View Full Version : Zenith 5311U / 24MC32 restoration


bandersen
02-24-2017, 11:30 AM
Yes, I finally got myself a roundie courtesy of drh4683! I figured I needed a new color TV to go in my new house :yes:

It's a Zenith model 5311U with a 24MC32 chassis he scored at an estate sale.

He said it does not work (no B+) but the original 21FBP22 tests strong.

It has a vinyl clad metal cabinet and looks to be in very good, all original condition.

Here's are some photos from the ebay listing and it arriving in my garage.

https://c1.staticflickr.com/3/2739/33049500166_d5f648f12c_c.jpg (https://flic.kr/p/SmtjYo)

https://c1.staticflickr.com/3/2492/33091219715_c025591eed_c.jpg (https://flic.kr/p/Sqa9JX)

https://c1.staticflickr.com/3/2651/33091219575_1077271ae7_c.jpg (https://flic.kr/p/Sqa9Gx)

https://c1.staticflickr.com/4/3876/33024687436_47dfc86d95_c.jpg (https://flic.kr/p/Sjha1G)

https://c1.staticflickr.com/3/2505/33024691446_42fd9f8ef5_c.jpg (https://flic.kr/p/SjhbcQ)

benman94
02-24-2017, 11:39 AM
I was wondering when we'd see you restore a color roundie. Very nice set Bob. :tresbon:

Kevin Kuehn
02-24-2017, 12:15 PM
Oh oh. I see a possible new collecting addiction coming on. Good thing you have the bigger house. :D That's a very sharp looking set.

Findm-Keepm
02-24-2017, 12:23 PM
Callin Caps, Integrators, Elmenco Tubulars, oh my! I wonder which you will encounter......:D

DavGoodlin
02-24-2017, 02:50 PM
Great set there Bob. Put that on a custom dolly and wheel it into your new kitchen. Nothing beats a Zenith color for cartoons over breakfast :D

Electronic M
02-24-2017, 04:18 PM
Ahh, so you won that set. That era of zenith, assuming the tuner/IF are good, are real easy to fix and usually rather reliable.

old_coot88
02-24-2017, 05:18 PM
The very first thing I would do is verify that the H efficiency coil is intact. The coil form tends to crystalize over time which lets the windings go loose, detuning the coil. If that happens, you can't tune it for the required 'dip' in H output tube cathode current.

The coil form material that's most often affected is whitish, semi-translucent plastic. If the coil form is brown phenolic, yellow, or solid opaque white, it's probably OK.

If the eff. coil is busted it renders the set dead in the water until replaced.

bandersen
02-25-2017, 12:01 PM
Thanks for the tip. I dug out this Zenith service manual I've been lugging around since the 80s and found the schematic. Crazy that I've had it for decades and finally have a use for it!

Not sure which is the efficiency coil. Where does it connect in the circuit?

https://flic.kr/p/Sd19Bu

dieseljeep
02-25-2017, 12:22 PM
Ahh, so you won that set. That era of zenith, assuming the tuner/IF are good, are real easy to fix and usually rather reliable.

I see, some hack left off the X-ray cage around the 6BK4! It also has the GVG tuner. I would've bet it had the Oak or the standard Coil. The base models usually did. It also seems to have a 21FB with a separate safety glass, which is great with me! :thmbsp:

Kevin Kuehn
02-25-2017, 05:47 PM
Thanks for the tip. I dug out this Zenith service manual I've been lugging around since the 80s and found the schematic. Crazy that I've had it for decades and finally have a use for it!

Not sure which is the efficiency coil. Where does it connect in the circuit?

https://flic.kr/p/Sd19Bu

Usually in the plate circuit of the damper tube, but I don't think your chassis has the adjustable coil. I have the same Goodman book and they don't show it on the schematic. If you look at the schematics prior to this chassis they have the coil labeled as such.

old_coot88
02-25-2017, 07:00 PM
On Zeniths of this vintage that I've seen, the eff. coil is usually mounted in one of those holes in the rear chassis apron, on the far right end. It's 'snap-in' mounted from inside the apron, with the end of the form protruding out. The slug is adjustable from outside with a 'diddle stick' tool. If this set doesn't have one, I'll hafta add this to my "learn something new every day" list.

On some makes of color TVs the eff. coil is labeled "linearity coil"

EdKozk2
02-26-2017, 07:52 PM
Bob, Glad to see you got that set. I bid on it the first time it was auctioned. Seems the previous winning bidder didn't notice the words ' Local Pickup Only ".
I ended up buying a color roundie in Michigan that week. I used to watch BOZO at a friend's house on a 1964 Zenith Roundie.:thmbsp:

zeno
02-26-2017, 09:47 PM
Very nice set. Will have an almost unbeatable pix in
a dark room with early content such as Bonanza. I
had one in my bedroom (12X10' !) in the early 70's and
would watch things that sucked just for the realistic color.
Fun to work on too ! You do have to watch the H. eff coil
or you will be buying expensive H outs.......

