Opto-Key MiniMoog Upgrade

Opto-Key MiniMoog upgrade

Synthfool’s Opto-Key Installed

The MiniMoog, along with many vintage synths, suffers from oxidization of the key contacts. It needs all keys to be pressed regularly to break the building oxidization, before it becomes a problem. The symptoms of the keys going bad are they become “squirelly”, i.e. multi-triggering, or dead due to not triggering at all. Another issue you see on keyboards is that as the keyboard generates CV from a resistance chain (1volt/Octave being common), any resistance in the contact alters the voltage out, thus frequency.

The folks at www.synthfool.com came up with an optical method of detecting key presses, called the Opto-Key. This incorporates a micro-controller in the Stripping the keybed for re-bushingdesign, making it possible for them to also add MIDI In/Out. Jason, the owner of this early MiniMoog, decided that as it was in need of service, he would ask me to implement Opto-Key, rather than continue with the key contact clean regime.Removing the keys

The keyboard was re-bushed while disassembled for the upgrade, and I can report that it works nicely. A service was also carried out, and some pots View of Opto-Key controller and optical sensorshad to be opened in order to clean them and banish crackles. For reliability the disintegrating C280 “Tropical Fish” capacitors were replaced, the power supply re-capped, re-greased, and bridge rectifier replaced. All switches and open-back pots were cleaned, and the unit set to spec. Plays nicely now.

 

Ace Tone Rhythm Ace

Ace Tone Rhythm Ace

Ace Tone Rhythm Ace

I have an interest in old, analog, drum machines, and take them in for service. Sheldon brought to of these model FR-1 units in for service; one was in pieces, the other had gummed up switches, and was generally sad. The biggest issue I has was a lack of schematic, so if anyone has oneAce Tone Rhythm Ace FR-1 to share I would appreciate it. They also wired the boards into these units in a way that makes it extremely difficult to work on them. A full service was carried out on both, and both were fully re-cap’d as one had low volume, and the other excessive hum.

Ace Tone Parts ReplacedThere was also a severe crackle on one unit that was traced to a Ace Tone Internalsnoisy germanium transistor, that thankfully NTE had a replacement for (NTE103A). You had to adjust the bias afterward, but the pot fell apart on touching it, so that was replaced and all was well.

Roland Juno 60

Roland Juno 60This unit needed a deep cleaning session and service.It was disassembled and cleaned-up, with fluff etc vacuumed away.Juno 60 Key contact fluff The sliders and volume control had switch cleaner applied to cure the crackles, and key contacts were cleaned. One bank switch was not working, so I removed, opened it, and cleaned it. The battery was replaced, and FCO applied for dropping into manual mode (I have never had one come in that had Juno 60 FCO at Power Supply endthis dealer applied; it addresses the fact that the power to the front panels goes through a couple of small connector pins, and this was insufficient, so direct power connections are added). Patches re-loaded, and unit put on burn-in test for a week.

Korg MS-20

Korg MS-20 Restored

Korg MS-20 Restored

This MS-20 had sat in a basement for some 30 years, and was in a grubby state with corrosion on the jack nuts etc. One key was broken, and the power cable was damaged beyond use. I took it completely apart, cleaning everything, lubricating all pots and jacks. The caps were leaking, so a re-cap was performed. The customer obtained a replacement key from Japan, and I fitted that, along with a new power cable.

 

A benefit, and curse on the MS-20, are all the jack nuts. Korg MS-20 start of clean-upWhen you take the patch panel out, there is another set on a plate over the jacks to remove in order to access the circuit board. Korg MS-20, so many jack-nuts!The benefit is that these nuts can be swapped for the outer ones, the washers flipped over, and then it looks nice and shiny. The MS-20 came in looking sad, and not making a sound, after restoration it looked and played great!

Octave Cat Restoration

Octave Cat Restored, just needs knobs and switch caps

Octave Cat Restored

I have done various Octave Cat’s and Kittens, from the original version, through SRM II. What they have in common is that they are tough to get going, and sorting out the keyboard contacts is always a major pain. This one though was the worst of the worst. It had been stored in a bad environment for many years, giving it corrosion and a bad case of filth. Worst of all though was that the bottom was missing, and the buss-bars/keyboard contacts were mangled, along with broken resistor packs. It was missing 5 of the j-wire activators, and all of the knobs and slider caps.

