Motorola 19K1 restoration

[bandersen]

I've tried everything I can think of and the HV just won't get up above 12kv. The voltages and waveforms on the 6CD6 seem reasonable.

• swapping out the 6CD6 with a couple other 6CD6s
• swapping out the 6W4 with other 6W4s, 6AX4s and 6AU4s
• double checking all the associated components
• swapping out the doorknob capacitor

On the positive side, the picture remained unchanged after any of those swaps. I even put some of the tubes that were originally in this set that tested weak or bad and it kept playing just fine. This must be one well designed set.

That leaves me with the flyback. It's tests OK with my EICO 944 and I've had the set playing for a couple hours so I think it is good, but maybe the Thordarson FLY-40 isn't a good substitute for this particular set ?

Here's a portion of the schematic with the resistance values and what I'm actually measuring. That 10.2 vs. 0.6 is the one that's got me concerned. Now that I think about it, that could explain why the horizontal size coil is getting hot. A larger resistance on the tap would mean a higher potential I would think. So that coil would have too much voltage across it.



Unfortunately, I don't have any replacements for it and struck out with Moyers. Does anyone have any of these flybacks ? Even if someone can just measure the resistance on a FLY-40 it would be helpful.

Motorola 24C792691
Thordarson FLY-40
Merit HVO-6

I do have these flys on hand. Maybe one of them is close enough to try
FLY-49
FLY-51
FLY-55
FLY-58
FLY-59
FLY-81

[bandersen]

A Stancor A-8130 "universal" flyback is on the way. While skimming a Wallace Telaide for Zenith 1947-1953, I came across this section on Barkhausen oscillation. I think I'll try suggestion 5 if the new flyback doesn't work any better.

This oscillation usually appears on the picture tube screen as one or several dark vertical lines and is most prevalent under weak signal conditions. One of the following suggestions can be used to correct the condition:

1. Turn the Horizontal Drive Control to a point where the lines disappear. The Width Control should then be adjusted to obtain proper width.

2. Replace the 6BG6G horizontal output tube. It must be noted that a tube which produces a Barkhausen oscillation in one receiver may be entirely satisfactory in another.

3. Mount and adjust a small magnet on the 6BG6G tube until the oscillation is removed.

4. In some early receivers, the 6BG6G cathode was by-passed with a 40 Mid electrolytic capacitor. Remove the cathode lead from this capacitor and connect it to the 20 Mid unused capacitor which is directly adjacent to the 40 Mid unit.

5. Try a different value by-pass capacitor in the screen circuit of the 6BG6G horizontal output tube. A value of .001 or .002 Mid usually will be found satisfactory.

[bandersen]

I'm still plugging away at my HV issues, but figured I'd button up everything else.

That 2200 uF bi-polar capacitor does indeed work great in place of the old 1ohm @ 60Hz one. Since it was easy to unmount I decided to restuff it by uncrimping the can.

I used a small knife and flat bladed screwdriver to open up the crimp.


I used a heat gun to soften up all that old tar. Then I drilled a couple small holes and feed through the capacitor leads.


I used a small hammer and slowly, carefully worked my way around the base to fold the aluminum lip back over. I've heard that a hose clamp can help maintain the round shape while crimping too.


Here it is installed back in the set. Definitely tedious, but it does look nice I think.


Very cool that a modern Ohmite resistor is nearly identical to the old one.

[mbates14]

I watched your youtube on how you done that capacitor. nice job.

[bandersen]

Thanks!

It's been suggested that I go over the glass/metal seams on the 19AP4 with something called VacuSeal. Can anyone fill me in on the benefits of this product and where to get it ?

[jeyurkon]

It's a high vacuum leak sealant. You can find it at www.2spi.com

It's quite expensive.

John

[bandersen]

Yes, that sounds like the stuff. I was told it would be expensive. I just wonder if it's worth it.

[bandersen]

A little googling brought my to Phil's excellent CT-100 restoration in which he used it on a 15GP22.

Assuming that a 0.5 oz bottle is enough, I'll have to run the $36 + shipping costs by the set's owner.

[leadlike]

I have a Thordarson cross-reference book that would tell you what alternate flys you can use. Since you already have the universal fly on the way, you sound like you are okay. Let me know and I'll dig it up for you. BTW, it does not just cover Thordarson, but all of the common parts suppliers of the time (RAM, Merit, etc.)

[bandersen]

I have the universal replacement, but haven't tried it yet. It doesn't fit well on the chassis and the leads to the tube caps are a bit short.
It's also used and a little undersized compared to the existing one.


I have the Thordarson guide from 1978, but it doesn't list other brands. Please check your guide when you get a chance. Thanks!

[Phil Nelson]

Originally Posted by bandersen

A little googling brought my to Phil's excellent CT-100 restoration in which he used it on a 15GP22.

Assuming that a 0.5 oz bottle is enough, I'll have to run the $36 + shipping costs by the set's owner.

I applied Vacseal generously to the seams around two 15GP22s, which used up perhaps 1/6 of the 3-oz bottle. A little goes a long way! I have no idea what sort of seams a 19AP4 has, though.

Phil Nelson

[leadlike]

I could only find Fly-40 as a replacement. I have another Merit only book, and it seems to skip right over the parts for this model entirely. Looking over the schematics for the Merit flys, I could not find one that was even close. Motorola part # is #24C792691

[bandersen]

OK, thanks. The Sams mentions a Merit HVO-6 as a replacement, but I haven't been able to track one down.

[miniman82]

There's a few HVO-7's out there, maybe they would be close enough?

http://cgi.ebay.com/12-Emerson-TV-pa...item45f54c775a

Not affiliated

[bandersen]

Hmmm. Hard to say without a datasheet, but I looked at the other HVO-7 he has listed and this is in the description:

"Merit HV0O-7 Horiz. Output Approx 14K.V. Output with AFC replaces HVO-6 for tues up to 24 inch. "

That sounds promising! Thanks for the link.