How to fix a Moog synth (and hidden PCB art)

In this video I show how I replaced a bad potentiometer for the filter cutoff on my Moog Grandmother synthesizer. I also find some cool hidden art printed onto the PCBs that you can only see when fully disassembled.

[@nodfactor8808]

I definitely appreciate seeing how that was done in case I ever have to replace a pot. Thanks, man!

[@atlas9097]

Thanks a lot for sharing, I will be replacing the plastic side panels with wooden ones and this helped a lot in taking the thing apart!:)

[@mikkelfrederiksen5567]

Hey! Where have you bought those, or have you made them you self? I would LOOVE a pair of wooden sides on my black GM. I think the sound will improve as well ;)

[@atlas9097]

​@@mikkelfrederiksen5567 Hey! I've made them myself, but if you don't want to do that, I can recommend Curry Cases. They should have the GM panels in stock again soon, just ask them, the owner is a very nice guy and they ship internationally :) The tone of course increases immensely with the tonal wood and all ;)

[@mikkelfrederiksen5567]

@@atlas9097 thanks for the advice! I'll do that 🙌

[@justkawz7275]

Thanks for sharing the process!!

[@greenvelvet]

Wow! that's so brutal how you have to take every single nut off just to get to that pot. Congratulations on fixing the problem. It's so intimidating taking those things apart

[@Rhythmicons]

Yes that is bullshit.

[@Rgdonaire_07]

Same scratchy pot here. Looks kind of finicky to fix, I’m a total noob with these things. I’ll probably take it to a repair shop close to where I live. But thanks a lot for sharing this! I’ve had several qa issues with the grandmother. Love the synth but quality is not top notch.

[@craigtillman5988]

Thank you sir.

[@nielsbreugelmans876]

What kind of solder do you use and wich thickeness? I have the same problem with my pot

[@sibbyeskie]

Great video, I appreciate you documenting the steps. I might have to fix my LFO. Does yours sometimes take a while to come to life? The other oscillators make sound immediately but the LFO is usually silent for a while then eventually wakes up. Also FM tracks better across the keyboard on osc1 while osc2 gets wonky much quicker when modulation depth is kind of high. Not sure how normal any of this is.

[@christianlenatube]

Hi Mike, thanks for this video! My GM suddenly doesn't turn on anymore. I wasn't even using it. It was under the current socket like all the other rack synths. I'm not much expert could it be just the power fuse?

[@lordjoshuarobindumbleton275]

Great video man!

[@lukasantipoff9596]

Hey man, this is exactly the video I was desperately looking for. I also have a scratchy filter pot and reverb pot on mine unit, and couldn't find a solution online. It's a common problem with recent Moog products which is really a shame. How much time did it take you in total and what is that green tool called you used for taking the buttons and rings off?

[@SISKworks]

Well it took me ALL day but that was because I was filming it. Making a video makes it take so much longer. I would guess without the video it probably would have taken anywhere from 2-4 hours. Those green tools are called Rocket Sockets from Love My Switcher and they help SO much, I highly recommend them. lovemyswitches.com/rocket-sockets-pedal-building-socket-set/

[@acrylicrecording]

Great video thanks!!!

[@SISKworks]

Thank you

[@brentondwyer4684]

Hey there Mike, I just purchased a brand new Moog Grandmother and am having an issue with the attack decay sustain release. When I press a note and allow it to get into the sustain portion, as soon as I release the note it retriggers the same note at a higher volume. Someone had commented that it sounds like the VCA bias needs a slight calibration by turning the associated internal trimpot. Did you notice a trimpot in that area when you took apart your Grandma? I don't see one in the video.

[@SISKworks]

Yes there are some internal trim pots. I just confirmed by looking at some pictures I took when it was apart. But I’m not really sure how to solve your problem. Maybe take a pic or mark where pots were set before making any changes. They are all pretty small and they all seemed to be marked VR (variable resistor). Good luck! Hope it all works out for you.

[@joshcutler845]

What nut driver set are you using to pull all the hardware from the faceplate?

[@SISKworks]

They are called “Rocket Sockets” from Love My Switches. They are extremely helpful and I’m so happy I purchased them. lovemyswitches.com/rocket-sockets-pedal-building-socket-set/

[@Rhythmicons]

There is a number of 101 Moogerfoofer filters that have the Bob Moog Foundation logo in there.

[@SISKworks]

Nice. I’ve heard others also have stuff printed on the circuit boards but the grandmother is the only one I’ve seen.

[@VacancyOfDisco]

did it seem like it would be possible to add mods to the circuit? like adding CV control for the envelope decay or anything like that?

[@SISKworks]

There wasn't specific labeled mod points like the Korg Volcas have. But envelope decay DOES already have a knob/pot. Pots are just variable resistors. So you could in theory just connect a vactrol to the points the pot is connected to in order to get basic CV control. A vactrol is just basically just a light dependent resistor (LRD) with and LED stuck to the front. The LED gets brighter or dimmer with the amount of CV it it given which in turn changes the mount of resistance in the LDR which would change the amount of decay. I've done this a different circuit bending projects but just now on any of my real synths but it should still work the same way.

