Saved a Dumont - Page 2 - Videokarma.org TV - Video

pdr-fml · #16 09-24-2022, 02:33 PM

Quote:

Originally Posted by Electronic M

It looks like a replacement cap. It would have originally been paper, and it's likely that replacement is paper too. I'd replace it based on the bulge in the side of it alone...Even if it tests good now that bulge is probably the result of a past failure.

Yes to be safe I will replace them. I thought at first they were like a orange drop cap which I would have left in but they probably are paper. Plus I don't like the color.

Edit: A few minutes later. Well I'm kind of surprised I removed the rubbery Mallory cap and ripped it open and it actually is a film cap no paper at all and was probably fine. The bump was just the rubber coating. I will leave the other 2 of this type in.

cj_reha · #17 09-24-2022, 04:11 PM

Quote:

Originally Posted by pdr-fml

In process of recapping the DuMont and not sure if the pictured Mallory cap is a paper cap in disguise. It has a rubbery coating instead of the hard shell. There are several of these on the set.

Cornell Dubilier actually still has the datasheet for this cap series on their website. It's an obsolete series now, but they are polyester film caps. I would be inclined to leave them if they're not shorted or something.

pdr-fml · #18 10-04-2022, 09:46 PM

Have been making good progress recapping but tonight found a bad filter choke even though I thought I had ohmed it out before. It is supposed to be 62 to 68 ohms but is reading around 12k. Sams has a rating of 260mA for that filter. The Stancor cross has a rating of 1Hy 300mA 43ohms. If I found another similar Stancor with rating 2.8Hy 300ma 60ohms would that be close enough? Thanks.

Notimetolooz · #19 10-05-2022, 08:24 AM

What is the inductance rating of the original?
The current rating and inductance are the most important numbers.
The resistance is the least. The resistance is useful because it is easier to measure for finding if there is a failure.

pdr-fml · #20 10-05-2022, 08:49 AM

I'm not sure of inductance rating of original it is not in the documentation I have but the Stancore replacement for it has inductance of 1 Henry according to Stancore documentation.

pdr-fml · #21 10-30-2022, 10:55 PM

In the picture below you see the little metal ring where the high voltage lead is supposed to be attached. The lead is not attached due to my action when I first got the set but it can be easily soldered back on. My question is how does this wire ring make up to the crt metal cone? Evidently the metal cone part is painted because it doesn't ohm out at all. Is there some paint scratched off the cone where this wire ring is mounted? I am going to eventually remove crt because it is not positioned 100% correctly and some debris has fallen on the face of the tube. I would like to know how all this works. Thanks.

19AP4 metal cone.jpg

Kevin Kuehn · #22 11-02-2022, 12:46 AM

Quote:

Originally Posted by pdr-fml

In the picture below you see the little metal ring where the high voltage lead is supposed to be attached. The lead is not attached due to my action when I first got the set but it can be easily soldered back on. My question is how does this wire ring make up to the crt metal cone? Evidently the metal cone part is painted because it doesn't ohm out at all. Is there some paint scratched off the cone where this wire ring is mounted? I am going to eventually remove crt because it is not positioned 100% correctly and some debris has fallen on the face of the tube. I would like to know how all this works. Thanks.

Attachment 205003

The outer rim is where it makes contact with the solder loop terminal. It appears your CRT has a clear plastic insulator over the rear of the bell. Most are painted but don't assume that alone will insulate you from coming in contact with high voltage.

pdr-fml · #23 11-02-2022, 01:02 PM

Quote:

Originally Posted by Kevin Kuehn

The outer rim is where it makes contact with the solder loop terminal. It appears your CRT has a clear plastic insulator over the rear of the bell. Most are painted but don't assume that alone will insulate you from coming in contact with high voltage.

Thanks. I just didn't see where there was bare metal I will look more closely along the rim as you say. I am going to try my best to avoid crt when it is energized.

pdr-fml · #24 11-12-2022, 01:53 PM

Today I will put chassis back in and check for raster on the old 19AP4. I am leaving tuner module out for right now because I have more work to do due to a cracked gear in mechanism (same problem Phil had on his RA-113). Parts replaced thus far shown in pic below not showing a several tubes replaced also. I will update later.
parts replaced.jpg

pdr-fml · #25 11-13-2022, 06:00 PM

Quote:

Originally Posted by pdr-fml

Today I will put chassis back in and check for raster on the old 19AP4. I am leaving tuner module out for right now because I have more work to do due to a cracked gear in mechanism (same problem Phil had on his RA-113). Parts replaced thus far shown in pic below not showing a several tubes replaced also. I will update later.
Attachment 205047

Hooked everything up with the exception of tuner and speaker and applied power and it appears I am not getting high voltage. I couldn't do screwdriver test on Horiz out tube since it is insulated on top so I touched connector that joins high voltage lead from chassis to CRT high voltage lead and don't get any spark at all. Nothing on CRT screen either. I can hear the vertical working and can hear it change with control adjustment. Fly back was checked out with ohm meter before hopefully that is still ok. Going to start investigating and will ask for help if I am stumped. Too bad I don't have a test CRT tube.

pdr-fml · #26 11-29-2022, 09:37 AM

Things are looking good for the moment. Found the reason for no high voltage it turned out to be me forgetting to solder one side of replacement resistor. Along the way also found I installed a 0.2 mF cap instead of 0.02 cap. After those repairs I got a raster. Tuner is still not installed so no signal yet. Right now in process of reinstalling crt after cleaning real good. Bottom line so far it has been worth all the work now that I know the crt is good. ☺

Kevin Kuehn · #27 11-29-2022, 04:48 PM

Good for you finding the mistaken cap.

pdr-fml · #28 02-12-2023, 10:22 PM

Here is short video of my Dumont RA-112 off my google drive. Got a decent raster at least. I know positioning of raster needs some work but will work on that later. Have some repair work to do on tuner before I reinstall it. Really happy about having a working metal cone CRT and learning about them.

https://drive.google.com/file/d/1uTx...ew?usp=sharing