Hi Folks,
I'll be restarting this one again. I got a NOS delay relay installed and working Last power up, I had smoke from the area of the vertical output transformer. After much analysis revealing the value of a VTVM in testing coil winding integrity, I found no damage to the VOT. This doesn't mean I'm certain this was the source of the smoke...just that it was coming from this area. I sourced a new 1Kohm focus rheostat from Surplus Sales. I'm going to install it on the back of the chassis as the shaft is not long enough for a direct replacement. Tom C. gave me some advice on extending this but I can't remember what he said and I'm too lazy to search for it!!!! So I'll be on a journey through this in the next few months and I hope you will be along there for the ride. Just wanted to get things started!

I believe ACE hardware sells 1/4" shaft couplers...if the new shaft sticks out close to 3/8" or more one should work...just saw the shaft off the old pot after measuring how far it sticks out and stick it in the other end of the shaft coupler (and make sure it sticks out the same length as the old one did). If ace doesn't have it Amazon or some online vendors will. You can get rigid and flexible shaft couplers...This application is probably better with the rigid kind. (Last spring ETF I turned down a nice doghouse because someone had deleted the focus knob and put on wrong knobs elsewhere and I thought it looked real bad like that).

I forget where the vertical output transformer is but if it's near the candohm chassis mount power resistors those are more likely to be the source of the smoke....I haven't had any fail for me, but of the 5 RA-103s I've had 3 of them had 40s-50s power resistors cobbled in to replace those resistors or sections of them. The one near the vert osc transformer (and the osc transformer itself) are common to find failed.

Last time I was at Moyers, I started rattling off the values of power reaustors I needed for my 30s GE table radio.

Before I was done, he interrupted me and said “Candohm?”

Those things are famous for shorting and going open, and in general, just foung annoying stuff.

OK here we go. Let me preface this with two things because in the past, when I have posted pictures of work that I have done, I've received a few nasty comments about lousy soldering, poor organization etc. I started this hobby in late 2020 and there's no question some of my restorations have looked amateurish. I'm 64 years old now with shaky hands. Despite this, most of my electrical work is solid and reliable. I by no means try to pass myself off as an experienced electronics restorer. Constructive advice is always welcome, in fact, it's desired but I'm sure some here will not participate or lose interest when the journey reveals stupid mistakes or poor technique. So be it. I desperately want to get this TV working but it was altered significantly by previous work over decades and I've done my best to attempt to problem solve. With all this in mind, I'll make my second point.

I started work on this TV a couple of years ago when I had a significantly different approach to restoration. Today I use the standard method of trying to baseline the TV through a slow power up on original parts. Once that's done, I do methodical replacement of components where I think the failure points are and then check function. But a few years ago, I shotgun recapped my restorations and I had a reliable bookkeeping method but I did create errors that were then difficult to run down. That's the method I used and describes the current state of this TV. I have some rudimentary function in the relay/rectifier section but then I start to hit walls.

I had the great fortune to run across this on eBay and snatched it up.

https://imagizer.imageshack.com/v2/800x600q70/924/Wws80c.jpg

This was a great acquisition because of the quality of the available resources. I can't read the Sams schematic. The copy quality is poor and the print is microscopic. The Riders service data is much more useful and I've been using it as an adjunct to the publication above. Below is the Dumont Service Manual schematic for the RA-103

https://imagizer.imageshack.com/v2/1024x768q70/923/Jkn2qC.jpg

Below is the detail of the section I have had success with. The relay works and the circuit closes powering the entire TV

https://imagizer.imageshack.com/v2/1024x768q70/924/moMelw.jpg

OK, here are some pictures of the chassis. I did relocate the focus pot and I am in the middle of wiring it up. It's mounted on the side of the rear of the chassis under the HV cage. The wiring in the rectifier section is a mess and I will clean it up. I tested function on 4 relays so there was a lot of extension wiring to test it unmounted. Oh hell...I'll just post them all! Go ahead, let me have it! :bash::bash::bash:

https://imagizer.imageshack.com/v2/1024x768q70/923/2bMqGY.jpg

https://imagizer.imageshack.com/v2/1024x768q70/923/Zb4Jw7.jpg

https://imagizer.imageshack.com/v2/1024x768q70/923/qhZYpT.jpg

Relocation of the focus pot, not yet wired up. Should I use Tom's suggestion of a shaft extender :scratch2::scratch2: I'll move it back to the original position.

