Sony SL-5200 Servo / Video Problems

[Chris F.]

This unit seems to have two separate problems, though they may be related.
The first occurs only on B2 speed; the capstan speed is too slow, even with
the B2 speed adjustment at max. Seems OK otherwise. The other problem is
only with B3 mode; the picture is fluttering back and forth. The drum speed
is stable so it is not the source of this problem. Can't test the BI
playback as I don't have any BI tapes.....
I've replaced the usual belts & tires, as well as all blue Sanyo
capacitors on the servo board. No adjustment of the pots can iron out these
problems (and yes I did mark the original positions before moving them). Are
there other caps I should be checking out somewhere else, or is this likely
to be something more complicated?
Any advice would be appreciated.

 

[jdiaz5513]

I doubt it's a capacitor issue. I will speak from Betacam SP deck
experience here:

The problem seems to be electrical to me. Hopefully you've got the
service manual - dive your nose in there and check what components/
circuits are unique to each playback speed. It probably has a separate
circuit for the B1 speed, another for B2, etc.. Check EVERY component
that is unique to that circuit! Pull them out of the circuit if
necessary. If there are any large power transistors involved, I would
even go as far as measuring the hFE and making sure it's at least >25
(you will need a good DMM). It's also possible the B2 speed adjustment
pot is bad! I've had a serious head-scratcher once where this was the
case.

If the problem is mechanical then the capstan motor might have met its
end. Motor windings in general become stressed over time due to heat
(the insulation starts to fail) and you'll find that it takes more and
more current to achieve the same speed. You can try shoving more
current into it with jumper wire from a viable current source to
bypass the limitation of the adjustment pot, but that's not advised
unless you're very careful! This will accelerate the motor's decay and
possibly let loose some "magic smoke".

Check the friction of the capstan shaft by spinning it with your
thumb; it should spin freely and come to a stop slowly! I don't know
how difficult it is to remove, but try removing the capstan assembly
and giving it a thorough cleaning. Compressed air will be a godsend
here. Excessive tape tension could slow down the capstan motor, though
it would definitely slow the drum rotation too so I doubt that's the
case. Does this thing have a pinch roller? I'd take a close look at
that if it's present - too much/too little pressure could cause
problems.

I'm going to bet that if the capstan motor hasn't been replaced yet,
it's definitely time! As far as the video issue on B3 goes, fix the
capstan speed on B2 first. It's possible there could be more wrong
with the VTR but you won't be able to accurately diagnose it yet,
especially since the two problems may be related. Oh and I think it
should go without saying but make sure you're always using fresh
adjustment tapes. Sometimes I forget they have a limited lifetime...

Curious to see what happens!

-Julian

On Apr 12, 7:05 pm, "Chris F." <zappy...@hotmail.com> wrote:

  This unit seems to have two separate problems, though they may be related.
The first occurs only on B2 speed; the capstan speed is too slow, even with
the B2 speed adjustment at max. Seems OK otherwise. The other problem is
only with B3 mode; the picture is fluttering back and forth. The drum speed
is stable so it is not the source of this problem. Can't test the BI
playback as I don't have any BI tapes.....
  I've replaced the usual belts & tires, as well as all blue Sanyo
capacitors on the servo board. No adjustment of the pots can iron out these
problems (and yes I did mark the original positions before moving them). Are
there other caps I should be checking out somewhere else, or is this likely
to be something more complicated?
  Any advice would be appreciated.

 

[Chris F.]

I think I'm going to have to invest in an ESR meter before going much
further on this thing.... it's hard to say how many caps may be faulty. I
can't find any factory alignment tapes, all I have are some prerecorded
movies etc. I also have an SL-5020 which works, so I may swap parts like the
capstan motor and see if that narrows it down.
I've set this aside for now while I catch up on some more important
projects, but when I get back to it I'll try to post an update.
Thanks for the info.

"jdiaz5513" <jdiaz5513@gmail.com> wrote in message
news:330906f2-392a-4ed4-9bf3-017ca8836c13@v15g2000yqn.googlegroups.com...
I doubt it's a capacitor issue. I will speak from Betacam SP deck
experience here:

The problem seems to be electrical to me. Hopefully you've got the
service manual - dive your nose in there and check what components/
circuits are unique to each playback speed. It probably has a separate
circuit for the B1 speed, another for B2, etc.. Check EVERY component
that is unique to that circuit! Pull them out of the circuit if
necessary. If there are any large power transistors involved, I would
even go as far as measuring the hFE and making sure it's at least >25
(you will need a good DMM). It's also possible the B2 speed adjustment
pot is bad! I've had a serious head-scratcher once where this was the
case.

If the problem is mechanical then the capstan motor might have met its
end. Motor windings in general become stressed over time due to heat
(the insulation starts to fail) and you'll find that it takes more and
more current to achieve the same speed. You can try shoving more
current into it with jumper wire from a viable current source to
bypass the limitation of the adjustment pot, but that's not advised
unless you're very careful! This will accelerate the motor's decay and
possibly let loose some "magic smoke".

Check the friction of the capstan shaft by spinning it with your
thumb; it should spin freely and come to a stop slowly! I don't know
how difficult it is to remove, but try removing the capstan assembly
and giving it a thorough cleaning. Compressed air will be a godsend
here. Excessive tape tension could slow down the capstan motor, though
it would definitely slow the drum rotation too so I doubt that's the
case. Does this thing have a pinch roller? I'd take a close look at
that if it's present - too much/too little pressure could cause
problems.

I'm going to bet that if the capstan motor hasn't been replaced yet,
it's definitely time! As far as the video issue on B3 goes, fix the
capstan speed on B2 first. It's possible there could be more wrong
with the VTR but you won't be able to accurately diagnose it yet,
especially since the two problems may be related. Oh and I think it
should go without saying but make sure you're always using fresh
adjustment tapes. Sometimes I forget they have a limited lifetime...

Curious to see what happens!

-Julian

On Apr 12, 7:05 pm, "Chris F." <zappy...@hotmail.com> wrote:

This unit seems to have two separate problems, though they may be related.
The first occurs only on B2 speed; the capstan speed is too slow, even
with
the B2 speed adjustment at max. Seems OK otherwise. The other problem is
only with B3 mode; the picture is fluttering back and forth. The drum
speed
is stable so it is not the source of this problem. Can't test the BI
playback as I don't have any BI tapes.....
I've replaced the usual belts & tires, as well as all blue Sanyo
capacitors on the servo board. No adjustment of the pots can iron out
these
problems (and yes I did mark the original positions before moving them).
Are
there other caps I should be checking out somewhere else, or is this
likely
to be something more complicated?
Any advice would be appreciated.