Pyle PLRG23
I had the unit out, on the bench, troubleshooting no FM lock. AM was
fine. I had power/ground connected to the plug, which also carries the
speaker circuits. These are female connectors.The radio was on, at min
volume. I did not have speakers connected. During initial testing with a
logic probe in the tuner section, the radio shut off. I found high
current draw in the power supply, and turned it off immediately. On
checking, the radio would not power up, and drew 10A from the supply. I
determined the monolithic stereo output chip (TDA-burn) was dead short
to ground. The heatsink was quite hot.
Q:
Could the chip fry from no load connected? I'm certain I didn't short it
at the plug, and wasn't even in the output stage with my tests.
JR

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Home Page: http://www.seanet.com/~jasonrnorth

"JR North" wrote in message
news
Pyle PLRG23
I had the unit out, on the bench, troubleshooting no FM lock. AM was fine.
I had power/ground connected to the plug, which also carries the speaker
circuits. These are female connectors.The radio was on, at min volume. I
did not have speakers connected. During initial testing with a logic probe
in the tuner section, the radio shut off. I found high current draw in the
power supply, and turned it off immediately. On checking, the radio would
not power up, and drew 10A from the supply. I determined the monolithic
stereo output chip (TDA-burn) was dead short to ground. The heatsink was
quite hot.
Q:
Could the chip fry from no load connected? I'm certain I didn't short it
at the plug, and wasn't even in the output stage with my tests.
JR


Under normal circumstances, I would have said absolutely not, but strangely,
today, I was discussing exactly this with a colleague, who installs and
repairs car entertainment kit for a living. I was picking up a large Sony AV
amp from his shop for repair, and he said that it had symptoms of output
failure, and he thought that this was most likely because the owner did not
use the front channels on it, only the surround ones, so did not have any
load connected to those fronts. I expressed doubt at this, telling him that
the general rule of thumb was that semiconductor outputs didn't like shorts,
and valve outputs didn't like opens. but then he told me that he sees car
radios all the time, that have the sides blown out of the output ICs, caused
by the speaker connections being left open, when the owners use external
blaster amps, driven from low-level line outputs, rather than from the
speakers.

So, based on that, and the fact that he is generally good at what he does,
and knows what he's talking about, I would have to revise my opinion of your
question, and say "yes, very possibly ... "

Arfa

Greetings..

Just a crazy question but, WHY were you in there with a "logic
probe" in the first place?

Granted, after repairing HF, VHF and UHF radios for years in the
amateur service I realize the computerization of radios these
days, but I'm just curious.

Do you have electrical schematics for this unit? Ultimately a
service manual for this type of situation?

No?

Simple solution, IF you want to pay for correcting the issue -
back to the certified manufacturer repair depot. Otherwise, scrap
or shotgun guesswork (and associated expense) without schematics,
voltage levels, waveform diagrams and alignment procedures.

Cheers,
Mr. Mentor



"Meat Plow" wrote in message
...
| On Fri, 25 Apr 2008 15:32:05 -0700, JR North wrote:
|
| Pyle PLRG23
| I had the unit out, on the bench, troubleshooting no FM lock.
AM was
| fine. I had power/ground connected to the plug, which also
carries the
| speaker circuits. These are female connectors.The radio was
on, at min
| volume. I did not have speakers connected. During initial
testing with a
| logic probe in the tuner section, the radio shut off. I found
high
| current draw in the power supply, and turned it off
immediately. On
| checking, the radio would not power up, and drew 10A from the
supply. I
| determined the monolithic stereo output chip (TDA-burn) was
dead short
| to ground. The heatsink was quite hot.
| Q:
| Could the chip fry from no load connected? I'm certain I
didn't short it
| at the plug, and wasn't even in the output stage with my
tests.
| JR
|
| Getting my start in mobile audio some seeming centuries ago, I
would say
| yes it is possible. I was taught to always load the outputs
regardless.
| I feel for you. I've spent many hours righting accidental
wrongs and
| wrongs that in your case appeared secondary to the cause for
repair and
| weren't justified as billable.

I'm no car stereo expert, but-
Common failures in car stereos (besides shorted outputs) are vibration
induced opens in solder joints, particularly through boards connected
at 90° . These are easy to find with simple tools. Thats what I was
doing initially, hoping for a quicky. This isn't the sort of radio one
invests too much time in.
JR


On Sat, 26 Apr 2008 08:55:53 GMT, "dBc"
wrote:

Greetings..

Just a crazy question but, WHY were you in there with a "logic
probe" in the first place?

Granted, after repairing HF, VHF and UHF radios for years in the
amateur service I realize the computerization of radios these
days, but I'm just curious.

Do you have electrical schematics for this unit? Ultimately a
service manual for this type of situation?

No?

Simple solution, IF you want to pay for correcting the issue -
back to the certified manufacturer repair depot. Otherwise, scrap
or shotgun guesswork (and associated expense) without schematics,
voltage levels, waveform diagrams and alignment procedures.

Cheers,
Mr. Mentor



"Meat Plow" wrote in message
...
| On Fri, 25 Apr 2008 15:32:05 -0700, JR North wrote:
|
| Pyle PLRG23
| I had the unit out, on the bench, troubleshooting no FM lock.
AM was
| fine. I had power/ground connected to the plug, which also
carries the
| speaker circuits. These are female connectors.The radio was
on, at min
| volume. I did not have speakers connected. During initial
testing with a
| logic probe in the tuner section, the radio shut off. I found
high
| current draw in the power supply, and turned it off
immediately. On
| checking, the radio would not power up, and drew 10A from the
supply. I
| determined the monolithic stereo output chip (TDA-burn) was
dead short
| to ground. The heatsink was quite hot.
| Q:
| Could the chip fry from no load connected? I'm certain I
didn't short it
| at the plug, and wasn't even in the output stage with my
tests.
| JR
|
| Getting my start in mobile audio some seeming centuries ago, I
would say
| yes it is possible. I was taught to always load the outputs
regardless.
| I feel for you. I've spent many hours righting accidental
wrongs and
| wrongs that in your case appeared secondary to the cause for
repair and
| weren't justified as billable.