Potential new project! Color Admiral!

[LukeSimon]

I recently restored a Magnavox T931, which is very similar to the T933. I think the T933 added horizontal centering circuitry and maybe horizontal size controls. Instead of using DC restoration via a diode clamper, Magnavox used partial DC coupling of the DC bias from the video detector. This makes the brightness less consistent than what you get with a diode clamper DC restoration design, but it is better than nothing.

The TV’s focus coil is a bit weird too. It can be locked into position, and unlocking it is sometimes a challenge. I wish they just kept it a normal screw type adjustment slug transformer. I am curious to see the state of your T933’s flyback.

If at any point you give up on that TV, I am interested in buying spare parts for my Magnavox. I need a replacement “clover” style dynamic convergence assembly, as mine is cracked due to over tightening. So I’d be interested in buying parts from you.

[Yamamaya42]

Just placed a order for a bunch of electrolytic capacitors for the set, as I'm sure they are no good as always.

The flyback transformer looks clean, shockingly clean, TOO CLEAN almost, it has had an easy life, or has been replaced, never seen one this nice before.
http://suzaku.live-evil.org/0522230602a.jpg

This is obviously a custom cabinet, because one dumb thing about it, there is no room to get to and open the side cover on the HV box w/o swinging the chassis out for room.

Another thing that was noticed was, all the screen controls were turned all the way up almost, this does not match with the rather decent emissions that were shown with the CRT tester, meaning some fault with the chassis to be worked out, likely a weak selenium boost rectifier like I had in the Hoffman Colorcaster, or some other fault in the CRT circuitry.

[LukeSimon]

My T931 had screen cranked even though CRT emissions was good. It turned out that the horizontal blanker tube V19 (6GH8A) was tired, and when that tube gets tired the DC bias of the picture tube G1 anodes becomes very low. So you should try swapping that blanker tube for one that is know to be good.

In fact, the only low emissions tubes in my T931 were the three 6GH8A tubes. Chroma demod didn’t work until I replaced the 6GH8A that was used for the chroma oscillator. The T933 chassis is almost identical, so consider swapping those 3 6GH8A tubes out for NOS.

All of the electrolytics were still within spec too, except the two on the convergence control board.

My T931’s flyback looks great too. I think it is due to the fact that the horizontal efficiency coil was tuned for absolute minimum horizontal output tube cathode current. Tuning that coil doesn’t just decrease wear of the HOT, since the HOT is in series with the flyback transformer, that coil’s tuning decreases the wear and tear of the flyback transformer.

[Yamamaya42]

http://suzaku.live-evil.org/0522231939.jpg

Very very dirty chassis, and smells of smoke, (tobacco)

http://suzaku.live-evil.org/0522232147.jpg
much better!

not gonna even try to power it up till the weekend, it will have plenty of time to dry.

[LukeSimon]

Some of the coils are made out of magnet wire wrapped around a cardboard cylinder. Won’t water damage them?

[Yamamaya42]

Originally Posted by LukeSimon

Some of the coils are made out of magnet wire wrapped around a cardboard cylinder. Won’t water damage them?

No, the paper types are impregnated with a high temp substance that makes them water proof, just don't use harsh cleaners on them.

[Yamamaya42]

http://suzaku.live-evil.org/0523230557.jpg

you can see it in this bad coil from a BW set, it's sealed with some sort of enamel material.

[Zenith26kc20]

I did my t933 some years ago. I also had the blanker tube make the picture tube look bad. Over the years of owning it the degauss themister/varistor failed, the high meg resistors in the vertical failed and one of the convergence coils on the clover opened up. Mine has all original power supply electrolytics and the original flyback. I adjust the HOT current whenever I replace the output tube. I use it an hour once a week.
They can make a good picture!

[zeno]

The blanker tubes went every few yrs. It may be why the G-2's are high.
TNR shield often missing or hanging loose in Magys. Tuners were constantly dirty
& messy techs just tossed them. Maggy even tried tuner pads, no joy. Dont
remember who built them but they were in other sets & didnt have problems.
Go figure
Part you found looks like its part of a coil form with the slug.
Look on the CONV panel.

73 Zeno
LFOD !

[Yamamaya42]

Originally Posted by zeno

The blanker tubes went every few yrs. It may be why the G-2's are high.
TNR shield often missing or hanging loose in Magys. Tuners were constantly dirty
& messy techs just tossed them. Maggy even tried tuner pads, no joy. Dont
remember who built them but they were in other sets & didnt have problems.
Go figure
Part you found looks like its part of a coil form with the slug.
Look on the CONV panel.

73 Zeno
LFOD !

Correct, that mystery broken coil part does look like it is from the convergence PCB, but all of them are intact!
one must have been broken and replaced in the past, no telling HOW LONG that piece has been in there!

[Yamamaya42]

DAMN! there is NO ROOM to reach under the chassis to change out C1, it's just too tight under there.

[LukeSimon]

Originally Posted by Yamamaya42

DAMN! there is NO ROOM to reach under the chassis to change out C1, it's just too tight under there.

Why did they design the chassis to tilt that capacitor? Was it to tilt it away from the isolation transformer’s heat?

[Yamamaya42]

Originally Posted by LukeSimon

Why did they design the chassis to tilt that capacitor? Was it to tilt it away from the isolation transformer’s heat?

I.m gonna have to do something drastic to replace it, cause I have noise in the B+ line

[Yamamaya42]

https://www.youtube.com/watch?v=QFl25sRnB0E

many weak tubes
most are still the original.

gonna have to check all the resistors as well

but FIRST video

[Yamamaya42]

Yeah, the tuner was very dirty, it was a bitch to get out because of the silly front screw in system they use that you have some odd key to unscrew.
Even after cleaning the contacts for chan 3, had problems getting a clear pic due to what I believe to be tired/ worn tuner tubes, only after hooking in a 15db rf amp was I able to tune in a clear video w/o snow.
Cause as mentioned, it seems that almost every tube is OEM and most likely worn/ tired.
I did try a couple of 6GH8As in the V19 socket ( h-blanker / bandpass) that were of unknown state, the first one made no change in the picture at all, the other must have been VERY bad, cause something smoked as soon as it was turned on, but STILL WORKED when the previous tube was put back, will no doubt find what it was when I check resistors, most likely many will be out of tolerance and need to be replaced.

Tubes ordered so far, based on what was observed, both tuner tubes, video output tube ( the video was being overpowered by color ) and the R-Y B-Y G-Y compactron, what color there was , is very off balance like one of the Y-amps was weak, though this could be bad resistors, but a 50+ year tube can also do it.

As mentioned, C1 is going to be a big pain to replace, C2 C3, are not so bad, but it looks like C1 was put in first, soldered in a very tight area, and then everything else wired in neatly and tightly in layers under it, there is no way to reach the bottom of C1 w/o ripping it all up.

What I may end up doing is attacking C1 with a dremel cutting wheel, won't be pretty but should work, cut around the base remove can and guts, work down to attach 3 new caps using solderable base of old C1 while leaving wiring to it under it undisturbed. ( idea anyway ).

But for now, gonna start with checking resistors on the chroma / luminance board.