MAC 1700 mystery capacitor

[cdawson]

Hi all,

I'm beginning a restoration of a non-functioning MAC1700 that I inherited from my dad years ago. I think I'll start a thread or blog of the process once I really get going. For now I'm working on assessing what needs to be done and compiling a parts list for re-capping. I found a capacitor on the pre-amp PCB that is not in the schematic that I have, and I can't figure out what it does. It looks original. It's a tantalum (1uF 20V I believe). It is in parallel with R147/148. I've attached a picture of the PCB and of the relevant schematic.

Has anyone else come across this? I'm not sure what it's for, so I'm not sure what to do with it. Should I replace it? Remove it? It's a 40-50 year old tantalum so I'm hesitant to just leave it.

Thanks!

 

[smartin53]

That's fairly common. Double check that your service manual matches your serial number. McIntosh continually made adjustments to most of their products based on feedback and experience through their sales life. Most of the time they would release a new service manual indicating the changes though I know a few instances where an incremental change was done and only a service bulletin was released instead. As for the cap itself, I've personally not messed with those little ones most of the time but it likely would not do any harm if you just replace it with a modern film or electrolytic cap of the same spec.