View Full Version : 21" '77 E21 chassis Philco


radiotvnut
10-26-2010, 08:36 PM
This is a GTE-Philco 21" color TV from '77 that uses the E21 single board chassis. The CRT is an early large neck inline type. When I got it, the CRT was dead; but, rejuvenation brought it back. However, it still does not look the best. Also, the vertical circuit has issues (probably bad caps). I don't know if I'll fix this or junk it. Depends on how reasonable a CRT is.

http://i538.photobucket.com/albums/ff341/radiotvnut/2010_1026tv0078.jpg

http://i538.photobucket.com/albums/ff341/radiotvnut/2010_1026tv0079.jpg

Findm-Keepm
10-26-2010, 08:52 PM
Those are really reliable sets, aside from regulator and horizontal issues. I remember working a bunch of them in the 80's from the beachfront hotel industry - they had extra controls for volume limiter and the like. Most of our repairs were to tuners (Beachfront humidity of the corrosive nature) and triplers (again humidity). Folks liked to turn on the sets as soon as they got in the room, before the A/C had a chance to dehumidify things.

IIRC, that has the horizontal countdown IC that crosses to ECG792 or 793, hard to find even in the late 80's. If that chip ever went, I'd pass on a restoration.

Cheers,

sampson159
10-26-2010, 09:22 PM
had as few of those in the shop years ago.pretty good sets.check your high voltage.triplers can weaken and give apperance of other issues.clean vertical controls with de oxit.there are 2 little black caps that are side by side in vertical deflection.these often fail.dont know the values right off hand.there is a chip in the demod that would give loss of color also.i had one that our top guy swore was a crt.we changed it out and same problem.weak tripler.replaced tripler and the crt was weak!original was good.swapped back and set was fine.one of the few dave was wrong on.i remember 2 in 30 years

radiotvnut
07-06-2011, 08:21 PM
I pulled this set out and I'm a little stumped at the moment. The 115 volt B+ was about 15 volts low and I discovered that the B+ adjust pot had been turned down. After resetting the B+, the vertical problem was still there. All electrolytic caps and B+ voltages to the vertical circuit check OK. The only voltage that checks wrong is the voltage at pin 1 of the vertical osc/driver IC (NTE794). It is supposed to be 1.25 volts; but, checks around 3.8 volts. I replaced one cap that I suspected could be leaky and causing the higher voltage and checked the resistors having to do with that part of the circuit; but, everything checks OK. I'm wondering if the IC itself could be at fault. Of course, an NTE794 is NLA; so, I'd have to find a NOS one somewhere.

I really don't want to spend a lot of time or money on this set, since the CRT is a little soft. If I can get it going without putting much more time in it, I may keep it for a spare TV. Otherwise, it's going to the dump.

ctc17
07-06-2011, 09:31 PM
Is it pulled in on the sides too?

radiotvnut
07-06-2011, 10:30 PM
It was, until I adjusted the B+ to the correct value.

ctc17
07-06-2011, 10:49 PM
Its a long shot, but how about the vert out transistors. If one was leaky or the gain was off.
I guess one of those big bypass caps in the vert out section could cause it too as well as the IC.
Let me know if you want to try the IC, Im sure there is one floating around here somewhere..

radiotvnut
07-07-2011, 03:28 PM
Of course, the local parts house does not have an NTE794. They have a 793 and a 95; but, no 94. I'm still not 100% sure that the IC is bad; but, nothing else is turning up bad, either. If someone has a new or used good IC, I'd like to try one. Until I find an IC, I'm going to re-check everything in case I overlooked something. I did check the output transistors and their voltages. Everything checks fine there. Like I said before, the only voltage that's way off is pin 1 of the vertical osc/driver IC.

radiotvnut
07-07-2011, 05:35 PM
OK, I fixed the problem. It turned out to be a bad 1000 uf cap in the flyback supplied 29 volt supply to the vertical output stage. I'd already checked the voltage; but, I failed to check for excessive ripple with an oscilloscope. Once I noticed a bunch of trash on the 29 volt line, I tested the cap and it measured 380 uf, instead of it's rated 1000 uf. Now, I have a filled out raster; but, there are now intermittent horizontal streaks at the top and bottom of the screen that bounce around. Hopefully, it will be caused by bad solder connections.

The lesson here is to always check all power supply sources for proper voltage and excessive ripple before digging into a circuit. I already knew this; but, this was one of those times where I decided to skip a step and it ended up taking me longer to find the problem.

ctc17
07-07-2011, 05:45 PM
Cool. When I was in high school my friends family had a GE console that I would have to replace big bypass caps in. They were always the filter ones near the flyback too.

radiotvnut
07-08-2011, 12:33 PM
I resoldered some connections; but, it still has the intermittent streaks. It will run for awhile and then the white horizontal streaks will appear at the top and bottom of the screen. They also bounce vertically and they will often fade in and out. Sometimes, they will fade out and the TV will run for a long time without the streaks. Also, the video is not as sharp as it should be. Probably more bad caps.

holmesuser01
07-08-2011, 02:01 PM
Did you re-check the B+ after the capacitor replacement?

Maybe you are seeing blanking errors. Also, could easily be more capacitors.

radiotvnut
07-08-2011, 02:15 PM
Yes, the B+ is where it's supposed to be. If I can catch it in the act, I'll try to get some pictures.