View Full Version : Rca 21D641 HV issue.


SwizzyMan
10-15-2017, 05:27 PM
So I have replaced the filters to start off and that is all the work I have done so far just so I can get a baseline. With no yoke plugged in I pull about maybe 7 kv (I have a shorting bar in the socket so hv will come up.), but when i plug in the yoke and power up the set the hv droops to 100v with brightness at max and 2.8kv with brightness at minimum. I have a bad feeling my yoke may be bad. I ohmed out the yoke and the results were inconclusive. The vertical section reads normal, but when i measure the horizontal winding I get maybe 6.9k wit the target being 29 ohms(provided I am measuring the right pins). Not sure if my yoke may be bad or not. Here is a picture of the yoke from what I gather vertical winding is from pins 1 and 2 and the horizontal is from pins 8 and 4. Your thoughts?

SwizzyMan
10-15-2017, 07:55 PM
oops. I posted in the wrong fourm. Wasn't paying attention when I wrote this up. Could someone move this to early B&W?

SwizzyMan
10-16-2017, 10:02 AM
I think the ETF may have a new yoke for this set. Can anyone verify if my yoke may be bad before I buy the new one? From what I gathered, my yoke is bad.

Tom9589
10-16-2017, 10:55 AM
Measure between pins 4 and 5 and then from pins 5 and 8. They both should read the same and about half of the total spec of 29 ohms.

dieseljeep
10-16-2017, 11:14 AM
oops. I posted in the wrong fourm. Wasn't paying attention when I wrote this up. Could someone move this to early B&W?
Always use chassis numbers! Model numbers don't mean squat to us old timers.
I'll look up the model number in Riders. I might have a good used yoke. :thmbsp:

dieseljeep
10-16-2017, 11:26 AM
Always use chassis numbers! Model numbers don't mean squat to us old timers.
I'll look up the model number in Riders. I might have a good used yoke. :thmbsp:
According to Riders, it's a KCS97 chassis. With a good CRT and a recap, it's an excellent performing set!
It's a 90 deg yoke, don't have one I can spare! Dave. :sigh:

SwizzyMan
10-16-2017, 11:39 AM
Measure between pins 4 and 5 and then from pins 5 and 8. They both should read the same and about half of the total spec of 29 ohms.

5 and 8 read 9k and 4 and 5 read 700 ohms. Now I am pretty sure the yoke is bad.

Eric H
10-16-2017, 12:48 PM
I may have one. Got some. NOS stuff in a box, can anyone come up with a part number, Stancor, Merit, Triad?

SwizzyMan
10-16-2017, 01:00 PM
I may have one. Got some. NOS stuff in a box, can anyone come up with a part number, Stancor, Merit, Triad?

Stancor DY-16A Merit MDF-92 Triad Y-41-1

If you can find one eric, I'll take it.

Eric H
10-16-2017, 01:13 PM
Y41 sounds familiar, I’ll check when I get home this evening.

Tom9589
10-16-2017, 02:36 PM
Where are you reading the yoke resistance? On the octal plug or on the yoke terminals where the wires attach? Try reading on the yoke itself - the person soldering the octal socket might have been having a bad day.

SwizzyMan
10-16-2017, 04:49 PM
Testing the yoke from the actual yoke terminals with the ring tester reveals it is BAD. I need a new yoke ASAP, this project has to be finished before November. Eric, if you have it consider it sold.

miniman82
10-16-2017, 07:59 PM
Before you assume your current yoke is beyond repair, how about trying to repair it first? Iíve seen yokes before that had some corrosion on the copper wires near where they join to the solder lugs, and a cold solder joint isnít outside the realm of possibility either. Poke around, not like you have anything to lose at this point.

SwizzyMan
10-16-2017, 08:50 PM
Before you assume your current yoke is beyond repair, how about trying to repair it first? Iíve seen yokes before that had some corrosion on the copper wires near where they join to the solder lugs, and a cold solder joint isnít outside the realm of possibility either. Poke around, not like you have anything to lose at this point.

The windings that fit on the tube neck have an area of corrosion and I believe i see a broken wire and almost all the varnish on those windings are gone so its shorting too. Its dead.

Eric H
10-16-2017, 09:05 PM
Okay, I found one, a Triad Y-41 (no -1 suffix) assuming it's in the right box (check pictures) it's a 90 deg yoke, 24 Ohm horiz 39 Ohm Vert.

It looks new although some of the soldering on the inside looks a little rough, possibly someone installed the Network components since they seem to be there. There is a small chip in the Bakelite that won't affect anything, there is no cover because they never came with one.

It's yours for shipping.

Due to my work schedule I won't be able to ship until Thursday.

SwizzyMan
10-16-2017, 09:11 PM
Okay, I found one, a Triad Y-41 (no -1 suffix) assuming it's in the right box (check pictures) it's a 90 deg yoke, 24 Ohm horiz 39 Ohm Vert.

It looks new although some of the soldering on the inside looks a little rough, possibly someone installed the Network components since they seem to be there. There is a small chip in the Bakelite that won't affect anything, there is no cover because they never came with one.

