Polytone Schematics

[Steve L]

Here are a few hard to find Polytone schematics.

Steve

Polytone 110W (Non-IC) Power Amp Schematic.pdf
Polytone 378 Power Amp Schematic.pdf
Polytone Brute Series Preamp Schematic.pdf
Polytone Mini Brute Preamp Schematic.pdf

[walex]

PA378B PCB Layout

I have reconstructed the layout of the soldering side and the component side of the Polytone PA378B Power Amp from the original printed circuit board and the schematic drawing from murchmusic.com. --> see attachment (PA378B_complete.pdf).

On the second document (PA378B_modified.pdf), I marked a resistor of 2.5 kOhm, that was mounted additionally on the soldering side of my amp. My amp seems to be produced in 1988.
The base of this document is a PDF, that I took somewhere from this forum.

PA378B_complete.pdf
PA378B_modified.pdf

Greetings
Wilfried

[drewl]

Thanks, I usually get a couple of these a year.

[gbono]

If the LM391N-80 is damaged what's your work around? It looks like they (Polytone) issued a "discrete" design of the power amp getting rid of U1. Does the layout that Walex put up work in all the tiny minis?