McIntosh MC-75 in unknown condition, what do I do?

Almarg,

Thanks for the info. Is there a reliable way to check tubes or is this something that really requires a tube checker? The tubes appear to be originals. I suspect the lab bought the amp for some long forgotten experiment then allowed it to sit for decades. The tubes are 3 Telefunkens, 1 McIntosh by RCA and 2 Genelex KT-88s.

The amp has a reasonable amount of surface rust. Nothing that keeps you from reading the labels but far from clean. Any suggestions for cleaning the chrome?

Oddly enough I have a Radio Shack driver from the same pile! It's been modified such that the air displaced by the cone is pumped into a 1" pipe. I'm not at all sure if the amp and the driver were ever used together.

Nsgarch,

Of course I can't say with certainty that the tubes are the original units. I can say with certainty that they are Genelex KT-88s made in the UK (as stated on the tubes). The tops appear quite silvery. The sides look to be somewhat brown. I would also like to clean the tubes as it's clear people have touched them over the years and left some finger prints.

The caps for this model are all inside the base. Any suggestions for testing the caps?

I do appreciate the cautionary comments. I have a reasonable amount of experience working with electronics and some higher voltage stuff. However, my classes seemed to have skipped the section on tube based circuits ;)

I'm not sure I have easy access to a variac but I will check if I decide to plug it in. I also will give Terry a call.

Almarg,
The cleaning/ polish plan sounds like what I had in mind. Brasso and lots of TLC.

Nsgarch,

Thanks for the tips! I don't recall seeing Gold Lion on them. I'll take another look when I'm back in the lab tomorrow.

The chassis chrome is generally good. The top could easily be cleaned without ever touching the printing. The worst parts are the bends in the metal and the back where all the specs are printed. Everything is still 100% readable but hardly clean.

The hardest part of this whole thing is resisting the urge just to try the amp!

IT WORKS!

I've given the amp some TLC over the last few days. I took the lighter fluid advice and cleaned the tubes themselves. I've been carefully using brasso to clean the chrome surfaces. The rust pits are their for good but it's MUCH better. The guts looked good so slowly powered the amp up. It does in fact work. The RCA plug certainly could stand to be cleaned. It's connection to the cheap Y-cable from my mp3 player was iffy at best. The amp drove my MMG to a reasonable level.

I can't say anything about true sound quality at this point as I never feed it a good signal and really, I just have one.

I sure is a pretty thing with some cleanup. It makes me wish I could find a second dumpster 75! I haven't actually figured out what to do with this one. I would like to keep it but it's not well suited for either my MMGs nor my NHT 2.5i's. The cost of a second amp is questionable budget wise, adding new speakers on top of that is a non-starter. It's a bit like being given a Ferrari with a bad transmission. You know it's capable of so much but until you sink the cost of a nice car into the transmission you have nothing but a beautiful garage queen.

Thanks for the help all!