Sylvania 580 chassis (CTC-15 clone): Insufficient width. - Videokarma.org TV - Video

nasadowsk · #1 12-19-2012, 08:36 PM

Ok, so I'm going over my Sylvania 580. It's got the following issues:

* The high voltage is a touch weak - I can get 22.5kv, not 23.5kv spec'd, without any major drive lines on the screen. If I go for the 23.5kv, I get a drive line on the screen (or at least I'm getting vertical lines that look like drive lines). I'm about 1,000 volts shy, here.

* The width: It, in a word, sucks. I'm about 2 inches too narrow, really more like 3 or so. I've got about an inch edge on either side of the screen.

I haven't touched the horizontal efficiency coil. Current is about 160ma, which just seems too low.

Am I looking at an issue of insufficient drive here, or should I just go in and turn up the current via the horizontal efficiency coil? I'd rather not stress the flyback more than it is, but from what I've typically heard, it's a struggle on these sets to get it below 220ma without major picture/HV issues.

Any ideas guys?

Thanks!

nasadowsk · #2 12-19-2012, 09:00 PM

Ok - I just tried tweaking the efficiency coil. I can't get the current to come up above 170ma at all. Slug all the way in, partially out, fully out. It just won't get up there.

Should I even bother trying to swap out the Horz Output tube and or damper for new ones?

Ok, another thing - tapping the blanker tube (actually, pulling it out partly) causes the current to rise up to narly 200ma, the width to go to darn near normal, and the HV to get a bit punchier. I have a *blanker* issue?

ctc17 · #3 12-19-2012, 10:22 PM

Its common on the rcas for a trace on the edge of the board to crack and cause exactly this. I dont know if the sylvanias have this but its worth checking out.
The voltage you want to check first is the horizontal output SCREEN and the grid.
If the grid is too negitive (should be something like -50, if it -60 that the problem) and if the screen is low check the resistor providing power to it. This is also the symptom of a weak horizontal output tube, in that case the screen would be high.

The trace that cracks on the rcas basically causes excessive drive and low horizontal output/width/hv....your exact issue.

I should add that the trace connects to the grid of the 6GU7 horizontal blanker tube. There is a 390k resistor on the grid of the 6GU7 that goes from grid to ground and the trace connects that 390k to ground. If the trace or resistor goes the grid of the 6GU7 foats

nasadowsk · #4 12-19-2012, 10:58 PM

Yep. That's what it is - bad ground on the 390k resistor. I jumped it with a piece of wire and the set acts a LOT better. I can JUST get 23.5kv out of it, but the regulation is a bit poor. So I might have another issue in there (I'm recapping the sweep board anyway, so I'll check it tomorrow), but temp jumper helped out a LOT. The 6BK4 is glowing nicely, so I'm sure I'll glow in the dark tonight!

Horizontal current (untweaked) is about 195ma. I can get 23.5kv if I turn the HV adjust full up. Width is awesome

So, I'm getting there. I wonder how repairmen felt about RCA vs Zenith, in terms of serviceability - the Zenith just seems a cleaner design overall (I've got a 25LC20 coming up as the next contestant).

ctc17 · #5 12-19-2012, 11:21 PM

RCAs always work better for me even with all their quirks. Zeniths always seem to have a noizy picture and the color is warmer on RCA. People get too hung up on that point to point wiring crap. I also hate the zenith puls HV reguLator, never have got one to work right

ctc17 · #6 12-19-2012, 11:31 PM

I doubt the caps are bad, the tube sockets do break up easy. Is it a D01-2? Never leave it on un attended. I found one in a shop that had caught fire

nasadowsk · #7 12-19-2012, 11:50 PM

It's a 580 chassis. The one right before the DO1. It's a clone of the CTC-15 as far as I can tell. I have the Sams for it anyway.

As for caps? I'm not replacing them all, just a few in the sweep sections. After all these years of getting wacked with high voltage pulses, I'd imagine a few are tired. What's interesting is the orange drop replacements are almost the exact size as the original brown caps. The 1.5meg resistors in the HV regulator circuit were both way off, which wasn't helping the HV adjustment. I have a matched pair in there now (which the Sams says they should be).

Right now, the big issues are:

* At 23.5 kv, the picture is fine until the brightness is turned a bit too high, then it loses focus and blooms. I'm not sure what's up with that (is it normal?). "too high" here means almost decent brightness - the CRT is a RCA Hi Lite replacement...

* The convergence sucks. I haven't even tried to do it, yet, though. That'll be the next battle - this set's historically been a bit bad in that department.

* Tuning in a color picture also tends to mean a bit of noise in the picture. Chroma alignment?

It's getting there, though.

marty59 · #8 12-20-2012, 08:14 AM

Your 3A3 may be weak/bad causing your blooming issue and the convergence could be a couple things voltage related (convergence diodes) for first things to look at.

If you have a tuner subber I'd see if that helps with the color issue, for starters..

ctc17 · #9 12-20-2012, 09:48 AM

Change the 3, .01 caps that drive the grids of the 6GU7s. they sit in a very hot spot and tend to short.

The blooming could also be you have the screens and or bias up to high. You have to keep in mind these these sets were never designed to be that bright and limit the brightness

dieseljeep · #10 12-20-2012, 10:11 AM

Quote:

Originally Posted by ctc17

RCAs always work better for me even with all their quirks. Zeniths always seem to have a noizy picture and the color is warmer on RCA. People get too hung up on that point to point wiring crap. I also hate the zenith puls HV reguLator, never have got one to work right

I acquired a new respect for the RCA sets.
You're right about that regulator issue on Zenith's. I had nothing but grief with H.V. regulation on 16Z8 and 14A9 series chassis.

ctc17 · #11 12-20-2012, 10:54 AM

Heres the video of the burned up Sylvania chassis we found. http://youtu.be/uCPYnQpJmFE
This is a bit newer but still, this is why you never leave a vintage set on unattended. If you have to for some reason, fuse everything.

I have a bulletin from Zenith on a mod for that hv regulation. I should scan that and post it.

I will say this about Sylvania,,,I am a fan, the sets have a great picture but they can be super hard to fix. I have a fairly large collection of them, they are all the newer Gibraltar series tube chassis

timmy · #12 12-20-2012, 11:36 AM

oh boy this sounds like some of the issues i had with my silvertone, video overdriving, lowering the brightness, voltages at the video output tube.

old_coot88 · #13 12-20-2012, 01:21 PM

Quote:

Originally Posted by ctc17

Heres the video of the burned up Sylvania chassis we found. http://youtu.be/uCPYnQpJmFE

Tarnation. That mus' be whutcha call a hot chassis.

nasadowsk · #14 12-20-2012, 08:02 PM

Well, I got the blanker all sorted and did a quick and dirty convergence and setup. It's quite watchable, though not perfect, yet.

One thing, while I was replacing the HV lead (the old one was, well, leaky), I cracked one of the posts in the cup that holds the HV rectifier socket. Apparently, it's the most brittle plastic on earth

So I have to hunt a spare down. I'm guessing it is the same as a CTC-15's, the HV box on this set looks identical to the '15.

DaveWM · #15 12-20-2012, 08:15 PM

I have been able use 5 min epoxy to fix those, it best to let the epoxy start to setup, and you need to have everything out in the open. Just a little bit will do the trick, and run the screw in and out as it completley sets up. You have to work fast as the working time of 5 min goes fast once it starts to kick off. If you do it too soon it becomes a royal mess, too late and it will not give you enough time to get it positioned correctly.