Anyone know how I go about getting removed from this list? Thanks! ----- Original Message ----- From: "graytv" <graytv@xxxxxxx> To: <tvservice@xxxxxxxxxxxxx> Sent: Tuesday, April 27, 2004 9:15 AM Subject: [tvservice] Re: FW: Re: New Post--Fuse keeps blowing; Dead TV > Shorted collector to ground is wrong. > > Horizontal output transistors in circuit should normally read, with black > (-) to ground: > Emitter to ground short- possibly a coil or very low ohm resistor between > emitter and ground, but generally emitter is ground. > Base to ground short - reading through horizontal driver transformer > windings to ground. > Collector to ground no short - should be very high ohms to infinity, > depending on design, however the inintial reading may be skewed by > capacitors charging up, hold the probes in place for 10 seconds. > > Out of circuit the only low ohm reading should be from base to emitter. > Collector to base and collector to emitter should be high ohms. > > If after you removed the transistor, there was still a reading from the > collector pad to ground, then there is a short somewhere along the B+ line. > Colud be the flyback, timing caps, filtering caps, rectifiers, or in some > cases (Panasonics especially), there could be a zener diode to ground off > the B+ > > You mentioned ohming the transistor. Don't you have a diode checker setting > on your multimeter to properly check a transistor junction?. Also, a flyback > (or any coil for that matter), cannot be checked by simply ohming the > winding. You need to have an inductor tester to ring the flyback. Even then > this is not an infallible test for flybacks, as they can fail in ways that > cannot be tested without specialized, expensive equipment. > > When you disabled the B+, did you check to see if the voltages were there? > This set, along with most other newer sets, run in an always on standby > state for many of the power supply voltages, waiting for the microprocessor > to put the set into the run mode. At the very least you shoud have a standby > 5v, and with this set you should also have B+. > > 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: Monday, April 26, 2004 8:21 PM > Subject: [tvservice] FW: Re: New Post--Fuse keeps blowing; Dead TV > > > > > > Further to my message below, I checked all the pin-to-pin readings on the > > flyback xformer and one checked out ok. Bad horiz output tranistor? See > > readings below. > > > > ----Original Message Follows---- > > From: "Mike Selnick" <selnick@xxxxxxxxxxx> > > Reply-To: tvservice@xxxxxxxxxxxxx > > To: tvservice@xxxxxxxxxxxxx > > Subject: [tvservice] Re: New Post--Fuse keeps blowing; Dead TV > > 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 > > properly. > > > > 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 > > turn > > 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 > > replaced. > > > 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 > > from > > > it. > > > > > > Russ Hoyt > > > Hoyt's TV > > > Exeter, NH > > > > _________________________________________________________________ > > Test your 'Travel Quotient' and get the chance to win your dream trip! > > http://travel.msn.com > > > > _________________________________________________________________ > > Test your 'Travel Quotient' and get the chance to win your dream trip! > > http://travel.msn.com > > > > > > >