[Greg]

I've just finished my 37-116 (less grill cloth replacement) and am moving on to something a bit different, a DuMont RA-112 (first TV).

We had one when I was a little kid. It was in the basement and never worked. I think my mom gave it to the furnace repairman to get it out of the house, early 1960's.

I'd been looking for one for a while. Then this one literally came to me. A friend of a friend found it and the owner, who never got around to restoring it, offered to deliver it to me. It was nearly free... So now it's made it to the head of the queue, with lots to work on behind it.

The chassis' relatively huge, so I made a enlarged version of the stand I use for radios. It seems sturdy enough and gives me good access to the underside of the chassis. I have to check to see if the dial can wack the cross piece if I were to let it rotate it that far. That would be bad.

If anybody's had experience with one of these, is there anything special to "look out for"? The tuner is a bit "seized up" and looks mechanically complicated . I figure this project will take a while .

   

   

   

[Simon Wa3uay]

Very nice shop you have there- is that in your garage? Also can see you are a woodworker, shelves and the stand etc.
-Simon

[GarySP]

The only suggestion I can give is to buy stock in a capacitor manufacturer! You're gonna need lots of them. Also hope you saved a digital converter so you can watch it when you are finished restoring it. Can't say for certain, but might need a CRT rebuild as well. I don't mean to sound discouraging. It's just not quite as simple as a radio. However, since you just finished restoring a 37-116 this should be simple for you! Keep us in the loop of this rebuild; Dumont televisions were excellent TV's in their day. Take care and BE HEALTHY! Gary

[Greg]

Simon -
My shop is the corner of the basement under the family room. I have to confess, the shelves are from IKEA. But the chassis stand is my doing. I need a proper workbench. I currently use a 37 year old wooden table from when I first got out of school. It works.

Gary -
The installed CRT is weak and has a brightener - not a good sign. The spare, supposedly tests good. Also, I know someone who has a good one.
I do need to order some HV caps. I think I have all the others (less mica which should be OK).
I have a converter or two. Also there are HDMI to NTSC modulators (need to investigate):
https://www.ebay.com/itm/185023854299


The plan is to first get the audio working via the FM radio. The problem with that is I'll need to free up the tuner first. It's not totally seized, but...

I also have access to a test CRT when it comes working on the video. I was warned about fooling with a real 19AP4 while debugging. It has a metal cone with ~13KV on it. Wouldn't want to get too close .

[mikethedruid]

Don't feel self conscious about your work bench. Mine is an old steel desk I inherited from my Mother, She got it from the hospital where she worked last as a computer coder of medical records. She was a registered nurse, but studied computer programming in the 1960s because she realized that soon medical records would be computerized, and she figured right. Anyway, the hospital decided to re-do their offices, so my mother was able to buy her old steel desk very cheaply. I use it now as my work bench, and it works very well. I made some shelves to go at the back of it from 1x8 pine, to hold some of my equipment, and that serves just fine too. "If it works, use it," that's what I say.

[PaxPumpkin]

That looks like a super-fun project! I wish you the best with it!

I've done some more modern ones, tiny portables, but this would be a complete showpiece for certain. 

Side note, I saw this in the photo and had to laugh, because I'm staring at one very similar, if not exact, right now. 
   

[MrFixr55]

I have the same one, was my grandparents' first TV. these were totally "Top of the Line" except for another DuMont model with the same CRT but a giant transformer 2 5U4s, 2 6BG6s 2 1X2s as voltage doubler. Can't remember that model; fixed for a neighbor when I was a 13 year old kid. If the gang thinks that you would go broke recapping an RA112 , this other model would increase the national debt! I have not gotten to mine recently, but the Tuner (Mallory-Ware "Inductuner") will have to come out of the chassis to service it. Several U Tubes and internet articles on restoration on a RA113 (Same set but with 17" rectangular glass CRT).

Good luck, keep us posted, mine is another retirement project for me.

[radiorich]

Hello Greg,
wow what nice tv and I love the big chassis stand that would work great with my RCA 8T240 chassis since i have like two of them plus the RCA model 811k radio chassis that is one my customers it really is a monster .
Back in the day there was a Tuner rebuild company called PTS that I would get my tuner's rebuilt by .
When my shop was running full steam I did a lot warranty along with radios and tv's.

Sincerely Richard

[Greg]

Progress, but not recently. I've got most of the re-capping done, including re-stuffing the electrolytic cans, replacing a few, off value resistors and replacing the very bad, focus-control rheostat. It's been done for several weeks. I need to replace the line filter caps and move on to the high-voltage... At some point I need to take apart and clean the tuner. It's currently seized up pretty well.

