Sovtek mig 50 - Transformer change.

[Poffa]

Hello

does anybody know which replacement transformers i need for my sovtek mig50 tube amp head ?

from schematic it seems as there are 8 connections on the mains trafo - I have - 230 volts on the primary.

the outputs are 4,8 and 16 ohms in 50watts
power tubes are 6l6/5881 - preamps are 12ax7 (I think)

also schematics would be nice
pcb is printed "007"

Appreciate your help

Poffa

[52 Bill]

does anybody know which replacement transformers i need for my sovtek mig50 tube amp head ?

from schematic it seems as there are 8 connections on the mains trafo - I have - 230 volts on the primary.

the outputs are 4,8 and 16 ohms in 50watts
power tubes are 6l6/5881 - preamps are 12ax7 (I think)

also schematics would be nice
pcb is printed "007"

I just worked on one this week. As I recall, they made a few different versions, but all were based on the Bassman/Marshall circuit. If you need to replace a transformer, any Marshall 50w style should work well. There seems to be plenty of room on the chassis to fit what ever transformer you want there. Why do you need to replace a transformer?

[Albert Kreuzer]

Yes, why do you need to replace a transformer? As Bill said, a Marshall 50W will work, but you'll probably have to change the bias circuit. Just look up the according Marshall schematics.

Hope this helps.

Cheers,
Albert

[Poffa]

I'm not sure if I actually need to replace the transformer, but the one that's in the amp looks kind of unoriginal. it don't seem to have the right voltages, as there are resistors at some of the out and inputs. do you know approximate secondary voltages in this amp ?
I'm worried about maybe have copled the rectifier incorrectly.. Measured 340v ac on the solid state rectifier..



Thanks
Frode

[Albert Kreuzer]

Could those resistors be R42, R48 and possibly RV1 (that one looks rather like a cap though)?
HV is around 500V DC or above in these, so 340V AC before the rectifier is in the ballpark.
Even if the PT is not original - in case it works, why replace it with another non-original one?

Cheers,
Albert

[Poffa]

don't think so , as they were soldered directly to power-trafo. took them both of and trafo didn't work - soldered them both onto a small circuitboard and put them in a little box (picture), then the trafo did work again. they are printed - 47mohm, and seem to be connected between phase and common(in series)..
anyways took some pictures of trafo and others .



can also see from schematic that there are 3 diodes.
my amp has only one.

hmm.

Frode

[drewl]

Actually the one diode is for the bias circuit, there's a bridge rectifier (square black thing) for the high voltage.
New Sensor sells Sovtek replacement trannys ( I used a 100w power trans for a build since it was cheap) but you could probably do better tonewise.