73 Zeno:smoke:
LFOD !

Tubejunke
02-28-2017, 03:01 AM
I have an identical set in appearance, with the exception of the U.H.F. tuner. Also, my chassis must be some other run as what I see around the HV area is configured differently. If I was home I could give my chassis number, but probably not important. My efficiency coil was the first problem I noticed when I got mine and a replacement was almost impossible to find. I finally did get one and was advised to open the cathode of the H.O. tube and insert an ammeter to monitor cathode current and set that coil to something like 200mV. in order to NOT burn up the flyback.
That was a few years back. I wound up having to run the set on a variac at a slightly reduced voltage in order to keep the cathode current where it should be. Probably just leaky caps in the H.O. circuitry. Other than that, the set played well enough and produced a decent enough color picture needing what looks like some dynamic convergence work, which I have never done myself. Frankly, and sadly the set has been put to the side due to the introduction of a woman in the home. LOL! Together we simply just had too much stuff & it was/is in the kitchen surrounded by stuff. No way to pull the chassis and change the caps. Now I actually have my room back, but thus far have no plan of restoration. I’ve regressed back to radio interests and vintage test equipment. Smaller and easier. I may wind up letting it go.
This set Banderson got looks like a very nice set, and although most of the posts here seem to be about RCA sets, these Zeniths are supposedly better built and more reliable. Good luck with the set and don’t burn that flyback!

DavGoodlin
02-28-2017, 10:06 AM
The 24MC32 and mid-65's 24NC31 was a departure from the 25MC30 series and earlier roundy zeniths. It was more compact, having the HV cage on top of the chassis rather than beside it.

"learn something new every day" - Old coot, you also never stop seeing new (to you at least) Zenith sets on this forum.

bandersen
02-28-2017, 12:27 PM
I think you guys are referring to the coil on the plate of the damper tube ? It doesn't appear to be adjustable.
https://c1.staticflickr.com/1/623/32356886293_e14cd97f9c_z.jpg (https://flic.kr/p/RiguZT)

I have a nifty SECO HC8 cathode current monitor I can use.
https://c1.staticflickr.com/4/3783/33130859796_d689e4ec71_z.jpg (https://flic.kr/p/StEjmC)

Kevin Kuehn
02-28-2017, 01:17 PM
This is the 25LC30 circuit everyone's been woopin' and hollerin' about ;)
Looks like you could add in your own horizontal efficiency coil.

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/Zenith%20Eff%20Coil%20004_zpses52ugfv.jpg

bandersen
02-28-2017, 01:45 PM
Thanks. Looks like I have the simplified design. I'll see about adding that in when I pull the chassis. Wouldn't be surprised if there's space for the extra components.

dieseljeep
02-28-2017, 09:20 PM
Thanks. Looks like I have the simplified design. I'll see about adding that in when I pull the chassis. Wouldn't be surprised if there's space for the extra components.
Get rid of the R35, while you're at it. It's a common failure item and not needed. 1500 ohm, 1 watt.

Kevin Kuehn
02-28-2017, 10:14 PM
Get rid of the R35, while you're at it. It's a common failure item and not needed. 1500 ohm, 1 watt.

Isn't that suppose to act as a current limiter in the event something goes terribly wrong?

dieseljeep
02-28-2017, 10:30 PM
Isn't that suppose to act as a current limiter in the event something goes terribly wrong?

Zenith engineering recommended eliminating it. It was the subject of a thread, quite a while ago. :scratch2:

Robert Grant
03-01-2017, 01:42 AM
At first, I thought you found the very same model I have, only realizing that mine has a wood cabinet with its front legs consisting of extensions of the front face of the cabinet continuing to floor level.

I had been working on it, after gathering a new tube for every tube except the 21FJ (which tests good), but there had been a lot of nonstandard work under the chassis, and something went "pop" one night I was testing it out.

It's quite compact for a color roundie with legs. I think I can say with certainty that it is the only color roundie that has ever been transported in a Prius.

