1957-58 Zenith Z2230RZ (Ch. 19Z32) 21" B&W tabletop project log

[cj_reha]

I acquired this set a little over a year ago from a guy who said it'd been in storage for about thirty years and was originally his father's. It's in surprisingly good shape for its age, still has the back as well as four screw-on "legs" to convert it into a floorstanding set. After vacuuming out all the cobwebs, it almost looks new.

There is ONE cosmetic issue, though: a few of the front control knobs are broken. One is snapped in half (the seller gave me the broken piece, funnily enough), another one bent severely and cracked. Is there a good way to remove them so I can use some JB Weld or some other adhesive to glue them back together? They appear to be held on by some sort of locking mechanism (see attached photo), and as they are quite brittle, I'd rather not break more by trying to just pull them off.

I haven't really done much with it besides buying the Sams folder online (set 385, folder 4), and since I'm taking a break from fighting my Predicta, I thought I'd give it a little attention since I've grown tired of looking at it and feeling bad I haven't even touched the insides yet.

First thing I did was to check the CRT with my Sencore CR70. Initial results made me think I had a minty parts set on my hands, as the needle barely moved at all; however, after about ten minutes of letting it cook on the tester, emissions slowly climbed into the good range. There's barely any cutoff, so I'm not expecting a superb picture, but the CRT is at least good enough to the point where I'm comfortable putting time into repairing it.

Next was the hard powerup. I pressed the power button while closely monitoring the tubes and temperature of the electrolytics, and unfortunately, the 5U4 rectifier started redplating almost immediately as one of the cans started getting hot, so I quickly cut the power. I'm assuming a section or two is shorted, and I was planning on restuffing the cans anyway, so it's no big deal.

This will be a fun project! These old Zeniths seem to be very well built, so I expect it won't need much to work again besides lots of caps, maybe a few resistors and the vertical integrators replaced. It's definitely one of the nicest looking sets in my collection. More to come soon, I've got a few other projects hogging my bench right now but they will be wrapped up as soon as possible.

[Electronic M]

That ain't a locking mech on the knobs. Just a spring to help them grip/keep the plastic from splitting. Don't try to remove the springs, just pull the knobs normally as they were designed to be.

If you plan on collecting more sets you really should get a variac or make a dimbulb tester to soft power your sets.

[cj_reha]

Originally Posted by Electronic M

That ain't a locking mech on the knobs. Just a spring to help them grip/keep the plastic from splitting. Don't try to remove the springs, just pull the knobs normally as they were designed to be.

If you plan on collecting more sets you really should get a variac or make a dimbulb tester to soft power your sets.

Thanks for the heads up. I'll try to gently pull off the broken knobs later, hopefully they won't put up too much of a fight. Patience is key...

As for needing a variac/dim bulb tester, I am well aware. I'll get around to it somepoint, this is one of the few exceptions in which I powered on the TV before going through the caps/resistors/etc.

[zeno]

As Tom C said the knobs just pull off. On some sets the horz hold
is an exception. The knobs are common & used up till abt 1970
with different sizes etc.
You will enjoy restoring this much more than the Philco. They were
not famous for there ease of service ! Zeniths are easy & as well built
as any & better than most if not all.

73 Zeno
LFOD !

[cj_reha]

Originally Posted by zeno

As Tom C said the knobs just pull off. On some sets the horz hold
is an exception. The knobs are common & used up till abt 1970
with different sizes etc.
You will enjoy restoring this much more than the Philco. They were
not famous for there ease of service ! Zeniths are easy & as well built
as any & better than most if not all.

73 Zeno
LFOD !

The knobs turned out to be much easier to remove than I thought, I found an old clamp used originally for pulling ICs out of their sockets and it worked flawlessly. You guys were right! Hoping this'll be a nice break from the pain and suffering that is the Predicta chassis, point-to-point soldering is very therapeutic. Parts are on order...

[cj_reha]

I pulled the chassis tonight, took a bit of elbow grease but it eventually slid out. Looks relatively unmolested, lots of ceramic encased paper caps and bumblebees. I already see a cap which wasn't listed in the Sams, a .0015uF ceramic.

The CRT is branded Channel Master, appears to be a rebuild. I also spy some non-Zenith tubes littering the chassis (the horizontal output and damper tubes are GE), so it's obviously got some hours on it, but nothing appears to be majorly worn out.

Parts are being shipped right now, so I can hopefully start recapping in the next few days...

[Electronic M]

Looks like a good restorable specimen.

If you do or plan to do a good bit of radio/tv resto work a good move is to get one of those small drawer cabinets for nuts and bolts and stock 5-100 pieces of each value cap you might need. Buying bulk for a 6-12 months of restore can save a lot of moolah in shipping and bulk pricing VS 1-2 orders per set....the organization also speeds recap work if you have a bunch of labeled drawers.

