[TechAssist] Re: Panasonic KV27S15 Q591

  • From: "Leonard Caillouet" <lcaillo@xxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Tue, 10 Feb 2004 12:37:51 -0500

It depends on what parts you are talking about, but for HOTs and regulators
it is NOT necessary to use parts supplied by Sony in most cases.  It IS
necessary to understand the circuit well enough to find ALL of the defective
components and problems AND to be sure that you are using original parts
(meaning made by the company that the label says, Sony is not the maker for
most of these parts).

For the infamous 2SC4834, I have begun using nothing but the P rank version,
which has a higher gain and runs cooler.  Sony specifies M, N, or P rank
depending on the set, but I have never received anything but the N from
them.   A Sony tech once stressed the importance of using their parts
because of the tighter quality control and getting matched parts for these
pairs, but testing the parts from Sony I found that I can get better
matching by buying lots of 10 from any reputable supplier and matching them
myself.  Actually, trial and error tells me that the matching of the caps in
these circuits affects the duty cycle more than the matching of the
transistors.  I still match them for gain and junction bias as closely as I
can.  Currently Acme has the best price on the P rank 2SC4834.  The
manufacturer is Shindingen whether you get them from Sony or not.

For the 2SC4927 I always replace them with a 2SD1881.  It runs cooler and
after having a couple of repeat sets with repeat failures using the
ridiculously expensive Sony replacement a couple of years ago I started
looking for alternatives.  Of course, you have to resolder the components in
the H drive circuit, particularly the transformer and check the caps.  For
the MX0841 and MX0541 I have found no problems with buying them from good
suppliers.

My usual suppliers are Tritronics, B&D, or Acme.  They all say that they
will take back any bad parts, but I never have any failures that I cannot
trace to something that I missed in the circuit.  For instance, I recently
had set blowing the regulator pair after running a couple of hours.  Duty
cycle was 50+/-1%, all the parts tested fine and matched very closely.
Turned out to be a bad transformer.  The new one measured somewhat
differently than the one in the set but upon closer inspection I could see
the windings had been thermally stressed, likely causing an intermittent
short.

Always check the related caps carefully, check the VDRs, and check the
resistors and diodes and resolder everything that looks marginal and then
some.  Being thorough saves lots of headaches and parts.  My experience
tells me that the parts issue is much less of a factor than the technician
issue.  But then, I use only vendors that I can trust and who will take back
any bad parts.

Interestingly, the OEM (of the equipment as opposed to the parts) may not be
the best supplier.  I just repaired an amp in which I used an old stock
transistors from Yamaha.  The maker was Sanken, but the part failed shortly
after installation.  I had matched the parts (that is why I used the old
stock part) to the others in the unit, and was thorough in testing.  After
examining the bad part, I could see that the Sanken logo was different on
the one from Yamaha.  Apparently they got some fakes somehow at some point.
I now only buy a particular part from the same vendor only and keep only a
few extras so I know where they come from and can return them if bad.

I use the Peak Atlas analyzer for gain and my DMM for junction bias when I
match the transistors, btw.  Ultimately, the scope and temperature are final
QC.

Joe, If you are reading this, I have not forgotten about your request, just
been experimenting more and testing to be sure...

Leonard Caillouet
Electronics World




----- Original Message ----- 
From: "Hoyt's TV" <hoytstv@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Tuesday, February 10, 2004 10:21 AM
Subject: [TechAssist] Re: Panasonic KV27S15 Q591


> How do the rest of you feel about using non-Sony transistors as
> replacements.
>
> I had a BiiiiG Sony in last year and had to do the HOT, regulator, fuse
> resistor, thing.
> Got a "kit" from my local distributor and was very lucky that it sat on my
> bench for a couple days running (it was too big to move till I was ready
to
> take it back). Then they all wiped out again. Sure glad I didn't take it
> back and have to go get it again. It took three men and a boy to move it.
>
> I Called Fulton's tech line and was told this was typical, and I HAD to
use
> Sony replacements. They sent them, plus the four caps they said it needed
> also. It's still running as far as I know. They said there are a lot of
> counterfeit Sony parts out there. These did appear to have Sony labels on
> them.
>
> I don't know if it was the caps that did the trick or if I really needed
> gen-u-wine Sony parts.
>
> Russ Hoyt
> Hoyt's TV
> Exeter, NH
>
>
> ----- Original Message ----- 
> From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Tuesday, February 10, 2004 9:19 AM
> Subject: [TechAssist] Re: Panasonic KV27S15 Q591
>
>
> > That would be a 2SC4927-01, Sony part# 8-729-016-32.
> >
> > Bob Waterman, CET® #RI-28
> > Master Technician License #9109
> > Service Manager / Parts Manager
> > Gemini Computer, TV, & Security Alarms
> > (508)695-7302
> > (508)695-7769 FAX
> > geminitv@xxxxxxxxxxxxxxxx
> > geminitv@xxxxxxx
> > www.geminicomputertvsecurityalarms.com
> >
> >
> > ----- Original Message ----- 
> > From: <avsgi@xxxxxxxxxxxxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Tuesday, February 10, 2004 9:02 AM
> > Subject: [TechAssist] Panasonic KV27S15 Q591
> >
> >
> > > Hello Fellow Techs, wonder if a Sony service center or otherwise
provide
> > the part # for
> > > Q591 Horizontal Output Transistor in a Sony model number KV27S-15.
Any
> > help would be
> > > appreciated.
> > > Thanks,
> > > -- 
> > > Walter....
> > >
> > >   Audio Video Service of Granville, Inc.
> > >     2106 Sunset Road
> > >          Oxford, N.C. 27565
> > >              919.693.1066
> > > www.audiovideoservice.com
> > >
> > >
> >
>
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