https://imagizer.imageshack.com/v2/1024x768q70/922/3JZYUY.jpg

The original focus pot still in place but out of circuit. The 750ohm resistor hanging off the chassis is something I put in circuit to test TV function in the absence of a working 1K focus rheostat. It's no longer in circuit.

https://imagizer.imageshack.com/v2/1024x768q70/922/OrLpgc.jpg

More of the chassis

https://imagizer.imageshack.com/v2/1024x768q70/922/di3UT3.jpg

Area under the HV cage

https://imagizer.imageshack.com/v2/1024x768q70/922/X2a5vM.jpg

OK...so, when the relay kicks in, I have a dead short...somewhere. I'm certainly not asking anyone to review these photos and tell me where it is. I'd just like some guidance on where to start methodically running it down. My first thought was to go through my replacements one by one checking for accuracy but IDK if that's the best way. If desired, I can post photos and details of any area on the chassis and describe what's going on. Any and all advice is greatly appreciated!!!!

Sorry if my ranting about criticisms offended anyone. I'm embarrassed by some of the dumb things I do! The Top Dogs here have always been kind, encouraging, helpful and reassuring.

This post is not as comprehensive as I would have liked it to be but I wanted to get something out there to get started.

Cheers!

A good way to run down a hard short is ohming out the main B+ line. If you can detect the short with a DMM unhook all branches from the main line and recheck the main. If the main isn't shorted check the unhooked branches. If one branch has a short leave it unhooked (you can reconnect the others) and disconnect what branches from it and check those. Rinse and repeat till you find it or narrow it down to a few parts and wires and check those.

In one of your photos a red and green wire meet in the foreground and don't appear to be soldered... might want to do that.

Yes that’s the focus pot hook up not yet soldered

The first place I would start is the candohm resistors. They have a nasty habit of shorting to chassis. If you replace the candohm resistors be sure to unhook all the wire connections to the terminals on the candohms. You cannot use the terminals as tie points for your new resistors. If they are not shorted now they may become so in the future.

Measure all the terminals of the candohms to chassis and see if that is where your short is then disconnect the wire and measure again if it is the candohm or the connections that are shorted. If it is not the candohm then follow the wires and the short to where it goes, disconnecting things as Tom has mentioned until you find it.

Use your eyes and check for errant solder blobs and wires that may be touching.

Great. I will try that this evening. Not to dismiss Tom’s suggestion but disconnecting B+ leads in bulk sounds too daunting for me right now. Both original resistor cans are in circuit and in use. I’ll take a comprehensive look and document it then post.

Great. I will try that this evening. Not to dismiss Tom’s suggestion but disconnecting B+ leads in bulk sounds too daunting for me right now. Both original resistor cans are in circuit and in use. I’ll take a comprehensive look and document it then post.

On most other sets I'd say have more faith in yourself. Dumonts with those harnesses usually aren't fun sets to trace leads on....Says a guy who made one good harness out of 2 half mouse eaten ones (it took a day and was a huge PITA, but I did it).

Yeah it's a spider web, a mouse trap and hedge maze held together with hundreds of 1948 style zip ties...these annoying wax covered string knots. I had a thought. The main distribution switch for the B+ appears to be the selector switch on the front for phono, FM Tel and Tel without pilot light (why?). Do you think it would be helpful to power it up with phono selected and see if it shorts when the relay closes? Do the same perhaps with the FM position selected? Could this approach eliminate some sections as the source of the problem?

I relocated the new focus rheostat in the original position and hooked it up. I don't need new problems that I might make from running new wires etc...

The original canned resistors seem to be OK. The only terminal that has continuity with the chassis is the one that is connected to ground.

Well it was worth a try. I have had 3 sets with one or the other candohm shorted to ground. Yes, that seems a good idea. Easy way to separate B+.

Ditto on a Candohm resistor shorting to the chassis.

OT: I restored a 16" Admiral set, 26R12 and all was well. Reading many threads on the Antique Radio Site, there was much mention about Candohm resistors shorting to the metal casing. Many radios used them.

The set was unused for a while and I wanted to watch a movie. When I turned on the set, I was greeted with quite a light show inside of the 5U4G (Admiral Labeled!) It burned open the filament of the tube rendering it useless of course. Fast forward, the Candohm was in fact shorted internally and shorted the B+ to Ground. I replaced it with a terminal strip and a ceramic resistor.

