Altec 1591 Compressor Question

[Johnny1234]

Hi all,
My friend sent me a Altec1591 compressor to try to restore. He had tried some mods on it that obviously failed. I have it almost working right but I think the selector switch is wrong and the schematic is awful at best .
I just wanted to ask if someone with the unit could take a picture of the selector switch.
Many Thanks

 

[Johnny1234]

The thing that is driving my crazy is the schematic shows 3 poles on the switch, and the unit only has 2 poles on the switch.
Also in the off position shouldn't pin F go to ground. A far as I can see there is no contact on the switch that connects to ground.

 

[Johnny1234]

Here is a picture of the switch and the circuit.

 

[MagnetoSound]

According to the schematic, in the OFF position pad F goes nowhere. Pad F is coming from the base of Q10.

Perhaps somebody swapped out the switch, lost their way and then gave up.

The switch wiring looks pretty straightforward. If you can identify all the relevant pads on the board, you can just buy a 3-pole switch and get it back to stock.

 

[Johnny1234]

Thank you,
MagnetoSound

 

[Johnny1234]

Revisiting the Altec 1591 compressor. Since my first post almost a year ago, I did figure out the switch problem. However the unit did not work even remotely correct. I put it on the shelf for a while as I was totally sick of it. Today I made an extender cable and decided to jump back in. Something kept leading me to transistor Q10. Again I was starting to get frustrated. Finally I removed R7...10k ohm and put a 25K pot in its place. Lo and behold when the pot reached around 5K ohm bamm...started working perfectly. Meter zeroed and got lots of compression. Any have any clues why. I know I am changing the operating point of the transistor. Many Beta issue, just curious to know why? A better schematic can be found on the gdiy close topic
https://www.diyaudio.com/community/threads/altec-1591a-output-transformer-questions.353502/