Zenith 25LC20 - the Hinsdale

[DavGoodlin]

After working on lots of other things including RCA's delicate, fussy and over-driven horizontal output and high voltage stages, I handily restored this Zenith. Last one I did was 24NC31Z, issues a bit more involved but still very responsive.

I picked this up at Kutztown last May from another collector and tried in vain to get it working at the show. I brought it back last September hoping to flip it as a good project and actually had a young collector interested. He was leery of working on HV so I promised to fix THAT part and bring it back.

Meanwhile, certain that both the original 21FBP22 was good and flyback checked out and, this would NOT be like and RCA but have a few very obvious issues that are easy to deal with. I was not wrong I suspect that this TV (originally from NJ) followed this failure script thus " 6HF5 horizontal output tube burns vertical yoke lead which may have been dressed too close to the HOT's plate cap" Testing three multi-section electrolytics, I found one drippling black stuff and another that all four sections were open! New caps soldered right in without crowding, doubler cap was good and so was two sections of another, both Mallory OEM.

Having just one NIB 6HF5 (saved for my other Zenith 21" color SC400) and the bad one that was in the TV when I got it. I had a half-dozen 6JS6, so I added components and rewired the HOT socket to use a 6JS6 just like a 25MC30 and later sets. It didn't take much and HV was back at 24 kV and just 170 mA via the cathode of HOT. Never have I ever gotten an RCA down to numbers like that so easily.

Issues that remain, possibly for the next owner, are a bit of raster size changes based on scene brightness, taped convergence color sync may be touchy and hue changes. The convergence cloverleaf needs something better and that is evident in the picture. But that brightness and contrast sure promise a better picture is possible. Sound is unusually good for such a skinny oval speaker.
Zenith 25LC20 -1964 Hinsdale red.jpg

[Electronic M]

Nice work.
I recently did a second 21CT55 for another collector and unlike the first set (my set) the cathode current wanted to be around 150-170mA. I was kind of shocked since mine you have to coddle (voltage regulating power isolation transformer and a bucking transformer to feed it a constant specific voltage) to keep around IIRC 200-210.
I'm kinda jealous of that chassis I just did... It's better than my chassis in several ways albeit less complete.

[DavGoodlin]

I just wanted to post this as a reminder that these and earlier Zenith 29JC, 27KC & 25LC be the ones to look for in 21" round color. With service-saver panel on bottom of cabinet, flipping the set on side for testing/recapping is preferred to a jig up. The later roundie chassis 25MC, 24 MC, etc were troubled by vertical output transformers, replicated and now made in Poland.

Now that I have this for the summer, field testing in the garage could generate some more issues, likely HV arcs The buyer will not be getting it until September, after said burn-in period. I have a 24NC31 chassis coming to complete a parted-out "Harvard" 21" (Carla on "Cheers" started the famous thanksgiving "food fight" after the gang watches a game on it at her MCM house) more Zenith fun while watching the 25LC.
24NC31Z 1967 Harvard.jpg
23-25" color Zeniths I have to restore AND re-home at least 3 (I can't go back to RCA 21" just yet) will be posted under chassis numbers and model names:
25MC36 combo, 20X1C38, 20Y1C50, 16Z7C50 and finally my family's 12B14C52, all out of service due to "HV regulator VDR" issue. I will post thread on that gem DRH led us to - Thanks Doug!!!.