Help God, Possessed VCR !!

[TA7205]

I'm working on a Sony SLV-750HF.

I'm getting a blue screen and no audio when it's in the play mode.
If I "tap" on, or near the capstan or A/C head, Video will appear (with
audio)
for about a second. Then, back to a mute, blue screen. If I hit pause, I get a
good
still picture. I also get video when cueing or reviewing through the tape.

If I swing the A/C head a lttle back and forth while playing a tape, video and
audio
return until I stop.

It does not care about which speed the tape runs at.
I have hard-wired connectors on the A/C head and on the Capstan motor.
I have replaced the capstan motor. I have resoldered the PCB under the
deck and have checked resistors and caps there as well.

I have cleaned the video and A/C head over and over again.

This guy wants this thing fixed ! So I gotta do it !
Any suggestions gladly accepted.
Thanks,

Rick

 

[Steve(JazzHunter)]

I'm working on a Sony SLV-750HF.

I'm getting a blue screen and no audio when it's in the play mode.
If I "tap" on, or near the capstan or A/C head, Video will appear (with
audio)
for about a second. Then, back to a mute, blue screen. If I hit pause, I get a
good
still picture. I also get video when cueing or reviewing through the tape.

If I swing the A/C head a lttle back and forth while playing a tape, video and
audio
return until I stop.

It does not care about which speed the tape runs at.
I have hard-wired connectors on the A/C head and on the Capstan motor.
I have replaced the capstan motor. I have resoldered the PCB under the
deck and have checked resistors and caps there as well.

I have cleaned the video and A/C head over and over again.

This guy wants this thing fixed ! So I gotta do it !
Any suggestions gladly accepted.
Thanks,

That is simply tracking, or more accurately tape path alignment. The
tape is crawling up or down the audio/CTL head - the control track is
lost and the picture blanks. One immediate thing that might work is
putting in a new capstan pinch roller. Beyond that it's tracking
alignment, which is very tricky on this type of Betamax. The 750,
900, 1000, 600 etc. all seem to go out of proper tape path alignment
after a while. When it becomes really bad any tape you load will
receive edge damage, which you should check for in this case.

. Steve .

 

[LASERandDVDfan]

One immediate thing that might work is

putting in a new capstan pinch roller. Beyond that it's tracking
alignment, which is very tricky on this type of Betamax

The original poster is talking about the **SLV**750HF VHS Hi-Fi VCR, not the
SL-HF750.

However, I would advise checking the capstan to see if it needs cleaning or
not. I would also check the condition of the capstan bearing on the motor as
those are notorious for warping, causing all sorts of problems with tape travel
and with the capstan motor stators.

I would advise checking the pinch roller for excessive wobble in the bearings
and the pinch roller arm for excessive warpage, which is another notorious
part.

I would check the mode switch and clean or replace if necessary.

In addition, I would also recommend checking the condition of the plastic gears
which directly move the guideposts to their load and unload positions. Those
gears are notorious for cracking. - Reinhart

 

[Mark D. Zacharias]

Let us not forget the infamous 1/2 load arm assembly lubrication problems.

Mark Z.

 

[Steve(JazzHunter)]

The original poster is talking about the **SLV**750HF VHS Hi-Fi VCR, not the
SL-HF750.

Oh! (heheh) I still have to deal with Betamax machines around here.
Still as you say the Pinch should be checked, and it still sounds like
the tape wandering off the head. Besides the loading arms etc. also
doesn't the exit-side (or entry) tape guide loosen and rotate
sometimes, upsetting tracking?
. Steve .

 

[TA7205]

One thing I did not look at closely was the pinch rollrer. However, I did clean
it.
as well as the capstan, hell. I replaced the whole capstan motor.

I forgot to mention that I did try adjusting the alignment of the ac head and I
did clean the mode switch...oh yes, the pre-load arm is working fine (I should
be so lucky)

Thanks for the input guys, if you have any other ideas, please let me know.

Rick