(Note: this is a picture before I restored the set)

Well, maybe not so fast on my dismissal of the Candohm resistors. I tried it on the phono setting and it didn't dead short however, R285, the 1.28K resistor began to smoke and got blazing hot. That's the Candohm right off the choke with 435V DC on it. It didn't test as shorted to the chassis when I tested it for continuity but something major is going on there.

I isolated R285 and tested it to ground and for resistance. It tests perfect. I am going to replace all of these CO resistors at some point but while I'm troubleshooting, I'm not going to complicate things. I have my suspicions the issue is in how I hooked up the relay. I'm going to start with the lead that feeds the articulating top contact. As it sits, the relay closes when the 6AL5 tells it to do so. The issue is after that happens.

So this is the area of interest...again!

https://imagizer.imageshack.com/v2/1024x768q70/923/zhBxjm.jpg

Here are the relay details.

https://imagizer.imageshack.com/v2/1024x768q70/922/prJvKA.jpg

I thought the purpose of this was to give the 2 5U4 rectifiers time before they are connected to the rest of the TV but this schematic confuses me a bit. The rectifier circuit feeds into the relay at the point indicated by the bottom open circle and the arrow indicates that is the articulating contact in the relay switch correct? The top open circle is everything else and is the stationary contact?

...the bottom open circle and the arrow indicates that is the articulating contact in the relay switch correct? The top open circle is everything else and is the stationary contact?

No, in schematic arcana, the arrow is always the stationary contact and the moving contact is always what the coil "pulls" on.

No, in schematic arcana, the arrow is always the stationary contact and the moving contact is always what the coil "pulls" on.

GREAT!!! Thank you for that piece of knowledge! I think I have the relay hooked up correctly. The stationary contact has the tied together pin #8s from both 5U4s and the yellow lead from the small secondary coil soldered to it as well. I'm going to double check the wiring in the rectifier circuit then move on to checking the moving contact leads and how they trace out.

A couple of things:
The resistor that's smoking, if it tests fine then it's smoking because the short is on (or not far down stream of) the side of the resistor not connected to the high B+ rail....That resistors is the somewhat literal metaphorical smoking gun that points you to at least one killer short.

There were a few purposes to the relay. The main one is to delay the B+ until the tubes have warmed up to stable operation so when the set comes on you get a perfect picture and sound instantly without any concerning warmup instability. (Realistically you can delete the relay by shorting the contacts and the set will still work fine... At least for sets that work with the relay there) The other purpose is to protect most of the lytics from warmup surge.... Basically since the 5U4s are filament tubes they warmup almost instantly, but all the other tubes take ~11 sec.... During that time the B+ has no load from the signal/sweep tubes and skyrockets briefly this can be hard on the lytics and or require higher voltage lytics to cope.

Since the high B+ rail goes directly to the area of the focus control and H centering pot, I'd bet money that the short will be in that area (circuit-wise), most likely involving the focus control. The schematic is too fuzzy to read print, so if you could post a blow-up of the lower-right corner of the schematic, it should be pretty easy to nail the culprit.

Here it is. Unfortunately, I'm at work so no troubleshooting until I get home!!!

https://imagizer.imageshack.com/v2/1024x768q70/923/NMjFwq.jpg

A couple of things:
The resistor that's smoking, if it tests fine then it's smoking because the short is on (or not far down stream of) the side of the resistor not connected to the high B+ rail....That resistors is the somewhat literal metaphorical smoking gun that points you to at least one killer short.

There were a few purposes to the relay. The main one is to delay the B+ until the tubes have warmed up to stable operation so when the set comes on you get a perfect picture and sound instantly without any concerning warmup instability. (Realistically you can delete the relay by shorting the contacts and the set will still work fine... At least for sets that work with the relay there) The other purpose is to protect most of the lytics from warmup surge.... Basically since the 5U4s are filament tubes they warmup almost instantly, but all the other tubes take ~11 sec.... During that time the B+ has no load from the signal/sweep tubes and skyrockets briefly this can be hard on the lytics and or require higher voltage lytics to cope.

So I had it backwards in terms of what happens. The relay delay is for the rest of the TV to warm up before they get slammed with B+ from the 5U4s.

…and maybe when u get time Tom, for my education, can you explain how you knew the short was after the CO resistor when it got screaming hot? Some things about DC voltage I just don’t get.

