[TechAssist] Re: GE VCR VG2021 - ZD6 Shorting
- From: "J Silverman" <greentron@xxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Fri, 26 Mar 2004 15:46:30 -0500
We must have fixed a thousand of those over the years and we kept a good
record of what happens for each part that fails in any way. When everything
is working, the output voltages are normal without a load. I usually start
them up with 60 volts AC applied and my scope on the 6 volt DC output and
pull the plug quick if the voltage goes too high. If you apply less than 40
volts AC, the outputs will go a little high All the zeners except ZD4 are
for overvoltage protection. Sometimes they come in with the output voltages
low. We find a bad part and then the voltages go high and blow the zeners,
so we dont replace them until the voltages are normal. For high output
voltage I have IC1 or IC2 (always replace both), R03 low in value, R14 high
in value, C04 high ESR, D03 (1N4148) leaky. Just about everything else
caused low output, no output, pulsating output.
Jerry Silverman
Greentron Inc
4 Newland Ave
Greenville SC 29609
864 232 3889
Fax 271 2080
mailto:greentron@xxxxxxx
----- Original Message -----
From: "John at Main TV" <maintv2004@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, March 26, 2004 12:33 PM
Subject: [TechAssist] Re: GE VCR VG2021 - ZD6 Shorting
> I would assume ZD5 shorted simply because of over-voltage from the power
> supply. You mentioned that this occured when you removed the PS to the
> bench. I would suggest using the 2 100 ohm resistors from pins 5 and 6 to
> ground. If the PS is unloaded it does not regulate right. You said you
had
> too much voltage on (C17 ? a 4.7uf @ 50v), I assume you mean C20. I have
> seldom seen a problem with thes other than caps. Always change C09 ( maybe
> it needs to be a nonpolar) and C04 (4.7-200v) in the primary circuit and
> C14 and C15 (220-16v and 330-25v) in the secondary. When kits were
> available for this PS, it included ZD5 and ZD6 so I guess they did fail
> also. Like someone else suggested, troubleshoot the PS out of the VCR
(but
> load it) and get the V's down before you worry about replacing the zeners.
> The zeners should only be for failsafe protection. I can send you a parts
> list of the repair kit if you think that would help. John.
>
> John Mielke
> Main TV
> 636 main St.
> Longmont, Co
> phone 303 776 6955
> fax 303 776 0792
> maintv2004@xxxxxxxxxxx
> ----- Original Message -----
> From: "David Lessard" <mr_fixit@xxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, March 26, 2004 1:24 PM
> Subject: [TechAssist] Re: GE VCR VG2021 - ZD6 Shorting
>
>
> > Thank for your reply John. Yes, the VCR does work for a minute,
> > sometimes longer. I believe the 33V zener I put in is breaking down
> > under load, someone told me it was a 33V zener, looking closer at the
> > part I see a marking "43", so it must be that simple - 43 volts. Board
> > assembly markings are: 69097-123-100, PWB markings are: 66029-0233-00.
> > What could/are the other problems now that ZD5 shorted?
> >
> > David Lessard
> > Alexandria Electronics
> > Ontario, Canada
> > mr_fixit@xxxxxxxxxxxx
> >
> > -----Original Message-----
> > From: techassist-bounce@xxxxxxxxxxxxx
> > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of John at Main TV
> > Sent: Thursday, March 25, 2004 11:52 PM
> > To: techassist@xxxxxxxxxxxxx
> > Subject: [TechAssist] Re: GE VCR VG2021 - ZD6 Shorting
> >
> > Yes, ZD6 should be a 43v, half watt (UZP43B). It is on the Always 33v
> > line.
> > C17 is on the Always 19v line. If you power this supply out of the VCR,
> > you
> > should attatch 2 resistors, 100 ohms each, from pins 5 and 6 to ground
> > and
> > then power it with 25VAC. There is also an extension cable for the PS,
> > 215566, part of kit 215564. If ZD5 shorted you may now have more
> > problems.
> > It should be a UZP18B, 18v, half watt. If it works fgor a minute, the
> > problem may just be the wrong zener voltage. Does the VCR work for that
> > minute? What is the number of the power supply board? This is a Samsung
> > made VCR. John.
> >
> > John Mielke
> > Main TV
> > 636 main St.
> > Longmont, Co
> > phone 303 776 6955
> > fax 303 776 0792
> > maintv2004@xxxxxxxxxxx
> > ----- Original Message -----
> > From: "David Lessard" <mr_fixit@xxxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Friday, March 26, 2004 8:44 AM
> > Subject: [TechAssist] GE VCR VG2021 - ZD6 Shorting
> >
> >
> > > This VCR was in for service a few weeks ago, SMPS was dead, replaced
> > the
> > > following:
> > >
> > > Q1 - C4418
> > > Q2 - ECG382
> > > D02 - IN4148
> > > C09 - 22uf/16v
> > >
> > > Then the display was blinking when powered up, found ZD6 leaky,
> > replaced
> > > it with 33V/1W zener (I think this is supposed to be a 43V zener?),
> > > anyway, ZD6 blows within a minute of VCR being powered up. What could
> > be
> > > causing this? What circuit(s) does this supply?
> > >
> > > Thanks in advance,
> > >
> > > David Lessard
> > > Alexandria Electronics
> > > Alexandria, Ontario, Canada
> > > mr_fixit@xxxxxxxxxxxx
> > >
> > >
> > >
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