Check out this beauty! It's a Sovtek Mig-50 model 001 guitar head. If you look closely, you'll notice that they misspelled "Presence". I was told that this means that it's a rare first issue, which might explain why it doesn't work.
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| In Soviet Russia, guitar plays you. |
This amp has been broken and in the possession of one of my bandmates for quite some time. A month or two ago, he and his father attempted to fix it, and briefly succeeded by replacing a resistor (so I'm told). The amp lasted for about 2 hours of play time before it just quit working again. We're going to open it up and try to figure out what went wrong.
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| Removed the wooden cabinet. This is the equivalent of a circuit in it's underwear. Stay tuned for bare circuits |
Turning over the chassis revealed the problem immediately. Two of the power resistors are scorched, and one is completely missing. There's another less scorched resistor out of frame. We tried for an hour or so to find a schematic for this amp online, but to no avail. This is the closest thing we could find (http://music-electronics-forum.com/attachments/8148d1266759648-mig-50-oem-full-crop-print-landscape.jpg), but the resistors in the schematic and on the board (R34, R27, etc) don't match the schematic. I traced the components by hand to figure out which resistors had burnt out according to the schematic. I found another Mig 50 schematic which the same power supply design which actually listed the power rating for the resistors, and hopefully this is going to work.
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| R34?!? Where are you R34? |
I have every value of 1/8 watt through hole resistors you can buy, but I don't have any of these mammoth 2 and 3 watt resistors. Lucky for me, Digi Key exists, and I found all of the parts I needed, and a few spares for about $7.
Now, we play the waiting game...
