I read it's best to run a dim bulb tester or use a variac to bring voltage up slowly to help reform caps that have been sitting. Dim bulb tester helps if there is a short, the bulb will take the load instead of the circuitry. At least from what I have read that's how it seems... I'm not necessarily beating myself up as much as I should have done some more research on starting up an old amp before powering it up all the way. I'm just sad she popped like a fire cracker..
You are correct. It is best to bring gear that has been sitting up slowly with a Variac. You usually get away with it, but not always. It is an essential part of any repair desk.
I have one just like this.
I learned the hard way as a kid. I started up an old Sobell radio of my late grandmothers, and the power supply cap exploded on turn on, peppering me with shrapnel. I was lucky not to be badly hurt.
So yes, when I obtain an older unit I always bring it up on a my Variac, slowly and cautiously.
I would just replace those two components. There are lots of Variacs to be had on eBay for little money.
After your repair I would bring it up very cautiously on the Variac.
This problem of caps exploding after not being used for a long time, is well known.
Think I just found my amp on another forum... it was purchased as is and I expected it may have some issues. I was not able to audition this amp because now I'm learning that the owner knew this thing was blowing up and did not tell me about his findings...
You can google B&K 200.7 blowing caps and find the thread on the other forum. I was told it was working when it went into storage and its current condition is unknown since he did not have the equipment to test it...
I'm not mad but do value honesty which I feel I was not given.
I think your major problem was not researching the amp before hand. Not an amp I was familiar with. However it was a disaster from day one apparently now find.
Not only does it spectacularly blow those Tinatalum caps with abandon, but worse the output MOSFET devices become leaky and the units are known for variable DC off set as high as 70 volts. I get the impression there is no DC offset protection so they are known for burning up speakers.
Those output devices are no longer available.
My strong recommendation is not to repair that amp, but send it promptly to the recycling center.
The sad fact is that will be your cheapest solution, as if you persist more likely than not you will be out more than the cost of that amp.
In future remember that when buying second hand it is easier to spot duds than buying new. Old units have a paper trail and your unit has a disaster trail in its wake.
