Got a lead on an early DuMont TV locally
 

Hello everyone, I was looking through facebook marketplace a week ago or so and I saw someone locally had an early DuMont TV for sale that I thought about getting but I wasn't sure about the price they were asking (they were asking over $100 for the set and I wasn't sure if they were going to budge from the price) so I didn't pop on it, well a week later and I saw the same tv posted on an antique TV group on facebook that someone was posting about the TV on there to see if there was any interest on there even if it was to just make it into a fish tank, and I had commented on the thread mentioning that I was local to the TV (and the relative that the person was posting the TV on behalf of) and that I was interested in the TV but I wasn't willing to pay anymore than $50 for the set because it was going to likely need more than that just to fix it up, and the guy sent me a PM telling me that his relative was willing to go down to $100, but he said that if it didn't sell for $100 after a week he would take my $50 offer. I told him that I thought that the $100 would work and that I would come pick it up either Friday or Saturday. It is a console DuMont.

What would be the best way to transport this TV? Take the Chassis out of the cabinet and load that into the car separately from the cabinet and then load the cabinet in separately? I'm asking because I would be moving this TV myself and I know quite a few of you guys on here have experience moving old console TVs by yourselves.

Thanks for your help.

In terms of weight removing the chassis and CRT from the cabinet will make it easier to carry. Make sure it'll fit in your vehicle before you go to avoid wasting gas.

OK, that's what I was figuring. I have a Honda Pilot from 2006 Which I think should be able to fit the TV fine, especially if i fold all of the seats down in the back.

I picked up the TV today, Its a Model RA-108A Bradford, the cabinet is in kind of rough shape but it seems to be all there including the orginal back cover.

The tuner seems to have that all too common "white mold" that is often times on early plastics which should just come off with bleach water, or dawn dishsoap.

I was expecting this TV to be extremely heavy but me and the guy I bought the TV off of were able to load the TV into the back of my Honda Pilot pretty easily without any issues, (I didn't end up disassembling it like I thought I would because I wasn't sure how to get the back off without damaging anything.)

Are you interested in a Royal Sovereign? It's pretty big. Four feet high and about 5 feet across. Near Atlanta. You would need a pickup or an Econoline van.

No Thanks, that would be too far away for me to drive, and also I've already got two other console TVs besides this DuMont I just I just picked up, and I'm already just about out of space for anymore TVs, like this, as my house is only a little over 900 Sq Ft of finished living space, I will be getting rid of one of my consoles eventually (a 1974 GTE Sylvania Color TV that has some issues with the tuner, but otherwise is like brand new because it was never used by the original owners of the set that I got the TV from, because they used it as a piece of furniture to decorate their basement with.)

The Dumont Doghouse I bought is the first tv of all of the ones I’ve collected that broke me. Could not handle carrying it alone. Beast of a machine.

I always removed the two chassis's and it's a lot lighter that way and 2 people can carry the box that way. I picked it up from a station I worked at in Charleston in an Econoline. And then I transported it to Atlanta in a Ranger pickup.

Well I got the two chassis out of the cabinet and the TV brought inside, with some help, this TV had an interesting modification in it, somone at some point in time had added a 5v filiment transformer to the side of the inside of the cabinet for some reason and the filiment transformer was wired in with the main power transformer which is a beast of a power transformer, its at least 6" tall and probably a good solid 20# of iron.

The TV does use 2 5U4G rectifier tubes so I wonder if the TV might have gotten hit by lightning at some point in its life which may have fried one of the 5v filiment windings in the original transformer so they had to install a new 5v filiment transformer to replce the dead 5v filiment winding in the power transformer?

Also another weird thing is that the picture tube had a dual stage picture tube booster (brightener) attached to the picture tube and I'm wondering if the picture tube was really in that bad of condition to warrant the use of a picture tube brightener; or if it was meant to be used as a way to boost the voltage for the picture tube because perhaps that 5v filiment transformer was actually being used to replace a bad 6.3V winding on the transformer and it needed an extra voltage boost to get the picture tube filiment voltage to where it needed to be voltage wise?

Just spitballing some ideas here, not claiming to know what's going on here, but would definitely like to hear what you guys think could have happened to the TV in its past to warrant these odd modifications (which I'll admit the picture tube brightener in of itself is not an odd modification, but that along with a replacement filiment transformer, is an odd modification.)

