H
Halfgaar
Hi,
I've got a very annoying intermittent-failure problem with my 25 year old
Kenwood KR-4070 receiver. I think some 6 years ago, my parents gave it to
me because it had failed. The output would drop, reappear, drop, reappear,
etc. Before I got it, it was sent in for repair first. They couldn't find
anything wrong with it, it just so happend that it was in working order
when in the repair shop. It worked for a while longer at home, but
eventually, no sound came from it at all anymore. That's when they gave it
to me. I used the tuner of it for quite some time, until someday I decided
to test whether the amplifier worked again. It did. After that, it had
worked for years. Then, it didn't work for a few days, and after those
days, it worked fine again for years. It's having the same problem again
now.
When it fails, it sounds just when like you shut it off. Shutting it off
procuces a "plop". When it starts to work again it also sounds like it is
switched on, a similair "plop" is audible. Both speakers and headphone
outputs are affected, and always both the left and right channel, never
either left or right. When giving it a signal, a faint distorted output is
audible when the volume is at maximum.
Because of the symptoms, I am inclined to think that power to the pre-amp
keeps failing. But, I am far from an expert. AC powerinput to the pre-amp
is present all the time.
Is it reasonable to think that it is a mechanical problem (like bad
connections or cold-solderjoints) as suppose to for example dried out
electrolytic capacitors, seeing as how the problem started some 6 years
ago? I already re-heated almost every solderjoint of what seems to be the
pre-amp. It didn't work.
Also, on www.repairfaq.org I read that the signal can be traced by a wet
finger. How exactly do I go about that? When I've reached a point after the
failure-point, should that be audible in the output? Also, is it safe to
touch all parts except those of the power-supply (which has it own PCB),
without shock-hazzard?
TIA
Halfgaar
I've got a very annoying intermittent-failure problem with my 25 year old
Kenwood KR-4070 receiver. I think some 6 years ago, my parents gave it to
me because it had failed. The output would drop, reappear, drop, reappear,
etc. Before I got it, it was sent in for repair first. They couldn't find
anything wrong with it, it just so happend that it was in working order
when in the repair shop. It worked for a while longer at home, but
eventually, no sound came from it at all anymore. That's when they gave it
to me. I used the tuner of it for quite some time, until someday I decided
to test whether the amplifier worked again. It did. After that, it had
worked for years. Then, it didn't work for a few days, and after those
days, it worked fine again for years. It's having the same problem again
now.
When it fails, it sounds just when like you shut it off. Shutting it off
procuces a "plop". When it starts to work again it also sounds like it is
switched on, a similair "plop" is audible. Both speakers and headphone
outputs are affected, and always both the left and right channel, never
either left or right. When giving it a signal, a faint distorted output is
audible when the volume is at maximum.
Because of the symptoms, I am inclined to think that power to the pre-amp
keeps failing. But, I am far from an expert. AC powerinput to the pre-amp
is present all the time.
Is it reasonable to think that it is a mechanical problem (like bad
connections or cold-solderjoints) as suppose to for example dried out
electrolytic capacitors, seeing as how the problem started some 6 years
ago? I already re-heated almost every solderjoint of what seems to be the
pre-amp. It didn't work.
Also, on www.repairfaq.org I read that the signal can be traced by a wet
finger. How exactly do I go about that? When I've reached a point after the
failure-point, should that be audible in the output? Also, is it safe to
touch all parts except those of the power-supply (which has it own PCB),
without shock-hazzard?
TIA
Halfgaar