I suspect some of the mica caps aren't original. There are a couple of places where there are two in parallel, like someone didn't have the exact value to replace with a single cap.

Regarding PaxPumpkin's recognition of the Philco chassis in the background of an earlier photo, it's a 38-2. It's restored and working. It needs to be aligned.... It's also awaiting the refinishing of its' home (cabinet).

   

[Greg]

Progress at a snail's pace, but progress. My plan is to first test the FM/audio and then move on to the video.

Testing the FM.

I powered up the TV for the first time without the HV. I forget exactly at which point (<90V), but as I turned up the variac I heard a snap. I immediately turned it off without looking for smoke, sparks, etc. I tried it again and the same thing happened.

I need to see what's up. I rotated the chassis so I could see the underside. I turned it on again and swear I saw an orange glow coming from the underside of the audio discriminator transformer and turned it off. Very bad. Almost, but not quite,  unobtanium if bad.

What's going on. Is it a stray wire clipping? Is it silver-mica whisker?

I removed the transformer to take a closer look. The primary and secondary had continuity and weren't shorted. I meant to measure the 2 caps in it but forgot. There was no way I could see a wire clipping or anything else getting inside of the can to short.

I didn't want to commit to taking it apart to see the 2 caps inside, so I reinstalled it. Maybe I was hallucinating or any "whiskers" that had formed had burned off (pure speculation).

I powered up again. Nothing exciting happened this time. The voltage was set to 117V and all was well, except no sound.

I checked the speaker. The primary was OK, the secondary and/or voice coil were OK. I decided to disconnected one of the secondary transformer wires from the speaker so I could independently check the secondary and the VC. Well the VC had no continuity. 

I grabbed a spare Transoceanic speaker and hooked it up and tried again. Finally I heard some noise. I then connected an "antenna" and received a few FM stations. The sound's not great, but it's alive.

The speaker connector plug and socket don't engage well. But that doesn't matter for now.

I'm trying to decide if I want to try to improve the FM reception before or after I try to get the video working.

The way I wrote this is a lot more orderly than the actual process was. Hey, it's my first TV and it has lots of parts

[radiorich]

Hello Greg,
Wow you have one of my Dream Sets a Dumont !!
I think you did fine with this thread and how do you like working on tv's more of a challenge right ?

Sincerely Richard
P.S. I need to restore one of my Tv's it has been years where I currently live is not where my Tv collection is .

[Greg]

Richard -

I remember we had one of these TVs when I was very young. It was probably ~15 years old, sat in the basement and never worked. Eventually we gave it to the furnace repairman. I never saw it working.

The cabinet style matches the one we had. There are RA-112's with nicer, less "plain" cabinets. I almost would have rather had gotten a similar RA-113 just because the 17", rectangular CRTs are still available. This one has a round, metal/glass 19AP4. The installed tube is a bit weak, but it came with a stronger one. There are no substitutes for it and currently nobody rebuilds them.

You're right, I think this could be a lot more challenging than a radio. A friend has an 8XP4 I can use to bring up and debug the video. Maybe I'll look for a cheap sweep generator at Kutztown next week. I broke down and bought a digital scope recently. I didn't get it specifically for TV debug, but it could be useful.

[TV MAN]

Your arcing could be the silver mica disease in one of the IF cans. Some have the mica caps in the base of the can and can fail, causing arcing, static etc. They can be cut our/disconnected and regular micas soldered in. I oft do TV's in steps against the advice of some. Makes it easier to find any errors. I usually start with the power supply, then horizontal, vertical and sound in that order. Keep the brightness and contrast turned way down just in case you power up with no vertical sweep, and in some cases, no sweep at all. It may save you burning a line or spot on your tube.

[Greg]

First power up as a TV (not just FM audio) and it works!

Tonight I powered it up with the HV enabled and with a test picture tube. After some tweaking there was a decent picture with not so decent sound. That needs looking into, even FM radio isn't great. But it was the first time I tested the whole thing. My TV knowledgeable friend was over for the spectacle for advice an moral. Fortunately nothing went terribly wrong. Failure is always an option, just not a good one.

It turns out the "snapping" was due to arcing when B+ was hit its peak on power up before dropping to its "normal" value. It went away after some lead dressing in the area. I still need to understand it a bit better and possibly place sleeving on some of the wires in the area.

I found the location of the arcing by turning off the lights and taking a video with my phone during powering up. It was pretty obvious without 300W of lighting beating down on it.

I still need a replacement speaker. I'll look for one at Kutztown in the morning...

It still needs some work, but it seems to be 90% there.

The biggest problem was finding a signal source. My VCR's were both messed up. I think they have belt problems. The DVD players don't have RF outputs. I ended up running a cable across the basement from our CTV splitter and using the one analog decoder box we have.