I service beta VCR's for resale, and right now I've got a Sony SL-810D
that's driving me up the wall. When I acquired it, it was totally dead.
Replacing the STK regulator on the power supply got it going, but the tape
would only operate in reverse (even when it was supposed to be playing
normally) and was also going way too fast. I replaced the capstan motor with
a known-good one, this restored the correct bi-directional function, but the
speed issue remains. When in normal playback mode, the tape runs at near
fast-forward speed. When in slow-mo, it runs at just above normal playback
speed. Pause, fast forward, and rewind work normally. The capstan free speed
adjust potentiometer does have some effect, but doesn't bring the speed
anywhere near within range.
The problem is present both during playback and record, and it correctly
senses BII or BIII recordings, ruling out any issues with the A/C head or
associated circuitry. I've spent countless hours pouring over the service
diagrams, and have swapped numerous IC's from the ST-18 board with
known-good ones from another VCR, all to no avail. I've also checked all the
caps in that area for ESR.
Without a thorough knowledge of VCR design, all I can do at this point is
swap parts. I thought I had enough skill, but I cannot grasp enough of this
particular circuit design to effectively troubleshoot the problem. A good
place to start would be knowing where to find the reference voltage or
signal that determines the overall capstan speed.
Can anyone give me any ideas, or better yet, does anyone have another one
of these units for parts?

Does the service manual show waveforms? Try checking those. This might
narrow down the problem.

Also, given the unit's presumed age, look for something electrical, rather
than electronic -- bad board or cable connections.

By the way, it's pore, not pour.

Chris F. wrote:
I service beta VCR's for resale, and right now I've got a Sony
SL-810D that's driving me up the wall. When I acquired it, it was
totally dead. Replacing the STK regulator on the power supply got it
going, but the tape would only operate in reverse (even when it was
supposed to be playing normally) and was also going way too fast. I
replaced the capstan motor with a known-good one, this restored the
correct bi-directional function, but the speed issue remains. When in
normal playback mode, the tape runs at near fast-forward speed. When
in slow-mo, it runs at just above normal playback speed. Pause, fast
forward, and rewind work normally. The capstan free speed adjust
potentiometer does have some effect, but doesn't bring the speed
anywhere near within range. The problem is present both during
playback and record, and it correctly senses BII or BIII recordings,
ruling out any issues with the A/C head or associated circuitry. I've
spent countless hours pouring over the service diagrams, and have
swapped numerous IC's from the ST-18 board with known-good ones from
another VCR, all to no avail. I've also checked all the caps in that
area for ESR. Without a thorough knowledge of VCR design, all I can
do at this point is swap parts. I thought I had enough skill, but I
cannot grasp enough of this particular circuit design to effectively
troubleshoot the problem. A good place to start would be knowing
where to find the reference voltage or signal that determines the
overall capstan speed. Can anyone give me any ideas, or better yet,
does anyone have another one of these units for parts?

Hi Chris,

Some basic things to check: Is the pinch roller engaging properly? Is the
capstan motor actually moving the tape or is it getting some help by perhaps
a take up motor or clutch that has too much torque? Try and add some drag to
the pinch roller by squeezing it gently with your fingers. If that doesn't
slow it down, then the tape is being pulled by the take up motor instead of
being locked into the speed of the capstan motor. If the capstan motor
really is turning too fast, you're going to have to figure out the servo
control system. Or another approach is to just give the circuit boards a
good visual check. A bad connection or cold solder joint could cause some
strange things to happen. Does tapping on any of the boards have any effect
on the speed?

Good luck.

--
David Farber
Los Osos, CA

On Wed, 13 Jul 2011 11:38:00 -0700, "Chris F."
wrote:

I service beta VCR's for resale, and right now I've got a Sony SL-810D
that's driving me up the wall.

Is there actually a market for Beta VCR's? I never would have guessed
that.
Dave

Turns out the capstan motor I subbed was not quite the same, and had a
different hall effect IC for the FG circuit. I managed to swap the IC from
the old capstan and that appears to have corrected the problem. Another
lesson learned......

"William Sommerwerck" wrote in message
...
Does the service manual show waveforms? Try checking those. This might
narrow down the problem.

Also, given the unit's presumed age, look for something electrical, rather
than electronic -- bad board or cable connections.

By the way, it's pore, not pour.

On Jul 14, 1:10*pm, "Chris F." wrote:
Turns out the capstan motor I subbed was not quite the same, and had a
different hall effect IC for the FG circuit. I managed to swap the IC from
the old capstan and that appears to have corrected the problem. Another
lesson learned......

"William Sommerwerck" wrote in message

...



Does the service manual show waveforms? Try checking those. This might
narrow down the problem.

Also, given the unit's presumed age, look for something electrical, rather
than electronic -- bad board or cable connections.

