After cleaning the dust out of an old SB-221, I pulled out the trusty
POWERSTAT to slowly bring up the amp.
I checked the POWERSTAT with the VOM so I knew where 55 volts were
and especially where 110 volts was. (Amp was received wired for
120V. I have not done anything to the amp other than to dust it
out. It has been sitting for probably 20 years.)
I'm not saying I did this right, but I started at ZERO, turned on the
amp, and slowly brought up the POWERSTAT until the light came on, the
tubes began to glow, and the fan was spinning. I let it sit there
for a couple of minutes and brought it up a little further. The
lights got brighter, the fan spun faster and the tubes glowed nicely.
At about 75%, I got smoke! A whole lot of smoke! POWERSTAT to zero
and I flipped the switch off!
After removing the outer cover, I see where the 1mH choke on pin 4 of
the inside tube (socket N) smoked.
#1 Where can I get a replacement?
#2 What caused the failure (or where do I start looking)?
Dino - K6RIX
dino@k6rix.com
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