Hi everyone, so I picked up my first moog mg-1, knowing it wasn’t working properly with the intent of fixing it yet I’m still stuck!
So here is my problem all I get is a very faint sound of the synth coming out of the headphone jack and nothing out of the RCA outputs. I can hear the lfo switching on and off tho. So I started messing with the vca balance adjustment and the service manual says to “monitor pin 6 of U1011 with AC voltmeter”. But I’m not sure what I’m looking for?
Then it says “adjust vca balance trim R1094 for minimum output level”, when I adjust it the output of the headphone jack gets louder and I can hear the synth a bit more and the lfo gets louder too.
So I’m lost I don’t know what to really look for… Any help?
I have some advice: Don’t take up medicinal surgery on a lark!
Seriously, if you don’t know electronics or something else complex, what is it that made you think you could fix it?
I’m not speaking to you specifically; I’m talking about anyone who embraces such a viewpoint.
So I’m not trying to be a d*ck… I don’t even know you.
I’m just confused about the mindset here. (and thus anyone could answer my questions, not just you.)
I suppose if you got it for $20 and have little to lose, maybe it would be a learning experience.
Maybe it could turned into some interesting piece of art.
But synths are filled with parts connected in ways based on complex theories.
I can’t imagine just deciding to practice dental surgery, law or DNA analysis.
What is it about a broken synth that says to someone “this should be easy to fix?”
Fwiw, I do repair synths professionally and have seen countless synths ruined or badly damaged because the owner assumed they could fix it with no experience and often no test equipment or proper tools.
Had they brought it straight to a tech, maybe they’d pay, say, $100.
But fiddle around inside, turn trimmers, disconnect connectors and maybe put them back on wrong or countless other scenarios that could happen and that same tech might have to charge you much more.
If I had a sick Ferrari, I wouldn’t just go poking inside and turning things hoping for success.
It’s more likely I’d make it worse, not better, because I have no experience fixing Ferraris.
But regardless, I’ll try and lend a hand…
The VCA balance trimmer is used to null the DC offset from the audio.
Even on a properly working synth, it shouldn’t have a huge effect on the volume of the sound.
It’s there to trim out a tiny bit of residual DC passing from the CV input to the audio output.
The correct setting is where the synth has the most minimal “thump” in the audio when a key is pressed using a fast envelope or just full sustain.
Now this explanation above probably didn’t help you much, but it’s not Moog’s fault, nor yours or mine.
But this is what you’re dealing with here: many interconnected parts designed to perform specific functions based on theory.
If you don’t understand electronic theory or terms, it makes it only that much harder to fix, even for a tech that later gets it.
You have to study and learn first, then apply the knowledge.
There’s no button inside labeled “fix me.”
I would like to help you.. seriously… but I wouldn’t even know where to start.
Sure, I know the synth, but I don’t know you.
So first I’d have to ask:
Do you have any experience fixing analog electronics?
Do you have a decent soldering iron?
Do you have test equipment such as a DMM or oscilloscope?
Do you understand the terminology used? (trim, balance, null, offset, ohms, volts, current, polarity, etc, etc, etc.)
Do you have documentation on the instrument?
Can you read schematics?
Have you performed basic initial tests? (is the power supply putting out the correct voltages, are the VCOs working, etc.)
Finally, I think it’s easier and takes less time to fix a synth in person than via email or on a forum.
It took me about 25 mins to write this post.
As others chime in and try to help, that time could add up to hours and not all advice given on a forum is good or proper advice either.
In other words, I suggest contacting a professional where time isn’t wasted and a good job is performed.
Otherwise, you risk making the synth worse and wasting people’s time.
Again, this is nothing personal.
I just wouldn’t want someone working on my synth that couldn’t answer “yes” to all seven of the questions above.
You need a tech, just like a sick cat or dog would need a vet.
Second, I couldn’t agree more with Kevin Lightner.
I’m not a tech, just a self-taught (by reading lots of books, and lots of fixing things afterwards) electronics hobbyist for many years (started in my teens and I’m 48 now).
The first thing I do when trying to fix an electronic device is to get the service manual and analyze the schematics to get and idea of where the problem could be. Then I proceed to take measurements with specialized tools to verify that they show proper values, at specified testpoints, according to said service manual.
Sometimes when I get stomped and can’t find what’s wrong, despite my knowledge and experience, I go on forums like this to get advice and suggestions.
Has the foam-of-death even been removed on your MG-1 ?
Thanks for the advice guys but to answer some of your questions, i have an idea about this stuff or i wouldnt have thought i could do it. I work on cars and their electronics and i know how to use my Fluke DVM and an oscilloscope (but dont have one) and im pretty good at soldering. Although the terminallogy might be the same, i have never worked on analog synths before and its something i wasnt prepared to do but as i was removing the black foam i figured i would at least take swing at it. I printed out the service manual and have been looking at the symtom & remedy page to see if it might help.
I did get this synth very cheap and from a christian school that left it deep in their storage closet for 15 years, so i just was tryin to make this deal even better by fixing it myself. I cant seem to find a decent synth repair shop around here, Chicago, but that might be my best bet.
Thank you guys, i will continue to study the schematics and might come back for more help if i really need it.
btw this is a cool little forum here, lots of info all over!
I need to do the restoration on my MG-1 before too long; I’d be interested hearing how you handle the foam gunk removal!
I’m in a similar situation, experience- wise. Plenty of experience dealing with electronics, but the MG-1 will be my first effort exploring the innards of an analog synth…
Good luck with yours!
BTW -
Does anyone know of a source that still carries parts for the MG-1?
(Linear pots, knobs, switches, etc.)
If you are in Chicago, take it to Deltronics. I bought a Prodigy relatively cheap, but it needed some serious modding to get the oscillators to track properly. They were able to fix it up proper for less than $200.
Unfortunately, I’m no where near Chicago, so that woudn’t be a cost-effective option right now.
From what I have read elsewhere on this forum, “Technology Transfer” doesn’t seem to be very responsive, but if I can get them to respond via e-mail I might give them a try.
The Chicago thing was for slumlord. He said he lives here.
As far as Transplant, I haven’t dealt with them in a while, but I did buy the slider pots for a rogue from them and didn’t have an issue. But this coulda been because it was through PayPal.
