"Richard Knoppow" wrote in message
...
"Nelson Gietz" wrote in message
...
...hardly qualifies as a boatanchor I guess, so forgive
me for this...
I have an SPR4 I bought some time ago, and believe
it's been idle for some years. Anything I should watch
out for, as in electrolytic caps, before I fire it up?
Cheers,
Nelson
Filter caps are always questionable. You can measure
them for shorts before applying power. Also, inspect them
visually, any cap with indications of leakage or bulging
should be replaced before applying power.
Another good precaution is to bring the equipment up on
a variable transformer like a Variac. I have a metered
Variac which will indicate a high current condition quickly
enough to prevent burning out power transformers but a non
metered one will do. Even through the filiments may not be
fully powered up the rectifier will still pass enough
current to indicate bad caps.
Despite their bad reputation electrolytic caps are
pretty long lived, even when not powered up. An electrolytic
depends on having voltage across it to maintain the thin
film which forms on electrode. The film will disappear given
long enough without the voltage but it may take many years.
The film will usually re-form after voltage is applied.
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Richard Knoppow
Los Angeles, CA, USA
Thanks Richard. This is a 12 volt radio, Drake's first solid state
product apparently. I'll run it up on a variac just in case. Don't
relish the prospect of tracking down a toasted transistor, since I'm
more familiar with tube circuits, so I'll try to err on the side of
caution.
Cheers,
Nelson