color stripes on screen (slyvania roundy)

[technicolor]

well, checked all tubes, surprisingly only the high voltage tube was barely weak, low end of green, so i replaced it.

Colors are all messed up, when i dial in the fine tuning, i get what appears to color stripes on top of a back and white picture.

It also has a crt booster plugged into it.


any ideas, please tell me recapping this will fix this

[Charlie]

Color stripes on a b&w picture... check the color oscillator tube... 6GH8. It may be tired (they usually are). It's always good to have spare 6GH8 tubes on hand for color sets.

Weak/leaky caps could cause this as well... so yes, a recap might correct it.

The oscillator crystal under the chassis could be bad (cheap and easy to replace).

Even after replacing the above parts, you may still need to adjust the fine tuner to get a color lock.

[technicolor]

Originally Posted by Charlie

Color stripes on a b&w picture... check the color oscillator tube... 6GH8. It may be tired (they usually are). It's always good to have spare 6GH8 tubes on hand for color sets.

Weak/leaky caps could cause this as well... so yes, a recap might correct it.

The oscillator crystal under the chassis could be bad (cheap and easy to replace).

Even after replacing the above parts, you may still need to adjust the fine tuner to get a color lock.

Charlie, can u post a tube diagram layout, i followed the tubes that were in there, as most of the paper was ripped off the hv tower

I don't trust what was installed, maybe somebody made a mistake previously.


I seem to recall 2 6gh8, they both tested ok


also, what chassis is this?

[Charlie]

I am not home... I am on board ship... I have no access to a tube layout.

Maybe we can try this from memory (I smell something burning already).

I'm just going to assume your chassis is an RCA clone...similar to a CTC-15. With that being said, the color board is the one in the middle... at the rear of the set. This board has two rows of tubes... the forward row has 4 tubes, and the aft row has five. The 6GH8 you're looking for would be in the row of five... tube number 3... in the middle.

I've seen some 6GH8's that did not provide a lock... or was slow to do so... and still tested good in the tester. In my CTC15, I plugged in several different tubes before I got one that gave me a good, fast color lock.

[technicolor]

Originally Posted by Charlie

I am not home... I am on board ship... I have no access to a tube layout.

Maybe we can try this from memory (I smell something burning already).

I'm just going to assume your chassis is an RCA clone...similar to a CTC-15. With that being said, the color board is the one in the middle... at the rear of the set. This board has two rows of tubes... the forward row has 4 tubes, and the aft row has five. The 6GH8 you're looking for would be in the row of five... tube number 3... in the middle.

I've seen some 6GH8's that did not provide a lock... or was slow to do so... and still tested good in the tester. In my CTC15, I plugged in several different tubes before I got one that gave me a good, fast color lock.

my roundie combo sitting right next to it is a ctc-15, so that tip helped a lot.

I replaced the two 6gh8's with new ge, colors are stronger but still in a striping fashion.

Thanks for the tip on the crystal, looks like it's time to start recapping.

[reeferman]

Try this. Ground the grid of the 3.58 tube. Adjust the osc. transformer for this combination: minimum number of color bars AND to where they stop floating.
Use a color generator if possible.

[technicolor]

Originally Posted by reeferman

Try this. Ground the grid of the 3.58 tube. Adjust the osc. transformer for this combination: minimum number of color bars AND to where they stop floating.
Use a color generator if possible.

I'm ignorant of this, and u just went 40,000 feet right over my head.

[technicolor]

[Kamakiri]

I still say it's that .01 @ 1 kV white Elemenco on the board. That is exactly what happens when it goes BANG. Happened on my CTC-36. Replace the cap, and watch TV

[technicolor]

Originally Posted by Kamakiri

I still say it's that .01 @ 1 kV white Elemenco on the board. That is exactly what happens when it goes BANG. Happened on my CTC-36. Replace the cap, and watch TV

Thanks for the great advice, but slight correction, .001 and 2000 freaking volts. Just radios has that in 6000 volts. for like $5 each.

Time to pull a chassis and start making a list.

[Kamakiri]

Well, whatever it is, betcha that's the bad one. The one on my 36 was 1 kV iirc.....

[Username1]

Color is way off frequency, the more bars you can see the more off frequency it is......

If you don't have a tube chart (layout) look on top, or bottom of chassis for a color crystal, its aluminum, about 3/8 thick, and maybe 1 1/8" long, curved on the sides, about 1" tall, flat on top, and most likely has 3.58mhz or just 3.589 stamped in the top. The set will have only 1. Your color circuit is right near this item. This is your color oscillator crystal.

Your color osc. tube will be near it, the cap former Captain Picard is talking about should be near this item. 6GH8A's have short lives, you should keep a few NOS spares, you can switch out from that set to another to try, or with another in that set if you don't have another, you might see a difference if its weak or bad.

For this problem, look to color oscillator, or color afc, circuit, there is a rectangle 3 wire afc diode in that part of the color circuit. Its usually black plastic - almost same size as the color crystal.

PS both the crystal, and the 3 wire diode often are not the problem.

Actually now that I think about it more.... I think the 3 wire diode is the Horiz afc, and not color afc, so forget I said that... getting old....

Also, those caps with the thousands of volts are high tolerance caps, and high voltage rating because it is a critical value not to drift in value, don't worry there is not that much voltage there, its to keep the value stable.

[kramden66]

a 1600 volt cap would sub ? just a guess .

mike

[DaveWM]

oy vey

tweek the freaking osc coil 1/4 turn tall right next to the 6GH8 go 1/4 one way if more bars go the other way. Don't go crazy if it does not help its prob the crystal.

oh yea and use the correct tool so you don't break the core.

This is what reeferman was telling you a while ago, just without grounding the grid 1st.

[DaveWM]

Originally Posted by technicolor

well, checked all tubes, surprisingly only the high voltage tube was barely weak, low end of green, so i replaced it.

when you say HV tube what tube are you talking about? IF you mean the HV rectifier, then a tube tester is not much good unless its really bad, those operate at 25kv plate voltage, way above a tube tester. Besides most tube testers test them with a simple pass fail measurement should be marked on the testerd "diode" most likely at the bottom. Besides all the above color lock has nothing to do with HV anyway.