Zenith Custom 23 Super H Chassis: FIXED

[Kamakiri]

So here I am on the next one . Here's where we stand....

Did a basic recap of the mylars. Hoping that the filters were good, just because I get lucky once in a while on 1960s Zeniths . It's not proving to be the case.

Attached is a pic of what I'm getting on the screen at the moment, perfect sound, and I can adjust the picture to come in great with great sync lock, even if it's only 2" tall.....lol.

Two other things I need to point out. First, the flyback's plastic coating seems to have melted off, and is sitting in the bottom of the HV cage. Ever eat a DQ Dilly Bar, and one of the pieces of the chocolate coating comes off in the shape of the bar, kinda rounded? That's what the flyback coating looks like. It's not arcing, but wanted opinions to see if I can re-seal it somehow.

Second, is this really weird 3 wire disc cap. It says 87* on it, and to be honest, I can't ever remember seeing one like this before that needed replacement. It's cracked like dry dirt in the center, so I'm assuming that it needs to be replaced. But with what?

NOW.....yes, I know that I'm going to have to do the filters, as much as I dislike doing them . That's next. Wondering if anyone has any thoughts on the rest?

[DavGoodlin]

Tim,
Whats the chassis number? I can send you a schematic if its a pre-66 set. You will need it to figure out the disc.

The 87-disc is probably a dual capacitor but not quite an "integrator" and is most likely your trouble. It can be built from 2-3 separate caps/resistors. '
Also, Zeniths of this era had issues with open height/linearity/hold pots.

As for the flyback, replacing paper caps in and around the damper-boost circuits off the fly will cool it down, as it probably got hot before the vertical crapped out. Its all related. Long ago I fixed the arc-trashed flyback in my RCA CTC12 with a brush-on coating by GC, http://www.alliedelec.com/images/pro...S/70159781.pdf

DAve

[Kamakiri]

It's a model F2737E, dating it to 1961.....

[zeno]

The 87- is probably the problem. There is a color dot on it
that gives you the part #. Example yellow dot = 87-4 etc.
Use resistor color code...... If you cant get NOS look in the
SAMS they often have the break down of them.
If it were a Zenith double disc cap it would have a 22- part #
and usually be blue or tan.
The 87- integrators were high failure so start there. Must
have put in 100's of them in the good old days.

73 Zeno

[DavGoodlin]

Originally Posted by zeno

The 87- is probably the problem. There is a color dot on it
that gives you the part #. Example yellow dot = 87-4 etc.
Use resistor color code...... If you cant get NOS look in the
SAMS they often have the break down of them.
If it were a Zenith double disc cap it would have a 22- part #
and usually be blue or tan.
The 87- integrators were high failure so start there. Must
have put in 100's of them in the good old days.

73 Zeno

Good eye! and its in the feedback loop of the 6EM7. Sams 525 lists it as K2, replacements by Centralab PC-408, aerovox PA-764 or a Sprague V-14. I did not check the chassis 16F21 factory manual, but probably no clues there.

The equivalent circuit looks like a few series resistors with capacitors from each junction to ground. An RC network optimizing shape of the vertical sawtooth for linearity, it was simply designed to save labor and space.

Any guesses as to what those values really are, but a look at an RCA CTC-11has a 6EM7 and similar values. The CTC 11 circuit has two 680 pf to ground on either end of a 47K resistor in the feedback loop with a 100K on plate side and a .0068 mf on the grid side. Sub in those parts for the "K2"

[Kamakiri]

Interesting development here.

I parted out a '67 Zenith color set that was toast, in hopes I'd find one of those 87*'s, and sure enough, I did. But I also found something else pretty interesting.....a blue cap with a similar 3 pin configuration and a VALUE on it!!!

As you can see, it shows a "2 x .001 10%" on it. Using the center pole as a mutual ground, I tested the two outer ends, and it is exactly a double .001 cap.

Now, for the 87* , it tested at .00189 on both ends, or .002 each side, for all intents and purposes. What the devil the "87*" means, I have no idea, but there it is.

Now, I'll sub in the 87* from the other set, into this one and see what happens. I don't have any .002s on the shelf, and I hate putting in four .001s.

[Kamakiri]

Originally Posted by zeno

The 87- is probably the problem. There is a color dot on it
that gives you the part #. Example yellow dot = 87-4 etc.
Use resistor color code...... If you cant get NOS look in the
SAMS they often have the break down of them.
If it were a Zenith double disc cap it would have a 22- part #
and usually be blue or tan.
The 87- integrators were high failure so start there. Must
have put in 100's of them in the good old days.

73 Zeno

Oh, wait a minute wait a minute. I doubled back and re-read this, it's been a couple months. So is it NOT a cap? I'm confused.

[zeno]

Originally Posted by Kamakiri

Oh, wait a minute wait a minute. I doubled back and re-read this, it's been a couple months. So is it NOT a cap? I'm confused.

THE 87-* is the integrators. The color blotch on it is the 2nd part
of the part##. If one has a yellow dot its an 87-4 green dot is
87-5 etc. Use the resistor color code.

22- numbers are for most Zenith caps. The double caps I remember
were .001 They are usually light blue. I NEVER replaced one.
If your cans are still OEM they will also have 22-**** numbers.

The #1 vert problem on old Zeniths is the integrators ( 1 or 2).
#2 is electrolytic in cathode of vert. output. Its prob in
one of the cans. #3 is other caps in vert feedback loop,
from the output plate to the osc grid. That is 90% of
non tube failures.

Good luck

73 Zeno

[Kamakiri]

Okay, but what *is* an integrator. Is it a capacitor/resistor? Is it just a twin lead cap as my test would have me to believe?

Basically, I need to know what makes this thing tick, so I can substitute modern replacements. From what you're telling me, this seems like the 1960s version of the Philco bakelite block condenser.

[zeno]

IIRC inside is 2 resistors in series. A cap goes to ground
at each end and at the junction of the two. All the
values are the same.
I was right ! I duck duck goed it & found this....
http://www.boxcarcabin.com/integrator.html

73 Zeno

[Kamakiri]

When replacing, what would you use for wattage on the resistors, and voltage rating on the caps?

[zeno]

Originally Posted by Kamakiri

When replacing, what would you use for wattage on the resistors, and voltage rating on the caps?

IMHO 1/2 watt resistors & 600v caps. May want to go 1kv
to play it safe. Disc caps should be OK.

73 Zeno

[Kamakiri]

After replacing that suspect integrator and doing the filter caps, there's no change. Here's a shot of where I'm at now.

I've been advised that the next step is a vertical output transformer, so I'll be giving Moyer a call this week....

[Username1]

You gunna test that transformer first ?

Maybe test the voltages around the output...?

Check for open V-hold-Height-Lin pots...?

[Kamakiri]

I don't have a Sams for this particular set, so I don't have any reference as to what anything should read. Honestly, I'm okay with throwing a few parts at it, as my plan is to make this set my "daily driver".