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

  • From: "Greg W. Houchin" <greger@xxxxxxxxxxxxxx>
  • To: techassist@xxxxxxxxxxxxx
  • Date: Sat, 08 Nov 2003 04:16:24 -0800

thanks for the good info, it's a keeper!

Leonard G. Caillouet wrote:
> 
> 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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