement shafts for these on Ebay, but nothing was listed at this time. After much head scratching I decided
to raise the existing sliders by 8mm, and needed some precise flat blocks to do that with. I came up with a design and after many attempts (that’s 3D printing for you!) I produced a nicely printed set.
The sliders were removed, opened, cleaned, re-greased, then set on the blocks which I had super-glued to the 
circuit board. There were locators in the blocks for the original slider mounting, so when the wiring was added using a heavy gauge wire extension, all was firm and true. I re-assembled the unit and added some Omni-2 style slider caps I had previously printed. All working and crackle free. Next move was to tune and scale it.
One item remains on the Soloist, the after-touch used conductive foam which was known to only last 8 months, and had all by disappeared on this 1975 keyboard. I would have liked to have got some modern strain/pressure sensors and tried to make a solution, but the owner decided to defer that to another time.
This Old Synth acquires the exclusive rights to Synthfools Opto-key for MiniMoog project
As a tech I’m increasingly frustrated with the chore of trying to restore the (oxidized) key contacts on the MiniMoog to full operation, and unless it is frequently played the issue of “squirelly keys” comes back. I have been installing Opto-key for my customers which removes the key cleaning cycle, AND adds simple note-on/off MIDI.
I was concerned and saddened to hear that Kevin Lightner at Synthfool could not continue the Opto-key project as it addresses the biggest reliability/playability issue with the MiniMoog, and have negotiated with him to transfer ownership here.
Once the on-hand materials such as circuit cards arrive I will commence building the product to Kevin’s spec and make it available for sale.
As I’m also a software developer with experience in embedded systems I plan to enhance and support Opto-key moving forward. I’m really excited by this!
MTG Turbo CPU + MIDI + CV
Turbo CPU
I’m generally against modifications. I have seen too many vintage synths spoiled by badly drilled holes that hold fragile switches, connected through an “umbilical cord” to undocumented perf-board based mods made decades ago, and then more wires soldered to the circuit boards. Working on the gear becomes difficult as these wires are holding the case to the cards, and of course wires fatigue and come away, and you have a challenge as to where they once went, and how the mod is supposed to work.
I do see the benefits of a good MIDI implementation, and I have come across a couple of MIDI kits where the designers have come up with good clean designs that can be unplugged for service. In this entry I talk about the Turbo CPU upgrade kit from MTG (Music Technologies Group). Grant runs the MTG and I have found him responsive, friendly, and helpful so recommend doing business with him.
In a different post I will talk about a nice MIDI solution for the Roland TR-808 from another vendor.
All of the instructions are available to download from MTG (http://www.musictechnologiesgroup.com/index.html), so you can see what is involved. I’m on the list of experienced installers and would be happy to implement this for you, but note that I am not a reseller so you have to purchase the kit from MTG. Turbo CPU a simple removal of the CPU and install of the Turbo CPU module.
I think most folks would be interested in the MIDI interface which for a solid installation does mean drilling the base of case to mount the MIDI interface card, and the back of the case for the MIDI connectors.
I prefer the look of the MIDI connectors squeezed between the lettering, and made some identification labels for the 
MIDI ports. Both customers for this kit wanted the MIDI interface, plus the “DIY” CV interface which adds a tiny MCP4728 chip to the v2.00 MIDI board (I was fortunate that the MCP4728 was pre-installed on one unit, but had to order it from Mouser for the other.
Fine soldering skills are required to install this chip as it is surface mounted, so ask Grant if you can have a card with the MCP4728 pre-installed when you order :-). The DIY CV interface gives you MIDI control over 4 CV wires and is a great addition that requires no trace cutting or case butchering, so I like it!
For my implementation of DIY CV I installed a connector at the MIDI interface card for the 4 wires so it could be disconnected for service.
Linn 9000
My customer won this working unit on Ebay, and agreed to pick it up from the seller. Between the end of the sale, and it being picked up the seller decided to get his tech to replace the batteries as they were leaking. Following this it would partly boot but hang, not good! Thankfully a heavy discount was negotiated to cover repairs, and in it came to my shop.
I have not worked on one before, and I was amazed to find it 
is based on the first IBM PC, ISA bus and all. This one had a lot of Forat mods, including the SRAM256 card which I have read is a favorite for folks to blow up by inserting backwards. I checked the batteries that had been fitted, and was only getting 2.4v, and one read shorted. I purchased new lithium batteries and a charger which confirmed that one was indeed 
shorted. New batteries were fitted. Powering on found the screen blank, and this was traced to the CPU being stuck in reset. The transistor between the batteries and this line was bad, and replacing it released the reset. Checking the CPU clock found it running less than 1/10 correct speed. The osc chip SN74LS04 and its socket were badly corroded by the battery acid; parts replaced and clock working correctly.
We were back to it hanging, but things were now solid as the battery/acid damage was out of the way. Address line A6 was found to be low amplitude, and the SRAM256 card was 
dragging it low. Removing the card put the 9000 into a mode where it was looking for the SRAM 256 card (Forat firmware and card), so it would not come up. From the schematic, -12v would go to A6 on the SRAM card if it were reversed (surprise!). I traced the shorted A6 line to a PAL on the SRAM256 card, and socketed the chip. Lifting the PALs leg 
enabled the card to be plugged back in. Bruce Forat was contacted for parts, but by the time he came back with a price I was well into reverse engineering the card fitted detection in the PAL using a logic analyzer and 8080 disassembler. Clearly the address decoding part of the PAL was still good as after zapping the code that looks for the card everything came up. The customer wanted to go this route as he wanted to see what else was bad on the 9000 (i.e. was it a write-off) before spending more on it. As the PAL is socketed he can eventually order the PAL from Bruce, and fit it along with the original firmware eprom.
Testing showed the floppy controller was bad, and a chip change fixed that (did the cable get reversed at some point?). Last thing was to replace the screen with a more modern high contrast led back-lit one. Customer sent me a YouTube video of it in action that night, he is delighted!