So I had it backwards in terms of what happens. The relay delay is for the rest of the TV to warm up before they get slammed with B+ from the 5U4s.

Exactly. That's its primary function. Less high-end designs didn't use it by designing-in enough 'headroom' that the surge doesn't overvolt the filter caps' rating.

Horizontal position pot is shorted to ground. Based on the circuit, could it be a bad horizontal yoke coil in addition to a bad pot?

What point are you actually measuring from? Is it a dead short (zero ohms)? If not, how many ohms?

What point are you actually measuring from? Is it a dead short (zero ohms)? If not, how many ohms?

No not a dead short...48 ohms. From the two tied terminals on the pot. Am I measuring the horizontal yoke at 48 ohms?

Try lifting the lead that goes to the yoke coil.

Try lifting the lead that goes to the yoke coil.

I just did and forgive me now for the fact that I'm getting a little confused so I might give you information that doesn't make any sense or that makes no relevant sense to this troubleshooting. I lifted the lead off the positioning pot that goes to the horizontal yoke. There is no continuity to ground on the pot now..no tone on my DMM and the tab on the VP pot measures 98 ohms. The lead I removed reads a tone to ground at 48 ohms, the same reading I got when the lead was attached to the pot.

Is that the lead that goes to R286A 200 ohm candohm?

Is that the lead that goes to R286A 200 ohm candohm?

Yep

I think you may have found your problem.

I think you may have found your problem.

The terminal on R286A reads 48 ohms to chassis ground. And I lifted the leads from it and it measured 45 ohms to ground with a constant tone

yep, you found it. Replace the 200 and 250 ohm resistors and disconnect all terminals of the candohm. Use 15 watt for the 200 and 10 watt for the 250.

yep, you found it. Replace the 200 and 250 ohm resistors and disconnect all terminals of the candohm. Use 15 watt for the 200 and 10 watt for the 250.

Thanks Tim, Tom and "88"!! I have a parts chassis where all of the CO resistors were replaced with Ohmite ceramic wire wounds so I'm going to clip those out and just replace everything. I'll get new Ohmites but for further testing and resurrection, I'll go with the old resistors. I'm absolutely certain that's NOT the last issue of unknown origin I'll need help with running down but for now, I'll take a few hours tomorrow and replace the components. Thanks again all!

:thmbsp::banana::banana:

Glad you are making progress.
…and maybe when u get time Tom, for my education, can you explain how you knew the short was after the CO resistor when it got screaming hot? Some things about DC voltage I just don’t get.

The short answer is doing a fair bit of ohms law and voltage divider math and seeing the principles in action under similar circumstances.

The short answer is that every resistor has a power rating (watts = amps X volts), and will smoke if that power rating is exceeded. The short will increase the load the resistor is feeding and thus the power it has to feed it's load. There are a few ways of looking at it mathematically...The resistor and the things loading it (the loads can be modeled by a resistance who's value can be obtained by ohms law and by measuring the load current and voltage drop) are basically a voltage divider. If you short the load resistance dead the voltage across the candohm resistor increases (as does current thanks to ohms law) so power through the resistor will increase even faster.
Another way to look at it mathematically if the short isn't a dead short, is to say that the load resistance has dropped which in turn lowers the total resistance of the divider...If B+ hasn't significantly changed then ohms law arranged amps= volts/ohms indicates that current will increase which will increase the power through the candohm.

Kirchoff's current law and voltage law are also helpful in understanding voltage dividers and other series parallel resistor networks.

If you want a fun/useful exercise in designing voltage dividers and have some tube battery radios designing LM317/LM337 voltage regulator power supplies for unregulated rectified AC is a interesting way to practice.

I remember some of my college EE labs where some transistor or voltage divider circuit was to be tested and a LOT of my peers not bothering to check power requirements in the math and smoking half watt resistors. In some cases you could adjust the math to get what you need within available wattage, in other cases the professor made the error and to do the assigned problem you had to know that the parts desk had some wire wound power resistors and be first to ask for them, or build your circuit with several series/parallel 1/4W resistors to make a single 1-5W part...often if you needed that many resistors you'd have to justify it to the parts room troll, or build the circuit with undersized resistors and collect the data before it burned open...Good times!

