[tvservice] Re: New Post--Fuse keeps blowing; Dead TV

  • From: "Mike Selnick" <selnick@xxxxxxxxxxx>
  • To: tvservice@xxxxxxxxxxxxx
  • Date: Mon, 26 Apr 2004 19:56:35 -0400

Looked like a nice call at first.  I disabled B+, gave it a new fuse, 
plugged into 120vac, and the fuse did not blow.  The horizontal output 
transistor emitter and collector outer leads both seemed to be shorted to 
ground on the ohmmeter.  After I removed the transistor, I did some ohmmeter 
checks on it:  Emitter to collector reads 7k ohms, emitter to base reads 5k 
ohms, and base to collector reads infinity.  (Reverse ohmmeter polarity 
gives infinity for the same three readings.)

Do you still think it's a bad transistor or that other faults are grounding 
the emitter and collector?

----Original Message Follows----
From: "graytv" <graytv@xxxxxxx>
Reply-To: tvservice@xxxxxxxxxxxxx
To: <tvservice@xxxxxxxxxxxxx>
Subject: [tvservice] Re: New Post--Fuse keeps blowing; Dead TV
Date: Mon, 26 Apr 2004 10:06:25 -0400

First thing I would do is disable the B+ to the flyback and sacrifice
another fuse.

If it doesn't blow then check the horizontal output transistor for a short.
If it's ok then you might have a bac flyback.

If the fuse still blows, then check the secondaries for shorts.

BTW, a good check to see if the primary side is ok, after disconnecting the
B+, is to check pin 1 of U4101 for -40v to hot ground. If that is good then
the regulator circuit is almost certainly (never say never), working

hth, Russ Gray, A+, Pres.
Gray's Electronics Inc.
201-C Commonwealth Blvd.
Port Orange FL USA 32127
386-322-0904  voice
386-322-3809  fax
graytv@xxxxxxx  email

----- Original Message -----
From: "Mike Selnick" <selnick@xxxxxxxxxxx>
To: <tvservice@xxxxxxxxxxxxx>
Sent: Saturday, April 24, 2004 5:25 PM
Subject: [tvservice] Re: New Post--Fuse keeps blowing; Dead TV

 > Thanks, Russ.  Hello List members.  My first time aboard.  It's been
decades since I did TV repair work.
 > I'm working on a 31-inch RCA GE 31GT659, Code 45104, Chassis CTC 186/7
 > bought from Sears in Feb. 1996.  Set is completely dead.  Fuse f4001 is
 > open.
 > I replaced the 5A. fuse and 2.3-ohm 15-watt power resister r4001 and
plugged the power cord into 120VAC power.  Even *before* I had a chance to 
the set ON, the Fuse immediately opened and f4001 resister was very hot to 
the touch.  A good on-line troubleshooter recommended (for similar model RCA 
GE set) that ic U4101 (STK730-010) is probably shorted and should be 
  > I did quick ohmmeter checks of all the diodes and resistors in the power 
supply and they look ok.
 > Question: What jumps out as the most likely faulty component to replace 
and how would you test it beforehand?   ( B+ filter?  Degauss relay k4201 or 
thermistor rt4201, Switch Mode xformer T4101, Hybrid Switch Mode Reg U4101 
ic, Closed caption filterQ3302?)
 > ----Original Message Follows----
 > From: "Hoyt's TV" <hoytstv@xxxxxxxxxxx>
 > Reply-To: tvservice@xxxxxxxxxxxxx
 > To: <tvservice@xxxxxxxxxxxxx>
 > Subject: [tvservice] Re: New Post
 > Date: Sat, 24 Apr 2004 09:36:29 -0400
 > I think you have the honor of making the first post, Mike.
 > I signed up for the list on March 21st and yours is the first I've seen
 > it.
 > Russ Hoyt
 > Hoyt's TV
 > Exeter, NH

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