I'm trying to track down an intermittent problem in the right channel
whereby the output amplitude changes randomly and in response to PCB
bending and whacking but no cold solder joints are visible that I could
find.

The Radio Shack Web site has the parts diagrams and parts lists
but no schematics.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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Have seen this phenom before on a lot of electronic boards. I believe what
it is , is low quality solder. May appear to look ok under the mag lamp, but
only way to correct it is to remove the solder, and reflow with new solder.
Try doing that to the entire right channel components, first in the finals,
then in the pre amp. Since its a Radio Shack item, could be a rookie Tech
once operated on it, and used low quality solder.

Also, a remote possibility is a fractured leed on a transistor or other
component - while rare, usually you get a condition of full , to zero,
rather than what you describe , which is a more linear progression of change
from what I interpret.


"Sam Goldwasser" wrote in message
...
| I'm trying to track down an intermittent problem in the right channel
| whereby the output amplitude changes randomly and in response to PCB
| bending and whacking but no cold solder joints are visible that I could
| find.
|
| The Radio Shack Web site has the parts diagrams and parts lists
| but no schematics.
|
| Thanks.
|
| --- sam | Sci.Electronics.Repair FAQ Mirror:
http://repairfaq.ece.drexel.edu/
| Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
| +Lasers | Sam's Laser FAQ:
http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| | Mirror Sites:
http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html
|
| Note: These links are hopefully temporary until we can sort out the
excessive
| traffic on Repairfaq.org.
|
| Important: Anything sent to the email address in the message header above
is
| ignored unless my full name is included in the subject line. Or, you can
| contact me via the Feedback Form in the FAQs.

"Techforce" writes:

Have seen this phenom before on a lot of electronic boards. I believe what
it is , is low quality solder. May appear to look ok under the mag lamp, but
only way to correct it is to remove the solder, and reflow with new solder.
Try doing that to the entire right channel components, first in the finals,
then in the pre amp. Since its a Radio Shack item, could be a rookie Tech
once operated on it, and used low quality solder.

Could be even though the soldering looks very good. But this isn't exactly
what you'd call a high-end component.

Only problem is with no schematic and no parts layout, finding it won't be
easy and resoldering the entire PCB isn't something I would look forward to.

Also, a remote possibility is a fractured leed on a transistor or other
component - while rare, usually you get a condition of full , to zero,
rather than what you describe , which is a more linear progression of change
from what I interpret.

Right, not likely.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

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traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
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contact me via the Feedback Form in the FAQs.

Spray clean the R/P switch and check the solder connections all around it
?... also check the small flexible wires where they are soldered to the PB
head.
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


"Sam Goldwasser" wrote in message
...
I'm trying to track down an intermittent problem in the right channel
whereby the output amplitude changes randomly and in response to PCB
bending and whacking but no cold solder joints are visible that I could
find.

The Radio Shack Web site has the parts diagrams and parts lists
but no schematics.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Mirror:
http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ:
http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites:
http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the
excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above
is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

I've seen dirty record / play mode switches cause this (I'm assuming this is
a cassette deck).

Mark Z.


"Sam Goldwasser" wrote in message
...
"Techforce" writes:

Have seen this phenom before on a lot of electronic boards. I believe
what
it is , is low quality solder. May appear to look ok under the mag lamp,
but
only way to correct it is to remove the solder, and reflow with new
solder.
Try doing that to the entire right channel components, first in the
finals,
then in the pre amp. Since its a Radio Shack item, could be a rookie Tech
once operated on it, and used low quality solder.

Could be even though the soldering looks very good. But this isn't
exactly
what you'd call a high-end component.

Only problem is with no schematic and no parts layout, finding it won't be
easy and resoldering the entire PCB isn't something I would look forward
to.

Also, a remote possibility is a fractured leed on a transistor or other
component - while rare, usually you get a condition of full , to zero,
rather than what you describe , which is a more linear progression of
change
from what I interpret.

Right, not likely.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Mirror:
http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ:
http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites:
http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the
excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above
is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

"Mark D. Zacharias" writes:

I've seen dirty record / play mode switches cause this (I'm assuming this is
a cassette deck).

Yeah, I wiggled and cycled that with no effect.

I believe it may be one particular dirty or bad pot and have resoldered it.
I'm keeping my fingers cross. Definitely pushing on its terminals made a
difference. Not positive if that was the primary cause or just affecting
something else.

I hate intermittents.

Thanks.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
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Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

| Only problem is with no schematic and no parts layout, finding it won't be
| easy and resoldering the entire PCB isn't something I would look forward
to.

Just resolder the channel you have problems with. Start from the speaker
jack, and continue backwards till you come to the RP switch, ( I assume the
problem exsists on radio, tape , phono blah blah ?) go far back to the B+
supply(s) for that side too. I once had A Pioneer with a tricky problem like
this - it was a 1970's model, and the board was double sided with pretty
much bare unprotected copper. Turns out one of the feed thru lands developed
a 'cancer' that you could not see much even under the mag lamp.Redrilled it,
soldered in a solid wire, and case closed. That one was a pita.

How about heat and cold spray on some of the solder or even on an IC ?