It's yours for shipping.

Due to my work schedule I won't be able to ship until Thursday.

I'll take it. The connector is an octal socket right?

Eric H
10-16-2017, 09:28 PM
I'll take it. The connector is an octal socket right?


No, bare wires, you have to install the socket.

I'll get it shipped and let you know how much, send me your address in a P.M.

SwizzyMan
10-16-2017, 10:05 PM
PM sent

SwizzyMan
10-24-2017, 05:35 PM
Well thanks to Eric for the yoke. This solved my HV problem. Now I can see what I am dealing with. And I was greeted with this. Now this looks like no vertical deflection but the sine wave curves at the left end of the line are what is confusing. How the hell would that come about? The set looks more like an oscilloscope than anything now. At first I thought my yoke leads were wired wrong so I double checked and they are fine. I was able to make the line full length so we DO have full horizontal sweep. I will remind everyone that I have only replaced the filters so far so it may be a bit early to start asking questions like this, but I just need to know what could cause those curves on the end of the line. I do plan on a full recap though. Line is sharper in person.

bandersen
10-24-2017, 06:07 PM
Since it's full of leaky paper caps, I would expect all sort of strange behavior including weird ripple and oscillations. I'd start by recapping the vertical circuit and see what changes.

SwizzyMan
10-24-2017, 06:11 PM
Since it's full of leaky paper caps, I would expect all sort of strange behavior including weird ripple and oscillations. I'd start by recapping the vertical circuit and see what changes. I will just start by recapping. It does look like ripple from leaky caps now that you mention it. Thanks Bob.

Electronic M
10-24-2017, 06:13 PM
A lot of sets take the B+ boost from the fly and feed it to the vertical, the two sweeps could be interacting and the like.

Hit the sweep stages with fresh caps and see what that does before wasting time troubleshooting.

Eric H
10-24-2017, 07:29 PM
Are you certain you don't have the vertical and horizontal windings switched?

SwizzyMan
10-24-2017, 08:16 PM
Are you certain you don't have the vertical and horizontal windings switched?

Positive. I did have to rewire some connections though to exactly match the wiring of the old one. I double checked multiple times.

dieseljeep
10-24-2017, 08:36 PM
Well thanks to Eric for the yoke. This solved my HV problem. Now I can see what I am dealing with. And I was greeted with this. Now this looks like no vertical deflection but the sine wave curves at the left end of the line are what is confusing. How the hell would that come about? The set looks more like an oscilloscope than anything now. At first I thought my yoke leads were wired wrong so I double checked and they are fine. I was able to make the line full length so we DO have full horizontal sweep. I will remind everyone that I have only replaced the filters so far so it may be a bit early to start asking questions like this, but I just need to know what could cause those curves on the end of the line. I do plan on a full recap though. Line is sharper in person.
I've worked on a lot of those RCA's and I've yet to see a display like that!
It has to be a miswire problem. Go through the wiring proceedure again.

SwizzyMan
10-24-2017, 09:06 PM
Just checked the yoke with the ring tester and looked once again at my wiring. Everything is GOOD. This has to clear up with just a little maintenance.

Eric H
10-24-2017, 09:30 PM
Just for fun you might try swapping the vertical and horizontal connections at the plug.
Sometimes after market parts are wired differently and if you just copied the connections from the old one it may be wrong.

Easier still, just hook up the horizontal and see if you can get a flat line across the screen (brightness low).

I have hooked up yokes wrong before and the results looked a lot like this, not that it can't be caused by bad caps but it is an odd pattern.

You could also just start recapping the set and see if it gets better, if it hasn't improved after recapping the horizontal then you might revisit the yoke connections.

SwizzyMan
10-25-2017, 12:06 PM
This is whack. So i did some searching through the sams and I found some different wiring instructions for the yoke. I rewired as it states and added c108 over terminals 2 and 7. The result is full horizontal but no vertical and those waves are still there. Im starting to think this is some kind of problem with the yoke. I'll keep investigating. https://gyazo.com/6810887174ded912a8eb1f383df51011

bandersen
10-25-2017, 12:57 PM
The vertical yoke coils will have a larger resistance than the horizontal. Double check with an ohmmeter.

tom.j.fla
10-25-2017, 02:24 PM
If you are now sure the yoke is wired correctly you need to see if there are any strange signals on the B+ boost supply. Boost also feeds horiz. osc as well as the vertical height control and crt. Best tool for that job is a good scope and knowing how to use it. Look at your sams there are 3 caps that filter the boost supply, my guess is that one or all three are open. Your snapshot sure looks like horiz sweep feeding back on itself. Just my 1.5 cents worth. All the best, Tom.J

SwizzyMan
10-26-2017, 09:46 PM
The yoke has to be wired correctly. I double checked and the wiring change I made was needed. Too bad it didnt do anything.

SwizzyMan
11-01-2017, 10:55 PM
Going to get some caps tomorrow. I really dont think the yoke is the problem. Let's just hope it is a cap problem. Anyone else have any ideas?