maggie roundie
 

hey all, this maggie i have all of a sudden i turned it on and there is no color b@w only then the color bars start to fade in and a few minutes later the color is fine. in the beginning it was missing a color then it popped in but now its all the colors. does this look like a demod problem or a tube?

Bad crystal/6GH8
Try 6KE8 instead of 6GH8. You can adjust the osc coil but if the crystal is going bad it will continue to drift. I keep a stock of them because most bad so often go after awhile use

the crystal being bad would allow the color to sync up after a few minutes? would these crystals be standard, 3.58mz or were there others. this chassis is a ctc16 clone.

Exactly, drift as it warms up. Any of those 3.58 crystals seem to work. The modern small package ones work fine and dont have silver in them so they should last forever. timmy flavored :banana: bread

ok well if the tube dont work then i guess i am pulling the chassis. but if it has a different number on it other then 3.58 then i guess i should get that one, if i can.

I have, i can send to share one with you.

Classic symptom of 3.58 oscillator drifting, you get rainbow bars. Phil is intimately aware of this problem.

There can be 3 reasons why this happens:

1. the crystal is going out, and the reactance tube can't pull it in to lock solid
2. a problem with the oscillator circuit itself (try twiddling the frequency coil near the tube)
3. alignment is so far off that the 3.58 information contained in the signal is too weak for the set to lock on to

Of course check the tubes, but you'll likely find a bad crystal or the oscillator coil out of whack. When you tweak the coil, you have to ground the signal coming from the phase detector or it'll just wander all over the place. You should see the rainbow bars float by slower and slower then they will lock in. Right before it locks, you'll notice the number of bars is getting smaller and smaller as the frequency gets closer and closer to being right.

Maggie Roundie
 

Agree with all the above. Also check all caps and resistors in the color sync circuit while you are at it, and clean the tube socket contacts.

I agree the short answer is most likely the crystal.

In answer to your other question, I don't think any color sets of the old variety ever used a crystal with a frequency of anything other than 3.58 Mhz. Especially not Magnavox, RCA, Zenith, Sylvania, GE, Curtis Mathes... you get my point. :D

would you know if moyer carry these crystals or are they a specialty item.

Nte359 or was it 358. Super common any electronics store or ebay.

also try the color killer tube, I had the same problem and it was that tube, otherwise you looking at component level troubleshooting in the color circuits

I have been having the same problem with my 1981 Magnavox T815 and everyone ignores me when i ask a question. Been asking for months.

Firebird,
I went back and looked at your posts. You have not been ignored. You have been not following many of the suggestions made, and have been wildly replacing things with no diagnosis.

If you would follow the repeated suggestions to get a schematic and take some measurements, you would have a much better chance of fixing what's wrong, and not creating new problems, which your scattershot approach seems to be doing.

Slow down and try to diagnose your problems first - people here can help, but only if you pay attention and work more methodically.

also you have a solid state set.much different that the roundie.in this forum are the greatest techs alive and they are always willing to help anyone.relax,post pictures when you can and your problem will be solved.this is like magic and treat it that way!

I'll add solder joints to that list. On my Silvertone CTC15 clone it would come on good then within a minute go to looking like those screen shots above and soon after go to a monochrome picture with all saturated color elements displaying as green. After running for half an hour normal color would pop in. I lived with it for about a year before a PS cap I had already replaced once failed. While I was in there to fix that I resoldered all the chroma reference osc. traces on the board...After that(and a tweak to the osc. coil slug) the color synch has been ROCK solid.

While working at Sears, long long ago, I was servicing a Wells Gardner monster 25" console hybrid with stereo and turntable. Problem was, TV could be playing, with great color, and if you turned up the volume, the color would unlock for a moment, then lock again. I was the 5th tech to have a look at it, and the customer was getting huffy, and threatening to call Chicago, etc, etc. I asked her to sit down and watch me troubleshoot. I had her tell me everytime it lost color, which she did, with gusto. I was poking around with a wood dowel, and almost everywhere I bumped the color PCB would make it lose lock. A previous "tech" had already hard-soldered the board connector pins, so it wasn't a bad connection there. Another tech had replaced the crystal, but I noticed the crystal was touching the chassis. If I flexed the chassis, the color would bounce out and back.

I resoldered the crystal and drastically shortened its connecting wires. I couldn't get the color to unlock after this. I have often wondered if the vibration of the crystal wires, or the fact that it was vibrating against the chassis caused it to lose sync.

I sat there while the customer cranked her system up to earsplitting volume over and over, until she was satisfied that I had fixed the problem.

I got fussed at by our Tech Services Dept. because I spent almost 2 hours on this set instead of the 45 minutes I was alloted. Didnt matter that I managed to complete the call on the first attempt!!

I was requested by the customer to return when we did the annual maintenance check per her maintenance agreements. I never had to do anything to the set again other than maybe touching up the screen controls, and replacing a weak video output tube, twice.

I know the store repair department sure didnt want to get this set back. It weighed over 200 pounds, and was, like I said, HUGE!!

Aahhh, memories...

i had that same set!it was a penncrest combo made by wells gardner.rauland crt and it had the best sounding stereo!rocked the block.tv had a fine picture and we used for 3-4 years.never a problem.i sold it to a friend who still has it.the crt has a green halo but it still works.a little dim but the radio is crystal clear.heavy as hell but really a good piece.this might be the exception.saw other wgs that were dogs

If they are so great why don't they know what is wrong with my set? Arrogance is easily replaced with answers.

Post the schematic for your color circuit and we will point out the actual items to try replacing. Just scan the color section of the factory or Sams schematic, edit if necessary, and paste :banana: I assume this is a solid-state TV?

Is anyone else here getting more than a little annoyed with Firebird's attitude? I've been on here a short time myself, and I'll admit that I probably know less than most, but I also found out that if you ask POLITELY, you'll alwas get an answer.

I'm sure that those on here experienced with solid state equipment are knowledgeable on common issues regarding most specific sets, but without a schematic, and if the person who actually has the set does not want to help trouble shoot the set with test equip, then short of the owner bringing the set to someone who will do the trouble shooting, all the help you get will likely be WA Guesses at best.

...We are not phsyc..psyc..Telepaths, and we can't troubleshoot a set without having the actual set in front of us, or having the owner act as our eyes, ears, and hands.

I'm not trying to sound mean....I'm just stating the facts.

firebird is just a little annoyed with the lack of response.post some screen shots and these techs will point you in the right direction.ask and you will receive.demand and you will wait forever!just kidding.relax,we will help you

What sams

???

Hmm....

'Sams' is a series of manuals devoted to the TV servicing industry They contain service info and schematic diagrams of most/all North American model TV sets.--Even I know that, and Ive never seen one--living in the UK, we have the 'Newns' manuals and 'Trader' sheets which are a loose equivalent.

Here you go, Look up your set--

https://www.samswebsite.com/en/photofact/search/types

You'll need to find the schematic of Your Actual set in this series of manuals or from its makers/other sources, and copy the chroma/sound/IF stages, parts of it here so a diagnosis can be made. You'll need to include as much info as you can,--things you've done, voltages checked, parts changed etc.....

Otherwise its like saying--My car wont go. --Why?--Not trying to be clever, but fault-finding is a detailed process, needing as much info as possible....

Magnavox
 

[QUOTE=Firebird;3049977]I have been having the same problem with my 1981 Magnavox T815 and everyone ignores me when i ask a question. Been asking for months.[/QUOTE

If it is a modular set, start by changing modules...keep a saved watch for MAGNAVOX MODULE on ebay.

Duane