[TechAssist] Magnasonic TV model GCT5532 B+ not regulating
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 07 Aug 2003 18:12:00 -0400
I have a Magnasonic TV model GCT5532 (unknown chassis no.) which I
replaced the HOT, shorted darlington B+ regulator transistor Q601
(2SD1197), and an open 3.9 ohm 5W resistor also in power supply. The B+
to the HOT will climb to 140V or more if I increase the variac AC input
up toward 120 VAC. The set works otherwise. I don't know exactly what
the normal operational B+ level is supposed to run at and I don't notice
any labels on the board specifying so either.
I have checked all the resistors and caps in the regulator circuit plus
the 5.5V regulator IC651 (has 5.5V output). The 220 Ohm 20W bypass
resistor is ok. The B+ adjust trim pot tests ok and varying it doesn't
make any difference in the B+ output.
THanks for any help.
--
Gary McCartney
McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: gary (at) number63.ca
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