Kevin Kuehn
03-01-2017, 10:38 AM
Zenith engineering recommended eliminating it. It was the subject of a thread, quite a while ago. :scratch2:

Robert Goodman also says to get it out of there.(Zenith Color TV Service Manual,Vol I,Tab Books) Same book Bandersen showed us earlier. Robert mentions a couple different situations, which at first impression leads one to believe he's talking about two different resistors, however there only seems to be that one 1.5K associated with the HV?

http://i452.photobucket.com/albums/qq245/Kuehn/VK%20Pictures/Zenith%20HV%20Series%20Resistor%20001_zpsvrlzjd4n. jpg

bandersen
03-01-2017, 11:58 AM
Thanks for the info. It'll be interesting to see if that resistor has been removed or jumpered.

Tubejunke
03-02-2017, 02:49 AM
Yep, my resistor popped under that rectifier. The socket was also burned which is why there was an annoying hissing before the repair which was replacement of the socket and jumping the pins where the resistor would have been. This is a good thread! It's making me think of working on mine again.

bandersen
03-06-2017, 12:39 PM
I got a copy of the Sams I'm itching to pop the back off this set, but I've got a ton of post move stuff to do first including setting up a new workbench.

https://c1.staticflickr.com/4/3901/33237190195_6d8c5185a3_z.jpg (https://flic.kr/p/SD4hFn)

bandersen
03-08-2017, 11:00 AM
I popped the back off last night and took some more pictures. I like how the back is held on with clips rather than screws. Very easy to get on and off.

https://c1.staticflickr.com/4/3922/32942206250_0986b1f063_c.jpg (https://flic.kr/p/SbZqeh)

So far I see a mix of bumblebee and maroon caps.
I assume the bumblebee are paper inside and should be replaced but what about the maroon type ? Are these plastic film and generally OK or should I shotgun them ?
https://c1.staticflickr.com/1/697/32510503853_eb259247fa_c.jpg (https://flic.kr/p/RwQQ9v)

Also any thoughts about the missing x-ray shielding ? Would some galvanized or aluminum sheet metal be sufficient ?
https://c1.staticflickr.com/1/765/32510504253_8414dafd87_c.jpg (https://flic.kr/p/RwQQgp)

Findm-Keepm
03-08-2017, 03:27 PM
The Maroon Elmencos can stay - they are film, just like an Orange Drop. RCA and Zenith loved them - I've never seen one go bad.

As to shielding, any ferrous metal will work - I've used perforated (1/16" holes) metal before - came straight off of an old Phase Angle Voltmeter. Also, make sure you have the 6BK4C regulator, or a 6EL4A. They are the regulator tubes with the longer anode that provides the optimum X-ray protection. Of note, patented by a female RCA engineer!!

bandersen
03-28-2017, 03:52 PM
Thanks for the tips. It does have a 6BK4C/6EL4A installed :)

A friend stopped by over the weekend and we organized the basement a little. It's not much of a workbench, but this card table is a start ;)
https://c1.staticflickr.com/4/3851/32838447594_b8b7dcc43c_c.jpg (https://flic.kr/p/S2PCoW)

After getting his Farnsworth radio working, I figured why not take a whack at this Zenith?

Doug said he had tried powering it up and there was no B+. I hooked it up to a Sencore PR57 so we could monitor the current draw and turned it on.

The tubes lit up but no B+. I gave the circuit breaker a couple nudges and viola - power. A few moments later, the tell tale crackle of HV and a raster :D

https://c1.staticflickr.com/3/2944/33552143991_83f6a95478_c.jpg (https://flic.kr/p/T7Tvte)

That was quickly followed by a lighting show around the CRT anode lead. I moved some wires out of the way and that mostly tamed it.

Now we still have an analog OTA LP NTSC station on channel 6 and it's very handy for testing. Try as we might, we got nothing.
There was some noise and static as we changed channels, but no hint of reception. So I dug into the tuner to swap out the tubes.

While doing so I noticed some bits of wire dangling from what I think is a CRT grounding wire :scratch2:
https://c1.staticflickr.com/4/3838/33525120742_035c605556_c.jpg (https://flic.kr/p/T5v1p9)

Anyway, after some cursing I managed to get the two tuner tubes swapped out. The dial lamp is out too, but I'll save that for another day.
Is partially visible in the bottom-right. Is there any easy way to get at it ?
https://c1.staticflickr.com/4/3757/33525120142_7d6425c49b_c.jpg (https://flic.kr/p/T5v1dN)

That did the trick! We had great sound, but a horribly out of focus picture. The focus control had no effect.
https://c1.staticflickr.com/4/3671/33552142841_cfa2f84b93_c.jpg (https://flic.kr/p/T7Tv8p)

Seemed like the obvious thing to do was replace the 1V2 focus rectifier. Bam! We had a sharp, bright image, but no color.
https://c1.staticflickr.com/3/2811/32868243443_d1a4118252_c.jpg (https://flic.kr/p/S5skEt)

