Shots from the workshop
Workbench 1Workbench 2Emu Emulator II Test RigRoland SH-5
Mother and Son ReunionBroken (cooked) Gleeman connectorGleeman with rare see-through caseRoland Jupiter-8
 

Portfolio of Repairs

A moment in time in the shopI'm at the point now where the number of vintage synth and amp repairs undertaken means that I cannot keep this log up to date. I hope that the information here has helped other repairers and I welcome their contact with questions. I have added a Blog to make adding repair data easier in the future.

Moog Variants

Realistic Moog MG-1 Realistic Concertmate Moog MG-1 Restoring this mini synth was a long process as the electronics in it is highly interactive and tends to mask the root cause. A previous repairer had replaced all of the sliders and switches, along with cleaning all of the goo from the control panel where the original foam had deteriorated. The switches and sliders still needed vast amounts of switchMoog MG-1 Control card cleaner to get them crackle free. Cleaned the keyboard contacts also. The symptoms were then a thin sound, crackles, and the contour was misbehaving. A mod had been wrongly applied which injected earlier audio onto the volume control  Moog MG-1 Keyboard and second circuit boardrather than aux-in; removed this mod. Transistor Q28 which is associated with the audio out (LM3080) was causing the crackling and very low sound from cold. The contour issue was the LM741 (U8) which is a summing amp. Thankfully Anchor Electronics had some of these obsolete LM741's.

Realistic MG-1Realistic MG-1 Moog This unit needed the sticky foam removed, and all of the switches and sliders replaced (because the foam ruins them). I ordered a replacement sliders/switches/slider & pot caps from Technology Transplant. I was concerned as these parts ship from China and communications were non-existent, but parts turned up within a week and were fine. This unit was inRealistic MG-1 pot and slider replacement excellent condition and after new parts and knob hardware were fitted it was like new. Customer was ecstatic, except Technology Transplant supply a bright blue led that is too bright for use in a darkened concert hall. I'm now fitting green, yellow, or red leds! Sorry for the bright blue Lance!

Realistic MG-1Realistic MG-1 Moog This unit also had its sticky foam removed and new sliders and pots fitted. It had a number of electronic issues to be resolved, many of which I'm convinced are due to sticky foam sitting on components - is this stuff conductive? Sticky foam removal from a MG-1One of the poly chips had failed and luckily some folks in the UK have recreated the chip. The circuit board had a fracture through the tracks which were bridged. The trans conductance amp (CA3080E) had failed, and there was a hard to find intermittent fault in the VCF (CA3084). After this it was reliable and works great!

Moog Rogue This one was not working after an attempt to move the wall-wart on-board. All issues resolved.

MicroMoog Touch Control repairMicroMoog The touch control was the issue here.MicroMoog Touch Control repair Parts were not available. The control was rebuilt and its connections to the main unit had the bad solder joints remade. Tested and working fine.

Moog Opus 3 RepairMoog Opus 3 This unit is nicely laid out on the control panels in order to make it easier to understand, in fact, even I could understand it! It had two mainMoog Opus 3 chip replacement problems: The chorus section was not working due to fractured tracks on the circuit board, and strings were not working due to a control chip (CD4070?) failure.

Moog Opus 3 A second unit came in with a severe case of deteriorated foam having ruined all of the sliders and switches, along with other issues. A deep clean was performed, all sliders and switches removed, board washed, and then re-populated. The other issues could then be isolated and repaired. I believe the foam is getting conductive and destroys chips, especially the CA3080E; best not to power it on when you find one with the foam issue and to get it cleaned up first.

MiniMoogMiniMoog This was a flea-market purchase, WOW! It was in a sorry state. The keys were sticky andPratt-Reed failed bushing wavy, power cord was rotten, it looked dreadful, and did not work to boot! The cabinet was tidied, new keyboard bushings installed, power cord replaced, unit re-cap'd,Pratt-Reed failed bushing oscillator resistors MiniMoog Resistor balance checkbalanced, all connectors, pots, and switches cleaned. It seems that his unit was riddled with electronic, connector, wiring,Pratt-Reed with new bushings and component issues. All issues were resolved and the unit was set-up using a scope and frequency counter. It sounded great and I was sorry to see the owner take this keyboard away OK; on to the next one!

