Help on JVC EX-TD55R - no sound

[Bruno Willi]

Hi,

my JVC EX-TD55R (a compact stereo system) works fine, just without any
sound coming out...

There are two relays on the amplifier-pcb. The always 'clicked' when
the thing was switched on - no they keep silent. There are some big
capacitors (2x 2200ľF, 2x 3300ľF) - could they make the problem?

Maybe someone can send me schematic of this compact system, it would
help me a lot.

Bruno

 

[Sofie]

Bruno Willi:
If you are thinking that the "some big capacitors....." are causing the
symptoms you are reporting with the JVC stereo system then I am just about
certain that the schematic will not be of any help to you. A schematic is
only most helpful to experienced and knowledgeable techs with the proper
test equipment, tools and replacement parts..... there are no step by step
troubleshooting instructions on the schematics or manual that will offer
much help to the novice.
There is a lot of troubleshooting that can be done right now without the
schematic..... Most shop techs fix the majority of equipment without the
expensive and sometimes hard to obtain service manual and schematic.
Certainly the PS is a good place to start but it is quite unlikely that the
big capacitors are bad..... more than likely there are other components
such a open resistors, leaky or shorted smaller capacitors, faulty
semiconductors, etc..... also do some tests on the APO stage and check for
shorted, open or faulty components there.... check for DC on the speaker
rails before the protection relay. These are all things that can cause
the "no sound" symptom..... also lots of other things too.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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"Bruno Willi" <bruno*nospamplease*@brunowilli.de> wrote in message
news:tuhlivghihhsn01blt9trrhs5ktf8pmfeb@4ax.com...

Hi,

my JVC EX-TD55R (a compact stereo system) works fine, just without any
sound coming out...

There are two relays on the amplifier-pcb. The always 'clicked' when
the thing was switched on - no they keep silent. There are some big
capacitors (2x 2200ľF, 2x 3300ľF) - could they make the problem?

Maybe someone can send me schematic of this compact system, it would
help me a lot.

Bruno

 

[Wdyorchid]

You might not need a schematic. Just right under the relay are some point you
want to tap in on them. With a speaker wire to ground and the other to sound
part of the relay, (not the 6-12 volt or -6-12volt pin) you should hear a
sound. If not then then it needs to be brought in for repairs. On these make
I've seen or experince a blown amp a lot.

Hi,

my JVC EX-TD55R (a compact stereo system) works fine, just without any
sound coming out...

There are two relays on the amplifier-pcb. The always 'clicked' when
the thing was switched on - no they keep silent. There are some big
capacitors (2x 2200ľF, 2x 3300ľF) - could they make the problem?

Maybe someone can send me schematic of this compact system, it would
help me a lot.

Bruno

 

[Wdyorchid]

The 'click' when switching on is the PROTECTION circuity.
I am reposting this post correctly below in its intirety due to its valuable
content. I hope the original poster does not mind for the sake of expanding
knowledge for humanity:

Begin:
I am glad that you CORRECTLY corrected yourself.
There seems to be a common mis-conception about the PROTECTION circuity in
audio amplifiers and stereo receivers...... especially among the non-tech
types.... but even some "techs" may get it twisted a little.
Here is my treatise on this matter:

My many years of repair experience with all kinds of audio equipment
suggests that the "protection" circuity actually protects the speaker NOT
the amplifier, in most designs.

When the protection circuitry in the amp senses DC on the speaker
rails due to an audio stage component failure, the protection relay
will drop out thus disconnecting and PROTECTING the speakers from the
very damaging DC... usually full power supply B+ voltage and current
which can fry the voice coils in most speakers just about instantly.

Failures in the amplifier circuitry can be easily caused by shorted
speaker wires, running too many speakers, too loud of a volume driving
the amp into severe distortion, other component and circuity failures
due to heat, stressed components, bad solder connections, old age and
"just because" it was time for a part to fail.

In most designs, an amp will "try" to drive all of it's power into a
short or overload (too many speakers) and will quickly cause component
failures that can NOT be reset.... the protection circuity will sense
DC on the speaker rails which indicates component and circuitry
failures that MUST BE REPAIRED ..... in most designs it will NOT
sense shorted speaker wires and will not PROTECT the amplifier..... the
purpose is to PROTECT your speakers. Usually when an amplifier displays a
"protect" message or the protection relay does not click or energize.....
IT IS TOO LATE...... repairs and replacement parts are needed......
removing the shorted speaker wires or disconnecting the "too many" speakers
will not usually fix the problem.

Best Regards,
Daniel Sofie
Electronics Supply & Repair
End:

For complete thread see "Anyone know about repair of A/V receivers?" in this
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