A little control adjust took care of that :banana: Not bad for basement reception of a low power station using a scrap of wire for an antenna!
https://c1.staticflickr.com/3/2839/32868243043_caa35deef1_c.jpg (https://flic.kr/p/S5skxz)

The HV arcing happened a few more times while swapping the tubes so I wedged in a gob of HV putty.
That helped a lot but there is still the occasional hiss and whiff of ozone.
Seems to me the HV cup and anode wire are a little on the skimpy side. I'll be replacing them eventually.
https://c1.staticflickr.com/3/2854/33572560541_13e3fdf518_c.jpg (https://flic.kr/p/T9G9AH)

All in all not bad for a first power up. Don't recall ever having a set come back to life so well just by replacing a few tubes.

Electronic M
03-28-2017, 04:04 PM
That is a Zenith for you!

Robert Grant
03-28-2017, 09:14 PM
You SO make me want to take on my 5317U again, but I have several things ahead of it.

consoleguy67
03-29-2017, 10:03 AM
The dial bulb might be easier to access from the front of the set, by removing the knob.

bandersen
03-29-2017, 12:09 PM
I tried that but didn't see any obvious way to get the bulb

Electronic M
03-29-2017, 02:05 PM
The socket might be on a slide on-off mounting.

Tom9589
03-29-2017, 02:11 PM
You might want to simply pull the VHF tuner. Zeniths (at least the B&W ones) had the VHF tuner mounted with two screws in the cabinet back. I see what looks like rubber grommets on the side of the VHF tuner mounting bracket interfacing with pins on the front face plate.

bandersen
03-30-2017, 12:06 PM
I tried getting at it from the front and the knob came apart :(

I think the smoked plastic goes towards then then white paper then the clear plastic then the black ring :scratch2:
https://c1.staticflickr.com/4/3681/32896872194_86f6f62b0b_z.jpg (https://flic.kr/p/S7Z4ZC)

https://c1.staticflickr.com/3/2877/33610546251_4f2befe006_z.jpg (https://flic.kr/p/Td3QqK)

After a bit of poking around, I realized the bulb holder slid off pretty easily. The holder clip is the ground and the wire clips onto the tuner.

https://c1.staticflickr.com/4/3927/33610545151_7e12dacee7_z.jpg (https://flic.kr/p/Td3Q6M)

https://c1.staticflickr.com/4/3844/33610601231_eee3db24ba_z.jpg (https://flic.kr/p/Td47LF)

It appears to be a #240 bulb - 6.3V @ 0.36A.
Specs: http://www.taillightking.com/images/LightBulbs/LightBulbSpecs/Miniature%20light%20bulb%20lamp%20240%20USA.pdf
https://c1.staticflickr.com/4/3927/33698954616_fb84f5197b_z.jpg (https://flic.kr/p/TkRX9U)

All I had handy was some #1847 (long life #47) and an LED equivalent. They only draw 0.15A and I expect are not as bright.
https://c1.staticflickr.com/3/2873/33610544171_53e5d3a22e_z.jpg (https://flic.kr/p/Td3PNT)

It works but is really dim.
https://c1.staticflickr.com/4/3684/33610543701_f26438e981_z.jpg (https://flic.kr/p/Td3PEM)

bandersen
03-30-2017, 12:12 PM
I noticed the width slowly expands over several minutes when the set is first turned on. No doubt it's the old caps reforming.
https://c1.staticflickr.com/3/2911/33698952046_acb6b827bd_z.jpg (https://flic.kr/p/TkRWoA)

https://c1.staticflickr.com/3/2811/33610542531_0f917d71e4_z.jpg (https://flic.kr/p/Td3PjB)

Zentih sure went cheap on the control door.
https://c1.staticflickr.com/4/3932/33355244030_144c1be926_z.jpg (https://flic.kr/p/SPukYj)

All the controls appear to be working correctly. Going to put together an order, get some new caps and pull the chassis soon.
https://c1.staticflickr.com/4/3842/33740017545_e8c57a078c_z.jpg (https://flic.kr/p/TpupJr)

Findm-Keepm
03-30-2017, 12:27 PM
Be careful with that knob - that pot metal "cage" liked to break. I broke the one on our neighbors' Mother-in-Laws set....

https://flic.kr/p/Td3QqK


Cheers,

compucat
03-30-2017, 08:04 PM
I tried getting at it from the front and the knob came apart :(

I think the smoked plastic goes towards then then white paper then the clear plastic then the black ring :scratch2:
https://c1.staticflickr.com/4/3681/32896872194_86f6f62b0b_z.jpg (https://flic.kr/p/S7Z4ZC)

https://c1.staticflickr.com/3/2877/33610546251_4f2befe006_z.jpg (https://flic.kr/p/Td3QqK)