MiniMoogsMiniMoog The owner of this unit was having trouble finding someone to repair its dead oscillator and other issues because it had a homebrew CV interface installed that was not working. Homebrew CV interfaceThe bad CV interface was removed and painstakingly all wiring was put back to standard. The Re-cap a MiniMoogoscillator was then repaired, along with all other issues found during test. The unit was re-cap'd on the boards and power supply; followed by a set-up using a frequency counter and scope for accuracy. Customer tested it and is delighted with the results.

Taurus IIMoog Taurus II No sound due to a bad filter chip, and a service carried out.




Moog Sonic SixMoog Sonic Six This one needed the key deck straightening and re-bushing. A number of switches and sliders were broken or seized, and getting parts to fit this was difficult to say the least. Returned to customer fully functioning; and he gets to play a rare Moog variant now.

Moog Taurus 1 General service that concentrated on the footswitch contacts. New rubber feet were fitted to stabilize the unit, an a broken track that prevented the glide control from working was repaired.

MiniMoogMiniMoog This unit had been modified by adding a CV interface for which there was no documentation available, and then mods pots and switches added on top of that. It had a dead oscillator 3 and other repair folks had refused to work on it due to the mods and the fact that somebody in their infinite wisdom had once cut the wires from 3 connectors and badly hard wired the boards in. Ugly and unreliable hard wiringWhat a mess!!!! The hard-wiring was undone, connectors sorted out and machine got to the point where it could be fault found. The oscillator was dead due to a bad 741 and CA3046. The unit was set-up but osc 3 could not be tracked. This was fixed by fitting a missing capacitor. The unit was re-cap'd, resistors checked for balance and then set-up using a scope and frequency counter. All was well. The customer tested it and found basic operations spot on, and the mods provided a WOW factor. A humble DX100 was used to drive the mighty MiniMoog as a final test of the CV interface. OK, next!

Moog MusonicsMiniMoog Musonics This early unit (#242) needed some further work after another tech had worked on it. The keyboard had been re-bushed, but the bushing supports had not been straightened, which coupled with some badly stretched key return springs had left it un-playable. This was resolved, and once the set-up was completed (it had been tuned from C on the far left when in fact the first key is an F!) it played great.

Mother and Son ReunionMore and More Moog Repairs Moog repairs for me have become the sweet spot. A number of MiniMoog's have passed through other repairers and ended up here, and when they left me they were fully working and resulted in happy customers. The MiniMoog is the most popular Moog that comes in for repair; most are resolved by new keyboard bushings, re-cap's, and deepMoog Source membrane panel connector failing cleaning of contacts, switches, and potentiometers. I'm searching for a scruffy MiniMoog that I can use to repair and test customer cards such that they can send me the plug in modules rather than a complete machine. Other Moog Moog Modular Keyboardkeyboards that have come in include the Moog Source and Moog Prodigy, oh, and then there is the mother machine: a 1969 Moog Modular System 55 that was scored in Seattle and needed restoration after being powered off for 20 years as every pot and jack seemed to emit loud crackles, and the keyboard was in a sorry state. The case was cleaned and treatedChris meets the Mighty Moog Modular with lemon oil. The keyboard needed new bushings and the keys were cleaned and remounted onto Modular Keyboard type 950 Serial # 1063straightened and leveled hardware; cleaning all of the keyboard contacts got rid of squirrelly keys and the keyboard then tracked. Each module was then cleaned, re-cap'd, all pots were cleaned (which meant opening some 96 sealed pots!), and jacks and switches were cleaned. This clearly took a lot of time and careful attention to detail, but when we fired it up afterwards it was all worthwhile!

Keyboards

Yamaha DX-7 Power SupplyHere is a vintage (1983) Yamaha DX-7 synth that came in for repair with the symptom "powers up but no audio output". The issue was with the +15 regulator in the power supply. I fitted a new regulator and a happy customer was reunited with it.

Arp 2600Arp 2600
This just came in with squirrelly keys, and a drifting oscillator 2. The keyboard contacts were cleaned, and Osc 2 was scoped. The oscillator was found to have drifting output but stable inputs. The 2600 had sealed oscillators so an aftermarket replacement was ordered from CEM which arrived after some months and was duly fitted. Unit set-up and returned to customer.