More likely the 5v is for the damper tube. Can you trace out what tubes it is going to?

2 5U4Gts would take about 6A (3A x2), so if the 5v secondary winding was out, it would indeed take a beefy replacement to light the tubes safely, but keep in mind, the cathodes are always going to be at full LV bias potential, and thus isolated from all else, so the booster on the CRT must be for some other reason, cause it most likely is 6v and not tied to that line.

That too! :D

The RCA 630ts types have a 5V4GT that use 5v, but don't need as much power as 2 5U4GT, but have more HV on the circuit, so as he said above, find out where they wired it to!:yes:

perhaps T2 failed at one point, and the extra one is a replacement for it? :O

Edit, perhaps not.. This set is, confusing! :P

https://www.earlytelevision.org/pdf/...5b_sams_95.pdf

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Is the 19AP4 CRT Tube a tube that I need to worry about having issues with? I know some picture tubes have a metal bell that can go to air without any notice which can completely ruin the tube, is this one of those tubes?

Yes, it is. I'd be more concern about getting zapped while working on it. The entire metal bell is connecting to HV. It's not lethal but stings.

Good idea to use a 5AXP4 or 8XP4 while on the bench if you have one.

I have a 10BP4 tube in another TV that's functional, would that work? Other than that I don't have any Test CRTs.

I did trace out where that filiment transformer went to, it went to the second 5U4G tube. So perhaps a bad 5v filiment winding in the original power transformer? The original power transformer in this unit is a beast, I can't believe the transformer would of fried that easily...:scratch2:

You can use any CRT that will fit and has the same base pinout. 10BP4, 10FP4, 12LP4, etc. Bigger issue is mounting and supporting it. You'll also need to modify the HV connector.

Both 5U4 filaments should be wired in parallel. More likely there is leakage between windings than it is open. You could check it if you have a megger or leakage tester. Some devices like the Sencore PR-57 have a leakage tester built in.

Unfortunately I don't have a leakage tester, I do have a capacitor checker from the 1930s that tests for leakage in capacitors but I'm guessing that's not the same thing...:sigh:

Also if the winding in the power transformer for the 5v filiment turns out to be fine (not open, but maybe slightly leaky) would it be fine to just reuse the original transformer's 5v Filiment winding, the less modifications I have to contend with in this set, the better.

Slightly leaky would be bad. The transformer will get warm (maybe hot) which will likely cause it to get worse until it spirals out of control and goes up in smoke.

Personally, I've never encountered a bad transformer in a vintage TV but of course all things are possible.

I do have a couple Dumont RA-103 parts chassis. If the power transformer is the same, it's yours for the cost of shipping.

OK, that's fine. I'm really not sure how I would go aboout figuring out if this TV's Transformer is bad or not if I don't have a leakage tester, as test equipment doesn't come up for sale very often in my area, especially test equipment thats really specialized like a leakage tester, every once in a while I will come across a tube tester or a oscilloscope, but not much else.

A crude way is to pull the rectifier tubes and power it up. If the transformer gets hot after a few minutes (or less), it's bad.

OK, thanks for that little tip, I'll give that a shot.

Also another thing I noticed is that this TV has an RCA Jack on the back in place of the 300 Ohm screw terminals for the antenna and then from that there was a 300 Ohm twin-lead that was hanging off the back, I was wondering how the original Antenna terminals would of looked like on this TV so I could maybe try and get it put back right again.

And then I was testing some of the tubes in this TV and I noticed that one of the 5U4G Rectifier tubes measured shorted in both sections, would that happen to have anything to do with the "bad 5v Transformer winding" issue? The other 5U4G tube was fine by the way and it measured into the 90s emissions wise.

Most Dumonts from the end of WWII to the Emerson merger used a 72 Ohm (not 75 or 300) coaxial antenna hookup and had an RCA jack as the factory antenna connection. Every RA-103 I've seen and my manchu are setup in that manner.

OK, so the RCA Jack is actually original and the 300 Ohm Twin-lead wire in the back was added later on in an attempt to make it work with a "modern" 300 ohm twin-lead antenna hook-up if I'm understanding this correctly.

Is there any way to make this 72 ohm RCA antenna setup work with a more modern 75 ohm antenna setup like what is used on a digital converter box or a VCR or a RF Modulator?

