I'm working on a Technics stereo system from 1993. It has a separate
stereo tuner amplifier, SA-CH655,a CD changer, SL-CH555, and a stereo
sound processor, SH-CH650. The components are interconnected with a
flat ribbon data cable which connects to each unit in the back. The
problem is that at medium to high volume levels the display will go
blank, the sound will cut out and the unit will just stop working. It
doesn't seem to "power down" because you need to power it down to
"reset" this condition. These people really love this thing and very
much would like to have it repaired but I don't want to make a career
of it either. Does anyone have any experience with this condition on
this model? Thanks, Lenny

wrote in message
...
I'm working on a Technics stereo system from 1993. It has a separate
stereo tuner amplifier, SA-CH655,a CD changer, SL-CH555, and a stereo
sound processor, SH-CH650. The components are interconnected with a
flat ribbon data cable which connects to each unit in the back. The
problem is that at medium to high volume levels the display will go
blank, the sound will cut out and the unit will just stop working. It
doesn't seem to "power down" because you need to power it down to
"reset" this condition. These people really love this thing and very
much would like to have it repaired but I don't want to make a career
of it either. Does anyone have any experience with this condition on
this model? Thanks, Lenny

Some of the Technics models from around that time, employ a fan which is a
small DC motor much like a CD spindle motor. It is under an 'active' control
system, and runs based on the music content and volume setting. It used to
be a very common fault for these models to cut out at medium / high volume
levels, just as you describe, due to the fan motor being worn and kicking up
commutation noise, which then caused the system control micro to cut the
whole system off. Full 'official' repair involved fitting a new fan, and
adding a 0.1uF cap across its connections at the PCB, but often, just a cap
fitted with the existing motor, would do the job.

Set the sytem running, and then advance the volume control until you see the
fan start to run. If the system cuts out at that point or shortly after,
that will (probably) be your problem, but be aware that most Technics models
will also cut out if they see any kind of abnormal load across their
outputs. I have seen a defective speaker also cause the symptoms you
describe. It was perfectly ok at lower volumes, but as soon as the wick was
cranked up, the cone dragged, and caused the system to cut out.

Arfa

On Apr 7, 9:01*pm, "Arfa Daily" wrote:
wrote in message

...

I'm working on a Technics stereo system from 1993. It has a separate
stereo tuner amplifier, SA-CH655,a CD changer, SL-CH555, and a stereo
sound processor, SH-CH650. The components are interconnected with a
flat ribbon data cable which connects to each unit in the back. The
problem is that at medium to high volume levels the display will go
blank, the sound will cut out and the unit will just stop working. It
doesn't seem to "power down" because you need to power it down to
"reset" this condition. These people really love this thing and very
much would like to have it repaired but I don't want to make a career
of it either. Does anyone have any experience with this condition on
this model? Thanks, Lenny

Some of the Technics models from around that time, employ a fan which is a
small DC motor much like a CD spindle motor. It is under an 'active' control
system, and runs based on the music content and volume setting. It used to
be a very common fault for these models to cut out at medium / high volume
levels, just as you describe, due to the fan motor being worn and kicking up
commutation noise, which then caused the system control micro to cut the
whole system off. Full 'official' repair involved fitting a new fan, and
adding a 0.1uF cap across its connections at the PCB, but often, just a cap
fitted with the existing motor, would do the job.

Set the sytem running, and then advance the volume control until you see the
fan start to run. If the system cuts out at that point or shortly after,
that will (probably) be your problem, but be aware that most Technics models
will also cut out if they see any kind of abnormal load across their
outputs. I have seen a defective speaker also cause the symptoms you
describe. It was perfectly ok at lower volumes, but as soon as the wick was
cranked up, the cone dragged, and caused the system to cut out.

Arfa

Thats really very interesting. It seems like you may have nailed it. I
noted that the motor did seem to come on with volume setting as
opposed to heat sink temperature. I also noted that the bushings on
the fan seemed to be a little wobbly. I didn't pay it much attention
at the time but now I'm wondering if that could be whats happening
here. I'll try the cap tomorrow and see what happens. and I'll let you
know. Thanks very much. Lenny.

On Apr 9, 10:20*pm, wrote:
On Apr 7, 9:01*pm, "Arfa Daily" wrote:





wrote in message

...

