21" Zenith 20BC50 - Horizontal Lines Problem

[Palinurus]

That could be, though adjusting them have no impact on the retrace lines. Maybe it is a capacitor. I managed to find an inexpensive copy of the service manual on eBay and will be receiving it within the next few days. Fixing the problem may be more involved than I was hoping.

[dieseljeep]

Originally Posted by Palinurus

That could be, though adjusting them have no impact on the retrace lines. Maybe it is a capacitor. I managed to find an inexpensive copy of the service manual on eBay and will be receiving it within the next few days. Fixing the problem may be more involved than I was hoping.

That's the real odd-ball model!
It was built between the 12A and the 12B models. I think they built it using the floor-sweepings from the plant.

[Yamamaya42]

Originally Posted by dieseljeep

That's the real odd-ball model!
It was built between the 12A and the 12B models. I think they built it using the floor-sweepings from the plant.

Hybrids always were a bit weird...

my parents RCA CTC-53 Mural was an odd one as well.

[dieseljeep]

Originally Posted by Yamamaya42

Hybrids always were a bit weird...

my parents RCA CTC-53 Mural was an odd one as well.

The CTC53 Mural was an ex-hotel-motel set. Nasty einzell lens CRT.
The Zenith was just an odd set. Chassis number was even unconventional will the rest of the Zenith line. It didn't have 20 tubes.

[zeno]

Voltages are apx !
This is a delta CRT so there are 3 G-2 adjustments. Newer in line CRT's
have just one. The G-2 controls go to 300VDC on one side & 800 VDC boost
on the other. You can vary them in that range ( 300-800 ) A good CRT wont need much. The more G-2 voltage the brighter that color & if too high
you will get the retrace lines.
IIRC this had a transistor for blanking. If it was a sudden fail suspect that.
If a tube blanker its probably a 6KT8, Zeniths alternative to the junky
6GH8.

The B model year was interesting. You could get 14, 16, 18, 19, 20 & 23
and 25 inch sets. Included is the much loved 4 tube hybrid intro.

73 Zeno
LFOD !

[zeno]

Originally Posted by dieseljeep

The CTC53 Mural was an ex-hotel-motel set. Nasty einzell lens CRT.
The Zenith was just an odd set. Chassis number was even unconventional will the rest of the Zenith line. It didn't have 20 tubes.

This is the cross over year for chassis numbers.
Used to be tube count then model year.
Switched to screen size then model year.
1971 had both formats. Model numbers also started to change to
year letter - nonsense screen size ( 40## =19", 47##= 25" etc )
To real screen size but that change took at least 5 yrs before it
was across the board.
So anyhows the format for this chassis is
20 = screen size
B = model year 1971 ( released fall of 1970)
C = color TV
50= consecutive number, the higher the # the higher the feature level.

73 Zeno
LFOD !