It was stripped, cleaned, and gradually rebuilt. I managed to straighten out the buss-barsDirty Octave Cat and contacts, re-bush it, and hand-clean the keys. Everything was cleaned, and the sliders/pots/switches treated with switch-cleaner. Some of the switches had to be opened and Octave Cat Mangled key contactsdeep cleaned in order to get them working. Electronically, some CMOS chips had failed and were replaced. VCO1 would not run at its lowest frequency, and I could see that a previous repair attempt had changed all of the suspect chips, plus there were a lot of component changes/ additions. I was fortunate in that another one came in, so I could compare and put it back to standard, and fix the original issue!

Life was then repeatedly cleaning and adjusting keyboard contacts, and fine setting it up until it worked reliably, phew! We purchased some knobs from Frys, and found that Sam at Syntaur has the slider caps. Doug at Synthparts thankfully had some of the j-wire acticators

Roland Space Echo RE-201

RE-201 with Tape Jammed

RE-201 with Tape Jam issues and no control over motor speed

I have had many requests to service Space Echo’s in the past and have repaired a few. I had decided not to do any more as I needed to purchase a number of service items to service them properly, and I was finding a dire lack of parts such as heads, bearings, and motors. One of my regulars managed to squeeze one in, and then I got a request to service one that was in dire straights after it had been to another repairer that specializes in them.

My next move was to scout and purchase a head de-magnetizer, splicer, splicing tape, and the correct type of 1/4″ tape for these units (must be lubricated tape). The first unit was simple enough, just needing a full service. The one that had been to another repairer was a different story.

The capstan was barely moving, and the motor shaft had a Old and new drive motor upper bearingssignificant amount of play in it such that you had to push down on the shaft with your finger to get things moving. I removed the motor, and did a lot of research on line re replacing motor bearings. After a struggle I got the motor shaft out and measured the upper bearing race, eventually finding a replacement type. The lower bearing could also have done with being replaced, but this is a press-fit sleeve bearing and I could only find one on Ebay, shipped from Australia.

Felt that had incorrectly been glued in the tape pathCleaning the old grease from the motor and capstan shafts/bearings, and replacing the upper motor bearing restored operation and the speed control now worked. The tape loop was crumpled, so I made a new one and fitted it. I then found that the tape was not flowing smoothly in the cassette area. I cleaned a lot of old oxide and sticky stuff from the cassette chamber, and found that a big piece of felt had been glued in the chamber exit path (checked with the customer and the previous repairer had done this, perhaps trying to address the motor issues (the unit was sent to him due to the motor barely turning)). The felt was removed, along with the glue residue. The tape then rang for 6 hours without jamming at various settings of the speed control.

The final work was to glue the front panel back on where it was lifting, clean the tape path, tighten jack nuts, and clean the controls after which it was working nicely. Another 6 hours of test and I will return it to the customer!

 

Arp String Ensemble

Arp String Ensemble

Arp String Ensemble

I have had three of these come into the shop in the last 6 weeks, and the last of these was picked up yesterday by the owner. I’m seeing failures of rare and expensive divider chips such as the SAJ110 (QDIP pin layout but the only NOS parts I can find are DIP so an adapter socket needed to be made), and SAH190 can. The Mullard C280 series “tropical fish” striped capacitors are falling apart on touch (you see cracks appearing at the ends), but wherever possible I leave them alone in the signal path as newer mylar types may have a different tone (the C280’s are sought after by vintage pedal builders for there tone, which I guess means they are non-linear!).

An SAJ110 on one machine was sucking many amps (it measured 12 ohms) and hadArp String Ensemble Internal view caused the power supply to fail, on another it was a Arp String Ensemble capacitorsmissing output. I recapped the power supply on two units, and for one of them we did a mass replacement of electrolytic’s as part of a restoration (and a sample of physically tired looking capacitors showed they were drying out with severely reduced capacitance.

