View Full Version : I'm getting a Zenith Hybrid!


TUD1
05-02-2016, 10:08 PM
I was talking to my good friend Danny today, and we started talking about the TV that the CRT in my CTC-25 came from. Long story short, Danny wanted to make some space, and I was glad to take it off his hands. I think it's a 25BC50 chassis, but I cannot confirm this yet. Maybe y'all Zenith experts can help me out with a year and chassis no. I'll probably go and pick it up later this spring. Sometime in June.

TUD1
05-02-2016, 10:11 PM
Here is the front of the set.

sampson159
05-02-2016, 10:56 PM
i have the same set that i m going to scrap.the cabinet is way too bad to restore.these are fine sets and you will be proud to own.zenith s big downfall was they were too good.not much return business.they were built like tanks and performed.

TUD1
05-02-2016, 11:32 PM
I'm looking forward to finally having a "pencil box" Zenith, as I call them. Because of the little door on the bottom. I always liked that. I already know where I'm going to put this set. This set also has screw on legs, so it should be much easier to move than my CTC-25.

zeno
05-03-2016, 09:23 AM
The chassis # is on the red tag but cant quite read it.
Its the first of 3 hybrid chassii. This one has SS IF's,
an IC for color demodulation & a few other transistors.
Next one had one dura module, a few less tubes &
more transistors.
The last one is the one most think of, the four tube
hybrid. They were built by the millions from B through F line.

73 Zeno:smoke:

Electronic M
05-03-2016, 12:59 PM
I've got the next hybrid in line 12B13C52 chassis. The SS IF module IMHO is what really makes the hybrids shine....They seem to always be aligned to perfection allowing a really clear sharp picture it the CRT is focused right.

TUD1
05-03-2016, 09:39 PM
Danny e-mailed me and confirmed that this TV does indeed have a 20BC50 chassis. What kind of performance can I expect from it?

DavGoodlin
05-04-2016, 12:33 PM
Danny e-mailed me and confirmed that this TV does indeed have a 20BC50 chassis. What kind of performance can I expect from it?
I have intimate knowledge of the similar 12B14C50 and 12B14C52 but what IS the difference from this to a 20BC50????
Properly set up, that will look a tad bit better than your RCA.

Consoles with the "BC" number I am not familiar with but '72 and '74 sets like the (more SS than tubes)25CC50 and then just four-tube 23EC15 are the dwindling down of Zenith tube counts. Those OE CRT's were just the finest ever and take well to a gentle wake-up on a tester.

One piece of advice is watch out for that regulator VDR per DRH4683's post. My set is finally suffering this issue after many years of family use and waiting for me to administer the cure :sigh:

TUD1
06-15-2016, 11:26 PM
Well I'm finally getting around to sharing this set. Unfortunately, when we were loading it in the van, the one of the legs came off. The leg isn't broken - the fallaparticle board fell apart. My dad will be taking care of that when we get back from Chicago. (Leaving 2 am 6-16-16)

Electronic M
06-16-2016, 01:18 AM
As a general rule legged consoles travel better with less damage when the legs are unscrewed beforehand....At least when moving in the upright position.

TUD1
06-16-2016, 02:40 AM
Now you tell me... I turned this TV on for a little bit yesterday - excellent crisp static. I haven't had time to watch it yet.

tom.j.fla
06-16-2016, 10:09 AM
Lesson learned. All the best, Tom

TUD1
08-09-2016, 12:34 AM
I've been watching this set a little bit, and unfortunately, all is not well. You have to have the brightness down pretty low, otherwise the picture gets extremely blurry and blows outward.

TUD1
08-09-2016, 12:56 AM
Here is what it looks like with the brightness turned down. Note that it is not very pleasant to watch it like this.

old_coot88
08-09-2016, 01:52 AM
The HV regulator tube can cause that exact symptom in Zeniths. The only real test is to sub it with a known good one.

andy
08-09-2016, 02:17 AM
Those are the text book symptoms of the HV dropping below normal under load. If you keep the brightness low enough, the HV stays at the correct voltage, but under load it drops. Hopefully it's just a weak HV rectifier.

Electronic M
08-09-2016, 09:26 AM
Might want to check your H out tube if that black bar is horizontal underscan, and not pillar boxing (if it is pillar boxing I hope you don't regularly watch it like that).

TUD1
08-09-2016, 11:08 AM
Thanks, everybody. I'll definitely try some different tubes in it. Electronic M, that commercial just happened to be on when I took the picture. It isn't normally like that.

zeno
08-09-2016, 04:26 PM
Thanks, everybody. I'll definitely try some different tubes in it. Electronic M, that commercial just happened to be on when I took the picture. It isn't normally like that.

