Magnavox HD2632 - Videokarma.org TV - Video

DaveWM · #1 01-09-2011, 04:23 PM

no pic, just a click, all caps look ok (no domed shape or other indication of problems), I am checking the HOT now

DaveWM · #2 01-09-2011, 04:27 PM

ok HOT is shorted, so what the chance that is the only problem and something else is did not cause it to short?

DaveWM · #3 01-09-2011, 04:41 PM

looks like an NTE2353 phillps pn 610597m9137

I can get them from mouser or 10$, may try my local surplus store of if no joy there ebay, saw them there for a BIN or make offer 8.95, from ebay I would prob go 5$ free ship.

DaveWM · #4 01-09-2011, 05:03 PM

I assume the transistor is shorted I should say, I dont do a lot of SS work but I figure 1.5 ohm from C to E both ways is not good.

DaveWM · #5 01-09-2011, 05:04 PM

oh and it says assembled in Tenn, imagine that.

DaveWM · #6 01-09-2011, 05:06 PM

while fooling about with it I checked the CRT, tested very good on all guns, which is amazing to me since this tv has seen a lot use. On most every day for several hours a day since new (1991?)

DaveWM · #7 01-09-2011, 06:18 PM

getting some confusing readings on the horz driver, but its in circuit, so maybe that is ok.

radiotvnut · #8 01-09-2011, 06:57 PM

Yes, the HOT is shorted. I've worked on many Magnavox/Sylvania/Philco NAP sets from this era and most shorted HOT's are caused by loose connections or bad caps. However, I've seen a few with a bad flyback. Unfortunately, the only way to check the flyback is with a piece of equipment called a ringer. Otherwise, your only option is to replace the HOT and see what happens. Before replacing the HOT, resolder the horizontal driver transformer and any power resistors that are 1 watt or more. Also, check for bad caps in the power supply, horizontal drive circuit, and in the HOT collector circuit. These caps can look normal and still be bad.

DaveWM · #9 01-09-2011, 09:15 PM

I can only see a couple caps in the HOT collector, one is a square .01 1600v cap the ohter is a disk that looks like its HV, cant read it. I can't see any electros in the horz drive circuit, but its kinda hard tracing under the board.

I can prob dig up a .01 1600v (I cant really test that high). Do you know if it would do any harm to turn the set on with the HOT pulled just so I can scope the input side of the coupling transformer for a drive pulse? of course assuming it would even power up with the HOT pulled.

radiotvnut · #10 01-09-2011, 09:33 PM

It shouldn't hurt anything with the HOT removed. Some sets will actually power up and produce audio from the speaker. There will, of course, be no HV. While it's powered up, check the B+ going to the flyback. With the HOT removed, you can check it at the collector terminal. It should be somewhere between 125-135 volts DC.

DaveWM · #11 01-09-2011, 10:39 PM

roger will give it a try tomorrow getting late. I pulled some more E caps, some around the PS and some around the deflection 22uf 250v (two) a 100uf at 200v and a 10uf at 100v. They all checked out perfect, amazing, perhaps they were using good caps back then. None are glued down so none of that nasty brown conducting glue to deay with either. I pulled the .01 1600 and tested, fine for value and fine for leakage at least up to 450v. there was also a big film .5 uf 200v cap, tested fine and no leak at 250v. Well tomorrow I will see about getting that transistor and do the power up to check if the B+ comes up. Thanks for the help.

radiotvnut · #12 01-09-2011, 11:38 PM

Those NAP sets from the '80's and '90's were generally good sets and I rarely ever saw an unusable CRT in one. Around '99, their quality started going down and the silver cased ones from the early-mid 2000's are crap. Back in the mid '90's, I remember getting one sililar to yours with a bad flyback and shorted HOT. I replaced the flyback with an ECG generic and I'm sure it's still working somewhere.

DaveWM · #13 01-10-2011, 01:30 PM

ok found a local supply of 2SD1881 which showed as a cross to the NTE2353, will put it together tonight, war eagle...

DaveWM · #14 01-10-2011, 05:09 PM

heck that was easy, now if it will last for a while or will the HOT short for some reason that took out the orig.

radiotvnut · #15 01-10-2011, 06:06 PM

Glad it's working. Let it run for 5 or 10 minutes. Then, turn it off and feel the HOT heatsink. If it's too hot to touch, something is still wrong and the HOT will fail. If all is OK, continue to run the set while monitoring the heatsink temperature.