[init4fun]

Is it just me , or does the location of the 5U4 so far away from the power transformer look a bit odd ? I guess I'm just used to seeing the rectifier being placed way closer to the transformer , heck sometimes even mounted right on top of it , VS seeing it on the other side of the chassis being fed by a bundle of wires stretched across the top of the chassis like that .

It almost looks like a factory kludge to me , I wonder if maybe the chassis was originally designed to work with a separate power supply chassis , and this was Zenith's way of putting the power supply onto the main chassis as a quickie production change ?

[jr_tech]

I suspect that, along with the cooling fins, that it was an attempt to reduce the operating temperature of the power transformer. I bet the original design placed the tube in the corner of the chassis next to the transformer, causing it to run too hot, so the tube got moved.

jr

[cj_reha]

Small update: parts are still in transit, so I decided to go through the tubes and weed out any super dead ones. Turns out the 6BQ5 audio output tube has a cathode short and the 6CN7 horizontal phase detector tube tests completely and totally dead on the emissions test.

Ordered a NOS Russian tube to replace the 6BQ5 (can't beat $6 shipped), and I think I'll rob another Zenith set I own for the 6CN7, since the chassis is super similar. Recapping starts tomorrow, hopefully...

[AlanInSitges]

Careful with those 6P14s, they have a slightly different pin configuration than the 6BQ5.

[cj_reha]

Originally Posted by AlanInSitges

Careful with those 6P14s, they have a slightly different pin configuration than the 6BQ5.

The tube I bought is the 6P14P, which is supposedly a drop-in replacement.

[cj_reha]

Making some good progress! I fully recapped the chassis with the exception of two ceramic encased paper caps I have on order. The set appears to be quite stable with them left alone, so I am not worried about them for the time being.

I restuffed the electrolytics, reused the bases by drilling out the terminal lugs and feeding the legs through. Worked quite well! Turns out the 40uF section connected to the output of the rectifier tube was indeed bad and leaking, so the redplating 5U4 issue is solved. I don't think I will bother trying to glue down the tops, the set isn't really rare or super valuable and I'm fine with them as is.

Cautiously powered up the set post-recap, and I got a raster! Super out of whack, as I was fooling with the picture controls to clean them, but it didn't take much to dial in. I initially only got a blank screen with weak static, however some wiggling of the tuner got my DVD player/test pattern generator's picture coming in loud and clear. I'll clean up the tuner soon.

One annoyance I've encountered is the fine tuning. This set originally had a knob sticking out the back, but the previous owner evidently snapped it off at the base and I did not realize this until taking a look at the Sams. I've been jamming a flathead into the remnants of the stem, and while it works, it will be quite inconvenient when the set is all reassembled. I'll figure something out.

The picture tube is showing its age, the brightness needs to be cranked up quite a bit for the picture to come through properly and contrast mostly washes the picture out, but with enough fiddling I can get a pretty good image. I'm not too worried, won't be using this set as a daily watcher or anything like that.

Overall, very good results! It appears all crucial components are in good working order. I did make one really stupid mistake, though - the audio tube is a 6AQ5, not a 6BQ5. I have no idea how I made the conscious decision to test the 6AQ5, which is a completely different size and uses a different base, with the settings for the 6BQ5...I re-tested the tube with the correct settings, and it's fine. On the bright side, I guess I have a tested-good 6P14P for the tube stash.

[cj_reha]

The Zenith project is slowly coming to an end...replaced the last two paper caps that needed replacing and remounted everything in the case. I forgot how unwieldy the "all in one" Zenith chassis is to carry...

I get a pretty good picture (minus noise which I believe is due to a crappy RF modulator, as it also appears when connected to other sets), but the audio is incredibly buzzy. I know these sets are known to have buzz in the sound by design, but it still seems quite excessive and even overpowers the source audio sometimes (the severity seems to depend on the darkness/brightness of the picture). I've fiddled with the buzz control, but the change is almost negligible. I suspect there are some out-of-tolerance components in the audio circuit.

Tomorrow I will glue the broken knobs back together and drill some new holes in the front cover plate so it can be held closed by the springs again, as the original holes were drilled quite close to the edge of the metal and the springs wore their way through the metal until it broke.

Very close to wrapping up, it's been a blast!

[zeno]

For the buzz
1) be sure the AGC isnt to high
2) try buzz control
3) try the detector tube. Best to have a fresh one if you need to go to #4
4) adjust the detector ( quad ) coil. Be sure to flag it so
you can go back.
They were buzzy sets but they could be tamed. At most you may
still get a slow ticking on some scenes. Not having OTA makes matters
worse.

73 Zeno
LFOD !