After a bit of poking around, I realized the bulb holder slid off pretty easily. The holder clip is the ground and the wire clips onto the tuner.

https://c1.staticflickr.com/4/3927/33610545151_7e12dacee7_z.jpg (https://flic.kr/p/Td3Q6M)

https://c1.staticflickr.com/4/3844/33610601231_eee3db24ba_z.jpg (https://flic.kr/p/Td47LF)

It appears to be a #240 bulb - 6.3V @ 0.36A.
Specs: http://www.taillightking.com/images/LightBulbs/LightBulbSpecs/Miniature%20light%20bulb%20lamp%20240%20USA.pdf
https://c1.staticflickr.com/4/3927/33698954616_fb84f5197b_z.jpg (https://flic.kr/p/TkRX9U)

All I had handy was some #1847 (long life #47) and an LED equivalent. They only draw 0.15A and I expect are not as bright.
https://c1.staticflickr.com/3/2873/33610544171_53e5d3a22e_z.jpg (https://flic.kr/p/Td3PNT)

It works but is really dim.
https://c1.staticflickr.com/4/3684/33610543701_f26438e981_z.jpg (https://flic.kr/p/Td3PEM)

When I restored my 25MC33 Zenith roundie ten years ago now, I too had the tuning knob come apart. The two sections are just lightly crimped together. I had to use some JB Weld to make a more permanent fix. The channel display looks about as bright as mine does with the correct lamp. These are not very bright. I love the metal cabinet. I wish mine were in a metal cabinet. They are more compact and less prone to nicks and scratches. They are great sets and the color is unbeatable when everything is working right.

bandersen
03-30-2017, 10:48 PM
Thanks for the info :thmbsp:

I hooked the set up to a converter box and watched a little MeTV tonight. Definitely an improvment over the weak OTA reception! There vertical height is a little lacking and horizontal hold is at one extreme. Also some streaking when text appears. It ill be interesting to see how things change after a recap and weak tubes are replaced.

https://c1.staticflickr.com/3/2930/33748063845_9a5821941a_z.jpg (https://flic.kr/p/TqcDBK) https://c1.staticflickr.com/4/3894/33748063115_c2b7e96665_z.jpg (https://flic.kr/p/TqcDpa)

https://c1.staticflickr.com/3/2854/32904965654_88fb1e4cf1_z.jpg (https://flic.kr/p/S8GxU3) https://c1.staticflickr.com/3/2898/33748063355_9bc4a02653_z.jpg (https://flic.kr/p/TqcDti)

Electronic M
03-31-2017, 09:32 AM
Tip on the horizontal hold: the control is a coil, not a pot....So the stop is the knob's pointer hitting the metal tab in the pencil box. To get more range pull the knob out past the point where the pointer hits the stop then turn it some more. The knob should have a hex shaft so you could set it up so the pointer is at mid mech range at the center of the electrical sync range. I can't remember changing caps having much effect on H hold range in Zeniths.

DaveWM
03-31-2017, 09:55 AM
biggest issue with Zeniths was the coil forms, the plastic is an issue, other than that they pretty much just work, even with the old caps. Sometimes you may find a cold solder joint on a tube socket, IIRC the video out on later models had this issue, maybe not a prob on the roundies, but it would manifest as a overly bright pic esp near the bottom, solved with a smack of the cabinet. A good socket cleaning of all the tubes will get you 90% of the reliability back, and that's assuming it was stored where corrosion could take hold. Zeniths were built to last, the other plus is the HV was very robust with no flyback issues.

compucat
03-31-2017, 12:12 PM
biggest issue with Zeniths was the coil forms, the plastic is an issue, other than that they pretty much just work, even with the old caps. Sometimes you may find a cold solder joint on a tube socket, IIRC the video out on later models had this issue, maybe not a prob on the roundies, but it would manifest as a overly bright pic esp near the bottom, solved with a smack of the cabinet. A good socket cleaning of all the tubes will get you 90% of the reliability back, and that's assuming it was stored where corrosion could take hold. Zeniths were built to last, the other plus is the HV was very robust with no flyback issues.

Best of all is no printed wiring, no production shortcuts. You can run a Zenith all day without cooking it to death.

DaveWM
03-31-2017, 01:27 PM
Yea the RCA PCB's on high hour sets are frequently smoked.