The third unit had one dead key, and the owner had already changed a TDA0470 to no avail.Mullard C280 capacitor failed Looking with a scope the replacement chip was bad, and in fact it was ordered over Ebay from a vendor in China so who knows what it actually was. The original was put back in, and after much probing and deciphering of component layout the bug was traced to a bad resistor that had oxidized where the leg was cut off (they seem to have used some sort of pin flattening cutting tool in the factory which makes it hard to get components out), and then it had been re-soldered with a blob of solder over the top of the joint hiding the issue.

These keyboards sound great, but there are a lot of supporting components and rare chips that went into it so reliability is an issue.

Roland Juno 106

Roland Juno-106 800017a chip removed

Roland Juno-106 800017a board with chip removed

A number of these have come into the shop and for most of them it is a 80017a voice module issue. Roland put 3 chips (including the 3109) and supporting components onto a module, then covered it with a moisture sealing epoxy coating. There is a belief that the coating was required in order to protect surface mounted resistors from humidity change in order to stabilize their value, and/or protect their IP. This coating is thought to become 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 de-soldering station in order to get these Juno-106 Main cardchips 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 unit it was not obvious which chip it was but careful testing showed it, and it could be verified with an oscilloscope. A replacement was obtained and fitted; all seemed well. After 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.

I have been using the acetone strip method to try and re-use a bad module before Roland Juno-106 Stripped 80017a Modulesscouting a replacement. It takes 3 days of soaking and careful work to get residue out from between the chip pins. I silicone seal the module after washing it in order to seal the above mentioned resistors from humidity. This method has been pretty successful with crackly modules, but has not been good for completely dead ones, or where the VCF is drifting as we are looking at chip failures in those cases. It is a sad fact that all of these 800017a modules will eventually fail, and one unit eventually did have all 6 replaced. I have not tried the aftermarket replacements for the 800017a, but would advise folks to consider that. Also there are places that Roland Juno-106 on the benchyou can send the card and they will acetone strip all 6 modules; I’m not sure what the deal is when the strip does not work on a module though.

The bottom line is that if you are thinking of buying a Juno-106 then be aware of its issues and that they are not cheap to repair.

via This Old Synth – Vintage Analog Synthesizer Repair Portfolio Page.

Roland SH-101

Roland SH-101 in red

Roland SH-101

This is the red version, and this one had the hand-grip. It had several issues, the most common of which was a touchy power switch (causes oscillator drift). I go 2 ways on this repair, either wiring across the switch so it is permanently on (no-go if batteries are being used), or order a replacement from TechnologyTransplant; the customer voted for the latter.

 The switch arrived and was fitted.   Switch cleaner was applied to all pots, switches, and sliders. I then re-soldered tracks around audio out and modulation connector, restoring switch operation and getting rid of crackles, and also re-soldered around the frequency and filter sliders as things were intermittent there.

 The bender was only operating in one direction, the LFO push function did not work, and the unit needed adjustment as putting the VCO amount slider forward caused a frequency change. The last 2 items were cured by setting up the position of the bender on the pot shaft. The big issue was that the LFO switch was bad, and they did not make this repairable. I was unable to find a replacement (although having stripped that area out on a Juno-106 yesterday I see it looks similar). I managed to remove the old switch and modify it so that a micro-switch could be installed, and this works fine.

The unit was finally set-up to spec and sounds great!

Rhodes Mk1 73 Stage Piano

Rhodes Mk1 73 Stage Piano

Rhodes Mk1 73 Stage Piano

This unit was suffering from multiple dead keys, and things had been getting progressively worse. There were other mechanical issues, and once they were resolved the electrically dead notes could be focused on. By tapping the coils center pole 12 pickups were found to be dead, and on removing one it could be seen that the inner end of the winding had rusted through where it meets the pin. There is not enough wire left exposed for me to attach a bridge wire to, so the coil was deemed beyond repair.  As I researched the Rhodes Mk 1 Stage 73 I found out just how big a problem that rust on the coils was, and that most used parts on Ebay etc are remnants of machines  scrapped due to this problem, with statements in the ads like “rust cleaned off”. Continue reading