static on right channel of kenwood receiver
Sharon Leigh
Mine's slightly different, in that it goes away when I turn the balance all
the way left, and my headphones work fine. I cleaned every conceivable
contact and circuit and still have the static. The receiver's 32 years old
so I am suspecting something has died or fried along the way. anyone have
any ideas?
Sofie
Follow the troubleshooting advice I posted regarding the Marantz (it has a
static problem in the LEFT channel)..... first, look for faulty solder
connections, especially around the high heat producing components ... if
that is not the problem then with an oscilloscope and a test signal you
should be able to trace the problem to the faulty components (usually leaky
semiconductors or electrolytics) or problem area of the circuitry. As I
stated in that reply post.... the nice thing about working on stereo
equipment is that you have an identical and properly working LEFT channel
next to the faulty (static) RIGHT channel..... it doesn't get any better
than this.
If, after reading this, you are still not certain how to proceed then you
might be best advise to have a service shop do the repairs for you. There
are usually some shops that will do more of this kind of work than
others.... ask around.
****here is a copy of my above mentioned posting:
First, look for cracked, cold, or otherwise faulty
solder connections near and around the high heat
producing components..... especially in the left
channel circuitry. Since the static is almost
constant you should be able to trace it to a
fairly specific area of the left channel circuitry....
.....an oscilloscope should allow you to easily
find the static problem stage.... start at the
preamp and work your way to the power output
stage. Could be leaky semiconductors or
electrolytics anywhere in the chain.....
The nice thing about working on stereo equipment
is that you have an identical channel to compare
the suspected faulty circuitry with.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
-----------------------------
"Sharon Leigh" <sle...@aol.com> wrote in message
news:VA4Ra.1371$KZ.7...@news1.news.adelphia.net...
bigmike
Lot's of possibilities. Dirty or worn speaker switch contacts, bad relay
(if the old amp uses one) contacts, dried up caps, leaky transistors.
Headphones require very little power to produce sound, so some problems in
the output stage might not show up when using them. By the way, do you have
sound through the bad channel along with the static, or just static?
Sharon Leigh
is that it sounds like a radio station that's not tuned in properly. It's
staticy and garbled.
"bigmike" <big...@cornhusker.net> wrote in message
news:3f14de13$0$24599$9a6e...@news.newshosting.com...
Sofie
This sounds like driver or output stage problems...... bad semiconductor,
leaky electrolytic, open resistor, etc, etc, etc. .... of course it could be
other things too.... including cracked solder connections.
Dust off your O-scope and DMM and start troubleshooting.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
---------------------------
"Sharon Leigh" <sle...@aol.com> wrote in message
news:k4eRa.1876$KZ.9...@news1.news.adelphia.net...
Jeroni Paul
traced to a preamp module (an active filter) using an LM387 - bias points
right but a hiss noise was emanating from the LM387 ... a capacitor was
visibly broken, a 2.2nF cap that apparently smoothed out the amp feedback
loop. Replaced and problem cured.
Sofie wrote in sci.electronics.repair:
> Sharon Leigh:
> This sounds like driver or output stage problems...... bad
> semiconductor, leaky electrolytic, open resistor, etc, etc, etc. ....
> of course it could be other things too.... including cracked solder
> connections.
> Dust off your O-scope and DMM and start troubleshooting.
>
Jeff
Jeff
"Sharon Leigh" <sle...@aol.com> wrote in message
news:k4eRa.1876$KZ.9...@news1.news.adelphia.net...
Sofie
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
snipped:
"Jeff" <frontline_...@NSatt.net> wrote in message news:31lRa.57999
> Have you swapped the speakers?
> Jeff
---------------------
Jeff
Well if headphone works OK?
At least on the old ones that used to be the first question.
Ever seen a headphone resistor burnt open? (yep, twice)
So if it hums dont leave it plugged in.
Some of those old elements could realy take some power.
Jeff
"Sofie" <so...@olypen.com> wrote in message
news:vhbooh6...@corp.supernews.com...