DavGoodlin
04-02-2017, 12:16 PM
Yea the RCA PCB's on high hour sets are frequently smoked.
Unfortunately that was also true of clone sets by Philco sylvania magnavox GE Emerson etc. no wonder zenith got such a jump on everyone else🙂

Tubejunke
04-05-2017, 05:19 AM
The metal control panel door definitely isn't as tough as they made the chassis and such. I wish I knew where to get a better one. Those screen shots look good. Did you have to do dynamic convergence work? Hope I didn't miss the answer to that in this thread. Just curious as mine needs it. I can live without it, but the Zenith's make such a nice picture, it a shame to go without.

Electronic M
04-05-2017, 09:40 AM
The metal control panel door definitely isn't as tough as they made the chassis and such. I wish I knew where to get a better one. Those screen shots look good. Did you have to do dynamic convergence work? Hope I didn't miss the answer to that in this thread. Just curious as mine needs it. I can live without it, but the Zenith's make such a nice picture, it a shame to go without.

Got a test pattern gen, hex diddle stick, and a chassis #? You'll need a gen with cross hatch to do it, and a diddle stick. I've got some Zenith issued color service manuals....It would be a trivial matter for me to post pics of the convergence procedure documentation for your chassis (or the closest one I have lit for).

Most deltagun sets have the same convergence procedure and some makes/models were kind enough to essentially number controls to walk you through the procedure.

bandersen
04-05-2017, 10:13 AM
The metal control panel door definitely isn't as tough as they made the chassis and such. I wish I knew where to get a better one. Those screen shots look good. Did you have to do dynamic convergence work? Hope I didn't miss the answer to that in this thread. Just curious as mine needs it. I can live without it, but the Zenith's make such a nice picture, it a shame to go without.

I haven't done anything yet except replace three tubes. Guess I got lucky :) New caps should arrive today.

bandersen
04-06-2017, 11:48 AM
New caps from Digi-Key have arrived and they were very well packed.
I went with them because they have a decent selection of 500v caps. I wanted them to replace the six original 475v rated caps.

All the caps are rated for 105C and long life. The two caps in the B+ voltage doubler are also rated for high ripple current.

https://c1.staticflickr.com/3/2885/33835161576_61f4e3ee49_c.jpg (https://flic.kr/p/TxU3JL)

https://c1.staticflickr.com/4/3848/33835159976_9e6d0bfdce_c.jpg (https://flic.kr/p/TxU3gb)


The main B+ runs at 330 with a voltage divider tapped for 235 and 120 - all well below 475.
Then it occurred to me it uses a solid state rectifier so B+ will be available instantly while the tubes are still warming up.
I expect B+ runs fairly high until the tubes start conducting.
https://c1.staticflickr.com/3/2921/33835329766_217903cf8b_c.jpg (https://flic.kr/p/TxUUJA)

Two of the caps are 4uF and the only 500V+ ones at Digi-key below 10uF are surface mount.
10uF would probably work just fine but I decided to give these 3.9uF SMDs a shot. I think it'll be easy to solder on extension wires.

https://c1.staticflickr.com/3/2895/33835158936_ce7a82a13b_c.jpg (https://flic.kr/p/TxU2Xf)

bandersen
04-06-2017, 11:57 AM
I'm a little wary of pulling the chassis, but it needs to be done. The width slowly grows about 20% over 15 minutes from a cold power up, controls are dirty and some HV arcing persists. A recap, cleaning and new tubes should improve things.

roundscreen
04-08-2017, 07:30 AM
If cleaning does not cure the arcing problem, You may have to replace all of the hi voltage wires in the cage. Inc the wire to the crt anode. Had to do this to two of my Zenith color set's. The color circuits are working good so, DO NOT touch the coils in the color circuit. They get brittle from heat and will break if the core is turned to adjust. Another problem is you may see some slight bars in the picture on a black screen. I was not able to track down that problem. Not that noticeable, And most people would not even see them.
Ed

jstout66
04-08-2017, 10:13 AM
the set used mylar caps, so why are you doing a full re-cap? Slow width is a weak horizontal output tube.

benman94
04-08-2017, 10:43 AM
the set used mylar caps, so why are you doing a full re-cap? Slow width is a weak horizontal output tube.

He's right you know... the HO tube is just getting tired.

bandersen
04-08-2017, 12:25 PM
I was thinking it was electrolytic slowly forming up. I can check that by monitoring the B+. Wasn't planning on replacing all the caps - just the stripped bumblebees looking ones. Are you sure all the caps are mylar?

Electronic M
04-08-2017, 01:37 PM
I tend to change the bees and the tubular white ceramic cased ones...I've found bad or dying ones in sets of this vintage so if I'm in there for something I tend to change those.

