Recapped the Avanti and.... - Videokarma.org TV - Video

TinCanAlley · #1 07-26-2013, 05:06 PM

Well the recap went well. I had to readjust the contrast, vertical size and a few other adjustments. A few of the caps were 50% or more out of tolerance. I changed the 10uf 350V in hopes it would get rid of the jail bars (picture attached), but it didn't. They're pretty faint, but noticeable in dark scenes. Is there another area I should be looking to fix?

I also changed the subcarrier regenerator module as the current one wouldn't adjust the APC correctly (the pot had a messed up slot for the driver and the center leg was loose in the circuit board hole). I was unable to get the pot to turn correctly. By the damage to the face and the leg, it looks like someone put too much pressure on it, stripped it and pulled the leg out.

I started the convergence from scratch and after an hour or so, I got most of the screen converged (picture attached). The only part is the top center. I tried so hard to get it converged, but it wasn't meant to be. I can live with this over how it was.

lnx64 · #2 07-26-2013, 05:27 PM

Call me crazy, but those jailbars look just like my samsung when i tried a faulty out of spec flyback on it, until i replaced it with a higher quality flyback.

TinCanAlley · #3 07-26-2013, 06:04 PM

I'm assuming the flyback is part of the tripler? If so, it seems to be the original unit in the TV. For the most part, it's quiet and there's no smell. Beyond those two things, I have no idea how to figure out if it's working or up to specs.

Electronic M · #4 07-26-2013, 07:18 PM

The flyback supplies the input signal to the tripler and is not part of it.
This could be an issue with the horizontal drive or the tuned circuits around the HOT, flyback, yoke or damper system.

TinCanAlley · #5 07-26-2013, 08:15 PM

Quote:

Originally Posted by Electronic M

The flyback supplies the input signal to the tripler and is not part of it.
This could be an issue with the horizontal drive or the tuned circuits around the HOT, flyback, yoke or damper system.

I'm attaching a pic of the high voltage area. I see the tripler, but the other pieces are unknown to me. The SM doesn't go into detail about what things look like and they don't provide pics. The multi-wire plug on the side must be feeding the tripler, so if I trace it back I'll find the flyback?

Thanks

mstaton · #6 07-26-2013, 08:20 PM

The fly is the black thing with the red wire coming out the top with the black goo. The multi wire plug feeds the flyback

***Eric H*** · #7 07-26-2013, 08:39 PM

The Tripler is the gray square thing top right. I don't think it could cause jail bars but maybe someone else would know.

Did you just replace the Electrolytics? I know it uses modern film caps but they are still pushing 40 years old, I'd replace any in the Horiz sweep section just to be safe.

mstaton · #8 07-26-2013, 08:41 PM

Sometimes RF modulators can cause this also

TinCanAlley · #9 07-26-2013, 09:40 PM

Quote:

Originally Posted by Eric H

The Tripler is the gray square thing top right. I don't think it could cause jail bars but maybe someone else would know.

Did you just replace the Electrolytics? I know it uses modern film caps but they are still pushing 40 years old, I'd replace any in the Horiz sweep section just to be safe.

That's gonna be a tough one. They list electrolytic separately, but all others are lumped together without noting what kind.

TinCanAlley · #10 07-26-2013, 09:40 PM

Quote:

Originally Posted by mstaton

Sometimes RF modulators can cause this also

I thought about that, so I connected a VCR directly to the set and the same appears in dark scenes.

Findm-Keepm · #11 07-26-2013, 10:03 PM

'taint the flyback - most likely a filter cap in the B+, particularly the cap(s) feeding the horizontal driver/output and boost filter. Those Zenith flys usually arced internally when they fail, causing snivets and tearing in the picture.

What signal source are you using? RF Modulators in VCRs can cause this, as well as your humble cross-hatch generator.

I've also seen bad IF cables cause jailbars - usually the result of someone jerking too hard when removing them. Really bad on lowband VHF, which is what we use with most modulated signals now (Channels 3 or 4). It could be an IF cable isn't plugged in all the way , leaving a ground loop.

Check the caps first, then the IF Cables.

Cheers,

Findm-Keepm · #12 07-26-2013, 10:05 PM

Quote:

Originally Posted by TinCanAlley

I thought about that, so I connected a VCR directly to the set and the same appears in dark scenes.

Does the Avanti have direct video in? If not, then your are connecting through an RF modulator in the VCR, right?

Cheers,

TinCanAlley · #13 07-26-2013, 11:25 PM

Quote:

Originally Posted by Findm-Keepm

'taint the flyback - most likely a filter cap in the B+, particularly the cap(s) feeding the horizontal driver/output and boost filter. Those Zenith flys usually arced internally when they fail, causing snivets and tearing in the picture.

What signal source are you using? RF Modulators in VCRs can cause this, as well as your humble cross-hatch generator.

I've also seen bad IF cables cause jailbars - usually the result of someone jerking too hard when removing them. Really bad on lowband VHF, which is what we use with most modulated signals now (Channels 3 or 4). It could be an IF cable isn't plugged in all the way , leaving a ground loop.

Check the caps first, then the IF Cables.

Cheers,

Would the caps for the B+ be in the large canister? I've changed all other electrolytic caps except for the canister. I can't find a replacement and the replacement 400uf caps are 23 dollars each and requires two of them. The two 500uf caps are cheaper.

I was using the RF in the VCR as well as an RCA external modulator for my DVD and Roku players. The effect is still there no matter which one I use. I'll open the back tomorrow and check the IF lead.

mstaton · #14 07-27-2013, 01:01 AM

You dont have to buy the same type can caps. Use individual ones under the chassis or restuff the cans. What voltage are those caps?

Findm-Keepm · #15 07-27-2013, 04:43 AM

If those can caps (twistlocks, FPs, TVLs, can caps) are 450V or less, common 450V types are cheaper, and you dont' even have to restuff them, just isolate them and add the caps under the chassis. Radial 450V caps are cheaper (most less than 2 bucks each) than axial caps at Mouser. I've also used 450V Panasonic caps I got from Talon. JustRadios in Canada has them too in generics - both axial and radial types.

Doug's (DRH4683) capacitor restuff tutorial here on the forum is great if you choose to restuff the originals.

Cheers,