1959 zenith has no horz. hold?
 

hello
my 1959 zenith 21"
has no horiz hold! you gan get it so close to where it just barely moves then it starts going again!
whats wrong with it?
IVE CHECKED THE TUBES

Have you checked and or cleaned the pot? Recapped the set or checked for out of tolorence resistors?

yes the horz. curcits been recapped,
tubes replaced to, could it be the yoke?
becouse the yoke buzzes when the sets on
yes ive cleaned the controls, but vertical is just fine.

It's been ages since I worked on one of those. I don't have a schematic in front of me, so I cant comment much. Does that chassis use the dual phasing diode? It's a tiny black plastic three lead component.
If it has one of those, it's a strong possibility, that's your problem. :yes:
In your reply, include the chassis number.

is this the chaissis?
its on a green sticker that says 16e21?
on the back it says super h-20 chaissis
can someone show a picture of this dual phasing diode, becouse next to horz. tube on the scamatic it talks about some kind of diode

16E21 is the chassis number. Maybe that model used a plug in dual diode.
It's a little black or gray component, about 5/8 ot 3/4 long, by 3/8 thick, by 1/2 high. It has wire type pins on it. It comes in three different configurations: common cathode, series connected and common anode. The case is beveled on one end. :thmbsp:

This pic may give you the general idea. My 1959 Predicta uses this dual plug-in diode in a horizontal circuit.

Phil Nelson

http://www.antiqueradio.org/art/Phil...ratorDiode.jpg

ok heres what i found.....
theres something called an AFC DIODE on the scamatic.
is that it?
if so then its soldered underneath the chaissis
white with a tan top.

That's it! I looked at the Sams. It's under the chassis in front of the 6GH8 socket. It's a common cathode type.
Every time I had problems with the horizontal hold and there was one used, that was the first item I replaced. It corrected the problem 90% of the time. I always carried them in my tube caddy. :yes:

yep thats it! thanks!

I don't know why they used that type of component. It's a tiny selenium pack. I looked at my RCA CTC53 and it still uses one.
They might be still available, NOS. I also wonder if 1N4148 diodes can be used instead. :scratch2:

I imagine it was cheaper than using a 6AL5 dual diode tube like older sets did. 4148s might not be able to handle enough voltage. I recall ctc17 suggested that dual schottky diode diodes salvaged from PC power supplies can be used.

Sounds like a sync problem. I'd check any caps in the sync separator circuit, and from there to the horizontal oscillator circuit. As far as the horizontal hold control, it's usually a coil with a slug on Zeniths; not a pot. I don't know that exact chassis, but it might be on the back with the slug broken off, or white plastic shaft missing. That happened a lot because people would jam the back onto the set and be careless with threading the horizontal hold shaft through it's hole in the back cover.

Charles

Ditto here. But it was more like 99% of the time.:D And it was always a common cathode type. I honestly don't remember ever encountering or replacing a common-anode or series type, although the Boss kept all 3 types in stock, and in the caddy.

The NTE113 or ECG113 is a direct replacement for the common cathode types. No longer manufactured (certainly because of lack of demand), but still available from old stock at many distributors:

http://shop.vetcosurplus.com/catalog...oducts_id=1751

http://www.talonix.com/shop/item.aspx?itemid=11959

http://www.sphere.bc.ca/test/ecg.html

I remember using a series connected, but never a common anode. I think some Admirals used the series connected.
Admiral used the bullet shaped one, that was soldered in the pc board, where the 6AL5 would be. :yes:

I have a 59 Space Command with the 18C24Q chassis that I am forced to part out if you need any parts. I'm not sure if it is the same general chassis that was common in Zenith sets of that time period, or if you have something completely different. Mine is a big 24" and lack of a test crt and thus a way to power the chassis and perform voltage checks prevented me from restoring vertical sweep a few years ago.

A recap and resistance/transformer/yoke checks didn't help, so the project is cancelled and the space is needed. Inversely, I would buy a "known good" chassis and put it in my set if I were to find one for sale. The set is great looking and the 24" crt with remote sort of make it a bit special, but seemingly valuless on the market. I would like to have it as a regular use set.

Does yours have a thing on the scamatic called an afc diode?
once i get one of these mine is going to be an everyday watcher.

if its the same kind of diode does it matter if it came out of a color tv?
to replace the old one

If their both arranged the same way (i.e. common cathode) it's probably OK. You could also try using a couple common silicon diodes like the 1N4007 connected together.

I always wanted to do that, but never tried. The last time I replaced one, replacements were readily available and never gave it much thought. :boring:

1N4007 and similar rectifier diodes are likely too slow to turn on and turn off for horizontal work. But some diodes pulled from old computer switching supplies may work. The ones (Shotkey) that rectify the secondary of the high frequency switching transformer. Another possibility would be signal diodes, the kind used for detectors in radios. Or if you have some 6AL5s laying around, you could use those diodes. That's what they used to use back in the early days of TV.

I have used common 1 amp 600v silicone diodes to replace these, maybe not ideal but it works.

So have I with good results. I used some small signal switching 1N4148s in a bugeye set recently too. Those can't handle very much voltage though so might not be a good idea.

I've been using 2 1N4007s for these, it does work. But I just ordered some of those ECG113s, it'll be interesting to try them and see if there's any difference.

I will have to find my schematic and see on that question. I will throw this out there. I found that there is a video detector diode in mine which seemed to be a problem and the coil that I belive was in series with it is open. Problem for me was that the video section was not what I was battling. No, or very little vertical height and a volume adustable hum for sound is all this set had before and after a recap. I just never figured it all out with little time and no test crt or a scope for proper troubleshooting. Without a test crt there is no way to check test points with a scope. Some test points are on the surface I think on those connection points/strips.