Zenith26kc20
04-09-2017, 10:58 AM
Be watchful of those surface mount caps. Mitsubishi sets used them everywhere and the capacitor plaque was terrible. Just watch for goo coming out after a while.

jstout66
04-09-2017, 06:27 PM
For the most part, what Tom said.
Most are Mylar tho. It's not like the older sets you're used to where you have to change ALL of those horrid wax caps. Sets from about 1963 on up are pretty stable. You won't have to worry about capacitor plague. That was mainly a "Jap" set thing.....

Tubejunke
04-11-2017, 06:04 AM
Got a test pattern gen, hex diddle stick, and a chassis #? You'll need a gen with cross hatch to do it, and a diddle stick. I've got some Zenith issued color service manuals....It would be a trivial matter for me to post pics of the convergence procedure documentation for your chassis (or the closest one I have lit for).

Most deltagun sets have the same convergence procedure and some makes/models were kind enough to essentially number controls to walk you through the procedure.

I do in fact have an old RCA dot bar generator and a diddle stick. I would need to check the stability of the generator as I seem to remember it being a bit persnickety last I used it. Someone rigged the end of the input with a bunch of resistors in a haphazard way for some reason. Anyway, yes I would like to do that. I think I have the Sam's folder in .pdf for the set. Sorry, it's just been sitting for a few years waiting for the "significant" to vacate. :thmbsp:

marty59
04-24-2017, 12:32 PM
"Another problem is you may see some slight bars in the picture on a black screen. I was not able to track down that problem. Not that noticeable, And most people would not even see them."

I've always noticed them too, quite common on roundie Zeniths. About three light/transparent vertical bars, no foldover, just there!

compucat
04-25-2017, 12:13 PM
"Another problem is you may see some slight bars in the picture on a black screen. I was not able to track down that problem. Not that noticeable, And most people would not even see them."

I've always noticed them too, quite common on roundie Zeniths. About three light/transparent vertical bars, no foldover, just there!

Interesting you mention that. Mine has them too. They are not a problem, but just there.

rcaman
04-30-2017, 07:22 PM
There is no way i would use those surface mount caps unless you want to see a failure in a day or so. throw them in the garbage.

bandersen
05-23-2017, 10:46 AM
Why exactly ? Just because they are surface mount ? They'll work just fine.

Zenith26kc20
05-23-2017, 03:31 PM
Justradios dot com has 4 mfd@500 volts. I'm just leery of those type of caps. Keeping an eye on them would be good. If they do leak, be careful. If you are using a Weller soldering station, the goo eats the tips up in less than a day.

bandersen
05-23-2017, 04:11 PM
Meanwhile, I pulled all the tubes for testing. Unfortunately, careful as I was, the cap broke off the 6JS6 and let the air in :tears:

The tube looked well used and may have been weak, but now I'll never know for sure. I have 1,000s of tubes NOS and pulls but had a heck of a time finding a replacement.

As for the others, I check them with a TC-162 and found many had shorts or excessive grid leakage. Luckily, I had replacements for all on hand.
https://c1.staticflickr.com/5/4249/34786321646_cf3d625e68_c.jpg (https://flic.kr/p/UZWZuj)

https://c1.staticflickr.com/5/4182/34440118270_fd8cde6897_z.jpg (https://flic.kr/p/UtmBhA)

While searching I came across this Servicemaster 3AT2 made in Korea. I think it's the first Korean tube I've come across. Don't plan on using it, just though it was interesting.
https://c1.staticflickr.com/5/4268/34693857401_61c5fc65eb_z.jpg (https://flic.kr/p/URM66c)

Back to the 6JS6 saga. I finally dug up a used one that tested good and popped it in.

https://c1.staticflickr.com/5/4189/34440116380_095e87ffe8_z.jpg (https://flic.kr/p/UtmAJ1)

Hmm. Nothing on the screen. Let it run a while and slowly the screen lit up dimly with a weird image.
https://c1.staticflickr.com/5/4194/34016505803_87c80c57c8_z.jpg (https://flic.kr/p/TPVu4n)

A while later, it got a little better.
https://c1.staticflickr.com/5/4189/34663194672_d91f36dbba_z.jpg (https://flic.kr/p/UP4W8s)

I hooked up by Seco meter and found it was drawing less than 100mA. Schematic calls for 225. Time to search for another 6JS6....
https://c1.staticflickr.com/5/4162/34693853291_fc04c5faf0_c.jpg (https://flic.kr/p/URM4Sk)

bandersen
05-23-2017, 04:22 PM
Just as I was about to give up, I found one mixed in with my octal tubes :)

It certainly draws more current, but no HV at first then it suddenly sprang to life and I got a nice, bright image back. At least until I turned it off and back on. No HV, drawing 200mA and starting to red plate!
https://c1.staticflickr.com/5/4243/34663193322_5471822a79_c.jpg (https://flic.kr/p/UP4VJb)

I popped it back in the tester and found it has a short. I was able to tap the side a few times and clear it out.
Put it back in the set and it has been been working without trouble for a couple hours.

