Sovtek MIG50H (detailed)

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Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 17:28

I have a slightly better scan of the schematic than the one usually found on the net. If you want an even more detailed scan, please send me a message.
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 17:33

My particular amp (stock) differs from the schematic in several ways.

When there is nothing plugged into the high gain input, the screen of gets connected straight to earth without going through R10. There is another connection in green (on the enclosed schematic) which differs, as well as two extra resistors, and some with differing values.

I have also noted the correct fuse values and the AC voltages coming from the transformer.
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Last edited by Sir Fayzalot on 27 Jul 2018, 17:35, edited 1 time in total.
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 17:34

There are two resistors in the heater circuit, they are not on either schematic.
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 17:50

Here is the preamp section. Note that R52 is really a capacitor and it has a capacitor symbol on the schematic as well.

(C)R52 and C5 were originally blue Russian caps, and R4 was originally a reddish brown Russian resistor, They are not stock.
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 17:55

Here is the power amp section. Note that the black filter caps are not original. The amp came with Illinois Capacitors there (really).
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 18:02

Detail around the power valves. Note that the 15K ohm resistor is stock, not Russian and not on the schematic (I bought this amp new).
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » 27 Jul 2018, 18:04

Line output. I tried to record from this years ago, without success. I may try again.
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » Today, 09:10

I am not getting any signal out of the line output. I tried a 4-track cassette, a computer, and no signal. I checked the cable each time by plugging my guitar straight into it, and there was a signal that way.

I checked out the resistors earlier and resoldered them. No signal and I have never gotten any signal, as I tried this many years ago as well.

Anyone have any idea as to how this is supposed to work?

I guess I'll check the connections again later when I decide to open it up again, but I have a feeling I've done this before. I guess it's just as well that it doesn't work because I need an extra hole for mods, but it still bugs me.

-------

Another thing I wanted to point out about this amp is the cathode resistors. One was fried as in the above pic, and the other measures about 90K, which bumps the plate voltage to over 300V. Right now I have a long plate valve in there, but I'll put in another of closer value so I can put whatever valve I want in there.
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Re: Sovtek MIG50H (detailed)

Postby Sir Fayzalot » Today, 12:49

Sir Fayzalot wrote:Another thing I wanted to point out about this amp is the cathode resistors. One was fried as in the above pic, and the other measures about 90K, which bumps the plate voltage to over 300V. Right now I have a long plate valve in there, but I'll put in another of closer value so I can put whatever valve I want in there.

A 100K resistor is what I meant, if it's unclear.
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