[TechAssist] Re: Round & Round I went
- From: "Bill S" <billans@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Wed, 27 Feb 2002 09:54:55 -0800
How can the yoke be intermittently bad? Could there be a cap inside the
yoke or some other component?
Bill Sorensen
New Life Video & Audio
billans@xxxxxxxxxxxx
- - - - - - - - - - - - - - - - - - -
----- Original Message -----
From: <Hermantv@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Wednesday, February 27, 2002 5:07 AM
Subject: [TechAssist] Round & Round I went
>
> Just had a Hitachi 27CX7B (M3LXU Chassis) that came in "Supposedly Dead",
> however when I test the set it worked fine. Went over several solder
joints
> on the main board and bench tested for about an hour. Charged the customer
my
> minimum bench fee and sent it home. Came back the next day dead again. The
> set again worked fine for me. I noticed a width change only momentarily
but
> it would not stay long enough for any tests. The regulator and all DC
> voltages were within parameters.
> this time I let the set play for several days...then all at once it died
and
> would not restart. I Lifted the many shutdown components, one at a time
until
> I discovered that with D711 off the emitter of Q702 (HOT) lifted the unit
> would power up. Had sound and picture but the raster was distorted. Pulled
in
> at the top but even more at the bottom. The output transistor and all the
> stage timing caps checked OK. The Flyback rang good, and since the unit
would
> power up I decided the FBT was not the problem. chased my tail for most of
> the day...knowing I could not come out on this one however the "technician
> syndrome" kept me on the job even though I was loosing money on this one.
If
> I monitored the collector of the HOT I noticed the horizontal pulse would
> diminish after a few seconds until the unit would cut off. Finally after
> going round and found the horizontal circuit and power supply I rang the
> horizontal yoke and ...yes you guessed it ...it was the Yoke...the last
thing
> I checked. The bad part is this unit has a bonded yoke and there is no
part #
> for the yoke and rings.
> Just thought someone would like to know.
> Tommy Herman...Herman TV
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