Motorola 19K1 restoration

[bandersen]

Thanks. I hate the first power up after some major work. I'm always bracing for a cap to pop in my face. So far it's never happened though - just some occasional smoke

I've finished all the recapping and resistor checking except for the HOT area.


These old sand power resistors were especially crappy.


That leaves this corner to deal with. I've cleaned out most of the debris and smoky residue. I was able to replace the damaged pin #8 fairly easily so no need to replace the whole socket. I found no less than 4 cut wires associated with the HOT circuit so there's no way this set had a picture.




Even the fuse holder is broken


Perhaps someone gave up on the repairs. I was expecting to find an open coil, but so far so good.

I also just received replacements for the damaged yoke & focus coil plug from some helpful forum members.





I won't be long before I can try a full power up.

[nasadowsk]

Mine (I've got the console!) is on my bench - the horizontal section's giving me fits and it syncs like crap hopefully i'll get it sorted out this fall.

The knob on the lever is the fine tuning adujstment, for when the cover's off. It's a weird set, that's for sure...

(And yes, a 25L6 with a step up auto XFMR for the vert output. Like I said, it's a weird set...)

[bandersen]

Yeah, it's a weird one alright. I'm in the process of rebuild the whole horizontal output circuit. I hope to fire it up again in a day or two.

[bandersen]

Luckily, the oddball valued 400pF mica cap is still good. Every other component needed to be replaced.


Here's that burnt up corner all rebuilt. I used a flameproof metal oxide resistor so hopefully no more fires.


Speaking of fires, looks like the yoke connector got cooked pretty good too.

[bandersen]

The focus coil leads were deteriorating so I reinforced them with heatshrink tubing.




The horizontal yoke leads were even worse. Basically everything to do with the horizontal on this set has been mutilated So I threaded some new cloth covered wires up into the yoke. I also found that the two 560 ohm resistors were 760 and 810 and replaced them.




Now, I could finally rebuild that plug. I was able to polish off most of the gunk from the metal shroud.




I'm going to try another power up tonight.

[Eric H]

The Flyback looks a little cooked on the one side, or is it just black from static attracted dust? Hopefully it wasn't the cause of the meltdown.

[bandersen]

It is darker on one side. I think the culprit was the missing doorknob capacitor though. It would have been right next to the darkened area. I'll find out soon enough.

[bandersen]

Nuts. There's still something burning up in that corner even with the HO tube pulled.

None of the components are getting hot though. I think it's either the tube socket or the wiring.

I'm tempted to leave it on until I can definitely see some smoke to pinpoint it, but am afraid of burning out something.

[jr_tech]

Perhaps the terminal strip is charred/arcing?
jr

[bandersen]

Originally Posted by jr_tech

Perhaps the terminal strip is charred/arcing?
jr

That's a great idea!

I unlaced the wiring harness and separated the wiring, but that didn't make any difference. I don't think it's the tube socket either. That leaves the terminal strip or the stuff on the top of the chassis (horizontal width coil and flyback).

[bandersen]

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.


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.


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.

[bandersen]

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!


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

[bandersen]

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.

[Eric H]

Wow Bob, this one's a real adventure!

The suspense is killing me,
Keep the updates coming.

[bandersen]

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.