This monster of a receiver (a Pioneer SX-950, the size of a small Korean
car) was brought to it's subatomic knees by the tiny 2.2uf tantalum cap
(also attached).

The cap was in the tone control circuit. The problem was that any time you
had the receiver set up for 'normal' operation (tone controls in, filters
out) it would never allow the protection circuit to turn the amp on. If you
took the tone circuits out of the loop, or if you turned on the 'low'
filter, then the protection circuit would turn the amp on. Turning either of
those switches to the other position caused a very loud pop and the
protection circuit cut in.

I had this thing sitting on a shelf for literally a couple years. After the
first year, I bought a service manual for it. Took another year (and change)
before I got to scouring the schematics to find the one component (I pretty
much knew it was a cap) that could cause that problem. A few days ago, I
found it (on the schema). The next day, I got brave enough to tear the beast
down and replace the cap. I replaced it's brother in the opposite channel,
too.

This cap has a clear identity issue.. It thinks it's a 4.4K resistor..

Receiver works pretty well now.. but I do have to tear it down again/some
more to clean all the program switches.

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Say no to institutionalized interference.
Just say NO to HD/IBOC!

This isn't criticism (no way), just a question...

Do you think this was a rational repair, or was it a matter of luck?

I'd like to hear a bit about how you finally decided (or discovered) that
this cap was the problem.

"William Sommerwerck" wrote in message
. ..
This isn't criticism (no way), just a question...

Do you think this was a rational repair, or was it a matter of luck?

I'd like to hear a bit about how you finally decided (or discovered) that
this cap was the problem.


Very much a rational repair. I pride myself on my troubleshooting skills.

Upon observing what happened as I kicked the filters/tone controls in and
out, it was easy to surmise that it had to be either the tone control
circuit or the first stage of the power amp, and that it had to be a cap.

Digging into the schematic I found that there was only one active component
per channel in the tone control circuit, and that only one cap could cause
the same problem with either of the two switches in the positions that
caused the problem.

Brenda Ann wrote:

"William Sommerwerck" wrote in message
. ..
This isn't criticism (no way), just a question...

Do you think this was a rational repair, or was it a matter of luck?

I'd like to hear a bit about how you finally decided (or discovered) that
this cap was the problem.


Very much a rational repair. I pride myself on my troubleshooting skills.


Good for you Brenda. that ids the only way to learn what is really
causing problems, and over time it lets you develop a skill set that
will let you fix almost anything.


Upon observing what happened as I kicked the filters/tone controls in and
out, it was easy to surmise that it had to be either the tone control
circuit or the first stage of the power amp, and that it had to be a cap.

Digging into the schematic I found that there was only one active component
per channel in the tone control circuit, and that only one cap could cause
the same problem with either of the two switches in the positions that
caused the problem.


Those Japanese tantalums were irritating. I had 8,000 identical
Jerrold cable TV boxes that used a 3.3 µF 35 volt Japanese tantalum
across the tuning voltage to the RF module that had at least a dozen
failure modes. The worst was an intermittent leakage that cause drift,
but only when it felt like it. I think part of the problem was the way
they were installed, with some strain on the leads where it was wrapped
around a feedthru and a ground pin, with very short leads.


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The crazy, and the insane.
The first sign of insanity is denying that you're crazy.

"Brenda Ann" wrote in message
...

"William Sommerwerck" wrote in message
. ..

This isn't criticism (no way), just a question...
Do you think this was a rational repair, or was it a matter of luck?
I'd like to hear a bit about how you finally decided (or discovered) that
this cap was the problem.


Very much a rational repair. I pride myself on my troubleshooting skills.

Upon observing what happened as I kicked the filters/tone controls in and
out, it was easy to surmise that it had to be either the tone control
circuit or the first stage of the power amp, and that it had to be a cap.

Digging into the schematic I found that there was only one active
component
per channel in the tone control circuit, and that only one cap could cause
the same problem with either of the two switches in the positions that
caused the problem.

That's what I thought (given that, as you said, flipping the switch
activated the speaker protection -- which suggested a DC offset somewhere).
It just seemed odd that it took so long.

PS: The last line of my preceding post was meant as a neutral statement, not
as a subtle put-down.

"William Sommerwerck" wrote in message
. ..
PS: The last line of my preceding post was meant as a neutral statement,
not
as a subtle put-down.


No biggie. The reason it took so long was because I had concentrated on
other things, all the while leaving this on the shelf. It just wasn't even
on my priority list. A few days ago, I just decided that I wanted it up
and running, so I had something with a real honest power amp to hook into
our Bose 301's. Besides, like I said, it's as big as a small Korean car..
and will look impressive there under our big screen. (I think it's the
only receiver that could even begin to hold that beast)