Admiral 19A1, no vertical sweep (video attached)

[Kamakiri]

Originally Posted by jr_tech

And if the voltages are *still* too high, perhaps use your variac to reduce until they are normal and see how the horiz behaves.

Is 10 k resistor from horiz hold to the transformer ok? How about the 50 uuf cap to the sync circuit? Does the "parts set" have a good horizontal transformer if you need it?

jr

Tried it on the variac, and the only thing that happened is that the picture shrunk, and it shrunk as it was, it didn't come into sync.

I'll check the 10K resistor next. Everything on the parts set (except for the frozen controls) *looks* okay? But I haven't tested anything.

[Kamakiri]

Resistor reads just under 12K. Enough to cause what I'm facing? Might as well replace it while I'm in here.

[jr_tech]

Originally Posted by Kamakiri

Tried it on the variac, and the only thing that happened is that the picture shrunk, and it shrunk as it was, it didn't come into sync.

Darn... that actually worked on my 7" Philco... thing made a decent but small picture at about 90 volts line... I found some parts way out of spec!

jr

12K does not seem to be too far off, does the pot have it's full range of 20K?

[old_coot88]

Originally Posted by Kamakiri

Resistor reads just under 12K. Enough to cause what I'm facing? Might as well replace it while I'm in here.

Which direction are you turning the hold control when it's going 'toward' good sync? Is it the maximum-resistance or minimum-resistance direction?

[Kamakiri]

Pot smoothly ranges to 15K. I tested it in-circuit. Seems about midrange where the sync locks in to where it's shown in the video.

Changing the 10K resistor made no difference, but at least when it's done, the horizontal is going to be REALLY stable

[Sandy G]

Man, THIS has 'un really got you Buffaloed..No pun intended, either..

[Kamakiri]

Heh

It's snowing out like crazy, the wife was working most of the night, my Mouser order for DuMont and Halolite parts didn't show, so I had nothing else to do anyway. Besides which, this is extremely valuable experience that I'm getting

[Sandy G]

This l'il guy's a 7", correct ? Never understood how those worked, anyway... They look like they're missin' about half the parts..

[Kevin Kuehn]

What did you measure on pin 5 of V13B?

Maybe it's time to ohm out T2. Sams says 50 ohms primary, 150 ohms secondary. Interestingly Sams shows the same part number used for both horizontal and vertical blocking oscillator transforms(T2,T3). That makes it easy to compare windings.

[Kevin Kuehn]

Any chance there's an adjustable core down inside the top hole of T2? Sams doesn't mention it, but I just noticed the hole in the Sams top of chassis photo.

[jr_tech]

Originally Posted by Kamakiri

Pot smoothly ranges to 15K. I tested it in-circuit.

15K *not* 20K? My Sams sez it should be 20K... In-circuit measurement should not make any difference, as it appears that the pot is isolated DC wise from any shunting paths. What does the pot in the "parts set" measure?

jr

[Kamakiri]

Originally Posted by Kevin Kuehn

Any chance there's an adjustable core down inside the top hole of T2? Sams doesn't mention it, but I just noticed the hole in the Sams top of chassis photo.

Nah, no such luck. I'll ohm that out next.

One thing I should note. It looks like T4 was replaced at some point in time with something that was a little larger than the original. I decided to ohm that out first. Should be 250 ohms on the primary, and 200 on the secondary. I've got 225 on the primary and 190 on the secondary. Dunno if that could be a contributing factor.

[Kamakiri]

Originally Posted by jr_tech

15K *not* 20K? My Sams sez it should be 20K... In-circuit measurement should not make any difference, as it appears that the pot is isolated DC wise from any shunting paths. What does the pot in the "parts set" measure?

jr

I'm getting 16K on the pot on the parts set.

[Kamakiri]

Originally Posted by Kevin Kuehn

What did you measure on pin 5 of V13B?

Maybe it's time to ohm out T2. Sams says 50 ohms primary, 150 ohms secondary. Interestingly Sams shows the same part number used for both horizontal and vertical blocking oscillator transforms(T2,T3). That makes it easy to compare windings.

I'm getting 44 and 142 out of T2. This one I tested in circuit, which I don't usually do. It's just a PITA getting in there to unhook a side, but I will if I gotta

[old_coot88]

Going on the assumption that the H frequency is too high (rather than too low), you could experiment with slowing it down by subbing a couple of values.
The 10K resistor.. try something like 15K, 18K, or 22K
The .01 cap.. increase value by adding something like .002, .0033, or .0047 across it.

If this improves things, while not "fixing" it, it'd at least tell you it's moving the frequency in the right direction (ie., down).