We are not talking about the horizontal output here. These are the
switching transistors in the power supply. While in some sets a higher gain
HOT will run a little cooler and more reliably than the original, that is
another discussion altogether.

The problem in the H drive circuit on these sets is nearly always bad solder
connections at the HD transformer causing HOT failures. Anyone servicing
these sets effectively always resolders the HDT and related parts.

Leonard Caillouet

"Asimov" wrote in message
...
"Leonard Caillouet" bravely wrote to "All" (07 Nov 03 22:36:30)
--- on the heady topic of "FYI 2SC4834 Sony power supply Q601,Q602"

There might be a design issue with the horizontal driver circuit if the
gain of the hot is that critical. Is there some field service notes
issued about this problem? It just seems a shame to be burning up
expensive transistors when all along it was another problem...

LC Reply-To: "Leonard Caillouet"
LC Xref: aeinews sci.electronics.repair:10648

LC Heads up as per Jurb...hope this helps someone.

LC Just a few notes on these transistors and the results of some
LC experimenting. I had a KV27ts32 and a KV32s25 in the shop with the
LC classic HOT shorted and Q601,602 shorted. I had some 2SC4834M in
stock
LC and ordered some plain 2SC4834 from Tritronics and some 2SC4834P from
LC Acme Enterprises (Orlando). I tried each type in both sets and found
LC that the higher rank (higher letter, higher gain) transistors ran
LC progressively cooler. The unranked versions ran almost 20 degrees F
LC hotter than the best, the P rank version. I matched the transistors
LC from batches of 10 by forward bias voltage on the junctions then in
LC circuit for nearest to 50% duty cycle. I have found that swapping
LC pairs or swapping the caps on Q601,602 can often improve the ratio to
LC closer to 50%.

... Power is obtained by current meeting resistance