Ensonic SQ-80I discovered an 80's Ensoniq SQ-80
synth in Guitar Showcase that was being sold "as-is" as it had so many problems. There is renewed interest in this synth as it is an analogue to digital transitional product. The first job was to clean it inside and out, there was a fair amount of corrosion onEnsoniq SQ-80 undergoing repair the screw heads, thankfully an easy fix. Cleaning out what looked like dog hair was not so pleasant, and it meant a complete strip down of the keyboard was required. This synth suffers a number of stock faults, and this one had them all: Ensoniq SQ-80 original keyboard bridge wiringBack-up 3v lithium battery had expired, volume and data entry sliders had failed (50k linear, available from Mouser),Ensoniq SQ-80 new keyboard bridge wiring the bridge cable between the keyboard halves had disintegrated and had to be replaced, and the floppy cable had been trapped and a screw had cut into it. This keyboard is now rock solid.

Ritm-2 Russian SynthRitm-2 Russian Synth This was badly damaged by a transformer that broke away during transit and smashed a number of items. Rebuilt power supply, converting it to 120V. Repaired the damaged components, crafting switches to fit etc. This was difficult as the schematic was in Russian, and components were not available.

E-mu Emulator IIE-mu Emulator II This sampler workstation from the early 80's has the additional (to the 5 1/4) 3 1/2" floppy drive installed and this floppy was giving errors. Reseating cables cured that. The big issue here is that without the boot floppy (and you need an old Apple II to create the floppy) you have no way of booting this device. Also 3 1/2 HD media will not work, you have to find old DS-DD media. E-mu Emulator II rear viewManaged to create a copy of the 5 1/4 disk onto 3 1/2 and boot off of that so should be safe now! Also the small square button for disk utilities was missing. You can get the switch from Digikey; I found a similar one in Anchor Electronics on Walsh in San Jose and fitted that.

Emulator II internal viewEmu Emulator II
This one had a bad power supply, and the customer had been trying to fit more modern replacements. Re-soldering cold solder joints bought the base power supply back to life on the bench, and when fitted to the Emulator the root issue was shown to be a shorted tantalum capacitor on the input to the -15v regulator . This unit has a lot of corrosion and shows memory issues; next move is to clean the sockets with isopropyl.

Yamaha DX-7 with Grey Matter UpgradeA Trio of DX-7's
There are a lot of DX-7's out there, and age and a lot of use make these a common keyboard to come in for repair. These were all 1st generation (brown casing) machines, and two of them had Grey Matter enhancements. Repairs were a mix of new battery, bad keyboard contacts, andYamaha DX-7 with Grey Matter Upgrade - internal view poor volume/data entry sliders. It isn't uncommon to end up with no sound following a battery repair or remove/replace the Grey Matter card (corrupts ram). Go through the voice initialize process in the Grey Matter manual and then reload the patches; this should put things back right!

DX-7II
I have repaired many of these. Most just need a new battery, or maybe a broken key (same type as a DX-7). This is a very reliable variant of the DX-7 and has floppy storage too.

DX-100
I must have repaired 20 of these. Consistent issues are corroded power jacks. Dry jointed/cracked pcb connections to the power jacks. Expired batteries (OK, this is not a DX100 issue per-se). Broken case posts at the inner front of the keyboard (rigidity of structure impacted). Broken keys. This keyboard is small and does not seem to be built to take the rough handling it gets. Great DX sounds from a small portable package though!

Roland Juno-DRoland Juno-D
This keyboard had a growing plague of dead & intermittent keys. The keyboard was stripped and keys removed which revealed 5 rubber bubble strips held by small rubber prongs and sticky tape. Removing and replacing these strips without damaging them is a slow delicate operation. I cleaned both the board contacts and the black contact area inside the strips. Roland Juno-D rubber strips in keyboardFour of the sections showed a small amount of cleaned off residue and worked after re-assembly, the right hand strip did not and there are a couple of not so good keys still there (working but not fully functional). Customer will try it out for a week or so to see if things improve/degrade. Next move is to try to obtain a new rubber strip for the RHS and fit that.

