[TechAssist] Emerson TV/VCR VT1921, power supply squeals, shorts D509 [FIXED]

Thanks to all the great replies regarding this regulator circuit. Below
is a list of all the components I replaced. I believe the first
replacement STK73410 I tried was defective, whether it was my fault or
if it came that way, we'll never know. The second one came from the same
supplier but it had a different lot number on it. My B+ now is a
constant
104.7 Vdc.

C517, 220uF 160V
C514, 1000uF 25V
C518, 470uF 35V
C519, 47uF 25V
C509, 10uF 100V
C510, 0.47uF 50V (mylar?)
R506, 27 ohm 3W flameproof
R513, 33 ohm 2W flameproof
R502, 68K 1/4W
R503, 68K 1/4W
R523, 39K 1/8W
R505, 1.2K 1/4W
D509, R2M avalanche diode (across 103V B+ line)
IC501 STK73410 regulator IC


Gary McCartney

McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: number63@xxxxxxxxxxxxx






Date: Thu, 18 Apr 2002 17:55:01 -0400
From: Gary McCartney <number63@xxxxxxxxxxxxx>
Subject: Emerson TV/VCR VT1921, power supply squeals, shorts D509

This set had a pulsing picture (pulsing in size on the screen) so I
ordered regulator IC 501, an STK73410. Now I've installed the new IC and
while I was at it, also changed C509, 10uF, 100V. Powered set up and the
PS was squealing like crazy and it didn't start up. Checked my parts and
noticed I had accidently installed a 100uF, 10V instead of 10uF, 100V
for C509. Took this cap out and checked it. It was not shorted and still
checked good on ESR meter. Installed proper cap. PS still squealed.
Measured some more diodes and caps. Found D509 shorted. Symbol on
circuit board shows Zener but when I looked at number on diode, it was
R2M, = ECG570. This diode had never been changed before. Replaced it
with another R2M
and started set up. Squealed again and found D509 shorted again. Checked
HOT, not shorted.
Haven't rung flyback yet, but set worked before I changed the regulator
IC, so I find it hard to figure that the flyback would have died. Have
checked numerous caps, diodes, resistors.


Does anyone have a schematic for this set they could send, or if not,
why does symbol on PCB show D509 as a zener when original diode is an
R2M?

Could all of my damage been caused by installing the wrong cap as C509?

Any help appreciated.



Gary McCartney

McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: number63@xxxxxxxxxxxxx
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