"Paul" wrote in message
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"Arfa Daily" wrote in message
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"Morse" wrote in message
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"Paul" wrote in message
ups.com...
I was having trouble with CDs skipping on the factory radio in my 94
Trans Am..... How can I determine the polarity of the capacitors?
The
level of disassembly needed to get at these parts does not lend itself
to powering the unit up and measuring voltage accross the cap's.

At least some if not all of those caps should have the negative leads at
ground potential, so use your multimeter on Ohms or continuity setting
and find out which lead is negative that way, no need to power the unit
up. Or simply visually trace the cap lead to the ground plane on the
PCB.

Morse


What do you consider to be a "high" value for ESR on these caps ? 4u7 at
6.3v will likely have a correct ESR value of 15 ohms or more. You should
also be careful when replacing small electrolytics like this, that you
only replace with exact like for like. On many Sony HiFi CD players from
a few years ago, the CD servo board had several small caps of very
similar description to the ones you have there. One in particular used to
leak. If you tried to replace these caps with anything other than the
original low voltage surface mount types, the servos would never work
again.

Arfa

The ESR measures 50 ohms on my meter.
Typically fresh 4.7uF caps measure about 2 ohms on my meter.

Thanks for the warning that generic replacements might cause trouble.
So far, no luck finding original type replacements from Mouser, etc.
Don't suppose you can point me to a source???

Paul
Hi Paul. Agreed that a *standard* electrolytic of that value will read a
couple of ohms, but I've found that these very low voltage ones on the SM
bases tend to read much higher than that, even when new, although I think I
would, like you, consider 50 ohms to be too high. Just something to be
aware of for the future. As far as where to get them, I'm afraid I'm the
opposite side of the pond here, so not much help on that score, except to
say that I don't have any problem getting low voltage SM electrolytics
here, allbeit with a slightly larger footprint than the ones Sony
originally fit. I'm sure there must be others on here that can help with
that.

Arfa