Zenith 1M30T20 (12" B&W from 1966)

[Adam]

This is Zenith's first all transistor b/w TV, made in 1965/66.

The initial problem I had with this was no HV, which turned out to just be caused by a bad electrolytic cap. This set was full of those black ones with the red ends which are nearly always bad. I just wound up replacing all of them.

It works ok now. The CRT is a bit weaker than I would like. And there is that weird vertical line on the screen I pointed out in the picture. I do have the VHF fine tuning knob, but it's broken, and I don't have the antenna.

Lots of pics...

[Electronic M]

Nice.

Did you get a black one or a white one like mine?

I still need to recap mine to deal with vertical Shrinkage.

Probably not a better made monochrome portable out there.

[Adam]

It's the black one.

After watching it for about an hour the picture started getting intermittently jittery with horizontal lines in it. At first I thought dirty tuner - but after messing with the tuner for a while didn't fix it, I pulled out the tv analyst. The problem remains when I put an IF frequency signal prior to the 1st IF amplifier and after the tuner, but it is gone if I put a video signal after the IFs and directly before the video output transistor, limiting the problem to somewhere in the IF circuits.

[Electronic M]

Some Zeniths of the era will develop very hard to catch intermittent transistors...The video outputs in my 71 Chromacolor hybrid drove me nuts for over a year till they failed bad enough that putting a meter on wouldn't magically cause the set to work perfectly.

[Popester]

Amazing build quality that the pictures show. It’s just sad 😢 we don’t/won’t/can’t build consumer products like this anymore in USA.

[zeno]

Clean the IF transistor sockets first. If no joy use some freeze mist.
Unlike silicons those germaniums will go heat intermitant.
Congrats on the great find. It is said only 1000 of them were built.
Ive never seen one in person & I worked 40 yrs at a major Zenith
dealer / ASC

73 Zeno

LFOD !

[Electronic M]

Originally Posted by Popester

Amazing build quality that the pictures show. It’s just sad �� we don’t/won’t/can’t build consumer products like this anymore in USA.

Radios would be the only practical hand wired discreet transistor device we could make...even the simplest modern TVs, digital audio players, cell phones require enough computing power to require a wearhouse full of discreet transistor circuits...just imagine your mobile phone being so big you'd need multiple semis to pull it.
It would be interesting though if we hand wired chassis mount ICs together to make a product.

[Robert Grant]

Originally Posted by Adam

This is Zenith's first all transistor b/w TV, made in 1965/66.

The initial problem I had with this was no HV, which turned out to just be caused by a bad electrolytic cap. This set was full of those black ones with the red ends which are nearly always bad. I just wound up replacing all of them.

It works ok now. The CRT is a bit weaker than I would like. And there is that weird vertical line on the screen I pointed out in the picture. I do have the VHF fine tuning knob, but it's broken, and I don't have the antenna.

Lots of pics...

That vertical line is generated by the horizontal sweep circuit. It has a name, I think something like "Barkhausen lines". Please correct me if I've gotten it wrong.

[old_tv_nut]

Barkhausen oscillation is a VHF oscillation that occurs in tube horizontal outputs. A line in a solid state set is also caused by something in the horizontal sweep, but it may be something entering via a power supply or ground path to the video or by RF.
If the line looks ragged, it's RF, if smooth, probably getting in through the video section. In any case, you can verify that it originates in the sweep section by turning the horizontal hold and seeing that the picture moves left and right a bit but the line stays in the same place.

If there are flying wires that can be dressed differently, you can try moving them and see if that affects the line.

[zeno]

A.K.A. snivets. The ones I remember were straight vert lines that
squiggle. Sometimes the lines are broken. Cheap horz output
tubes usually the guilty party.
On yours be sure the hoz out is not running hot first. Trouble is
the line can be from anything in the hoz, blanking, or power supply.
Also can be picking up other garbage in the house.

73 Zeno
LFOD !

[Adam]

I cleaned the IF transistor sockets and ran the TV for a few hours. That problem didn't come back, I think that fixed it.

The vertical line doesn't move with the horizontal hold, but it does with the horizontal width.

I'd like to get a better CRT in this. Does anyone know if any other tubes cross with a 12BRP4?

[zeno]

Its probably a 12 volt filament & going to be super rare. See what the
EIA number on the CRT label is. If not 343 or 1101 Zenith didnt
build it & may give you a lead on other sources. GE, RCA, Motorola
& Sylvania all built this type set & may have used the same jug.

73 Zeno
LFOD !

Originally Posted by Adam

I cleaned the IF transistor sockets and ran the TV for a few hours. That problem didn't come back, I think that fixed it.

The vertical line doesn't move with the horizontal hold, but it does with the horizontal width.

I'd like to get a better CRT in this. Does anyone know if any other tubes cross with a 12BRP4?

[Adam]

It is 12v, and a Zenith tube, 1101.


I had hoped to put this one into regular use, but the tube's really too weak for that.

[zeno]

That jug looks pretty good to me. Lets try another direction.
Find the supply for the video output transistor. Should be apx
100 V . Look for an electrolytic off it. It can even cause the line
& the overly bright washed out looking pix.

73 Zeno
LFOD !

[tvtimeisfun]

Shango talked about that TV and he showed a commercial where they dropped it out of an airplane and when it landed on the ground it was still working too bad quality isn't like that anymore you drop a new TV once and it's dead