Not sure on this one but Zeniths need the right damper/ hv reg
tube pair. Check the tags on the HV cage & the layout chart !
There is also a VDR that was a COMMON fail. NOS ones go bad
on the shelf but Doug did great engineering to find a modern sub.

73 Zeno:smoke:

TUD1
08-10-2016, 08:56 PM
Finally got around to fixing the bottom of the set. When we loaded the set into the van back in June, the fallaparticle board fell apart, and there was no way to secure one of the legs. We poured some Durham's Rock Hard Water Putty into the busted area, so now the leg holder can be screwed in.

sampson159
08-10-2016, 09:26 PM
back in the very early 80s,my friend had a used furniture store.on the floor was a zenith hybrid console.dark wood,contemporary style.the absolute most memorable picture i had seen.people would sit around his shop just to watch tv.especially cartoons and wrestling.crystal clear with stunning colors.that set sold and was replaced with a sylvania gt matic.looked good but people would asked what happened to the zenith?i rank that zenith right up there with the first color set i saw,the first zenith roundie and the coming of the great sylvanias.this may be the best picture i ever saw in my lifetime.hope yours is every bit as good

TUD1
08-24-2016, 11:16 PM
I got this set installed in my bedroom (that makes eight TV's in here now, four consoles, four table sets) and checked the hi voltage. Oh boy. With the briteness all the way up, it read about 14.5 KV. On top of that, The UHF tuner is extremely touchy. I'll have to go in there and clean some connections.

Electronic M
08-25-2016, 07:39 AM
Amazing it even makes a picture at 14KV! It should be more like 22-25KV for a console like that. You should test the HV rect, try the HV adjustments, and look at any other things that could be dragging down the HV.

TUD1
08-25-2016, 08:55 AM
I tried the hi voltage adjustment, and I got it to about 21 KV. But that's with the brightness turned down. Turn it up to a watchable level, and it goes back down to 15 KV, and the focus goes out the window.

Electronic M
08-25-2016, 09:27 AM
Something is wrong. you should not see it dip below 21KV, and it's max should be over 27KV.
Either your set is not making enough HV (have you checked or subbed the HV rect yet?), or something is loading it down.

TUD1
08-25-2016, 10:14 AM
The first thing I'm going to try is a new 6JD5 regulator tube. I pulled it out, and the HV jumped to 30 KV. I was told that the varistors could be bad.

old_coot88
08-26-2016, 01:16 PM
To repeat what was sed in post# 15, sub the regulator tube. Back in the day, in Zeniths, that exact problem was always caused by the HV reg. tube. (Of course today, varistors may have gone bad also.) But in any case I would still sub the tube as the first order of business.

Zenith's pulse regulator system throttles the input side of the flyback, unlike the older system (using 6BK4 etc) which puts a shunt load on the output side of the HV supply.

TUD1
10-16-2016, 11:17 PM
Just got through checking the 6JD5 regulator, and its companion, the 6DN3. Both tested very strong. Still weak HV.

old_coot88
10-16-2016, 11:27 PM
That tube may test 'good' on a tester, yet fail in operation. Again, the only true test is to sub with a known good one.

TUD1
10-16-2016, 11:54 PM
Well shucks. I didn't bother testing the new one since the tubes tested indentical.

TUD1
10-17-2016, 08:33 PM
I tried the new regulator tube in the set. It got WORSE. The original Zenith tube at least makes the set somewhat watchable.

DaveWM
10-17-2016, 09:15 PM
sometimes you have to try several regulator tubes. don't forget they are often 40-50 yrs old, no telling how well they will work. That being said there is always the varister to consider. Doug H did a nice post a long time ago in search of a modern equivalent. Those varisters can have wildly different performance when tested, but from what I understand the design takes this into consideration. I would try more regulator tubes 1st.

dieseljeep
10-19-2016, 12:25 PM
I tried the new regulator tube in the set. It got WORSE. The original Zenith tube at least makes the set somewhat watchable.

You never mentioned that you subbed the HV rect tube, 3DB3??.
That's the first one, I always try.
Another strange thing, Zenith did was connect the HV reg and damper tube heaters in series. That's why, the label states that those tubes have to be in pairs. :scratch2:

Electronic M
10-19-2016, 02:26 PM
You never mentioned that you subbed the HV rect tube, 3DB3??.
That's the first one, I always try.
Another strange thing, Zenith did was connect the HV reg and damper tube heaters in series. That's why, the label states that those tubes have to be in pairs. :scratch2:

There were 2 workable damper types and two workable HV regs, but one pair had a different series heater current than the other. So if you put the XXXmA damper with the YYYmA HV reg one would not light, or one heater would burn up...