Sequential Circuits Split-EightSequential Circuits Split-Eight
This keyboard had no soundSequential Circuits Split-Eight bad ground pin output. If you turned the volume full on you would hear "motor boating" which leads you to the power supply or grounds. The power supply negative rail to the main board and rest of the system is through a single pin on a connector, and the pin had come apart. Pin replaced and all is now well!

Roland Juno-60Roland Juno-60
This came in with every 6th key dead. The problem was traced to one ofRoland Juno-60 keyboard cleaning the VCF's. I found an IR3109 VCF chip and finished this off. While working on this synth I found that other keys were intermittent and performed a keyboard contact clean in order to resolve this.

Korg M1 Korg M1
This came in as a dead unit and was in a grimy, previously worked on (missing screws, missing hardware, partially unsoldered chip, broken joystick (parts missing too), and a missing small round key top). The power supply was repaired (badKorg M1 Power Supply switching transistor and open circuit resistor) and the casing was cleaned (plus chip re-soldered). Korg M1 Alive!The keyboard now works and all of the stored sounds were still there! Unfortunately a replacement joystick could not be found but the unit worked perfectly otherwise and is now with a new owner.

Korg M500 MicroPreset
This was a very tired keyboard, and had lots of dirty contacts in the switches. Once the contact issues were resolved and a bad LM324 in the voice circuit was replaced all was well.

Roland SH-101 The last one that came in with some dead keys had a cracked circuit board under the keys, I'm amazed that this damage could occur without breaking any keys (skillful playing I guess). It also had drifting tuning due to a bad power switch; this had be scratching my head but it is in fact a common problem on this keyboard.


Kork 01/W LCD Korg 01/W This is a nice looking keyboard that came in for a backlight replacement as the LCD is dark. Part took forever to come, not satisfactory! Note that EVERYTHING has to be taken out layer by layer tKorg 01/w FD LCD Replacemento get to the LCD; this takes around an hour and it will take another hour to fit the backlight and put it all back together. The customer asked about updating the firmware and I passed on the advice I read online that as he is the original owner he can request it for free from Korg. I eventually found the latest (#62) firmware and fitted and tested it.

Octave Kitten
Lots of connector, pot, and contact issues resolved.

Gleeman PentaphonicGleeman Pentaphonic
This was a see-through one, and reportedly there were only 20 made.  This one had failed solder joints in the power supply, and on the front panel. The keyboard needed re-bushing, and there was an issue with every 6th key being louder, and issue with the switching chips also sending audio through the sequencer. We managed to swap chips around so we could use an unused chip section, and are trying to find another chip. The keyboard is being used without the sequencer for now.

Gleeman PentaphonicGleeman Pentaphonic this one had been killed by another repairer during a battery replacement. Thankfully the unit was not "blown up", the issue was a failed solder joint on a power connector that caused a connector pin to fail, and the wire connected to that pin to fail. Not too difficult aGleeman Pentaphonic bad connector repair, but it does cause concern about "techs" changing batteries but unable to do anything else and putting a rare and valuable keyboard at risk. I also re-bushed the keyboard and the customer was delighted to have his treasure back working as good as new!

Roland SH-505Roland SR-505 A number of these have come into the shop. I'm seeing power supply faults, corroded connectors (especially ones causing the bass keys to fail), and bad capacitors. Great sounding string synth.





Juno 60 with Sticky KeysJuno 60
This keyboard had "sticky keys". The issue was a previous repairers fix which was to drip epoxyJuno 60 key contacts in and lock the bad key to the one next to it. Replacement key obtained and fitted. The keyboard contacts also needed a clean. Keyboard restored to health.

