PM80 MKII : Possible add Pre-Out/Main In ?

[IAMRAF]

Hello,

my friend gave me a PM80 MKII amplifier.
I want to use it with my Bose 901 VI but I was not able to do the right required connections.
Is it possible to add Pre-Out / Main In in the amplifier ?
Someone did it ?

Regards

 

[Netlist]

Do I understand that you want to connect the equalizer to the PM80?
You can use the Pre-Out / Main In and also the tape out / tape in.

https://www.crutchfield.com/S-yGb3wedZmWJ/learn/how-to-connect-bose-901-eq.html

 

[IAMRAF]

Hello Netlist,I know normally how to do. I have Bose901 since 1986. (Yes I love it).
The issue is that there is no Pre-Out /Main in on the amp and the selector for REC has no different source selection...

 

[Netlist]

To add a Pre-out / Main-in, you will need the cut this trace and route them to four new RCA's at the back of the case.
Cutting before the 'Direct' switch will disable tone controls and balance, which you probably don't want, and retain the controls if you cut after the switch.

 

[IAMRAF]

Hello Netlist, and thak you so much for your reply.
I'm happy that you confirmed my first idea of how to implement this mod.
If you have possibility, please check the picture attached that I elaborate from the schematics service manual.
Going deeper in the analisys, I found that one possibility is to modify the cable between the Pre-amp PCB and the Amp PCB.
Can you confirm if my idea is correct ?
Thank you for your time.
Best Regards

 

[Netlist]

Perfect, that's the one. 👍
The four new to build RCA sockets should be isolated from chassis to avoid ground loops.

 

[IAMRAF]

Well !!
I'll buy all nececessary components and go.
I'll let you know.
Thank you.
Regards