[TechAssist] Re: Sony TV KV27V15, power supply problem
- From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 21 Oct 2003 11:40:48 -0400
You really have to be careful where you purchase these from. Sometimes I may
seem to harp on the generics and only recommend OEM components, but this is
only because I have heard of numerous situations like yours and it is hard
to tell who has the "good stuff" and who has the "junk" with respect to
generics. I usually get mine from B&D Enterprises who always has quality
products as they are a direct importer and a wonderful company to do
business with.
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: "Gary McCartney" <gary@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Tuesday, October 21, 2003 10:32 AM
Subject: [TechAssist] Re: Sony TV KV27V15, power supply problem
> Bob, I tried as you said and fired it up after gradually raising the
> variac voltage. The set did run but I found the square wave output of
> Q601 and Q602 to not be perefectly symetrical. I was getting something
> such as 2.6 uS on-time on half the pulse and 2.2 uS on the other half.
> Changing the pair of 2SC4834's to another pair solved the problem. These
> transistors came from my supplier in kits for this power supply along
> with the HOT 2SC4927 and the 0.1 ohm fusible resistor.
>
> I let the set run all through the night and this morning I measured
> temperatures of the transistors. The HOT
> (2SC4927, from the kit so I believe it to be a generic part but looks
> authentic) is running at 40 deg. C, measured directly on top of the
> transistor on the heatsink. The power supply Q601 and Q602 are running
> at 49 deg. C. I did purchase a 2SD1880 to use as the HOT but with the
> 2SC4927 running as cool as it is, I closed up the set with that left in.
>
>
>
>
> Gary McCartney
>
> McCartney Electronics
> Guelph Ontario Canada
> Est. 1984
> email: gary (at) number63.ca
>
>
>
>
>
>
>
> Gemini Computer & TV wrote:
> >
> > I think you are good to go. What happens if you try to fire it up at
normal
> > line voltage?
> >
> > 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: "Gary McCartney" <gary@xxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Monday, October 20, 2003 4:36 PM
> > Subject: [TechAssist] Sony TV KV27V15, power supply problem
> >
> > > I have this Sony KV27V15 which came in with the HOT and power supply
> > > transistors shorted. I replaced the HOT, resoldered the driver
Xformer,
> > > changed the 0.47uF, changed the 2 2SC4834's in the PS, plus the 3
VDR's,
> > > the 4 -0.22 caps, R607 (0.1 ohm) and changed R644 from 6.8 ohm to 4.7
> > > Ohm as per instructions. Checked all other parts in PS primary and
sec.
> > > for shorts, nothing else found.
> > >
> > > Fired set up at 30 AC and did measurements with ground lead of meter
and
> > > scope on the junction of the 2 main filter caps. C607 (-) and C608 (+)
> > >
> > >
> > > DC measurements:
> > >
> > > Q601:
> > >
> > > E= -1.5V
> > > B= -1.7V
> > > C= +49.6V
> > >
> > > Q602:
> > >
> > > E= -49.7V
> > > B= -49.7V
> > > C= -1.5V
> > >
> > > I get a square wave of 100V p-p on base of Q601 but no waveform is on
> > > base of Q602. I am expecting I should have 100V p-p only of out phase
> > > compared to the Q601 base waveform. I checked Q602 with ohmmeter and
it
> > > checks ok. I checked winding of T603 pins 1 to 2 and pins 5 to 6 both
> > > measure 0.6 ohms in circuit. I made a few other resistance comparisons
> > > between the Q601 circuit and Q602 circuit and didn't find anything out
> > > of line.
> > >
> > >
> > > Just want to verify that I am doing this testing correctly before I
> > > continue later tonight on this set. I will do more indepth invaluation
> > > of the components in the base circuit of Q602. I'm supposed to have
this
> > > set ready for the customer tomorrow.
> > > --
> > >
> > > Thanks for any help.
> > >
> > >
> > > Gary McCartney
> > >
> > > McCartney Electronics
> > > Guelph Ontario Canada
> > > Est. 1984
> > > email: gary (at) number63.ca
> > >
> > >
> >
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