Juno 106Roland Juno 106
A number of these have come into the shop and for most of them it is a 80017a VCF issue. Roland put 3 chips (including the 3109) and supporting components onto a module, then covered it with a moisture sealing coating. There is a belief that the coating was required in order to protect surfaceJuno 106 80017a mounted resistors from humidity change in order to stabilize their value, and that this coating becomes conductive after 20 years or so. The only source of replacement parts is through chip pulls from scrap machines, and they are rare so costly. A typical symptom is a hanging voice, and/or crackling. I recently invested in a special de-soldering station in order to get these chips out cleanly. The keyboard here was purchased on Craigslist by the customer for a good price but when he got it home he found it crackled badly, and a voice was hanging (you can isolate which of the 6 voices it is by putting the keyboard in test mode). For this one it was not obvious which chip it was but careful testing showed it. A replacement was obtained and fitted; all seemed well. Juno 106 80017a replacementAfter 3 hours of just sitting warming on the bench another chip started to crackle and had to be replaced. Speaking with the chip vendor this scenario is not unusual. The keyboard was not such a deal now that the cost of two replacement chips is factored in but the customer loves it and will get good use from it.

Roland SH-5Roland SH-5 This unit came in with two issues, LFO-2 not modulating with led dark, and pitch-up control not smooth. The LFO came back to life when the CA1458 (same as a LM1458 or 4558) was replaced. The pitch control is metal and Roland SH-5 Pitch Bendersome wear had taken place; this was greatly improved by stripping, cleaning, and lightly greasing the assembly. Both oscillators needed tuning and scaling (thankfully you can access the controls from the front panel), and once tweaked it sounded great.

Roland Jupiter-8Roland Jupiter-8 The customer had just purchased this keyboard and wanted it serviced as there Roland Jupiter-8 foamwas a lot of lint and slider gasket debris in the controls. The work order was to strip out the old gaskets and replace them with felt, clean all old debris from controls and circuit boards/case, lubricate the controls, and replace the battery. To back-up the patches Roland Jupiter-8 felt appliedprior to battery replacement (3.6v Lithium from Jameco) I brought an old Roland Jupiter-8 felt prepcassette player into service, and it worked like a dream! Thick (3mm?) foam of the type originally used could not be found, so we went with the most rigid felt that could be found. Felt is not as rigid as the foam, so a lot of double-sided tape had to be put around the controls to hold it. I Roland Jupiter-8 cleaning controlswould not recommend felt due to its lack of rigidity Roland Jupiter-8 bender panel feltedand shedding, but until a better material can be found then we are stuck with it! The unit looks really nice, and the customer was delighted!

Alesis QuadraSynth Plus Piano Alesis QuadraSynth Plus Piano This came in with the symptoms of bad smell, smoke, and losingAlesis QuadraSynth Plus Piano bad solder joint patches. A sniff test led me to the 5v regulator where the soldering had failed. Removed the regulator and cleaned the area. Reassembled using fresh thermal grease and tested all patches OK. Thankfully the spiking power does not seem to have done long term damage.

Electric Organs

Rheems Mark VIIRheems Mark VII The reported issue was a disintegrating power lead that was no longer un-pluggable, and a constant vibrato noise in the background. I also found the right hand octave had intermittent key contacts during test, and volume was low. This is a seriously old piece of equipment which requires a special optical pedal to work correctly. Searching the web IRheems Mark VII internal view found that this could be resolved by putting a jumper in 2 pins of the pedal socket; doing this puts both bass and regular outputs out of one socket, restoring full volume. You do not get any volume control of course and one switchable function is no longer available. The old power cable was removed as it had been hard wired in and the cabinet was routed to take an IEC power socket. This is niceRheems Mark VII keyboard contacts and neat now. Cleaning the RH keyboard contacts Card cage, look at those dovetail joints!requires the internal mounting board be removed, along with the keyboard. You eventually get access to small canned module with the contacts inside. All very fiddly, and a lot of careful cleaning was required to restore operations. The constant vibrato noise was due to a microphonic pre-amp/vibrato module. The input resistor is wirewound and a leg had fallen off, and the power rail copper tracks on the PCBAmplifier and vibrato module underside had fractures which were bolstered by tacking wire runs along the tracks. This work was carried out beneath the card so it retains its vintage look from above inspection. Noise issues were resolved and after some pot and switch cleaning all is working well.

Korg CX-3 Organ
Korg CX-3 Organ
A customer purchased this keyboard which had dead and intermittent switches, and a number of dead keys. Several passes of cleaning keyboard contacts had to be made in Korg CX-3 Organ Resolder Neededorder to get reliable keyboard operation. The dead switch was a "dry joint" which needed to be re-soldered. The intermittent switches were resolved by Korg CX-3 Organ Switch Paneldisassembling two of the option stitches and replacing the micro-switches (a LOT of these fail on vintage gear from many vendors, I just replaced 14 of these switches on an Akai MPC2000 as an instance of this).

