It turns out I was looking in the wrong area. With the chassis on it's side the stink was rising from further below and collecting in the corner. At times like this I wish I had one of those heat sensitive cameras.
Here's one of the culprits. It's a 470 ohm cathode resistor on the 25L6 vertical output tube. I really hope the vertical output transformer is OK.
I still haven't replaced the weird 1 ohm @ 60Hz vertical output capacitor either so it's a possibility too.
http://farm5.static.flickr.com/4076/...76c8f8ff_z.jpg

With that fried open, I let the set run a little longer and saw signs of life inside the HV cage. The 1B3 filament was glowing nicely.
I figure that's a good sign that the hor. tube and flyback are doing something useful.
http://farm5.static.flickr.com/4082/...8596c7e0_z.jpg

Finally, I found this 1K resistor getting toasty. It should have about 30 volts across it, but I'm measuring 100 ! Time for more checking.
http://farm5.static.flickr.com/4123/...5edd6629_z.jpg

I think I'm getting close. The 470 ohm resistor was getting cooked due to a really bad 6SN7.
Those short indicators are lit up like a Christmas tree!
http://farm5.static.flickr.com/4139/...e23e7ffd_z.jpg

It seems that the other resistor is cooking because one of the new electrolytics has failed. Time to dig up a replacement.

I'm really glad I didn't glue the cans back on :yes:

Hmmm. Now that I think about it, it's the same cap that was crudely repaired long ago. I'd better double check that wiring.
http://farm5.static.flickr.com/4136/...7e7927be03.jpg

Wow Bob, this one's a real adventure!

The suspense is killing me,
Keep the updates coming. :yes:

You got it!

I was wrong about which capacitor was hot. It was actually the cathode bypass across the 470 ohm resistor that burnt up previously. I've replaced that and have had the set running for about 15 minutes with no signs of any smoke or overheating. The main supply voltages look good too. I checked all the resistances using the Sams reference. They're all good. Now that the set seems stable, I'll check all the other voltages too.

No picture. I'm getting about 9kV at the CRT. It should be more like 14kV. I tweaked the hor. drive, size, linearity etc. but no change.

Also, no sound at all :( I need to take a break and go pick up a new toy. More later.

I've got sound
 

I've finally got some signs of life out of this beast. I had hooked up one end of this coupling capacitor wrong. That was preventing the final video amp stage, sync circuits and audio amp from getting a signal.
http://farm5.static.flickr.com/4102/...87b2f06f_z.jpg

Here's the output from the 6AS5 cathode follower final video amp stage.
http://farm5.static.flickr.com/4073/...a39e9acf_z.jpg

Output from 6V6 audio amp.
http://farm5.static.flickr.com/4093/...995f8c4a_z.jpg

The horizontal drive signal at the 6CD6G HOT looks OK. Still no picture though and the HV is a bit low. I'm going to check the damper tube, flyback and doorknob capacitor.
http://farm5.static.flickr.com/4094/...2aa0de98_z.jpg

The vertical oscilliator is running at 84 Hz and the amplitude is half of what it should be. I need to so some more checking there too.
http://farm5.static.flickr.com/4100/...447b0334_z.jpg

Since your HV is low you might try it with a 10 or 12" tube and see what happens.

Is that voltage taken without the CRT installed or with? Perhaps the metal cone is leaking to ground somewhere.

I'm getting about 9KV with the little 5AXP4. I figure I should be getting some sort of image. I'll check the voltages on the CRT cathode and grids.

Doh! I thought you were using the 19" tube for some reason.

I have another dumb suggestion, is the heater lit on the test tube?

I've chased my tail a few times looking for something else only to find i had a dirty CRT socket.

Could the doorknob cap be leaking HV, shunting it to ground? I once had a tv with low HV, it turns out the chassis was leaking HV to a metal rail that was part of the table it was sitting on! I measured about 9kv on the lead, and the table rail read about 1 kv.

Another possibility to explore-is that the proper flyback in the set? With all the hacked repairs someone was doing on the hv section, they may have been trying to put in a different flyback (hence the single doorknob cap-like they were trying to emulate the circuit the replacement fly came from?)

Yeah, it is - I wish it was that simple :D

Good call. I hadn't checked that before. It's a Thordarson FLY-40 which is actually the correct replacement for the original Motorola #24C792691.

I'll fire up my EICO 944 flyback & yoke tester and check it out. Might as well check the yoke too while I'm at it.
http://farm5.static.flickr.com/4135/...ae9bd923_z.jpg

Here's another look at the darkened area Eric noticed earlier. It looks like there may have been some arcing in the past.
http://farm5.static.flickr.com/4097/...b7b09f68_z.jpg

I think I can pull some doorknob caps out of my Admiral 19A15S. Someone replaced the old 6KV paper caps with several of them :rolleyes: I've been meaning to replace them with some nice ASC plastic HV caps. Might as well do it now.
http://farm5.static.flickr.com/4120/...ce2f3d2f_z.jpg

Well, I tested the flyback, yoke plus all the coils and transformers. They all check out OK, except for one tap on the flyback. It should be about 0.8 ohms and I'm getting around 12 which seems odd. I'd expect a bad winding to be either open or have a lower reading if there are any shorts. The EICO indicates that the fly is good though. Maybe the FLY-40 is a little different than the original Motorola ?

