Duncan's 1960 Magnavox

[Username1]

.

Good Morning - Just a quick note - Things to check - On pin 3-6 of V10 the vert output,
put your finger or a DVM probe on it with nothing attached and see if the line on the
screen moves up or down, or if you can put any 60Hz signal on it like from a Signal
gen, or radio speaker on it there should be deflection. If none - then you should
check for any voltage on the plate of V10, since there is no deflection, it should
be completely safe, looking for about 280V. If nothing, track through the T2
to see if you have it or if T2 has open windings. If you get deflection when
you touch G1 of V10, then you have to go Back into the Osc, Don't forget
to look at the feedback loop through R45, & 46. Also, most important -
Since this tv worked before you replaced parts, keep an open mind to
the possibility that you wired something wrong, My money is on a
mistake in wiring or part placement. Also, see that 25ma current
reading for the cathode of V10, that is often printed where they
tell you not to measure the plate voltage, You can lift one side
of R51 and check the current, to see if the tubie is conducting.
Also be ready to check voltages on V9 as well.... Also -
The Vert Hold has a plug & socket in the schematic - If you
have this on your tv be sure to check that if you had to
undo it to work on the set.... Good Luck!

.

[old_coot88]

You don't have to lift anything to see if the vert. out is conducting. Just look for voltage on the cathode; if there's voltage, the tube is conducting. And it'll vary with turning the v linearity pot (no matter whether sweep is occuring or not).

[Mr.Duncan]

Originally Posted by Username1

.

Good Morning - Just a quick note - Things to check - On pin 3-6 of V10 the vert output,
put your finger or a DVM probe on it with nothing attached and see if the line on the
screen moves up or down, or if you can put any 60Hz signal on it like from a Signal
gen, or radio speaker on it there should be deflection. If none - then you should
check for any voltage on the plate of V10, since there is no deflection, it should
be completely safe, looking for about 280V. If nothing, track through the T2
to see if you have it or if T2 has open windings. If you get deflection when
you touch G1 of V10, then you have to go Back into the Osc, Don't forget
to look at the feedback loop through R45, & 46.

Also, most important -
Since this tv worked before you replaced parts, keep an open mind to
the possibility that you wired something wrong, My money is on a
mistake in wiring or part placement. Also, see that 25ma current
reading for the cathode of V10, that is often printed where they
tell you not to measure the plate voltage, You can lift one side
of R51 and check the current, to see if the tubie is conducting.
Also be ready to check voltages on V9 as well.... Also -
The Vert Hold has a plug & socket in the schematic - If you
have this on your tv be sure to check that if you had to
undo it to work on the set.... Good Luck!

.

Will do! - I'll check these tonight.

I'm always open to me making a mistake, perhaps I just haven't seen it yet. I did replace capacitors one at a time, while using tape to mark the wire connections (as to not lose track of the positions when replacing)

C2 did blow up - which is the reason why I replaced ALL capacitors at the same time, I probably should have replaced JUST C2 first and done testing.

I assume when I touch pins 3-through-6 of V10 it will cause the output plate of V10 to cause vertical deflection?

Why does the schematic say "DO NOT MEASURE" the plate output / Pin# 9 of V10? - The voltage doesn't seem THAT high?

[Alex KL-1]

Originally Posted by Mr.Duncan

Will do! - I'll check these tonight.

I'm always open to me making a mistake, perhaps I just haven't seen it yet. I did replace capacitors one at a time, while using tape to mark the wire connections (as to not lose track of the positions when replacing)

C2 did blow up - which is the reason why I replaced ALL capacitors at the same time, I probably should have replaced JUST C2 first and done testing.

I assume when I touch pins 3-through-6 of V10 it will cause the output plate of V10 to cause vertical deflection?

Why does the schematic say "DO NOT MEASURE" the plate output / Pin# 9 of V10? - The voltage doesn't seem THAT high?

The DC voltage yes, will not that high. But, with deflection working, the retrace pulse/period produces a high amplitude spike in the primary, sometimes near 1.6kV. This for every frame, aka. 60 times per second of these pulses (for vertical stage; 50 times for a lot of another countries).

[Mr.Duncan]

Okay I think I found it. I did make a wiring mistake!

C35 was connected to the wrong pin of V9 / 6BF6.

