Scott 222 B tube amp

It's normally takes 3 min to 'fill up' caps. This much time I guess is needed.

04-27-11: Samhar
How slowly ... ?
Minutes? Hours?

Hours, perhaps 8 hours or even more, if the piece may not have been turned on for decades.

That allows the electrolytic capacitors to "reform," and can often (depending on many variables) make it possible to avoid having to replace them.

I've had many experiences with 1950's and 1960's tube audio components, as well as 1930's antique radios, where, having done that, it has not been necessary to replace those capacitors.

During that process, temperatures of the power transformer and the electrolytic caps (the ones that are enclosed in cans on top of the chassis, only!!) should be checked by hand periodically, because of the damage possibility that Ralph mentioned. Ideally, ac current draw should be monitored during the process as well, with the voltage not being raised to the next increment unless the current draw is stable for some period of time at the previous increment.

And of course before any of this is done, a check should be performed to verify that there is not a short between ac and chassis. AC leakage to chassis should also be monitored as full voltage is approached.

All of these things can be done with an instrument such as this one, which is what I use. An inexpensive variac and a multimeter would probably be good enough in most cases, though.

The OP may find this thread on vintage audio to be of interest.

Regards,
-- Al

Al

Thank you for the concise answer. Greatly appreciated!!! I've been given a McIntosh MR 71 tuner and don't want to ruin it as I think it's a decent tuner. I'll check the tubes first then power it up.

Thanks again.

Sam

Sam, best of luck with it. That is a fabulous tuner indeed. A few years ago I had one in my main system for a while, that I had repaired for a relative.

Best regards,
-- Al

The face is as stated by Atmasphere, bad filter cans can damage a power transformer. Unless someone has run the thing and determined the caps are ok, which is doubtful given the age of the Scott, I would never power up a unit like that unless you can monitor AC ripple and voltage while slowly running it up on a Variac. Normally, I just replace the caps and if that unit has a selenium rectifier, plan on replacing that too as they all too frequently leak voltage. No one should ever turn an old tube amp on without knowing how long it's been off and when it was serviced last. Finally, the twist lock caps in that unit should probably be replaced with current production single axial or radial caps. They can be installed underneath if there's room for them. That will make a big sonic improvement. The twist lock caps needn't be removed.