I also swapped out the doorknob cap. I fired the set back up and still only had 9 kv. I gave the horizontal lock a few clockwise turns and was able to get it up to 12 kv, but horrible high pitched squeals were coming from the flyback so I backed off. Still no image at all. I checked the voltages at the CRT pins - they're fine.

Before I called it a night I swapped out the 5AXP4 for an 8XP4 just for the heck of it. At last, a faint glimmer of life :thmbsp:
http://farm5.static.flickr.com/4075/...24d75874_z.jpg

I had to crank the focus control all the way which got me thinking maybe the focus coil could be having a bigger effect than I expected. These little test CRTs are auto-focus so don't need one anyway. I physically moved the focus coil around and got a much brighter trace!
http://farm5.static.flickr.com/4137/...0f8be1db_z.jpg

Just to make sure the 5AXP4 is OK, I put it back in. I never figured a focus coil position could have that much of an effect! (Yeah, I know that's not the safest HV anode lead :o)
http://farm5.static.flickr.com/4093/...f95578a7_z.jpg

Which leaves me with a nice bright trace with no horizontal at all. The width control barely has any effect.
So how is it possible for the flyback to put out HV when there's no horizontal deflection :scratch2: There is a mica cap inside on the horizontal winding inside the yoke. I'll check that tomorrow.

I finally found the problem - a bad horizontal yoke connection. :banana: The HV is up to about 14 kv now.

Here are the first images I got using the rectangular 8XP4. First, using a B&K 1077B which is in need of an overhaul. Next, a low power analog broadcast picked up with rabbit ears.
http://farm5.static.flickr.com/4140/...747d5047e4.jpg http://farm5.static.flickr.com/4075/...ded3ffc4d8.jpg

I'm getting some weird clipping so I switched back to the round 5AXP4 and did some tweaking.
http://farm5.static.flickr.com/4137/...4c2b60cefb.jpg

Almost every control is crammed into one corner. It's convenient, but a little tough when you have big hands.
http://farm5.static.flickr.com/4093/...95d6df80_z.jpg

Next, I fired up a Leader test pattern generator. The RF output on it is too weak to produce a decent picture so I fed it into a BT modulator. It's not just his set - the Leader RF is just too weak for any set I've tried it on.

Here are the alignment, convergence and multi-burst patterns. I'll hold off on making an more adjustments until the 19AP4 has been installed.
http://farm5.static.flickr.com/4141/...0e4b9ab7a2.jpg http://farm5.static.flickr.com/4098/...edea096b06.jpg http://farm5.static.flickr.com/4074/...6cffeaa71f.jpg

Finally, I hooked up a DTV convertor box. No sound, but I was expecting that. I have a couple of these Access HD DTA1010 boxes and get very weak or no sound on most of my vintage sets. One solution I've used is to feed the composite output from the converter into a BT modulator.
http://farm5.static.flickr.com/4081/...ef454596_z.jpg

I'm going to clean up some temporary repairs and clear off the workbench before remounting that 19AP4.

Its alive..... ITS ALLIIIIIIIIiiiive!!! :D

Holy short circuit Batman, it's working!!! :yes:

Great job Bob! This one looked like a real challenge that turned out to be totally worth the effort:yes: I can't wait to see it back in the cabinet and done!

Muwahahahaha....

Short circuit indeed between the horizontal winding and focus coil.

Thansk! Me too. I'm still not sure how that's going to happen though. I think the cabinet is still somewhere in Illinois. I just have the chassis and picture tube. Somehow they need to be brought together and reassembled at the sets owner's (Nixer) place in Tennessee :scratch2:

As I recall the cabinet was pretty beat up, is it being repaired too?

Yes, last I heard.

"I’ve actually talked to Sandy about Jim Obermeyer before and I’ll definitely be taking the cabinet there."

I'm really curious to see what a pro can do with it. I'm guessing the top needs to be re-veneered ? Just about everything in that darn antique shop it came from had some cabinet damage.

That was pretty fast detective work!

I have an Access also and it produces weak sound and awful picture via RF even on modern sets. Works great with a BT though.

That horizontal something coil looks like a real pain to adjust.

I'm anxiously awaiting to hear how the professional refinishing goes.

John

That's the "Horizontal Size" control and is very much a pain to get at. Once this chassis is back in the cabinet, all the adjustments will be even tougher to get at. If you look back at the start of this thread, there's an original ad where they promote the idea that only two controls are needed. We'll see about that.

Adjusting the hor. lock really helps with the sync on this set.

