Moog Music Forum

I have bad oscillator bleeding problems. Since my last post about this, I have calibrated the synth, performed the moog recommend way to get rid of bleeding (replace resistor with jumper wire), cleaned all board contacts, checked all connections and solder points everywhere, and I have tried running a thick gauge ground wire from the rectifier board to the oscillator board.

....What else can I do? When playing high notes the bleeding is extremely distracting. Here are the exact symptoms PLEAAAASE let me know if any recommendations that you may have. Thanks. I love this thing but right now my only choice for playing this right now is to get a compressor pedal.

My bleeding occurs with all oscillators and does not change at all when I turn any knob or throw any switch.
The oscillators are all audible before I hit any notes.
The osciillators that are off and bleeding sound even louder when a note is pressed.
The bleeding volume increases with volume knob increases.
All outputs yield the same result.
I want to thing that this is some sort of shielding issue or there is some other mod I can do where I add in another resistor somewhere to quiet it down, but I have never heard of this being a problem.

Hi,
Sorry to hear that you are having this trouble. However with out seeing the MiniMoog, it can be very dificult to troubleshoot.
What you need to do is trace the signal back through the synth starting at the output. You need experience with synth repair and the Mini in general
to fix this.
It sounds like you will need to go through the process of elimination. Are you sure the osc board is bleeding? You have said that turning any of the knobs does not change the bleeding.
Maybe there is something else causing the noise/sound.

Start by pulling the osc board out and seeing if the noise/sound goes away. If it does then it is indeed the osc's that are bleeding, if the sound continues then there is something else causing the problem.

Let us know what you find.

GD

Ah, the classic oscillator bleeding symptom.

Cause is one of the power supply contacts on the oscillator board sockets has gone bad. The flags have mechanically spread apart and is no longer making contact. They can be restored but I recommend a tech do the work. The service manual will tell you to short a resistor on the power supply - while this cures the symptom, this does not fix the problem.

Hmmmm, you make it sound like the spread out pins are the most common cause of the oscillator bleed. I have already cleaned all the contacts and visually checked all the ....ummmm .....pin grabber thingys. They didn't look spread out. Its good to know that it is most likely the power supply contacts. I will tighten these ones up a little.

It got me thinking. When I calibrated the thing the voltages read as 10.00 and 10.03. I was surprised that they were so accurate still. Was I wrong in thinking that having 10.03 on pin 1A was good enough. I decided not to touch the trim pots for the voltages since i assumed I wouldn't get it any closer to 10 than 10.03. Maybe this is just my problem. Do I need 10 exactly? I thought the manual just said to check the voltages with a .1 accuracy DMM.

Any help would be appreciated, but honestly, I kinda have come to terms with my osc. bleed. Its only annoying and very detectible through headphones.

If you're bored, watch this. I got bored and made a MEGAMOOG today!
http://www.youtube.com/watch?v=7uA9Tqr6GMA

Maybe a kb voltage thing, but I'm not a very experienced tech.. just a bit..

you said all oscs are sounding without a note depressed? Can you figure out which note it is? Is the contact spring on that note not touching the buss bar assembly correctly?

This is what I'd check.. But it sounds like that would be something you already checked.. Good luck though..

Have you powered it up without the keyboard connector attached? That would tell you if my theory is correct..

Hope you figure it out..

- nick

I agree with MC, even if you are sure you're getting good connections. There's the wires and their connection to the flags as well.. You would definitely benefit from a good tech.

I am a Hammond organ tech and I also do my own work on my Clavinet, Rhodes, Wurlitzer, Arp Omni, Moog Prodigy, Micromoog, Roland Juno, etc. etc. etc.
Sooo, I am the tech. I have tried shorting out the resistor that MC was talking about. Its not on the powersupply board though, and it didnt help my problem. I have visually checked all oscillator board contact teeth and they all have good spacing and are making good contact. A different tech wont help me there.

So the next step is...???? I am thinking, replacing the power supply caps. IDK, I've heard they cause a lot of the problems. Is this a good next step. Its nto the contacts.

Check the power rails for oscillator bleed

I have done this. The question is... are these voltages good enough? When calibrating the thing I got 10.00 and 10.03 for the two voltages. I was using a Fluke 87 that is accurate. I assume the 10.03 is good enough. I didn't want to touch the trim pot in fear of not being able to get it any closer to ten. I think the voltages are good because it recommends using a multimeter that is has at least 1% accuracy. I checked these voltages on the actual oscialltor board, not on the prongy things.

HERE IS AN ISSUE!!!!! Look what I just found while I was cleaning my back cover!!!!!!

:O Now the question I have is, what is it. If you cant tell in the pic, the end of it is broke off and the pin was barely making any connection where it broke (it is completely broken off). Its on the left hand side of the filter board when looking at the back of the minimoog. I know its a cap, but I'm not sure of its value. I have found color calculators online but the one I found doesnt have yellow as a choice for the third band.




Location on board


Does anyone know if this could cause the bleeding. Obviously I am getting it fixed either way. Any help on what to replace this with would help. Thanks.

it's a capacitor

http://www.kpsec.freeuk.com/components/capac.htm

brown/black/yellow = .1uF

Thanks. I couldnt find a color converter with yellow as the third band! Soooo, is that a poylester film cap. Thats my assumption. But I am not positive. Here are my choices.

NOTE: The polyester cap only has a 50v rating but the metal film cap has a 250v rating just as the one in the mini. But still, I want to get the right type and I'm too stupid to know whether the one on the minimoog is a polyester or metal film.

http://www.radioshack.com/product/index ... capacitors

http://www.radioshack.com/product/index ... capacitors

they don't cost that much...get both types and see if you can tell a difference in sound/performance. but i wouldn't go less than 250V rating...ever see a capacitor explode? it makes a mess.

http://cgi.ebay.com/2-1uf-10-400v-Mulla ... 5acdee6ac8

Thats incredibly awesome. Thanks for the tip! I have be re-realizing how awesome the internet is, now that I have been able to buy an original new-old-stock full set of minimoog keys, a full set of new knobs, and now the original capacitors for my minimoog all this week. ...Oh yeah, and I was easily able to find a minimoog to buy.

Hi.
I'm experiencing the same problem.
All OSCs are bleeding when no key is pressed.
Did the cap change solved this problem ?