Powering Up Mc 75's

[Toxicant]

Hello all,

I just got a pair of MC75's that were overhauled about 5 years ago. They have been sitting for 3 years now and I was wondering if I need to do the variac thing or not before using them.

If so, I'll use the light bulbs. Does anyone know what watt bulb to start with and how long do you have to power the amp with each different bulb?

Thanks,

Ron

[Guest " "]

I use variac's but know that a lot of folks use light bulbs....until an expert answer comes along, the below link may help start the thinking process and raise some questions.

http://www.antiqueradio.org/dimbulb.htm

[NOSValves]

I'd say with the value of a set of MC-75's I'd suggest spending a $125 and purchase a variac or have a qualified technician bring them up... Here is what I'd do at the very minimum. I'd also do some pre qualifying under the chassis before ever putting juice to them but those instructions would take more of my time then I can spare.

First test every single tube in the amps..... then clean all tube sockets and tube pins and controls with Caig D-5 contact cleaner.

Then setup the variac and set it to 50VAC also attach a set of cheapo speakers... plug the amp in and let it run for 2 hours at 50 volts... if no smoke or apparent strange things happen raise it to 65VAC for an hour.... then 75VAC one hour, then 85V one hour, then 100VAC one hour. At this point you can hook up a CD player (have the level control set to zero when plugging in source)...then after plugged in turn it up the level controls you should hear clear music... let it play for 3 or 4 hours at low volume then raise the it to 110VAC and then 120VAC.......if it passes all that your some what safe....

This advise is dependant on just how well they were overhauled.... One guys description of overhaul is replacing a couple bad parts.... To me an overhaul means about 30 parts per amplifier....