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Quasar VCR Model VH-420 - Testing of Power Supply?

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Peter Smith

Jan 1, 1970
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I'm trying to check out a Quasar VCR for a relative. The unit plays, but the
picture is badly garbled and the flow of the tape through the machine seems
to fluctuate every now and then. When just watching a TV channel through
it's tuner the picture also fluctuates. I was thinking that the power supply
was possibly going bad, how do I test it? I've found a diagram that shows
pins 1, 5, and 6 should all show 5.1 volts, but which other pin should I
connect to to measure the voltage? Should I pull the supply out and try to
measure the voltage without the mainboard connected or should the supply
have a load on it while testing?

Any help would be much appreciated, thanks.
 
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sofie

Jan 1, 1970
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Peter Smith:
Forget trying to measure voltages, if they were not near being proper the
machine would not be operating as well as it is, and if you were to measure
voltages you really need a scope to look for ripple and regulation
problems....
The fault is most likely dry, leaky or otherwise faulty electrolytics. If
you do not have an ESR meter to test them, just replace ALL of the
electrolytics in the SMPS, not that many and not that expensive.
After you are done fixing the power supply you need to clean the VCR tape
path paying special attention to the A/C head..... build up on the lower
part of that head will cause tracking problems and fluctuating tape
flow...... so will a bad tape.
 
The most probable diagnosis is high esr electrolytics in the power
supply. Don't waste your time trying to test them unless you have an
esr meter. Replacing all of them in the power supply (approx 8 - 12 )
will likely cure the problem you are having with the VCR.
electricitym
..
..
..
 
P

Peter Smith

Jan 1, 1970
0
Thanks for the fast replies.

Sofie, I cleaned the heads and the tape path first, and I didn't notice any
improvement.
I really am not comfortable repairing the PS myself, I was just going to
tell them the cost of a rebuilt supply if they wanted to get it fixed. I
doubt they'll want to spend much on this unit considering it's age, but I do
want to make sure that I made the correct diagnosis. Is there much of a
chance that it might be something else? To describe the picture a little
further, it's mostly black & white with a lot of snow and lines, in addition
to the speed fluctuating about twice per minute. Thanks Again.
 
K

Ken Weitzel

Jan 1, 1970
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Peter said:
Thanks for the fast replies.

Sofie, I cleaned the heads and the tape path first, and I didn't notice any
improvement.
I really am not comfortable repairing the PS myself, I was just going to
tell them the cost of a rebuilt supply if they wanted to get it fixed. I
doubt they'll want to spend much on this unit considering it's age, but I do
want to make sure that I made the correct diagnosis. Is there much of a
chance that it might be something else? To describe the picture a little
further, it's mostly black & white with a lot of snow and lines, in addition
to the speed fluctuating about twice per minute. Thanks Again.

Hi Peter...

Can't get my TV to turn on yet; but I've done about a
gazillion or so vcr's...

If I get a vote I cast it in favor of cleaning the tape
path. Pay extraordinary attention to the control head
(furthest left viewed from above, head the tape contacts
first before the video heads)

A few new q-tips and a little isopropyl alcohol. After you
finish cleaning it then clean it again :)

Then re-do the video heads. And again.

Don't be tricked into testing by playing a tape that's
been recorded on this same machine (at least not while
it was 'dirty') Playback a tape from a known good
machine. Or a commercial tape.

Take care.

Ken
 
S

sofie

Jan 1, 1970
0
Ken:
You are right about the control head, but actually Ken, the control head
(A/C Head) is the furthest right..... after the video heads and exit roller
guide.... right before the capstan and pinch roller. The lower part of
that head, if it has any kind of build-up or debris on it can cause the
symptoms Peter Smith mentioned in his original posting.
The head that you mentioned on the left that first head that the tape
touches on the left before it goes past the roller guides and video drum is
the FULL ERASE HEAD and problems with that head would not produce any bad
symptoms when playing back good pre-recorded tapes.
 
Ken Weitzel:
The head you just described is the full tape erase head and is only
activated when recording. The control head certainly could be the
culprit as described by Sofie. The A-C head (audio-control) head is
the LAST head that the tape touches the right side just before the
capstan and pinch roller... then the tape goes back into the cassette
housing. A thorough inspection and cleaning of that head is
warranted. Also trying other tapes as you suggested is a good plan
because as you know, damaged, worn, or improperly recorded tapes can
cause the exact symptoms.
electricitym
.. . . . . .
 
K

Ken Weitzel

Jan 1, 1970
0
sofie said:
Ken:
You are right about the control head, but actually Ken, the control head
(A/C Head) is the furthest right..... after the video heads and exit roller
guide.... right before the capstan and pinch roller. The lower part of
that head, if it has any kind of build-up or debris on it can cause the
symptoms Peter Smith mentioned in his original posting.
The head that you mentioned on the left that first head that the tape
touches on the left before it goes past the roller guides and video drum is
the FULL ERASE HEAD and problems with that head would not produce any bad
symptoms when playing back good pre-recorded tapes.

