Zenith 25MC33 - Videokarma.org TV - Video

oldtvman · #1 10-18-2014, 05:20 PM

I finally had some time to finish the 25MC33 I've had for some time. It required crt, crt socket and wiring major rework of chroma section along with alignment. These are preliminary photo's. It should be finished next week.

Steve D. · #2 10-18-2014, 05:53 PM

Larry,

The photos say it all. Looks like your efforts paid off big time. Very nice. Please post a photo showing the cabinet w/the set on.

-Steve D.

ceebee23 · #3 10-19-2014, 05:37 AM

wow ..watched bits of the Rutgers /Ohio game ..wow.. amazing to see stills of it on a roundie!

Username1 · #4 10-19-2014, 07:27 AM

Very cool.... Makes me think about working on mine this winter....

miniman82 · #5 10-19-2014, 07:42 AM

I like your wallpaper.

oldtvman · #6 10-19-2014, 07:53 AM

I think part of what makes the Zenith sets perform so well is the fact that the tubes set above the passive components. The ctc15 I'm working on has a lot of heat damage due to the fact that the tubes set right next to the components and the wires get brittle and components get exposed to excessive heat.

DaveWM · #7 10-19-2014, 08:33 AM

every ctc-12 thru at least ctc-17 that I have worked on had failing caps on the diff amp couplers (.01) at least the one that sits right between one of the 6GU7's and a power resistor. I think its the heat from those two things. Lots of time the pcb has crystalized looking solder on the bottoms as well.

The other thing is the zeniths seem to have less flyback failures, I think the vert outs are about the same for rca and zenith, with maybe a few more in the zeniths. This is from what I have seen and that is not a lot so I could be off on the stats.

compucat · #8 10-19-2014, 08:49 AM

I have the same set and they really look that good when restored. I like the hand wired chassis and the reliability it provides. Tubes and printed circuit boards are not a good combination. I prefer the Zenith chassis but I think RCA often had nicer cabinet styles.

DavGoodlin · #9 10-21-2014, 02:11 PM

My Aunt and Uncle had that exact model. It came from a local Department store and cost a bit over $400, a better value than an RCA! It also lasted 12 years with little trouble.
At the end, it seemed like everything got weak together, Vert and Horiz output tubes, CRT, etc. I wanted it but they traded it on a CCII vertical chassis.

The 25MC33-36 has separate tubes for sound detector and audio output 6BN6 and 6BQ5.
I just got a 24MC32, in a metal cabinet. It has a 6Z10 for the combined function.
Is anyone aware of any other differences?

The 24MC32-36 was a different model line but generally looks the same, but mine does not even have a lighted channel indicator, a loss leader model? I have not powered it up for fear of smoking the Vertical Output trans, which I am researching a way to "megger" test and vacuum-impregnate with silicone to increase insulation rating.

Zenith26kc20 · #10 10-21-2014, 02:27 PM

I have one I use sparingly. It's on vertical output transformer #4. They are fantastic performers and the convergence can be done so close it is amazing. If you figure out how to pot the transformer, please let us know! Apparently the transformer is a demon to make. Nobody wants to try to reproduce one!

DavGoodlin · #11 10-21-2014, 02:47 PM

Quote:

Originally Posted by Zenith26kc20

I have one I use sparingly. It's on vertical output transformer #4. They are fantastic performers and the convergence can be done so close it is amazing. If you figure out how to pot the transformer, please let us know! Apparently the transformer is a demon to make. Nobody wants to try to reproduce one!

I am really trying to use some high-voltage power testing resources to help save these transformers.
Its painful to read how many have failed.

old_coot88 · #12 10-21-2014, 05:36 PM

Do those xfmrs short to the frame, or is it an interwinding short?
If to the frame, could you float the unit on insulated mounts?

DaveWM · #13 10-21-2014, 06:08 PM

My zen vert out was a primary to convergence winding short.

Penthode · #14 10-22-2014, 01:04 AM

Quote:

Originally Posted by DaveWM

My zen vert out was a primary to convergence winding short.

Now I understand. The problem must have been due to a buddhist transformer.

Tubejunke · #15 10-22-2014, 01:44 AM

Mine is a 25LC30 Model 5111. It looks just like the pictures here except doesn't have the U.H.F. option and the cabinet is metal. I wonder what the difference is between this and the 25MC33, or 25MC32. It seems like there sure are a lot of different chassis to be basically the same set. I'm guessing that a lot of it is based on configuration for extras like Space Command, UHF, and the two types (that I know of) of c.r.t.s that they used.