Sharon Leigh
terminals. Guess what? Same problem.
"Jeff" <frontline_...@NSatt.net> wrote in message
news:31lRa.57999$0v4.3...@bgtnsc04-news.ops.worldnet.att.net...
Sofie
OK then...... the simple stuff is OK..... now the next step is for you to
troubleshoot the circuitry as described in all the reply posts that you have
received on this newsgroup. If you can do some of the technical stuff at
your end.... and you still can not fix it, you should post the ALL of the
results of your troubleshooting efforts, inspection and resoldering of
questionable connections, voltage readings, component tests, and if you can,
signal tracing with an oscilloscope..... if you can be our eyes, ears, and
hands, we might be able to give you some additional suggestions.
If, after reading all the reply posts, you still are not certain how to
proceed, and lack the test equipment, tools, basic electronics knowledge and
minimum repair experience needed, you might be best advised to take your
receiver to a service shop for a safe and proper repair, or at the very
least you should obtain a repair cost estimate so you can make an
intelligent repair decision with facts instead of internet guesses.
There are some shops that really specialize fixing the older stereo
equipment.... ask around.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
----------------------------------
"Sharon Leigh" <sle...@aol.com> wrote in message
news:WboRa.3034$KZ.11...@news1.news.adelphia.net...
bigmike
> Yes, I swapped speakers. I also moved the set over to the B speaker
> terminals. Guess what? Same problem.
>
the cause of that problem. Any switch on the front of that unit can have
dirty contacts and cause static. Be sure to try them all to see if they have
an effect, including the tone controls. They all have seperate contacts for
each channel. If it's not the switches, then I would check the board for any
bad solder joints. After that, it requires basic troubleshooting skills, a
few basic pieces of test gear, and some basic electronic skills. By the way,
what does this static sound like? Is it like a hiss, or is it a frying
sound? A frying sound tend to point one toward a bad transistor(s) in the
output stage. Maybe you could explain the sound a little better.
Sharon Leigh
the speaker terminals. No obvious burn marks or smells. I really don't think
the receiver is worth the effort to fix unless it's something fairly simple,
which it apparently isn't. I am, however, going to go through the boards one
more time with a magnifying glass to see if there's something I missed.
Thanks for your help everyone.
"bigmike" <big...@cornhusker.net> wrote in message
news:3f16179f$0$24529$9a6e...@news.newshosting.com...
bigmike
> I have done a pretty thorough visual inspection. Don't see any bad solder
at
> the speaker terminals. No obvious burn marks or smells. I really don't
think
> the receiver is worth the effort to fix unless it's something fairly
simple,
> which it apparently isn't. I am, however, going to go through the boards
one
> more time with a magnifying glass to see if there's something I missed.
>
> Thanks for your help everyone.
>
transistor or cap can be defective without any outward signs of a problem.
Something you might want to try is tapping on the board lighting with the
end of something plastic, like the reverse end of an ink pin, while the amp
is on. See if you hear the noise problem change. A bad solder joint could be
just about anywhere on the board, not just at the speaker connections, and
cause the problem. If you have limited abilities at troubleshooting, then
it's true, you will have to make a judgement call on whether it's worth
repairing or not. But, if your interested in learning more about
electronics, this amp would make a nice place to start.
bigmike
"bigmike" <big...@cornhusker.net> wrote in message news:...
Sharon Leigh
electronics (I haven't touched an oscilloscope or ohmmeter in about eight
years, since my days in computer school), but I fear I don't have the
patience for big problems...:)
"bigmike" <big...@cornhusker.net> wrote in message
news:3f1647fa$0$24508$9a6e...@news.newshosting.com...
bigmike
> Thanks, Mike, I will try that. I am trying to learn more about audio
> electronics (I haven't touched an oscilloscope or ohmmeter in about eight
> years, since my days in computer school), but I fear I don't have the
> patience for big problems...:)
>
I understand. The one thing in your favor is those old Kenwood amps were
built well. If you decide to give it a go, let us know, and we will try to
help you further...