Arghhh. You're right of course, Sofie.

I did warn you guys that I'm getting on in years, and
not handling it at all well, didn't I? :(

Sorry about that.

Ken
 
Ken:
Since Peter mentioned that the problem ALSO shows up on just the TUNER
output without the tape playing it is a good guess that the power
supply might be the problem. Faulty electrolytics in the SMPS can
cause all kinds of picture problems off the tuner and the tape playback
mode. Then as we all surmised a good cleaning of the audio-control
head and the entire tape path would be in order.
electricitym

..
..
 
I

Inty

Jan 1, 1970
0
I really am not comfortable repairing the PS myself, I was just going to
tell them the cost of a rebuilt supply if they wanted to get it fixed. I

Hum, are you sure that the price of the fix is worth the value of the VCR
and of a new VCR ?
I STRONGLY recommend you to repair your PS by yourself !!! But be careful,
there are 200-350VDC on the primary side !!! Let the capacitors descharge
before repair it, or connect a small bulb (i.e. 40-60W) to the terminals of
the biggest capacitors, to descharge it and work safely !!! To learn more
about safety and SMPS read this group's faq at www.repairfaq.org !!!

I.
 
W

WB2MEP

Jan 1, 1970
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Inty said:
Hum, are you sure that the price of the fix is worth the value of the VCR
and of a new VCR ?
I STRONGLY recommend you to repair your PS by yourself !!! But be careful,
there are 200-350VDC on the primary side !!! Let the capacitors descharge
before repair it, or connect a small bulb (i.e. 40-60W) to the terminals of
the biggest capacitors, to descharge it and work safely !!! To learn more
about safety and SMPS read this group's faq at www.repairfaq.org !!!

I.

It's definitely worth it recapping the power supply in that VCR.
That's an early-mid 90's Panasonic-made VCR, and those power supplies
were notorious for the electrolytics going bad. He's probably seeing
the early stages of capacitor failure, the VCR will eventually not
power up at all.

We have the same model VCRs in my wife's store for recording the
security cameras. It was in the store when we bought it in 1998,
and has been recording 16 hrs/day, 7 day/week since then. (The rest
of the video equip. has mfg. dates of 1996, so the VCR was likely
put in service about that time) I don't think any new VCR would hold
up under that kind of use. Which is why I plan on replacing the video
heads on it when they finally go(SP died a couple years ago, but EP is
still holding on.)

If the OP doesn't have an ESR meter to test the caps, just replace all
the electrolytic caps, except maybe the large 160 - 200 volt cap on the

primary side. I use low-ESR, 105 deg. Nichicon caps, I order from
Mouser Electronics. They don't have a minimum order (the caps will
total < $10), and they don't rip you off on shipping fees.

Mike
WB2MEP
 
I

Inty

Jan 1, 1970
0
It's definitely worth it recapping the power supply in that VCR.
That's an early-mid 90's Panasonic-made VCR, and those power supplies
were notorious for the electrolytics going bad. He's probably seeing
the early stages of capacitor failure, the VCR will eventually not
power up at all.
See:
http://repairfaq.ece.drexel.edu/sam/smpsfaq.htm
http://repairfaq.ece.drexel.edu/sam/vcrfaq.htm#vcrqtipsmps
http://repairfaq.ece.drexel.edu/sam/rball.htm#rb002

We have the same model VCRs in my wife's store for recording the
security cameras. It was in the store when we bought it in 1998,
and has been recording 16 hrs/day, 7 day/week since then. (The rest
of the video equip. has mfg. dates of 1996, so the VCR was likely
put in service about that time) I don't think any new VCR would hold
up under that kind of use. Which is why I plan on replacing the video
heads on it when they finally go(SP died a couple years ago, but EP is
still holding on.)

Those are great VCRs, but making the PSU work is a bit tricky :)
If the OP doesn't have an ESR meter to test the caps, just replace all
the electrolytic caps, except maybe the large 160 - 200 volt cap on the
primary side. I use low-ESR, 105 deg. Nichicon caps, I order from

It didn't need to be changed !!! Change all the caps on the secondary !!!

I.
 
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nolsar

Jan 1, 1970
0
I see vcr`s (4head hi-fi)at yardsales working for $5.00 get DVD recorder
 
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Inty

Jan 1, 1970
0
nolsar said:
I see vcr`s (4head hi-fi)at yardsales working for $5.00 get DVD recorder

Yess ! I *love* flea markets and yardsales, because people didn't know what
they do have, and I buy some interesting stuff most for 0.50?, 1?, 2? max.
5? !!!
At the flea-market of my city there was a good Philips VTR *6 HEADS -
HIFI*... the vendor said "I don't know if it works, but for 10? is good" !!!

I.
 
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