For the antenna all you need do is get it somehow connected. Both are unbalanced
coax and the impedance difference is immaterial. Adapters are readily available, but in my experience not exactly long run reliable. Just disconnect any 300 ohm stuff.

They make RCA to F-type adapters...one should be all you need. Or if you have the parts laying around just solder an RCA plug onto an end of a 75 ohm TV coax cable and call it good.

Well All I would be doing would be just hooking a VCR up to the TV to use it to watch old Black and White Movies on, or a converter box so I could watch old TV shows on it. So I think just using an adaptor of some sort should be plenty enough to get it to work. :thmbsp:

Sounds like a plan to me. :yes: :D

Unfortunately I have a sad update on this old DuMont TV, The 19AP4 Tube is a dud, I went to try and test it with my old picture tube tester and the tube filiments weren't glowing, so I'm guessing the tube must of went to air...:sigh::tears:

Before you declare it dead check the heater pins for continuity. Sometimes the solder in the pins fails or the wire outside the glass corrodes open...Both are usually fixable (the latter with a fair bit more effort than the former). If you have heater continuity and with 6.3V applied it doesn't glow but the neck gets very warm very fast then you can be confident it's gassy.

OK, Thanks I'll give that a try. If the Picture tube is indeed a dud, I'm guessing that means I'm going to have to give up on this TV? I say that because I don't want to buy a picture tube for this TV if its going to cost me over $100 and if there's a risk that the tube might fail during shipping.

I'm sorry nobody warned you about metal cone picture tubes often going to air, I guess to some it's such common knowledge they forget to mention it.

Yeah, Unfortunately I think this picture tube is a lost cause, because I checked it for continuity and it wouldn't respond to my DMM, it just read "OL".

I feel for you my friend. I've got an RCA cabinet model in beautiful condition with a just about dead 16GP4 metal cone CRT. The availability of these CRTs is a bit higher but still hard to find in good condition.

Is there any way to modify this set to get it to work with a picture tube that isn't of the metal cone variety?

I would assume if you can find an early 50s 19 or 21 inch tube that has the same socket, and you're willing to mount it, all that would be left to deal with would be the what the earlier yoke would do on a later tube... which means, if you simply plug a later tube in and stick the yoke on it, it might not fill the entire screen? Someone may have to correct me on that...

You could use the yoke for the later tube, but if it doesn't just "work", then science and math are involved, yuck!

There's several points Jeff is off on but, instead of poking holes I'm going to approach this as a rough how to guide.

When it comes to magnetic deflection CRTs the guns and bases were basically all the same between 1946 and 57. Ignoring glass cone VS Metal (which is more of a mechanical mounting and HV lead conversion process) there's 3 major things to consider in selecting an all glass replacement:
1.) Deflection angle: there were 3 main angles in that era ~60 degrees, ~90 Degrees, and ~110 degrees. Use the datasheet to figure out what angle your tube has and what your replacement candidates are. There were some in-between angles too. Jumping from a 60 to a 90 isn't a great idea but a 72 could probably work in either of the previous 2 angles.
2.) Focus type: some tubes are magnetic focus and others are magnetic. It's easiest to use a tube of the same type, but you can work around it by adding or deleting a purpose built focus magnet and sometimes adding focus voltage taps.
3.) screen size: you can technically fit any size CRT of the same deflection angle and focus type right into a set and make it work. Some companies used the same chassis without any changes to drive a 10BP4, 12LP4 or a 16AP4 (there were even some larger compatible tubes) depending on what screen size model was being made.... However if doing a modification and using the original mask you need something that fills the mask but fits the cabinet. A 24" tube in a 16" cabinet isn't going to work and a 10" tube in a 16" cabinet will look wrong.... Besides the obvious there can be issues with different dimensions between the neck shoulder and screen requiring the yoke mounting brackets to be moved, and a glass bell flaring out wider than a metal one and interfering with the chassis...

These are all problems that will vary widely depending on the model and tube you want to pair up. Most are not insurmountable, but picking the most compatible tube possible is important for minimizing headaches.

Absolutely well pointed by Electronic_M. Using same logic I subbed the CRT of a '60 Brazilian Admiral for another brand and model CRT. Paying attention to mechanical drawings and electrical limits/deflection angle (most are 110 or 114 degrees from that era).