Motorola 19K1 restoration

[bandersen]

I haven't run into anything like this before. It appears to be a huge non-polarized capacitor, but the rating is strange. 3VNP 1.0 ohm 60 Hz. Would that be 3 volts non-polarized with an impedance of 1 ohm @ 60 Hz ?

I plugged 60 Hz and 1 ohm impedance into this site and came up with 2.65258 mF (about 2,650 uF) :

Any thoughts on what to use for a replacement ?

Mouser has some 2,200uF non-polarized caps. Maybe that's close enough ?

It's C4 in the schematic.

[jeyurkon]

That's certainly what it seems to be. I'd think the 2.2 mF caps would be close enough. Probably well within the tolerance specs.

John

[leadlike]

This is a situation where a cheap cap checker would come in handy. You can test for unknown values simply by checking where the eye tube closes on the dial scale. All that aside, that has to be the most bizarre method of labeling a cap I have ever seen.

[bandersen]

Originally Posted by leadlike

This is a situation where a cheap cap checker would come in handy. You can test for unknown values simply by checking where the eye tube closes on the dial scale. All that aside, that has to be the most bizarre method of labeling a cap I have ever seen.

I do have a couple vintage RC bridges and will try them out. The ranges don't go anywhere near 2,600 uF though.

[bandersen]

The parts from Mouser and a bunch of NOS tubes have arrived. Now the fun can begin

[bandersen]

OK, finally back to the 19K1.

First up, a little cleaning. Luckily, the dust and dirt comes off easily with a soft brush. I followed that up with a rag and a little mineral spirits.




That's better. I really like that copper plating - not a speck of rust to deal with.


The flyback looks to be in excellent condition


Only a couple issues so far. One, a crude electrolytic repair. A wire to the right was cut, the ends stripped and the capacitor lead spliced in. I think I'll replace the whole wire and restuff the electrolytic can.


Two, the yoke & focus coil plug and socket are damaged. I posted in the classified section for a replacement. Plan B is to replace it with a more conventional octal plug & socket.


Otherwise, just loads of capacitors to replace. The wire-wound sand power resistors are in miserable condition too.

[Sandy G]

Dah-Yum, I'd be tempted to leave it outta its case...Dat's PURTY !!!

[batterymaker]

I have those octal plugs if you need one. They're actually battery plugs, using a pilot hole instead of a key--they were used in AB battery packs.

[bandersen]

I found some more damage and crude repairs around the horizontal output tube. The replacement resistor fell off when I touched it due to some very poor soldering. The socket is in bad shape too. Pin 8 is broken off and I need to solder a capacitor to it. It might be best to replace it and all the surrounding components




I also noticed that the Sams for this chassis shows two doorknob capacitors with a resistor between (PI filter). I've only got one. Maybe another crappy repair job ?

[jeyurkon]

Originally Posted by Sandy G

Dah-Yum, I'd be tempted to leave it outta its case...Dat's PURTY !!!

Yeah, but someone would probably get a real charge out of the 19AP4!

John

[bandersen]

Originally Posted by Sandy G

Dah-Yum, I'd be tempted to leave it outta its case...Dat's PURTY !!!

The cabinet is actually still back in the antique shop waiting for Nixer to pick it up. He's over your way in Tennessee. I'm only going to restore the chassis and somehow get it over to him.

I've seen you mention some folks that restore cabinets in other posts. Maybe they could fix up this one

Originally Posted by batterymaker

I have those octal plugs if you need one. They're actually battery plugs, using a pilot hole instead of a key--they were used in AB battery packs.

Oh yeah, they do look like battery plugs. PM Sent.

Originally Posted by jeyurkon

Yeah, but someone would probably get a real charge out of the 19AP4!

John

Ouch - for sure. Here's the itty-bitty little 5AXP4 I'm using while restoring it.

[Eric H]

Will the 5AXP4 handle the HV of a 19" tube?
Does that set use a doubler circuit for the HV?

I tried one in a 21" rectangular set and it arced inside from too much juice, the rectangular test tube (8YP4?) worked OK though.

[bandersen]

Good question. Nope, no doubler.

According to this handy website we have the following.

CRT, Typical, Max
19AP4, 14 kV, 16 kV
5AXP4, 14 kV, 19 kV
8YP4, 16 kV, 22 kV

I'm a little surprised. I though the 19AP4 would be a little higher than that. I need to rig up an anode cap, but otherwise should be OK.

I'll find out for sure soon I hope

[bandersen]

I've been making steady progress in between other projects.

First off, I found where that second doorknob capacitor should be. I think I can dig up another good one from another set. Meanwhile, I'll just stick with this one.


I've replaced the power resistors and electrolytics and most of the paper caps.


Time to do a little power up test with no tubes. No smoke and the transformer voltages look good.


One of the control lights lit up, but I think the other is burned out.


Next, I popped in a few tubes including one of the paralleled 5U4 rectifiers and slowly cranked up the variac.


All the voltages looked good, but I detected a nasty smell after a few minutes. A little sniffing located this fried capacitor. Time for a little more recaping All told, things are looking very good for a first power up.

[ChrisW6ATV]

Very nice progress on that set!