[ARC5] Resistance BC-453, BC-454

[David Stinson]

Good Morning, Chris.
I did not see the photo of the resistance numbers.
Had I seen them, my advice would have been different.

No matter what kind of instrument you use,
0 Ohms on your B+ buss is going to be a short
and you should resolve that first.  Did I read correctly,
that both of these receivers display the same
short readings?  That does make me suspect
something wrong with either the test instrument
or the test procedure, or an error in the
refurbishing process.

There's a quick and non-destructive way to tell
if that short is "real."  Do you have an old
"wall wart" power supply laying around that will
source 9 to 20 Volts or so, around a hundred milliamps?
They're very common.  Most households have them
in "junk drawers" from when cheap electronics
failed.   Let's say you have one for 9V good for
around 100 Mills, which is very common.

FIrst- remove the screws from the bottom
of the 5 uFd filter cap and insulate it from
the chassis or, if you replaced it externally,
disconnect the negative end.
Otherwise, that cap will load-down your
test supply voltage.
Put your volt meter across the little supply, then
touch it to the B+ buss.  If the short is "real,"
the supply voltage will immediately drop to zero
and stay there.
(might even blow the wall-wart, but no loss there).
You can also do this with a couple of 9V batteries.
Even with such a low voltage and current source,
don't leave it connected longer than the
few seconds needed to get the reading.

If you find the short to be "real" and you can't
find anything with a thorough visual inspection,
the advice to study the B+ distribution and
"divide and conquer" the branches individually
is good.  Also- pull the IF cans and coil pack.
Shorts in them are not unknown and it's a
quick check.  If the short goes away,
put them back one at a time until you
find your "bad boy."

GL OM ES 73 DE Dave AB5S



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