[TechAssist] Magnasonic TV model GCT5532 B+ not regulating [FIXED]
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Sat, 23 Aug 2003 13:55:20 -0400
The 2SD1197 darlington regulator transistor I had in stock was defective
(not shorted though). Ordered a new one and that solved the problem.
Interesting to note that the new transistor was from the same lot number
and the same supplier as the original one I installed. I had, however
installed the original one in a set previously but removed it and put it
back in stock.
After 2 hrs run, regulator heatsink is at 50 deg. C and cheap HOT sheet
metal heatsink is at 52 deg. C (org. HOT 2SD1845 was replaced with
2SD1879)
Gary McCartney
McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: gary (at) number63.ca
My original message:
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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