Even so I'm not crazy about leaving it in the set so took a chance and bought a NOS tube on ebay for $14. I got lucky and it works great!

The image now fills the screen, vertical linearity is pretty good and no more streaking.

I do still need to cleanout the HV cage and fabricate a shield for the HV shunt regulator. Eventually, I'll pull the chassis and go over it too.

Even though it's working pretty well, it's got issues. Like I sporadically loose vertical sync, and focus control is at one extreme, occasional arcing and dirty controls.
https://c1.staticflickr.com/5/4173/34786322216_473e63ea86.jpg (https://flic.kr/p/UZWZE9) https://c1.staticflickr.com/5/4193/34016500613_c2f333265c.jpg (https://flic.kr/p/TPVsvT)

bandersen
05-23-2017, 04:29 PM
One last thing for now, I stumbled across a NOS channel knob on eBay.
https://c1.staticflickr.com/5/4196/34790241706_abac8693d7_z.jpg (https://flic.kr/p/V1i5My)

https://c1.staticflickr.com/5/4179/34443946840_e3d373eb7d_z.jpg (https://flic.kr/p/UtGeoq)

https://c1.staticflickr.com/5/4171/34020216773_a524186493_z.jpg (https://flic.kr/p/TQfvcB)

After a bit of a struggle, I got the old knob off. The clear plastic fine tuning was filthy and got a good cleaning.

Here's how I've got the bulb sitting in it's holder. I'm not sure I've got it positioned quite right.
https://c1.staticflickr.com/5/4244/34790238666_5e15636261_z.jpg (https://flic.kr/p/V1i4T9)

Here's what I got after fighting with it a while. I really need to setup a mirror so I can see what's going on while I position the bulb.

Even so, it's definitely better than before.
https://c1.staticflickr.com/5/4244/34443946050_cc58f91d64_z.jpg (https://flic.kr/p/UtGe9N)

consoleguy67
05-23-2017, 06:42 PM
One of my favorite Zenith channel knobs!!

roundscreen
05-24-2017, 06:36 PM
Nice. You do good work on your set's.

compucat
05-24-2017, 08:44 PM
Just as I was about to give up, I found one mixed in with my octal tubes :)

It certainly draws more current, but no HV at first then it suddenly sprang to life and I got a nice, bright image back. At least until I turned it off and back on. No HV, drawing 200mA and starting to red plate!
https://c1.staticflickr.com/5/4243/34663193322_5471822a79_c.jpg (https://flic.kr/p/UP4VJb)

I popped it back in the tester and found it has a short. I was able to tap the side a few times and clear it out.
Put it back in the set and it has been been working without trouble for a couple hours.

Even so I'm not crazy about leaving it in the set so took a chance and bought a NOS tube on ebay for $14. I got lucky and it works great!

The image now fills the screen, vertical linearity is pretty good and no more streaking.

I do still need to cleanout the HV cage and fabricate a shield for the HV shunt regulator. Eventually, I'll pull the chassis and go over it too.

Even though it's working pretty well, it's got issues. Like I sporadically loose vertical sync, and focus control is at one extreme, occasional arcing and dirty controls.
https://c1.staticflickr.com/5/4173/34786322216_473e63ea86.jpg (https://flic.kr/p/UZWZE9) https://c1.staticflickr.com/5/4193/34016500613_c2f333265c.jpg (https://flic.kr/p/TPVsvT)

I occasionally lose vertical sync for a couple seconds. Also, the vertical looks like it is about to collapse then clears up. I have never replaced the vertical integrators so maybe that is the problem. The focus control on mine is at the end of its range even after replacing the string of focus resistors. I wonder if this was the case when new. I restored mine ten years ago and I am quite sure I need some new tubes here and there judging by the overall performance is not as perfect as it was before. I need to look on Ebay for spare parts. I would like to have a new convergence cloverleaf as I had to glue mine back together when I first got the set.

bandersen
05-25-2017, 09:49 AM
Replacing the tubes definitely helped. There is a HV adjustment control. It could be we need to tweak that and our focus would be good mid range on the control.

TUD1
09-30-2017, 02:53 AM
Has any more progress been made on this set? I'm interested to see how it turned out.

bandersen
09-30-2017, 03:07 AM
No, sorry I haven't had time for any projects the past few months. I've been too busy with work and fixing up my house.