By the way, it's pore, not pour.- Hide quoted text -

- Show quoted text -

Thanks for letting us know the fix

"David Farber" wrote in message
...
Chris F. wrote:
I service beta VCR's for resale, and right now I've got a Sony
SL-810D that's driving me up the wall. When I acquired it, it was
totally dead. Replacing the STK regulator on the power supply got it
going, but the tape would only operate in reverse (even when it was
supposed to be playing normally) and was also going way too fast. I
replaced the capstan motor with a known-good one, this restored the
correct bi-directional function, but the speed issue remains. When in
normal playback mode, the tape runs at near fast-forward speed. When
in slow-mo, it runs at just above normal playback speed. Pause, fast
forward, and rewind work normally. The capstan free speed adjust
potentiometer does have some effect, but doesn't bring the speed
anywhere near within range. The problem is present both during
playback and record, and it correctly senses BII or BIII recordings,
ruling out any issues with the A/C head or associated circuitry. I've
spent countless hours pouring over the service diagrams, and have
swapped numerous IC's from the ST-18 board with known-good ones from
another VCR, all to no avail. I've also checked all the caps in that
area for ESR. Without a thorough knowledge of VCR design, all I can
do at this point is swap parts. I thought I had enough skill, but I
cannot grasp enough of this particular circuit design to effectively
troubleshoot the problem. A good place to start would be knowing
where to find the reference voltage or signal that determines the
overall capstan speed. Can anyone give me any ideas, or better yet,
does anyone have another one of these units for parts?

Hi Chris,

Some basic things to check: Is the pinch roller engaging properly? Is the
capstan motor actually moving the tape or is it getting some help by
perhaps a take up motor or clutch that has too much torque? Try and add
some drag to the pinch roller by squeezing it gently with your fingers. If
that doesn't slow it down, then the tape is being pulled by the take up
motor instead of being locked into the speed of the capstan motor. If the
capstan motor really is turning too fast, you're going to have to figure
out the servo control system. Or another approach is to just give the
circuit boards a good visual check. A bad connection or cold solder joint
could cause some strange things to happen. Does tapping on any of the
boards have any effect on the speed?

Good luck.

--
David Farber
Los Osos, CA


Seen bad tracking potentiometers on some Sony Beta decks - the center tap
opens up. Cleaning doesn't help, since the tap is actually broken away from
its holder.
Some other Sony decks, like the SL-5000 had capacitor issues in the servo
circuits - there was a kit sold for those.

Mark Z.

On Jul 15, 8:08*am, "Mark Zacharias"
wrote:
"David Farber" wrote in message

...





Chris F. wrote:
*I service beta VCR's for resale, and right now I've got a Sony
SL-810D that's driving me up the wall. When I acquired it, it was
totally dead. Replacing the STK regulator on the power supply got it
going, but the tape would only operate in reverse (even when it was
supposed to be playing normally) and was also going way too fast. I
replaced the capstan motor with a known-good one, this restored the
correct bi-directional function, but the speed issue remains. When in
normal playback mode, the tape runs at near fast-forward speed. When
in slow-mo, it runs at just above normal playback speed. Pause, fast
forward, and rewind work normally. The capstan free speed adjust
potentiometer does have some effect, but doesn't bring the speed
*anywhere near within range. The problem is present both during
playback and record, and it correctly senses BII or BIII recordings,
ruling out any issues with the A/C head or associated circuitry. I've
spent countless hours pouring over the service diagrams, and have
swapped numerous IC's from the ST-18 board with known-good ones from
another VCR, all to no avail. I've also checked all the caps in that
*area for ESR. Without a thorough knowledge of VCR design, all I can
do at this point is swap parts. I thought I had enough skill, but I
cannot grasp enough of this particular circuit design to effectively
troubleshoot the problem. A good place to start would be knowing
where to find the reference voltage or signal that determines the
*overall capstan speed. Can anyone give me any ideas, or better yet,
does anyone have another one of these units for parts?

Hi Chris,

Some basic things to check: Is the pinch roller engaging properly? Is the
capstan motor actually moving the tape or is it getting some help by
perhaps a take up motor or clutch that has too much torque? Try and add
some drag to the pinch roller by squeezing it gently with your fingers. If
that doesn't slow it down, then the tape is being pulled by the take up
motor instead of being locked into the speed of the capstan motor. If the
capstan motor really is turning too fast, you're going to have to figure
out the servo control system. Or another approach is to just give the
circuit boards a good visual check. A bad connection or cold solder joint
could cause some strange things to happen. Does tapping on any of the
boards have any effect on the speed?

Good luck.

--
David Farber
Los Osos, CA

Seen bad tracking potentiometers on some Sony Beta decks - the center tap
opens up. Cleaning doesn't help, since the tap is actually broken away from
its holder.
Some other Sony decks, like the SL-5000 had capacitor issues in the servo
circuits - there was a kit sold for those.

Mark Z.- Hide quoted text -

- Show quoted text -

FWIW - The cap kits for the SL-5000s are still available. Installed a
kit a few weeks ago.

Dan