Sharp 13VT-R100

Hi,

I have a Sharp 13VT-R100 TV/VCR combo I was asked to look at. The
symptom is that when turned on, the picture just barely appears on the
screen when it shuts itself off. Once it's shut itself down, the "Timer"
LED starts flashing and it will not turn on again until it's unplugged
then plugged in again. This happens within about 6-7 seconds. What you
do see of the picture appears to be a full raster.

I tried bringing it up on a Variac, but as soon as it gets to the point
where the power relay will pull in (about 75-80VAC) the same thing
happens. I haven'y delved too far into it yet, but was just wondering if
anyone has had any experience with this set. I don't have a service
manual or schematic

Any help would be appreciated!

Thanks,

Irv

 

[Patch]

<irvin.diegel@verizon.net> wrote in message
news:3F297D9D.D1C8DC23@verizon.net...

Hi,

I have a Sharp 13VT-R100 TV/VCR combo I was asked to look at. The
symptom is that when turned on, the picture just barely appears on the
screen when it shuts itself off. Once it's shut itself down, the "Timer"
LED starts flashing and it will not turn on again until it's unplugged
then plugged in again. This happens within about 6-7 seconds. What you
do see of the picture appears to be a full raster.

I tried bringing it up on a Variac, but as soon as it gets to the point
where the power relay will pull in (about 75-80VAC) the same thing
happens. I haven'y delved too far into it yet, but was just wondering if
anyone has had any experience with this set. I don't have a service
manual or schematic

Any help would be appreciated!

Thanks,

Irv

When you first plug it in, do you hear a loading motor trying to run? If no,

can you manually load a tape into it & then plug it in? I'm not familiar
with that model, but most of the time when you have problems like that it's
a dirty\bad mode switch.

 

[Sofie]

Irv:
A service manual or schematic will not be of much help to you...... there
are no step by step troubleshooting instructions....... only a very
experienced tech may find the documentation helpful in "tough-dog" repairs
but generally most techs will repair the majority of problems like this
without a schematic or manual.
You probably need to focus your troubleshooting attention on the VCR and not
the Television. The cassette loading mechanism may be jammed, faulty IR
LED, faulty tape sensors, or a faulty mode-switch, etc, etc, all of these
things, and more, could be causing the shutdown.
As a side note, the "old" trick of bringing up the voltage slowly with your
variac does not work well with most newer equipment that uses a SMPS and
does not use a linear PS.......
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


<irvin.diegel@verizon.net> wrote in message
news:3F297D9D.D1C8DC23@verizon.net...

Hi,

I have a Sharp 13VT-R100 TV/VCR combo I was asked to look at. The
symptom is that when turned on, the picture just barely appears on the
screen when it shuts itself off. Once it's shut itself down, the "Timer"
LED starts flashing and it will not turn on again until it's unplugged
then plugged in again. This happens within about 6-7 seconds. What you
do see of the picture appears to be a full raster.

I tried bringing it up on a Variac, but as soon as it gets to the point
where the power relay will pull in (about 75-80VAC) the same thing
happens. I haven'y delved too far into it yet, but was just wondering if
anyone has had any experience with this set. I don't have a service
manual or schematic

Any help would be appreciated!

Thanks,

Irv

 

Hi Patch, Dan,

Thanks for your suggestions and advice! No, the loading motor does not try to
run when I first plug it in/turn it on. I pulled the transport, stuck a test
tape jig in it and loaded it manually by applying some DC to the loading motor.
The jig loads and unloads very smoothly.

My cheap infrared test strip shows that there is IR coming out of the prism that
sticks up into the transport. If I stick a tape into the transport and turn the
set on, the tape loads and starts to move forward. Then, the set shuts down but
the transport will then disengage the capstan idler from the capstan shaft.
After pulling the plug and turning it on again, I can eject the tape if I hit
the eject button fast enough before it shuts down again. For a mode switch, this
set uses two IR detectors on the main board, interrupted by tabs on the main
loading gear. I'm assuming these and the IR detectors on the sides of the tape
transport are okay since the tape will load/unload if I do it fast enough. I did
try cleaning them just in case.....

There is a 130V adjustment pot on the power supply board, so I assumed that I
should see this voltage across one of the filter caps. I found a 250 VDC cap so
I clipped a voltmeter across it. When I first plug the set in, I see about 131.4
VDC here. When I turn the set on, it drops to 130 VDC right on the button. After
the set shuts down, it goes back to 131.4 VDC. I haven't done any additional
voltage checks yet since the set was not designed with service in mind and the
cables to the yoke and CRT anode are very short so you can't pull the main board
out real far.

I have noticed though, that there's no sound for the short period that the set
is "energized". This seems kind of odd since normally the sound appears before a
raster does, especially when the set is cold. I'm wondering if the audio
circuitry might be loading down one of the other supply voltages and causing the
shutdown?? I tried the "volume up" button as soon as I turned the set on in case
the default power up for the sound was fully off, but that didn't do any good.
I'll have to do some further checking of the power supply voltages.

Again, thanks for your advice. The people in this newsgroup have always been
helpful and friendly!

Irv

Patch wrote:

irvin.diegel@verizon.net> wrote in message
news:3F297D9D.D1C8DC23@verizon.net...
Hi,

I have a Sharp 13VT-R100 TV/VCR combo I was asked to look at. The
symptom is that when turned on, the picture just barely appears on the
screen when it shuts itself off. Once it's shut itself down, the "Timer"
LED starts flashing and it will not turn on again until it's unplugged
then plugged in again. This happens within about 6-7 seconds. What you
do see of the picture appears to be a full raster.

I tried bringing it up on a Variac, but as soon as it gets to the point
where the power relay will pull in (about 75-80VAC) the same thing
happens. I haven'y delved too far into it yet, but was just wondering if
anyone has had any experience with this set. I don't have a service
manual or schematic

Any help would be appreciated!

Thanks,

Irv

When you first plug it in, do you hear a loading motor trying to run? If no,
can you manually load a tape into it & then plug it in? I'm not familiar
with that model, but most of the time when you have problems like that it's
a dirty\bad mode switch.