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

  • From: "tony saracco" <tcselectronics@xxxxxxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Sat, 8 Nov 2003 07:00:26 -0600

Hey leonard,

I used the HR flyback in a KV32S25 about 6 months ago and never seen the set
come back, they work very well.

Tony Saracco
TCS ELECTRONICS
Elgin , IL 60120
847-695-1928
tcselectronics@xxxxxxxxxxxxxxxx
----- Original Message -----
From: "Leonard G. Caillouet" <lcaillo@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, November 07, 2003 5:01 PM
Subject: [TechAssist] FYI 2SC4834 Sony power supply transistors Q601,Q602


> 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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