I'm working on a Technics stereo system from 1993. It has a separate
stereo tuner amplifier, SA-CH655,a CD changer, SL-CH555, and a stereo
sound processor, SH-CH650. The components are interconnected with a
flat ribbon data cable which connects to each unit in the back. The
problem is that at medium to high volume levels the display will go
blank, the sound will cut out and the unit will just stop working. It
doesn't seem to "power down" because you need to power it down to
"reset" this condition. These people really love this thing and very
much would like to have it repaired but I don't want to make a career
of it either. Does anyone have any experience with this condition on
this model? Thanks, Lenny

Some of the Technics models from around that time, employ a fan which is a
small DC motor much like a CD spindle motor. It is under an 'active' control
system, and runs based on the music content and volume setting. It used to
be a very common fault for these models to cut out at medium / high volume
levels, just as you describe, due to the fan motor being worn and kicking up
commutation noise, which then caused the system control micro to cut the
whole system off. Full 'official' repair involved fitting a new fan, and
adding a 0.1uF cap across its connections at the PCB, but often, just a cap
fitted with the existing motor, would do the job.

Set the sytem running, and then advance the volume control until you see the
fan start to run. If the system cuts out at that point or shortly after,
that will (probably) be your problem, but be aware that most Technics models
will also cut out if they see any kind of abnormal load across their
outputs. I have seen a defective speaker also cause the symptoms you
describe. It was perfectly ok at lower volumes, but as soon as the wick was
cranked up, the cone dragged, and caused the system to cut out.

Arfa

Thats really very interesting. It seems like you may have nailed it. I
noted that the motor did seem to come on with volume setting as
opposed to heat sink temperature. I also noted that the bushings on
the fan seemed to be a little wobbly. I didn't pay it much attention
at the time but now I'm wondering if that could be whats happening
here. I'll try the cap tomorrow and see what happens. and I'll let you
know. Thanks very much. Lenny.- Hide quoted text -

- Show quoted text -

So far my first test with loud volume levels did not kick the unit
off. I'll try again today, (while my wife is out of the house) and see
but I think that its fixed. Thanks a bunch. Lenny

wrote in message
...
On Apr 9, 10:20 pm, wrote:
On Apr 7, 9:01 pm, "Arfa Daily" wrote:





wrote in message

...

I'm working on a Technics stereo system from 1993. It has a separate
stereo tuner amplifier, SA-CH655,a CD changer, SL-CH555, and a stereo
sound processor, SH-CH650. The components are interconnected with a
flat ribbon data cable which connects to each unit in the back. The
problem is that at medium to high volume levels the display will go
blank, the sound will cut out and the unit will just stop working. It
doesn't seem to "power down" because you need to power it down to
"reset" this condition. These people really love this thing and very
much would like to have it repaired but I don't want to make a career
of it either. Does anyone have any experience with this condition on
this model? Thanks, Lenny

Some of the Technics models from around that time, employ a fan which is
a
small DC motor much like a CD spindle motor. It is under an 'active'
control
system, and runs based on the music content and volume setting. It used
to
be a very common fault for these models to cut out at medium / high
volume
levels, just as you describe, due to the fan motor being worn and
kicking up
commutation noise, which then caused the system control micro to cut the
whole system off. Full 'official' repair involved fitting a new fan, and
adding a 0.1uF cap across its connections at the PCB, but often, just a
cap
fitted with the existing motor, would do the job.

Set the sytem running, and then advance the volume control until you see
the
fan start to run. If the system cuts out at that point or shortly after,
that will (probably) be your problem, but be aware that most Technics
models
will also cut out if they see any kind of abnormal load across their
outputs. I have seen a defective speaker also cause the symptoms you
describe. It was perfectly ok at lower volumes, but as soon as the wick
was
cranked up, the cone dragged, and caused the system to cut out.

Arfa

Thats really very interesting. It seems like you may have nailed it. I
noted that the motor did seem to come on with volume setting as
opposed to heat sink temperature. I also noted that the bushings on
the fan seemed to be a little wobbly. I didn't pay it much attention
at the time but now I'm wondering if that could be whats happening
here. I'll try the cap tomorrow and see what happens. and I'll let you
know. Thanks very much. Lenny.- Hide quoted text -

- Show quoted text -

So far my first test with loud volume levels did not kick the unit
off. I'll try again today, (while my wife is out of the house) and see
but I think that its fixed. Thanks a bunch. Lenny


No probs Lenny. Glad I was able to help. If the fan pulses and runs on the
peaks, and the unit's not cutting out now, chances are that you have indeed
got a fix.

Arfa