Polytone Mini Brute lll, lV, M-PA schematics

[forthejazzman]

Hi,


I like playing guitar and messing around with electronics so once a year i buy myself a defective amp.

A few weeks ago i bought a defective Polytone Mini Brute lll, lV, M-PA.

Here's the damage report:

When turned on the amp produces a loud hum
The bridgerectifier was blown (explains the hum)
Some wires have molten isolation
Someone replaced the powertransistors
Some parts on the mainboard are missing

So i'm looking for some schematics or some pictures of the board.
Can somebody help me?

[52 Bill]

We've discussed a few Polytones here in the past and there have been a few schematics posted for various models. Have you searched the forum for yours?

Polytones used similar preamps with a couple of different power amps through the years. The main difference in the power amp designs was the use of an LM391 driver chip during the mid-late 1970's. How old is your amp and which power amp do you have?

[forthejazzman]

Hi Bill,

Mine is one with the LM391 in the poweramp so it must be late 70ies. I found a schematic of the older models. The amp's serial number is P 6415.
The power amp circuit board has the inscription PA 378A.
My main problem is the missing parts.

Thanks for your help!