[TechAssist] FYI 2SC4834 Sony power supply transistors Q601,Q602

  • From: "Leonard G. Caillouet" <lcaillo@xxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Fri, 7 Nov 2003 18:01:23 -0500

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

Interestingly, the higher gain transistors ran cooler by 10-20 degrees,
depending on the set, but the overall current drawn by the set was virtually
the same(~60-70 mA with & without a signal)

Summing up, it appears that the higher rank transistors are the better
choice.  Acme has them at a great price(10 for $15.95) and has free shipping
for the time being on orders over $25.  They are a new operation but Glen,
the main contact there was a manager for MCM at one time and seems
veryinterested in winning over the business of shops like us.  So far they
seem to be good to work with.

BTW, the KV32S25 was a bit atypical in that the HOT failure was due to a bad
FBT.  The price was pretty steep and the customer did not want to fix it, so
I gambled and tried an aftermarket transformer from HR.  It seems fine so
far and at the lower price the customer went for the fix.  We'll see if it
holds up.  I don't like subbing flybacks but these have had a good rep.

Leonard G. Caillouet
Electronics World
Gainesville, FL
352-332-5608
352-332-5668 (fax)

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