Thank you Tom. I was able to follow your reasoning. Best thing for me is to start reading the basic texts I have on electricity, magnetism, resistance, power and inductance. Life is really busy right now so the attention I want to give to it is probably a couple of years off. I'm a science guy but its all biochem and medical research. I do love physics and I'm fascinated by the theoretical musings from the big names but the details regarding electron movement, capacitance, vacuum tube function et. al. just don't jibe, at this point with the rhythms of my brain. I had a discussion once with an EE about my inability to understand alternating current and how do you get any work done with electrons having a net movement of zero. He said "you're not turning a paddle wheel with it. You're doing work. Think of sawing a board with a hand saw. The net movement in the saw's reciprocation is zero but the work and its movement is down through the board. Now I don't know if that's a ubiquitous explanation of AC in the EE world but it was a revelation for me!

I had a discussion once with an EE about my inability to understand alternating current and how do you get any work done with electrons having a net movement of zero. He said "you're not turning a paddle wheel with it. You're doing work. Think of sawing a board with a hand saw. The net movement in the saw's reciprocation is zero but the work and its movement is down through the board. Now I don't know if that's a ubiquitous explanation of AC in the EE world but it was a revelation for me!

Yes, part of the analogy is friction (in the case of the saw) or resistance (in a circuit).

If instead of a saw going back and forth, you had a pendulum in a vacuum with a frictionless pivot, it would go back and forth forever without losing any energy.

The action of the frictionless pendulum is transfer of energy between potential and kinetic forms - the pendulum at the top of its swing has potential energy, and at the bottom of the swing that has been exchanged for kinetic energy. The electrical analog is an LC circuit with an oscillating current. At one point of the cycle the electrons have maximum potential energy (voltage on the capacitor) and at the other part of the cycle they have maximum motion (current in the inductor).

Thank you so much for your insights and for further clarifying the picture!

Speaking of which, I did a horrific bodge job with the harvested power resistors from the parts chassis completely substituting for all of the Candohm resistors in my set. I prayed, chanted and lit some candles before I turned it on. When the relay kicked in...I HAD AN INSTANT PICTURE WITH RASTER!!!:banana::banana::banana::banana::banana:

That is first light on this Dumont! I have the resistors on order from DK and Mouser. Thank you guys for helping me get further with this TV than I ever have before and thank you Tim and Tom for pointing to the can resistors almost immediately in the process! Whoopeeee!!! Further updates and confusion/questions to come!

Lots and lots and lots of work to do but...Holy Crap guys! Thanks again!

https://imagizer.imageshack.com/v2/1024x768q70/923/FRyFtm.jpg

Think of sawing a board with a hand saw. The net movement in the saw's reciprocation is zero but the work and its movement is down through the board. Now I don't know if that's a ubiquitous explanation of AC in the EE world but it was a revelation for me!

Another good AC analogy is a steam locomotive. The force-driven reciprocation of the driving rods translates directly to forward propulsion of the whole machine down the track.

Lots and lots and lots of work to do but...Holy Crap guys! Thanks again!

https://imagizer.imageshack.com/v2/1024x768q70/923/FRyFtm.jpg

Super!

Looks fairly close to usable status. Good job.

Looks fairly close to usable status. Good job.

Thanks guys. There’s a lot of work I want to do on the underside including the resistor mounting plus a not so insignificant amount of wire replacement. Some of the insulation is cracked and crumbling from the chassis heat. I’m sure you guys noticed the ion burn on the screen. When I can turn this right side up and do all of the tweaking and chassis cleaning, I’m replacing the 12JP4 with a NOS 12QP4. I got it from a dealer in Florida who had an original ion trap as well. This is all very exciting!

Real nice to see good progress. Excellent job!

What a dumb and fruitless time unless you count frustration and knowing your limitations as experience building.

