Admiral 19A1, no vertical sweep (video attached)

[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.

[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 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).

[Kevin Kuehn]

Is it safe to assume we don't have a scope at the scene of this repair?

This set is certainly being a little stinker.

[Kamakiri]

Originally Posted by 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).

I subbed in a 20 K resistor. No change.

I added .0047 across the .01 cap. No change.

Man, this is really a tough dog. Should I start scouring Craigslist for a scope?

[jr_tech]

Originally Posted by Kamakiri

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

In-circuit measurement *should* be ok... I don't see an obvious DC path that would affect the reading other than the two 39K resistors, which would only slightly lower the readings. What does the vertical transformer measure? How about the transformers in the "parts set"?

jr

[Kamakiri]

Decided to swap the horizontal sweep transformer out of the parts set, and looky what I got!!!!

Obviously, it's not done, but I'm a HECK of a lost closer than I was!

Now the weird part was that the readings on the transformer that was in the set weren't far off spec, but it was some replacement that was larger than the original. I figured that maybe it was wound different or something, causing the issue. Bingo!!!

Now, to fix the vertical issue and the lousy focus. At least it's nice to end tonight on a win....sort of

[Kevin Kuehn]

Glad you got it working.

Oh, and you should have another backup in the spare vertical osc transformer. At least Sams calls them the same part number, which seems a little weird.