RCA 621ts Restoration

[vts1134]

My supplier of capacitors only has .002 which would put it right at the edge of 20% so I decided to go exact replacement value. I'm pretty sure .002 would have worked but so will .0025 .

[Electronic M]

I thought I was the only one who restuffed caps with two in that fashion.

If the tube has a large enough diameter one can dispense with the electrical tape, and put the side of the case of one against the wire of the other.

[Sandy G]

As Someone who knows NOTHING about the Electrical stuff...You GO , Kid...Save another 621 TS....We'll congratulllate you when the stuff separates out...

[vts1134]

Fired the set up for the first time and got a surprise. C128B (one of the main filter caps) blew up in a cloud of foul smelling smoke.
**THIS IS IMPORTANT TO ANY ONE WHO WILL READ THIS AND START A RESTORATION OF THEIR OWN**
The Rider schematic has a misprint. It incorrectly states the value of C128B.

Why is this important? Because C128B is supposed to be rated at 450v not 150v and I'd like to save you the look your wife will give you when you smell up the house.
After replacing the offending capacitor I fired the set up again. No explosions , however I didn't hear the horizontal oscillator so I investigated in that area. After swapping the 6SN7 out (it was one of the few non RCA branded NOS tubes) with another tube in the set I got the characteristic sound of the oscillator.
I took some voltage measurements and every thing was in the neighborhood so I installed the crt fired the set up and was greeted with.

No video or sound just yet but it seems like a good time to quite for the evening.

[vts1134]

Originally Posted by vts1134

Fired the set up for the first time and got a surprise. C128B (one of the main filter caps) blew up in a cloud of foul smelling smoke.
**THIS IS IMPORTANT TO ANY ONE WHO WILL READ THIS AND START A RESTORATION OF THEIR OWN**
The Rider schematic has a misprint. It incorrectly switches the placement of C128A and C128B.

Why is this important? Because C128B is rated at 150v not 450v and I'd like to save you the look your wife will give you when you smell up the house.
After replacing the offending capacitor I fired the set up again. No explosions , however I didn't hear the horizontal oscillator so I investigated in that area. After swapping the 6SN7 out (it was one of the few non RCA branded NOS tubes) with another tube in the set I got the characteristic sound of the oscillator.
I took some voltage measurements and every thing was in the neighborhood so I installed the crt fired the set up and was greeted with.

No video or sound just yet but it seems like a good time to quite for the evening.

I think the more important lesson to take is that I was frustrated and worked in a hurried manor that caused me to make a mistake. Learn from my bone headedness and when you get turn the lights off and return when you're .

[old_coot88]

I need to learn to re-read stuff. Doh.

[vts1134]

Making some more progress on the set. I went though every resistor in the horizontal circuit and replaced quite a few that were way out of spec, or completely open. I fired the set up after each replacement to make sure nothing went wrong, and to enjoy seeing the picture get better and better with each step. I still have (at least) two problems with the video currently. One problem I could not get completely sorted out with resistor replacement in the horizontal circuit was a bit of tearing at the top of the screen.

It was easiest to photograph the phenomenon by injecting video right at the grid of the video amp and adjusting contrast until it showed up. It is possible to get a stable picture most of the time, but when there is full motion video on screen it will occasionally tear horizontally at the top of the screen, just like the picture above but some times much worse. The last set I worked on had a Sams for it and gave a procedure for horizontal adjustment. I cannot seem to find one in the Rider for this set however. Maybe it's just a matter of adjustment that I'm missing?
My other problem is before the video amp. I'm getting some trailing ghosting in the picture.

I haven't dived into this problem just as I would like to get the horizontal sorted first but thought I'd share.

[Sandy G]

I would restore this thing to CURRENT standards...it's too valuable to restore, IMHO, to 1946 standards...

[Electronic M]

That is the money shot of any vintage set as it tells you the electronic unobtainium is in good shape.

Great job so far!

And don't worry your not the only one whom has popped a freshly installed lytic. Heck I've done it twice now. LOL

[vts1134]

Originally Posted by Electronic M

And don't worry your not the only one whom has popped a freshly installed lytic. Heck I've done it twice now. LOL

I've done it once before also, but that was entirely my fault. Doing it because the schematic was incorrect is a bugger . I'm sure it wont be the last time I run into that in my life and as I get better I'll be able to spot those mistakes before I make them. Had I analyzed the schematic and thought about where that capacitor was going/what it was doing instead of just going on faith I probably would have known it to be incorrect.

[Electronic M]

On multi-section cans I tend to check with the labeling of the can and the existant wiring to make sure of my work.

The first time I made that sort mistake I blew two lytics in a row because I could not find a way to get the chassis loose (the mounting nuts were recessed out of reach of a wrench), and a rubber AC mains line had disintegrated and shorted to one of the above chassis lytics.
The second time was a TV that I'd miss wired the replacements for the selenium doubler rectifiers on.....I was powering it up on a variac, went to have dinner, and started hearing a regular popping sound as the two sets of 5 22uF caps I had put in parallel to make up a replacement for each doubler cap started firing their guts out one by one.

[vts1134]

Well I have run into my first stumper. I'm having a problem with the vertical. There's a short video of the problem in the link below (the set is on it's side btw).
http://www.youtube.com/watch?v=WXtdZeuZpO8
I've gone through the resistors in the vertical section and they all read within 20% of spec. I've also swapped the 6SN7 out. The problem kind of looks like the oscillator is running too slowly but the dual "rolling" lines have me stumped. Any one got any ideas?

[old_coot88]

What does it look like with a regular picture?

[vts1134]

Originally Posted by old_coot88

What does it look like with a regular picture?

I haven't gotten that far yet. There's no output from the tuner/if stages. I am working backwards from the crt. The picture above was injected at the grid of the video amp. If you're asking for the same reason I wished I had a regular picture, to see if there is two complete pictures on the screen, then the answer is yes. One of the patterns available on my video injector is three horizontal lines. When I select this setting I get six lines on screen, with the "rolling" hum bars separating them. This is what makes me think that my oscillator is running too slowly.

[old_coot88]

If you adjust the vert hold control, will it lock to the hum bar? Or does the bar still "roll" irrespective of the v hold setting?