[TechAssist] Re: HELP! Goldstar VCR Model #GHV-1233M - Correct PS cap orientation?

  • From: "J Silverman" <greentron@xxxxxxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Wed, 9 Jul 2003 13:01:26 -0400

For a quickie, you could power it up without a cap and use a voltmeter or
scope to determine the polarity. You might use reduced line voltage JIC.
Jerry Silverman
Greentron Inc
4 Newland Ave
Greenville SC 29609
864 232 3889
Fax 271 2080
mailto:greentron@xxxxxxx
----- Original Message -----
From: "Don Cohen" <bond007d@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Wednesday, July 09, 2003 11:55 AM
Subject: [TechAssist] HELP! Goldstar VCR Model #GHV-1233M - Correct PS cap
orientation?


> Hello,
>
> This is an old 1986 model that customer really likes and wants fixed=
>  regardless of cost (to a point). Left side deck gears (looking from
front)=
>  were broken, so I replaced the whole deck with one from a newer model=
>  junker with same deck - gears looked fine. I did all the usual
maintenance=
>  and also replaced 3 caps on the power supply board. When I plugged unit
in,=
>  it looked like it was doing a reset operation, but something seemed=
>  binding, with the mode motor continuing to turn when it should have shut=
>  off. After about 5 seconds, there was a horrific pop and one of the caps
I=
>  had replaced blew up. There was no previous problem with VCR other than=
>  maintenance and broken gears. That cap was C112 on the power supply
board=
>  and is a 100uF/16V. I tested it before I put it in with an ESR meter and
it=
>  tested fine. Since the whole outer case blew right off, I am not able to=
>  check to make sure I even put it in correctly (polarity), but I am
pretty=
>  sure I did, as I always check that before finishing. I did not make note=
>  when I pulled it out if the part marking matched the silk screen info. I=
>  know that sometimes they are marked wrong. The silk screen on board says=
>  that the + leg goes to the center pin of IC102 (positive 9 volt
regulator=
>  AN78M09). That pin is ground. Also according to the silk screen, the=
>  negative leg is supposed to go to pin 1 of IC102, which is Vin. On the=
>  newer unit that I robbed the deck from, the power supply is designed=
>  differently, but the same regulator and cap are there (except the
voltage=
>  on the cap had apparently been upgraded to 25v) and the orientation is=
>  reversed for the cap - neg leg of cap to center IC pin and positive to
pin=
>  1. That is what I would expect.
>
> So, does anyone have an old schematic or service bulletin that they could=
>  verify that the silk screen info is indeed wrong? If not, does it sound=
>  correct that the cap's + leg should not go to the IC's (and board)
ground=
>  pin? Obviously I could just try to put another in again the way the silk=
>  screen says and assume I somehow put it in backwards, but I would rather=
>  not keep blowing parts and possibly doing other damage till I figure out=
>  what the issue is.
>
> Much thanks to anyone that can help out here.
>
>
> Don Cohen
> DC Electronics
> Shinglehouse, PA=20
>
>
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