[@eligioelini9194]

Very interesting. Congratulations for your professionalism. I am interested in buying the Grandmother and I have been able to closely observe how it is built. It seems to me very well done and I think I'll make up my mind. I wanted to ask if in your opinion the sound it has is worth the expense. I already have the Pro 3 and the Take 5 and they are wonderful but in my opinion they have different sounds. what do you think? Anyone else want to tell her?. I am an amateur. Greetings from Italy.

[@SISKworks]

Thank you. But to be honest…I’m probably not the best person to judge it’s value because I didn’t actually pay for mine. I was super lucky and won it from Moog in a circuit bending contest. But I DO think it’s an awesome synth. When I first got it I was super frustrated because it would always lock up when trying to use an external sequencer. But Moog released a firmware update that fixed that issue.

[@eligioelini9194]

@@SISKworks Thanks for the reply. Good music!🙂

[@Waldemar_la_Tendresse]

Thanks for the video, it helped a lot to see the repair before I will do mine. Some pots of my Grandmother are scratchy too. It took me half a day to think about a procudure how to test all the pots with an oscilloscope without taking it apart before getting the replacement parts. You don't happen to know the exact specs of the pots?

[@SISKworks]

The frequency cutoff is a B10K “alpha style” pot. Not sure if the other pot values though. But you can also just call the Moog service dept and they will tell probably tell you for free.

[@Waldemar_la_Tendresse]

@@SISKworks Yeah, thanks. I have written to their support and am waiting for an answer now.

[@Rhythmicons]

My Moog 10 has a scratchy pot after just a couple of years. They told me to put 3 in 1 oil in there much to the shock of former Moog engineers and techs I know.

[@SISKworks]

Hmmm. Idk anything about 3 in 1 oil. It might actually work better than something like a electronic “contact cleaner” spray. Contact cleaner pretty much ruins the feel of pots because it strips the lubricant from them. Maybe the 3 in 1 would clean and lube. But I would start with Deoxit fader F5 spray first as that product is intended for this very purpose. I tried this on mine first but it didn’t help so I ended up needing to replace it.

[@DS-nw4eq]

Video audio is very low. Not much of an issue until the ads come on and they're blowing my hair back. Just a note if you want to fix it. Thanks for posting.

[@SISKworks]

Thanks for the feedback. I think this was with a different camera that didn’t have an external mic.

[@andreas-wismann]

I came across your awesome video in search of a way to pull off the button caps (red, yellow, green, blue) on a Matriarch without opening the synth. Would you say that this is possible?

[@SISKworks]

I’m not 100% sure because I didn’t really inspect the button on mine. But I’m fairly certain that you would need to disassemble in order to change those button caps.

[@abhorrentmu8195]

after bought a new 1xxxx serial subsequent37, cutoff drooled some black stuff and got stucked, othe on/off buttons even if disconnected the knobs act anyway, noise knob is this cas is acting and a lfo somhow, C2key produces no sound, on my collection one of the best sounding synths i had for 2/3 weeks lifetime, Should i be stupid to buy another one while im still waiting from components from Moog Music? should i have a third one? for when 1 is repairing and the second one gets faulty while on process. My most recent synth i have was the first and only synth get faulty, and with so many issues

[@SISKworks]

I’m sorry but I’m not understanding what you are asking. If I were you I would repair the first synth before buying a second or third.

[@RC_Cola2020]

Is it possible for your to share the specifics of the potentiometer? I am trying to see if I can source the part to repair my moog. I also need the specifics for the spring reverb potentiometer. Thank you.

[@SISKworks]

The filter was a linear 10K PCB mount type, marked “B10K” But I have no idea about the spring. But you can just call the Moog service department and talk to someone and they will probably tell you.

[@seeyoulala]

hello sir , when l press my keyboard key then put off , but the sound don't release , the sound still there , but only certain keyboard keys . how can l fix , please help... thank you.

[@SISKworks]

I’m not sure. Could be an actual physical connection issue at the key contacts but hard to say. Have you opened it to inspect the contacts under the keys? That’s is probably where I would start. Also Moog has a service department that is really helpful. You could try calling them and explain the issue and they might be able to suggest what to check. I’ve done that and had them send me a new pot to fix this Grandmother.

[@syntheshwara]

My reverb pot is busted and Moog is sending me replacement pots. I live in India and I hope it comes through in good shape... Sucks man!!

[@SISKworks]

Good luck. It’s not hard. Just take your time. Also the pots are just the standard “alpha” style. So as long as you use the same value as original you should be good. If you can’t get the replacement from Moog you can just order from something like Tayda Electronics (Thailand)

[@syntheshwara]

@@SISKworks Moog agreed to send the pots free of charge. They are yet to confirm post shipping. The reverb pot has gone so bad that just by touching it, the reverb becomes 100% and it scratches like crazy. . I don't know how long it takes to arrive here but this is such a lovely sounding synth, even a small dent on it makes me want to cry :(

[@swaroopa1965]

Is that an antistatic mat?

[@SISKworks]

@@swaroopa1965 NOPE

[@carl7lamoureux]

Thanks for the video - I am about to do the same repair. Do you know the value or part number of the potentiometer? I also need to do this repair, but so far I have not gotten a response from Moog so I'm thinking I will just order the pot myself.

[@SISKworks]

It is a “B10K” pot. PCB mount.

[@ARBB1]

I'd be interesting if someone reverse engineered these circuits.