Zenith Roundy Adjustment Issues. - Page 3 - Videokarma.org TV - Video

DaveWM · #1 09-23-2015, 12:35 PM

its really not that big of a deal to restuff.

My approach is to use a bone saw to cut the can off at the shoulder (leave the can attached, do not disconnect anything.

using a small pin vise drill, drill holes from the under side UP right beside the terminals. you can also drill right besides the mounting tabs. go right thru the can bottom (not the chassis).

fish the radial lead tall skinny cap leads down from the top, soldering the terminals and the grounds as needed.

double check work (polarity, voltage, value)

I can do a 4 section in about 15-20 min. The beauty of this method is it leaves the lead dress and any parts (like resistors or small disk caps) alone, greatly speeding up the process. I think it would take longer if I had a new twist tab cap to install.

I don't bother with replacing the can tops. if you like you can dig out the guts from the top and use some alum duct tape to reattach.

the only real impediment to the process is if you lack good access to the cap with the saw. Also you should cover the chassis with paper towels taped down before sawing to keep the alum chips from gertting everywhere.

demo of the restuff
https://www.youtube.com/watch?v=kh2yurjt5sM

be very careful with cans that are mounted to insulating mounts. These are found in voltage doubler and as in the video, where the chassis is not the ground.

this is why I like to always attach the caps EXACTLY as the can so the check the can to confirm the polarity (yes there are time when the can may be the positive side). Make sure you connect up the cap so the neg is tagged the same way the can tab is.

Arcanine · #2 09-24-2015, 12:48 PM

Okay to the scrap bin with the idea of a NOS cap.

I went looking for axial lead caps of the correct values. The 40uF is easily found at 500V

The 50uF @ 475 to 500V is impossible to find in axial lead, however. I have found on multiple sites, 47uF @ 500V

It's only a hair below 50uF, would this be safe to use? I'm sure it has to be better then the old wore out can that's in there.

Because if I can sub the 50uF with the 47uF, I can just buy and install two of the same kind to replace the can below the chassis. I already know I can sub the 40uF with the 47uF and still be safe.

Arcanine · #3 09-24-2015, 12:58 PM

Actually.

http://www.ebay.com/itm/Qty-2-50UF-6...3D320606792940

At 10 bucks a cap, and the seller is in the US, I'll just purchase these. The seller has a 100% feedback rating and some vintage radio sites make mention of them on a positive light.

These high voltage filter caps are a massive pain in the neck to find.

I can't imagine subbing the 40uF with a 50uF will hurt anything on a filter cap like this. I subbed a 20uF 400V with a 100uF 450V once in a tube radio just to test it and see if it worked, and it did, and still does.

wa2ise · #4 09-24-2015, 01:31 PM

If you can get more green gain, the pictures will look better, especially football games. Or back off on the red and blue gains, assuming you'd still have a watchable image.

Electronic M · #5 09-24-2015, 03:51 PM

47uF should swap for 50 just fine. Most lytics of that era were -50%/+100% tolerance. Even some of the more finicky circuits should not mind the roughly 6% difference there.

In the late 50's-mid 70's the 'old' standard value system of caps phased out. The values used to be 1,2,3,4,5,6,7 (maybe more), but changed to 1,2.2,2.5,3.3,4.7,6.8,8.2 (all numbers were available in various powers of 10).

In radios and the audio and PS sections of TVs go with the nearest modern value and everything should be fine. In other circuits of TVs that may apply with the caveat of if everything else checks out, but it should work better than it is, try to better approximate the original values....

If I'm replacing say an 80uF lytic and I don't have anything bigger than a 47u at the needed voltage I usually put a 33 in parallel with a 47 to get 80. If you keep a good selection on .00x and.000x caps it is easy to get a more exact replacement for most odd ball papers through parallel connection.

Arcanine · #6 09-24-2015, 07:18 PM

Looks like I'm going to be subbing the 80uF 475V caps with 100uF 600V caps.

I want to replace all the electrolytic capacitors before I prod anything else. It's working this well on mostly original lytics? New ones could make all the difference in the world.

Electronic M · #7 09-24-2015, 10:34 PM

Quote:

Originally Posted by Arcanine

Looks like I'm going to be subbing the 80uF 475V caps with 100uF 600V caps.

I want to replace all the electrolytic capacitors before I prod anything else. It's working this well on mostly original lytics? New ones could make all the difference in the world.

That depends.... I have a Heathkit C3 cap tester that can test for leakage at up to 450V and capacitance from the pF range up to 2000uF, and have tested many caps with it in many sets. Pre-1960 stuff has a ~90% failure rate, but post 1960 stuff often has less than a 10% failure rate on lytics. It is not uncommon to find period lytics and many of the tubuars in a set like that still testing and working like a new cap...When they test good I leave them.
That set I don't think I tested anything but the PS doubler lytics and some tubulars since it did not act like it had bad PS caps.

Arcanine · #8 09-24-2015, 10:48 PM

After I replaced C6, one of the many electrolytic caps in the set, it made a huge improvement on image stability.

Also C5, the vertical section cap is leaking. I learned a long time ago to look around their contacts where they go in to the cap, and if it has white cruddies the cap is bad.

C5 has a lot of the white cruddies going on.

Arcanine · #9 09-26-2015, 12:21 PM

Let's discuss the Vertical Integrators.

Can anyone tell me how I would go about constructing these, or sourcing replacements? They've been mentioned to me multiple times, and I have seen it in other places, they are something I would like to know how to build, and what I would need to go pick up in order to replace them it becomes needed.

As far as I can tell; Three Capacitors tied to one common connection hooked in with two resistors in series.

http://boxcarcabin.com/integrator.html

I'm still learning how to do bigger repairs and understand a wider variety of parts.

old_coot88 · #10 09-26-2015, 01:07 PM

Quote:

Originally Posted by Electronic M

...The values used to be 1,2,3,4,5,6,7 (maybe more), but changed to 1,2.2, 2.5, 3.3,4.7,6.8,8.2 (all numbers were available in various powers of 10).

Minor quibble, but that would be 2.7.
(There's also a 3.9 and a 5.6 in there.)