Advice sought for 1968 RCA GL-644W

[Chad Hauris]

It's time for the real troubleshooting now, not just supposin'!
You need a schematic and go in there and check out your voltages and I would start with the supply to the IF stages. When you get past just checking tubes and visual inspection you need your schematic with voltage measurements or you will waste your time big time and be frustrated trying to find the problem.
If you don't have a copy I should be able to find one.

[Radiophile2001]

Chad,

Thanks, but I don't have the skill set needed here......I've never read a schematic (seen them though) and don't have the voltage meters needed. Have soldering iron will travel is about my limit. Not in the league of you all, but have a lot of respect nonetheless. My uncle was a TV repairman on the side, God rest his soul...! Never got a formal education from him! ;-)

Probably my last hope on this one is someday to get it out to Bryan Gadow's place when he's not too busy and leave it to his capable hands. Maybe someday I'll get down to brass tacks and learn proper troubleshooting and repair...!

Thanks again for all the help!!! Will update down the road.

[holmesuser01]

I have a feeling that some of those tubes you bought are not too good. OR, you have some really dirty tube sockets. Bouncing the set made me think of these things. If I were you, Id resolder any PC ground points, and anything else around the tube sockets that looks dull, or you see cracks in the solder. Any chance that you adjusted the AGC control a bit too much?

You really need access to a good tube tester. One that can really work the tubes in question. At the least, your set has all its deflection and HV circuits working. Thats one BIG problem in most of the old sets I see.

Have you messed with the tubes in the tuner at all? If nothing else, try reinstalling the original tubes, except for the damper, and the other one that you found bad. Even original weak tubes are sometimes better than ebay junk. People will sell anything there, and tell you that they have tested everything, etc, and still lie to your face. These are in the minority, but they are there. I, on the other hand, have only had one bad ebay experience. The seller sold me a load of tubes that tested good on his checker, and mine, but in the circuit, they were microphonic-- tap the tube and hear it 'tinging' in the speaker! Wouldn't take them back.

One other thing, dont adjust controls that you dont understand. Your set will work again, but you gotta go easy on her. You are so lucky to have that style set.

Any chance the normal/service switch is in the service position?

[bgadow]

A lot of things to check, and lots of good advice being given here. It would be nice if it was something simple-would be a lot of trouble to bring it down here, and then the pressure would really be on me to figure it out! Ha! You could just pull the chassis in that situation, and I could try to rig it up to my test jig, but that is still lots of trouble.

First thing I would do, if you haven't already, is take Holmes suggestion regarding the service switch. With the set on, work it back and forth a few times and see what happens. These get dirty contacts and cause problems.

[Radiophile2001]

Hi,

A few answers/questions:
Spun the AGC screw around a few times both ways, no difference.
The service switch--same thing (had messed with that one in the past too).
Is it possible these new tubes could go bad so quickly after working so good?
(putting all the old tubes back in will be next project if the answer is Yes).
Most tubes light up strong with blue halos inside.
Have wiggled most of the tubes around a bit while the set was running, but no difference except for the 12HG7 V/O--loud popping sound in the speakers. Still see that spark in there under one pin.
Did try this too with no change or improvement:
Ground up some steel bar on the grinder to get metallic powder. Carefully dumped some of it in the 12HG7 tube socket holes to get better contact in there. Didn't help nor hurt. Removed most of it with a magnet.

Bryan--no pressure, promise! You could take as much time as you wanted. At least I know the CRT is still good. If that hadn't come back on after the new damper tube was installed, I'd probably bag this one.

PS, should I spray contact cleaner in that service switch and try again?

Thanks again for the advice and have a great 4th!

Carl

[Radiophile2001]

Update #4:

Replaced all the tubes with the old ones....got the same white screen, but a bit dimmer and smaller with a black area at the bottom. Wavy, unstable illumination as well. Contact cleaned the tube sockets and service switch too. Replaced the new tubes again and back to stable white screen.
I also remember as the set was failing, when I changed VHF channels, the screen would go completely black for a split second before illuminating the channel. That only happened for about a day before it went totally kaput. No idea if that's a telltale clue...!

Thanks, as always!

Carl

[holmesuser01]

If I were you, I'd re-replace the old tubes and when you see the dark area at the bottom of the screen again, replace the 6GF7 vertical output tube with the new one that you have onhand. Leave all the originals in place, and continue to troubleshoot. Check your soldering, as you can easily have a solder bridge somewhere. I thinks you really need to pull the chassis and tuner so you can see whats what, and DONT grind up metal shavings to check the tube sockets. Metal shavings are BAD!

Chances are that most of your original tubes are probably still good. Ive seen some 45+ year old tubes that still check in the high GOOD area after some tubes in the same sets have been replaced again and again...

[Radiophile2001]

No points for creativity on the metal shavings thing, huh? ;-)

I thought my V/O tube was a 12HG7....is 6GF7 one as well?

I should specifically check the solders underneath that one, no?

[holmesuser01]

The 12HG7 is your video output tube. The 6GF7 is the vertical multivibrator/output tube. I still think that there are either solder bridges, or some bad connections somewhere. Best of luck to you.

[Radiophile2001]

Thanks,
I will update the next time I get to tinker with it.
Happy Friday.
Carl

[Radiophile2001]

Figured some may be interested in this one......1960 RCA color, MINT

http://cgi.ebay.com/WORKS-Collectabl...QQcmdZViewItem

[holmesuser01]

Do you really think that someone would pay that kind of money for that old set?

Having any luck with your set yet?

[Radiophile2001]

I think some might.....it's really first-generation color, right? It will be interesting to see what happens. No bids yet with 7 hours left. Seems it has a focus issue.

My set is kind of on hold right now, as we have house guests for a couple weeks (wife's siblings, kids) and one of my kids' birthday parties is tomorrow.

You are in Asheville. Ironically, I picked up the now-broken set in Clinton, SC--not too far from you. Someone I work with's grandmother had the old set there and gave it to me for free. That was a drive--483 miles each way. Insane, as well...! (I certainly paid for it in gas $$). That was the closest place I had found though, after weeks of searching on ebay.

I'd really like to find someone who can fix this set, as hopes for my own fix are dimming. I'm sure I will try again, probably next month, per your latest instructions.

The local repair shop said $125 to diagnose and $300-$1200 to fix...!
I will say, though, that CTC-38A gets great reception.

Currently, I am enjoying the two sets I bought from Bryan G. in MD: The 1969 RCA Mural TV (hotel set) and the 1968 Zenith 25". They are both hooked up to signal amplifiers and new rabbit ears. (separate for UHF and combined for VHF) Not too bad reception for 33 air miles south of DC and in the basement office! Also get Balto and Richmond stations to a degree.

Carl

[holmesuser01]

Carl:

Stay away from your local repair guy. Thats insane. It will be something fairly simple to repair, but the chassis needs to be pulled and examined CLOSELY with a good light. There are many heavy parts under the chassis that could have easily been jarred loose when you were bouncing the old girl It could be as easy as a bad connection on the tuner itself, which you cant see because the chassis is in the set. Too bad that none of us are close enough to you to lend you a hand in your work. I'd love to troubleshoot a big RCA again!

[Radiophile2001]

OK, how about this.....When I'm getting ready to fix it again, I call you and maybe you can walk me through a bit of this over the phone? I do have a 500-watt spot lamp.

Who knows? Surgeries have been done this way...why not TVs? Just an idea.

Thanks