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RCA vcr VR675HF DEAD
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Michael
Mar 11, 2003, 1:07:24 AM3/11/03
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I found a shorted zener in the power supply ref# d7. I cannot locate the
value for this zener. Would anyone know it's value. TIA, mike
value for this zener. Would anyone know it's value. TIA, mike
Mark D. Zacharias
Mar 11, 2003, 8:01:30 AM3/11/03
to
If a zener on the secondary side has shorted, the supply has lost regulation
and the output voltages went too high. You should unsolder the remaining
secondary zeners (Samsung-built models), and repair the supply OUTSIDE the
vcr itself. A substitute load of, say 470 ohms at 5 watts can be placed
across the 14 volt line.
I don't have the values of the zeners handy, but for example, based on the
Samsung-built models, a 43 volt zener is placed across the -30V line. An 18
volt zener may be across the 14V line, and so forth. A Panasonic-built model
will only have the 18 V zener. In the event of over-voltage, the zener
shorts, and (ideally) the supply just quits running with no other damage.
and the output voltages went too high. You should unsolder the remaining
secondary zeners (Samsung-built models), and repair the supply OUTSIDE the
vcr itself. A substitute load of, say 470 ohms at 5 watts can be placed
across the 14 volt line.
I don't have the values of the zeners handy, but for example, based on the
Samsung-built models, a 43 volt zener is placed across the -30V line. An 18
volt zener may be across the 14V line, and so forth. A Panasonic-built model
will only have the 18 V zener. In the event of over-voltage, the zener
shorts, and (ideally) the supply just quits running with no other damage.
The source of your regulation problem is likely the capacitors on the 5-volt
line, though as others will agree, it would be best to ESR - check or
replace all the secondary caps, along with the 4.7uF 250V cap in the primary
circuit.
Once the regulation problem is fixed, the supply can safely be re-installed
in the vcr.
Mark Z.
"Michael" <zim...@yahoo.com> wrote in message
news:Xns933BD215...@198.99.146.18...
Sofie
Mar 11, 2003, 10:03:55 AM3/11/03
to
exactly !
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"Mark D. Zacharias" <mzach...@yis.us> wrote in message
news:b4kmlh$1qbtrf$1...@ID-180484.news.dfncis.de...
Mark D. Zacharias
Mar 12, 2003, 8:03:08 AM3/12/03
to
Yeah, but I forgot to mention the infamous 22uF bipolar in the primary
(Samsung / RCA models) should be replaced on general principles!
(Samsung / RCA models) should be replaced on general principles!
mz
"Sofie" <so...@olypen.com> wrote in message
news:v6run8d...@corp.supernews.com...
Sofie
Mar 12, 2003, 11:08:59 AM3/12/03
to
Yes Mark, you are absolutely correct..... again.
"Usually" if only the 22uf @16NP that you mentioned is bad, the supply won't
start up and usually will not blow any protection zeners on the secondary.
It appears that some folks only replace the feedback cap (22uf @16V NP) that
you just mentioned and get the unit up and running.... BUT neglect to check
and replace the snubber (4.7 @200V) cap next to it on the primary side....
and neglect to check and replace the 5V filter caps (high uf @ 6.3V) on the
secondary side. Of course, as you undoubtedly know, ALL (yes, every one)
the other electrolytics in this SMPS must be checked and replaced as needed.
A short lived repair will usually result if ALL the suspect caps are not
checked with an ESR meter and replaced as needed.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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"Usually" if only the 22uf @16NP that you mentioned is bad, the supply won't
start up and usually will not blow any protection zeners on the secondary.
It appears that some folks only replace the feedback cap (22uf @16V NP) that
you just mentioned and get the unit up and running.... BUT neglect to check
and replace the snubber (4.7 @200V) cap next to it on the primary side....
and neglect to check and replace the 5V filter caps (high uf @ 6.3V) on the
secondary side. Of course, as you undoubtedly know, ALL (yes, every one)
the other electrolytics in this SMPS must be checked and replaced as needed.
A short lived repair will usually result if ALL the suspect caps are not
checked with an ESR meter and replaced as needed.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
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"Mark D. Zacharias" <mzach...@yis.us> wrote in message
news:b4nb41$20kkpo$1...@ID-180484.news.dfncis.de...
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