MiniMoog Help - OSC 1

[papajohn]

I have been given a minimoog model D, but don't really know much about it other than reading online for the past couple weeks. The problem I have is that OSC 1 is not audible, If I put headphones on I can really faintly hear it. The odd part is every so often one key will all of a sudden work for OSC 1, anyone have any ideas/advice? OSC 2/3 work fine. Thanks!

[thealien666]

If you're lucky enough to actually have been GIVEN a Minimoog D, you can certainly spend money on having a qualified tech take a look at it, don't you think ?

[JohnLRice]

I might guess either a partially failed solder connection relating to Osc 1 or oxidized contacts in one of more of the multi connectors that connect the different PCBs and keyboard etc together?

[papajohn]

Thanks for the replies.

If you're lucky enough to actually have been GIVEN a Minimoog D, you can certainly spend money on having a qualified tech take a look at it, don't you think ?

If I had the cash I most certainly would take it to a tech, but unfortunately I don't so I came here.

I might guess either a partially failed solder connection relating to Osc 1 or oxidized contacts in one of more of the multi connectors that connect the different PCBs and keyboard etc together?

I think you might be right! There's some pretty visible oxidized parts. From what I've read, the capacitors on these have about a 20yr lifespan (from what I know, mine is entirely original parts) so I'm guessing they're due for a replacement as well. Anyone have experience with this? I'm almost afraid to turn it on at this point until I can get a good grasp as to what needs done, it may end up sitting until I can gather some funds for a good tune-up!

[torinkrell]

Especially with a vintage Minimoog its often the simple things that need to be checked first. The 2 rotary switches and on/off switch associated with the reluctant oscillator need to be gently worked back and forth, and potentially the 2 connectors in the wiring harness under the mod wheels need to be cleaned.

[thealien666]

As the excellent tech Kevin Lightner (RIP) would say, 90% of the time it's not the electronics that are to blame in a Minimoog D, but rather dirty or oxidized connectors and contacts, mechanical switches, trimpots, etc...
Especially the ones underneath the mod wheel assembly (the Cinch-Jones bakelite type), as torinkrell wisely suggested.

But in your particular case, I also agree with JohnLRice about the edge connector for board #1 (oscillators) that probably needs cleaning.

As for aging capacitors, I've checked mine for elevated ESR, and they're all in excellent shape (ESR well below nominal values). I've only replaced the ones on the rectifier board as a preventive measure, since they're of vital importance to filter out ripples for the PSU board, and because it was easy to do. Mind you, the original ones also showed excellent results when tested but since I was in there I replaced them anyway.

My Mini is from 1975. What's the date on yours ? (small yellow tag in the back, or written by hand inside the panel)

[papajohn]

The sticker is pretty faded but looks like a 77. Thanks for the info guys, I'm a little apprehensive about fiddling too much with the innards, but my excitement of getting to learn and play on this thing is likely going to force me to figure it out!