String Driven Things

One day Andrew brought me a Wurlitzer to repair, and it needed mechanical as well as the electronics' repaired. Why I asked, "cos you are good with your hands" was the reply.

Wurlitzer 200Wurlitzer 200
The keys had a wave only sailors could love, keys stuck, hammers did not sound, the electrics were bad but the cable connector was obscure and lost so who really knew. I researched this and read that the service manual stated a mixture ofWurlitzer hammer lube Naphtha and silicone could be applied to clean and lube the hammer joints, but don't soak the wood. I made Wurlitzer 200 restorationthe mix and purchased an injector bottle, then took every one of the hammer mechanisms off and lubed it... this was a SLOW process and you had to be careful not to wet the wood, so every actuator was removed. Wurlitzer 200 under repairThe unit was the set-up and was mechanically excellent. The next job was to rout the cabinet for an IEC power connector and fit that. The electronics were re-cap'd and the whole Wurlitzer 200 restoration - amplifier re-capthing finally cleaned and set-up. Visitors to the shop had previously hit a couple of notes and shrugged their shoulder and walked away, now they sat and played it. The owner played it for 30 mins and then took it away. I now understand why Super Tramp used a Wurlitzer in their songs. The Wurlitzer expanded my skills, and now folks are bringing me Fender Rhodes and Hohner Clavinet's.

Drum Machines

E-Mu SP1200 Drum Machine internal viewE-mu SP1200 Drum Machine
This has a missing large touch-pad button, and no boot diskette. Without the diskette there is no way of finding out what else is required. Replacement dynamic pad buttons obtained from Forat, and a boot diskette was sourced. SP1200 with new backlightTwo more switches were replaced along with the LCD backlight and LCD cable (fell apart due to age). The grounds were cleaned and power supply heat-sink was enlarged. One slider was replaced as it failed final test. The final SP1200 data timing for floppyproblem was with memory corruption and crashes after the floppy drive was accessed; this unit had previously been sent to a specialist for this issue... there is a one shot 74LS221 that times access and replacing this chip and selecting a closer value timing capacitor made this SP1200 a solid performer again.

Roland TR-909
Roland TR-909
Three of these have come in recently with missing sounds or crackling sounds. Two components seem to be failing with time,4558 DIP on a SIP module 2sc2603 transistors are a common crackling sound cause (use something like a BC547 but watch out for different pin-outs). Sip chip replacement moduleDead sounds tend to be the M5218AL IC's. These are SIP's and getting rare. I have had great success with mounting a 4558 DIP on a SIP module.

Emu DrumulatorEmu Drumulator Blowing fuses due to a shorted capacitor in the mains power input. This unit has both a midi interface and switchable sound banks.






Emu DrumulatorEmu Drumulator Blowing fuses due to a shorted tantalum capacitor in the power supply. The power supply held the CPU in reset following this, and a CA3086 transistor array was replaced to resolve this, along with the related FCO from EMU. One switch was missing and replaced, the switches were cleaned, OS 3.0 was installed.


Korg Rythm 55Korg Rhythm 55 Hum on sounds and weak sounds. The 10uf capacitors were leaking, leaky capacitor that damaged the circuit boardand some had done damage to the circuit board. All 10uf and 1uf capacitors from the same manufacturer were replace. Should be good for another 20 years!

Univox SR-55Univox SR-55 Some sounds not working, this was simple but delicate work. The cable-form seems tooUnivox SR-55 wiring heavy for the fine wires so with years of the devices moving around the wires fracture. Strip and re-solder, then put the unit down gently!

Oberheim DXOberheim DX
All switches opened up and oxidization cleaned off. One of the 7 segment displays failed and was replaced. A new battery and general clean had this unit restored.

Roland TR-707Roland Drum Machines
The full range from Roland seems to have been through my door including the TR-808, TR-707, TR-606, and many TB-303's.


PAIA 5700PAIA 5700 I have worked on a number of vintage PAIA units, Here is a 5700 Drum Synth.