Sofie
Don't just toss it yet, what if the service shop repair price is less that
you think ?
If you are not certain how to proceed with the troubleshooting and don't
have the needed equipment and repair experience you probably won't be able
to successfully do the task...... visual observation alone won't be enough.
....BUT, there are shops out there that specialize in fixing this older
stereo equipment. My shop regularly does this kind of service and we keep
busy doing it........ the problem you describe may not necessarily be a
big deal to repair.... or it could be ???
Do yourself a favor and at least take it into a shop for a repair cost
estimate. Many smaller shops will give you an over-the-counter "rough idea"
what it may cost to fix ...... that is what my shop does with a lot of the
older equipment. A trained tech that has experience with the older
receivers can take a quick listen, make a few quick checks with the meter
and usually come up with a "fairly" accurate evaluation in a short
time....... then, with a repair cost number, you can make an intelligent
repair decision...... but without a repair cost number you would only be
guessing like all of us are now doing on this newsgroup.
My shop sees a fair number of these things that are fairly inexpensive to
repair, so don't throw it out yet, get the facts first.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
"Sharon Leigh" <sle...@aol.com> wrote in message news:TEvRa.3600
OldguyTeck
fancy or powerfull.. then just make up a probe [be shure to use a blocking
capacitor in series] and probe arround starting from the output... I have
found problems very easily useing this methode..
It's a little easier than useing the ole scope.. But if your good with the
scope.. and inject a tone into the amp of your unit you can find the
distortions easily as well.
Good luck on it...
Ed Oldguyteck
"Sharon Leigh" <sle...@aol.com> wrote in message
news:TEvRa.3600$KZ.12...@news1.news.adelphia.net...
Jeff
DC voltage across output when noisy?
Model? (strange the headphone would be OK)
Unless its only distorted/noisy when loaded.
Jeff
"Sharon Leigh" <sle...@aol.com> wrote in message
news:WboRa.3034$KZ.11...@news1.news.adelphia.net...
Sharon Leigh
It's a model 2120. It does have a pre-amp output, but I didn't test it. I'm
not really sure what I need to do.
"Jeff" <frontline_...@NSatt.net> wrote in message
news:y9FRa.59888$3o3.3...@bgtnsc05-news.ops.worldnet.att.net...
jakdedert
it's noisey as well. However, since you stated that the headphone output
was clean (right?), likely the problem is later in the signal chain. If
not, one way to check that output is to record something from it on tape and
listen to the playback on known-good gear. Another way is to hook up a
cheap set of computer speakers there. You will need the a RCA to mini
stereo plug adaptor to do so....
jak
"Sharon Leigh" <sle...@aol.com> wrote in message
news:YzJRa.4665$KZ.14...@news1.news.adelphia.net...
Jeff
using a known good RCA cable feed the suspect side
to the good channel, if the good channel stays quite then
the problem is in the output section. (right fed to left)
Make sure unit is off and volume is down when making
these connections.
Note: tape out is not feed thru tone sections.
So it must be pre/main RCA connections only.
I do not have the service manual to check.
Jeff
"Sharon Leigh" <sle...@aol.com> wrote in message
news:YzJRa.4665$KZ.14...@news1.news.adelphia.net...
Jeff
amp. It will be connected before pre/main in/out if the
unit has that.
Jeff
"jakdedert" <jde...@bellsouth.net> wrote in message
news:grXRa.697$wv6...@fe03.atl2.webusenet.com...
jakdedert
although the advice in your next post is sound. I was referring to
monitoring the pre/main jumpers. The idea below of crossing those in/outs
is a much more simple, elegant way to do so, though.
jak
"Jeff" <frontline_...@NSatt.net> wrote in message
news:06%Ra.61661$0v4.4...@bgtnsc04-news.ops.worldnet.att.net...
Jeff
Jeff
"jakdedert" <jde...@bellsouth.net> wrote in message
news:GLeSa.3258$wv6...@fe03.atl2.webusenet.com...