Admiral 19A1, no vertical sweep (video attached)

[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]

I have a Hickok 505A scope, but I don't think it's up to par yet. I threw some caps in it a few months back, but never finished the job because I was informed that this scope was useless without external sweep and RF generators.

[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.

[Kamakiri]

Good thing you made mention of that. I tested and replaced 3 of the resistors in the focus circuit, one of the 2.2 M was open. Powered up the set, no raster, and the transformer I just installed was starting to brown up. In all fairness, that transformer that I installed looked like dried out garbage, but it ohmed out fine.

Guess that's next on the list.

[Kamakiri]

Checked the transformer. Now I see why there was black tape on the one I removed.....seems that something happened to this transformer when I went to relocate the chassis ground (it was clip leaded for the test). Move the wire one way, open. Move it another, it's in spec, move it another, and it's WAY high.

Yep, transformer time.

[Kamakiri]

New transformer installed, and with the resistors I replaced, she's making a pretty nice picture. Sound is good too

The only thing that I have to address is the vertical height. Not ideal, but may not be noticeable once in the cabinet. Still, going to check all the resistors in the circuit to see where we're at. Of course, I still have to tweak the linearity, but I'm pretty pleased so far!

Pretty pretty pretty!

[Kamakiri]

Here's a video of where we're at now. I replaced a 10M and a 100K resistor that were about 30% high. Pulled in the picture somewhat better:

http://www.youtube.com/watch?v=r0MsL...ature=youtu.be

Still as you can tell, it's got slightly insufficient height. I had to adjust the linearity to compensate for it to get (close to) a full raster. The 6SL7 tests like new. I figure this is some type of low emission in the vertical output circuit, and the only component I can think of in there that I haven't changed or tested is a 100 PF cap.

Or am I being too picky?

[jr_tech]

Originally Posted by Kamakiri

Or am I being too picky?

You should be able to get the picture more linear than that... Are the voltages ok? Do you have other 6SN7s and 6SL7s to swap? (sometimes a tube test does not tell the whole story).... Once, in one of these sets I mixed up the 6SN7 and 6SL7 and the set worked *almost* ok, but had height problems.

jr

[Kamakiri]

I admit that right now with the set working somewhat decently, I'm starting to get lazy, and I don't wanna go back and test voltages . No other way though.

I have a boatload of 6SN7s, I should have some 6SL7s here too. I'll take time to do that tomorrow....I noticed that the horizontal width control has a flat spot big enough to drive a car through, and the flat spot is right where it should be, so I'll test the one out of the parts set and swap it over.

[Kamakiri]

New weird issue with the Admiral, after about 6 hours of use. Getting intermittent blanking of the horizontal sweep. Linearity's not perfect I know, but here's a video. I'm almost thinking that the used horizontal sweep transformer that I installed is starting to give way.

http://www.youtube.com/watch?v=wWhXO...ature=youtu.be

[bigaudioal]

To follow up, for the first 20 minutes the set is on, this blanking is not evident.

Seems to start after the set has been on for about 20 minutes.

[jr_tech]

I would also check the video, perhaps there is a noisy resistor in the video amp. Perhaps check for HV arcing as well? IMHO, the horizontal is looking nice and stable.
jr