It’s generally a bassman, what’s wrong with it? I have one, have had to fix it without schematicMickey242 wrote: Sun Aug 31, 2025 8:47 pm Really want to fix my Sovtek MIg-50 but cant find a reliable schematic.
Its EHX, there arent reliable schematics and there are variations, but in general the Mig 50 is a plexi type amp. Both of these schematics come up and are very close to each other, certainly enough for repair:Mickey242 wrote: Sun Aug 31, 2025 8:47 pm Really want to fix my Sovtek MIg-50 but cant find a reliable schematic.
Tweed Bassman, not SF/BF, but the disambiguation is key.
Which is an option. I've built 9 to 18vdc Change pumps in the past and it's pretty easy to do. I know they can add some high oscillation noise, and on a mic pre that might be more apparent than with a guitar pedal. These will be for me, so Maybe I'll experiment with my own lunchbox format. 6-8 channels is more than I need, but I'd like them to be spaced PRE-EQ, PRE-EQ, PRE-EQ... or, just a box of preamps, and a box of EQ's. Probably never actually get around to doing it. Just thinking it through.
I was about to suggest checking the schematic too. For the mic preamps you could simply use the mic input and then add an output post coupling cap of the mic preamp. For the EQs you could possibly use the line ins , and depending on where the inserts are placed in the circuit use those for outputs. Or just add an output where the board is connected to the fader. A box with 6 or 8 of those channels wouldn’t be huge.mdc wrote: Tue Sep 02, 2025 8:04 am Those particular yamaha boards sell for a not-insubstantial amount of money; you could always flip it for $$$ and buy something that's closer to the form factor you're after. I'm not too up on those boards, but iirc they're the ones with API-compatible discrete opamps in the 2-bus? Are the direct-outs on it pre or post-eq?
Yep. I need to find time to open it up and look again. We plugged it in and did a little test and you get nothing from the master section at all, but I was able to get signal from a bunch of the channels out of the insert send. It is in really bad physical condition. Worst case, I see people flip the transformers for these old Yamaha boards from time to time. Still would be cool to try to completely bring it back to life but time is expensive.bassdriver wrote: Tue Sep 02, 2025 11:12 amI was about to suggest checking the schematic too. For the mic preamps you could simply use the mic input and then add an output post coupling cap of the mic preamp. For the EQs you could possibly use the line ins , and depending on where the inserts are placed in the circuit use those for outputs. Or just add an output where the board is connected to the fader. A box with 6 or 8 of those channels wouldn’t be huge.mdc wrote: Tue Sep 02, 2025 8:04 am Those particular yamaha boards sell for a not-insubstantial amount of money; you could always flip it for $$$ and buy something that's closer to the form factor you're after. I'm not too up on those boards, but iirc they're the ones with API-compatible discrete opamps in the 2-bus? Are the direct-outs on it pre or post-eq?
The circuit board under the cap reads "47-1W-MF"GuyLaCroix wrote: Sat Aug 30, 2025 5:35 pm We picked up an Acoustic bass 410 in the practice space a while back with a 'free' sticker. Sat it under the main cabinet and forgot about it .
Got around to plugging it in- nothing. Pulled the box out of the back with the circuit board for the tweeter, speakon etc etc stuff in there. A capacitor has come loose and looks busted. I think it's just a replacement and we're good to go. Took it home to investigate further. Will report back.
This looks more like a resistor spec - 47 ohm, 1 watt, metal film. Did it look like one of these?
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