[TechAssist] Re: VS4551 mitsubishi ,no power up when cold: only thump-thump. still not fixed
- From: <damon101@xxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sun, 6 Mar 2005 08:51:58 -0500
I had a THUMPER several weeks ago.....it had the SMPS standalone board found
in the VS 4000 , VS5000, and VS 7000 series of TVs.
Turn it on .....thump...thump...thump...thump...thru the audio speakers for
about 30 - 90 seconds, with a solid picture. It eventually died (thumping)
and first
time out I had a shorted SMPS diode in the 130V line, 2nd time it died
(thumping) I
found a shorted Zener diode on the feedback winding of the 130V supply
transformer. It stopped after replacing the Zener.
Since most of these SMPS circuits are designed the same way, only difference
is the output IC type.....you may find the caps are good and the feedback
components are giving bad feedback signal. But I did first suspect dried out
caps. This zener was on the STRS6301 output used for 130V, and the audio
supply was on the same output. The zener was an OVP zener connected across
the output side of the Optoisolator....limited the feedback level to the
STRS6301.
Damon Brunger
Telrad Electronics
Fort Wayne IN
----- Original Message -----
From: "Phil Bader" <tjanphyl@xxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, March 05, 2005 10:54 AM
Subject: [TechAssist] VS4551 mitsubishi ,no power up when cold: only
thump-thump. still not fixed
> ARRRRG! I watched this set an hour last night, unplugged it, went home.
> This morning, again, plugged it in cold, pushed power: "Thump-Thump..."
> Same crappola.
> I immediately unplugged it, removed back, removed two screws holding the
> chassis frame in. Plugged it in, powered it up perfectly.Then I flexed,
> tapped,etc.No effect. I am still not sure if this is a borderline cap
> discharging overnight and cooling(bad ESR) or some bad connection. I'm
> stumped. I KNOW the cap i replaced last night was bad (see thread below).
> Phil Bader
>
>
> FIX?
> I may have fixed the start up problem. I first replaced IC9A1 , an SE130
> regulator.
> But I then ESRd caps all over. I came across one cap soldered to the
> bottom of the board to 5 pin regulator,IC9A2 (looked like soldered to
> pins 1,2) It was a 4.7mfd@50V. It was totally open.
> I replaced it.
> Unit came right up with good picture.. Tomorrow morning will be the test
> for the cold start.
> Phil Bader
>
> Phil Bader wrote:
>
> >The fix for the "arcing" vertical distortion was not the yoke
> >connection, but many cold solder joints on main board, especially the
> >board yoke plugs. Can't believe I missed them all. Resoldered, fixed.
> >I came in this morning, and the TV being cold and unplugged all night,
> >pushed power and I only heard a once per second "thump-thump-thump"
> >noise. We feel this may be one of the PS electrolytics with hi ESR, and
> >when cold, does this but if warms up, runs OK.
> >Anyone have any specific tech tip on this model for this???
> >This will be #3 repair to get this out the door!
> >Phil Bader
> >
> >This played two days OK. Then the vertical distorted like arcing,
> >pull-up, lines stretched,bowed etc.
> >I did resolder the vert output IC. If I hit the side of the setwhile
> >happening it cleared.
> >I saw somewhere in a fix email,was to solder the yoke pin.Sounded like
> >they meant actually at the yoke (as opposed to on the board) I quote:
> >
> >"Cure: Found bad solder connection at connector on red yoke. Reason for
no deflection is these connector run in seres to the other two CRT's."
> >Anyone care to clarify this?
> >Phil Bader
> >
> >
> >
> >
> >
>
> --
>
> Philip Bader
> Jan Phyl TV Inc. (estab. 1976)
> 3420 Recker Hwy. Winter Haven, Fl. 33880
> Fax (863) 299-8821
> email: tjanphyl@xxxxxxxxxxxxxxx
>
>
>
>
> --
>
> Philip Bader
> Jan Phyl TV Inc. (estab. 1976)
> 3420 Recker Hwy. Winter Haven, Fl. 33880
> Fax (863) 299-8821
> email: tjanphyl@xxxxxxxxxxxxxxx
>
>
>
> --
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