I must have been distracted, but its clearly on the wrong terminal.

Check the before/after photos below.

C35 was replaced with a MICA cap. .0051 uF @ 500v

I will remove the capacitor, check it, and reinstall (if okay) on the correct pin.

I wonder if this could have caused any harm?


Untitled by Thomas Duncan, on Flickr

tube by Thomas Duncan, on Flickr

[Alex KL-1]

Perhaps not, is worth to testing the TV now.

[Username1]

.

"I assume when I touch pins 3-through-6 of V10 it will cause the output plate of
V10 to cause vertical deflection? "

The Schematic says pin 3-6 which is usually pins 3&6 not 3,4,5,6 as in
3-through-6 you can see some pins to to heaters etc. Other stuff....


Also -

" The DC voltage yes, will not that high. But, with deflection working, the retrace
pulse/period produces a high amplitude spike in the primary, sometimes near
1.6kV. This for every frame, aka. 60 times per second of these pulses
(for vertical stage; 50 times for a lot of another countries). " Correct.

As long as the circuit is not functioning, no deflection, you can check the plate,
in a vert. or horiz. output circuit. And that is why in a case where "Do Not
Measure" is printed they often give a cathode current number you can
check. And proper way to check is to put the current meter in the circuit
by removing one leg of a resistor, or whatever runs from cathode
to ground. This is best practice. In this circuit you are also given
a voltage you can measure, but there is a reason they give you
current, and you should do it right, it can show other problems
in an otherwise working "looking" circuit. Too high a current
often means bias trouble, for example.


Cool that you found a possible cause for this trouble!

Good Night.


.

[Mr.Duncan]

And we got vertical!

It was just a wiring mistake on C35.

I still need to fine-tune everything, but its working well.

I was told not to run the vertical width to "fill the picture tube" as that's overdriving the unit and hard on the parts?

PXL_20240819_215644784 by Thomas Duncan, on Flickr

[Alex KL-1]

I believe that the correct size fill and linearity for the vertical will not over stress the parts.
But, the image show here are not fill in horizontal direction... the image feed have the lateral bars, or the horizontal needs some adjustment?

EDITED: changed the question.

[Mr.Duncan]

Originally Posted by Alex KL-1

I believe that the correct size fill and linearity for the vertical will not over stress the parts.
But, the image show here are not fill in horizontal direction... the image feed have the lateral bars, or the horizontal needs some adjustment?

EDITED: changed the question.

Yes, the image shown does contain lateral bars. I will broadcast some correct 4:3 images tonight to fine tune the horizontal and vert.

[Electronic M]

As a general rule the proper setup is to have the screen just filled (maybe 1" of overscan) in both axes at the lowest line voltage you would run the set at. Some sets don't give width control so you get what you get or have to improvise.
Shango tends to give that vertical underscan advice but it's mostly chicken shit because 1.) no TV maker or repair shop would EVER do that back when these were in service, 2.) it doesn't allow proper geometry unless you can also adjust for matching horizontal underscan.
The one place vertical underscan is somewhat advisable in consumer TVs is on 60s color Zeniths...those Zeniths tend to short between secondaries from insufficient insulation and on those sets underscan lowers the risk. Someone is rebuilding those transformers now so it's not that big of a deal anymore.

[Mr.Duncan]

I need to get a proper antenna for my Blonder Tongue, but so far I got the TV adjusted pretty good I think.

PXL_20240820_215721494 by Thomas Duncan, on Flickr

PXL_20240820_210946464 by Thomas Duncan, on Flickr

[Yamamaya42]

Hello fellow "big mamma" Maggie 24AHP4.owner!

[Mr.Duncan]

Originally Posted by Yamamaya42

Hello fellow "big mamma" Maggie 24AHP4.owner!

Oh! We're these tubes considered big in the early 1960's?

[Yamamaya42]

Originally Posted by Mr.Duncan

Oh! We're these tubes considered big in the early 1960's?

They were one of the biggest BW tubes ever made, however, they don't last very long, cause they tend to push the gun rather hard, mine works, but is on the weaker side.

I got it all for free, as it was just a chassis and CRT from a set that someone made into a pet bed, It's a newer one than yours, but still uses a 24AHP4.
https://www.youtube.com/watch?v=PvMHr4-WO8s