I took a closer look at the channel selector and still don't get the fine tuning. It looks to me like the only adjustment is the tuning slug for each channel. That level with a hole in it just acts as a guide for an adjustment tool. Is that what the service manual means by a fine tuning control :dunno:
http://farm5.static.flickr.com/4119/...9b9ca1af_z.jpg

I added a second HV cap and a carbon comp 470K resistor to form a PI filter like the schematic shows. I used rounded solder blobs and it seems to work OK. No arcing so far. I was able to get most of the dark crud off the flyback too. That red splattered stuff is high voltage insulating "paint" applied during some repair long ago.
http://farm5.static.flickr.com/4139/...690801f3_z.jpg

This seemed to produce a brighter, crisper picture, but two dark lines appeared on the left. I cranked the hor. drive all the way down (clockwise). That mostly got rid of them but the brightness suffered. I tried a couple different 6W4s, but that didn't make much difference. Also, the horizontal width coil is warm - not sure if that's normal. Perhaps I should remove that second HV cap after all :scratch2:
http://www.bobandersen.com/images/mo...creen02-01.jpg http://www.bobandersen.com/images/mo...creen02-02.jpg

http://www.bobandersen.com/images/mo...creen02-03.jpg http://www.bobandersen.com/images/mo...creen02-04.jpg

I decided to try out the 19AP4.
http://farm5.static.flickr.com/4095/...fa33a99c2f.jpg http://farm5.static.flickr.com/4116/...f5959c9516.jpg

That's a little disappointing - just a faint smudge. I guess 12kv won't cut it. The Sams doesn't mention the HV value, but I found a schematic in a Wallace Telaide that shows 17 kv.
http://farm5.static.flickr.com/4100/...9d00ac4199.jpg

I've contacted Moyers to see if they have a Motorola 24C792691 or Merit HVO-6 replacement. I'll do some more checking in the meantime.

In your last post you said the picture tube was a 19KP4. I can't find a data sheet for that number, yet earlier pictures show a 19AP4A which is a standard tube. If it's really a 19AP4A that your testing, did you forget the ion trap? That's an easy thing to overlook.

Ralph S

Nice catch! I meant 19AP4. And, yes, I completely forgot about the trap magnet :stupid: You get spoiled using the little test CRTs which don't need them.

After adding the ion trap magnet and a whole lot of tweaking to it, the centering magnets, focus coil, etc. I got these images. The brightness is cranked all the way up and the hor. drive adjusted for the least noticeable dark bar on the left. Too bad Sams doesn't include any directions for adjusting the controls.

It's a little disconcerting feeling all my arm hairs tingle when I reach for a control :yikes:
http://farm5.static.flickr.com/4116/...2696cee0f8.jpg http://farm5.static.flickr.com/4121/...851b71ca6b.jpg http://farm5.static.flickr.com/4094/...d450233d87.jpg

Hmmm. Looks like it works!

Yep - just needs more HV and a few bits need to be repaired like a broken fuse holder and loose lamp socket. Another batch of parts arrives Friday.

Hey, that's looking really good! Seeing that big CRT from the side, it really dwarfs the chassis in comparison. Kinda scary! :para:

What do you suppose is causing those dark vertical lines?

Thanks. It sure is scary. I'm used to working with CRTs half that size not to mention that most of the outer surface is at 12,000 volts!

I have those dark lines to some extent on a few of my sets. They can be caused by a bad damper tube or too much horizontal drive from what I've read. I imagine there are several other components that could be off or miss-adjusted that cause them.

Looks promising. Be careful around that thing!

Re the lines on the left side, if all else fails, read up on Barkhausen oscillations. I actually had that problem once. Even if it's not the cause, just reading about the topic makes you feel smarter :)

Phil Nelson

I'll be removing that big CRT while I tinker with the set some more. I wanted to make sure it was really good and see if the problems I saw on the little CRT would persist.

I saw that trick on your site with the magnet in the HV cage. I waved a magnet around this 6CD6 tube, but it had no effect. Oh well, there are still plenty of other components to tinker with in the horizontal circuitry.

Sure, I'd check obvious things first. For what it's worth, the lines in my Halli T-67 were cured by substituting horizontal output tubes. One of my books also mentions trying a circular magnet (such as an old ion trap magnet) around that tube.

Phil

It test really good in my Hickok, but I've seen plenty of comments that the only way to really test it is to try it in a set. I don't have any other 6CD6s on hand so I picked up a couple on eBay.

Shoot, I have a bunch of those all you need to do is ask! 6DQ5's too.

Oh well. I'll keep you in mind for the future. I got two of them plus a 19BG6 for $0.99.

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.
http://www.bobandersen.com/images/mo...K1/flyback.jpg


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 :scratch2:
FLY-49
FLY-51
FLY-55
FLY-58
FLY-59
FLY-81

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.

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.
http://farm5.static.flickr.com/4111/...51eaa283_z.jpg

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.
http://farm5.static.flickr.com/4144/...de7843ee_z.jpg

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.
http://farm5.static.flickr.com/4133/...2a18b381_z.jpg

Here it is installed back in the set. Definitely tedious, but it does look nice I think.
http://farm5.static.flickr.com/4152/...1254b8f8_z.jpg

Very cool that a modern Ohmite resistor is nearly identical to the old one.
http://farm5.static.flickr.com/4124/...0807c57c_z.jpg

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

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 ?