The resistors came and I spent hours mounting and installing them. The area under the canohms seemed a perfect spot for bolting on these chassis mount resistors but I discovered the area was inaccessible from the top of the chassis due to the lower strap supporting the CRT. After making the appropriate changes to the layout plans, I finished the work and did a few other things most importantly, getting modern safety caps on the AC line. I buttoned everything up and began the testing. Turned it on...nothing. Panic. It was completely dead so I began investigating the AC hookup and the on/off switch and wiring. Long story short, I accidently clipped one of the wires going to the switch when I installed the caps. This chassis is a crammed full mess with hard, heat cured wiring twisted and hidden everywhere. I fixed it and began again. It powered on but my relief was short lived. When the relay closed there was no change in the amps being drawn. Obviously I had messed something up in the resistor install right? I spent several days tracing every circuit and checking the schematic over and over but I couldn't find any mistakes. I looked a square inch at a time over anything I might have moved or accidently disconnected or dropped solder on. Nothing. I even began putting together a detailed presentation for you guys with pictures of the work and the schematic detail etc. Maybe something in the relay got messed up again??? I started tracing voltages. In plane crash investigations there's something called "confirmation bias". You take an action and soon after, something goes wrong. Obviously it's something you did and you begin to see all subsequent events through the lens of your actions and focus just on that. The big picture is missed. The source of my problem with the RA-103? When I zip tied together some of the dozens of wires feeding up the side and across the chassis, I must have tied one too tightly. The wire from the choke to R285 snapped like uncooked spaghetti but couldn't be seen because it was hidden inside a wire bundle. Five minutes later it was fixed and the TV was working like it was before. Five minute fix after five days of fruitless troubleshooting over work that "obviously I must have messed up"! Well, technically I did mess it up but I lost an unbiased approach to the troubleshooting. Lesson learned...maybe. Can't make any promises on that one! More updates on progress, I hope, in the days to come now that I'm out of the self-induced quicksand.

Are there 2 tuning dials for channel selection in various models of this tv? The brass gear on the back of my tuning dial stripped out at some point in its lifetime and I replaced it with the dial from my parts chassis and the 2 dials are completely different. The tv I’m servicing has the stripped gear and ascending channels when it’s turned clockwise. The parts chassis dial is the opposite…ascending channels when turned counterclockwise. I cleaned the tuner and the picture is so much better. Thought I was home free on this one:no::no:

Are there 2 tuning dials for channel selection in various models of this tv? The brass gear on the back of my tuning dial stripped out at some point in its lifetime and I replaced it with the dial from my parts chassis and the 2 dials are completely different. The tv I’m servicing has the stripped gear and ascending channels when it’s turned clockwise. The parts chassis dial is the opposite…ascending channels when turned counterclockwise. I cleaned the tuner and the picture is so much better. Thought I was home free on this one:no::no:

Not 2 but 3! There's 2 round dial RA-103s and a square dial. I've never owned a square dial but I have owned the other two. Yes one dial goes clockwise and the other counter clockwise. As I understand it the more common early round dial uses the tuner shaft for the knob shaft...which is bad since the portion inside the tuner is ceramic and tends to break if the user knob gets stuck on pressed on too hard. The later sets fixed that by using a separate knob shaft geared to the tuner shaft but at the expense of making the dial spiral the other direction and having to rotate the tuner superstructure 90 degrees.

What a dumb and fruitless time unless you count frustration and knowing your limitations as experience building.

The resistors came and I spent hours mounting and installing them. The area under the canohms seemed a perfect spot for bolting on these chassis mount resistors but I discovered the area was inaccessible from the top of the chassis due to the lower strap supporting the CRT. After making the appropriate changes to the layout plans, I finished the work and did a few other things most importantly, getting modern safety caps on the AC line. I buttoned everything up and began the testing. Turned it on...nothing. Panic. It was completely dead so I began investigating the AC hookup and the on/off switch and wiring. Long story short, I accidently clipped one of the wires going to the switch when I installed the caps. This chassis is a crammed full mess with hard, heat cured wiring twisted and hidden everywhere. I fixed it and began again. It powered on but my relief was short lived. When the relay closed there was no change in the amps being drawn. Obviously I had messed something up in the resistor install right? I spent several days tracing every circuit and checking the schematic over and over but I couldn't find any mistakes. I looked a square inch at a time over anything I might have moved or accidently disconnected or dropped solder on. Nothing. I even began putting together a detailed presentation for you guys with pictures of the work and the schematic detail etc. Maybe something in the relay got messed up again??? I started tracing voltages. In plane crash investigations there's something called "confirmation bias". You take an action and soon after, something goes wrong. Obviously it's something you did and you begin to see all subsequent events through the lens of your actions and focus just on that. The big picture is missed. The source of my problem with the RA-103? When I zip tied together some of the dozens of wires feeding up the side and across the chassis, I must have tied one too tightly. The wire from the choke to R285 snapped like uncooked spaghetti but couldn't be seen because it was hidden inside a wire bundle. Five minutes later it was fixed and the TV was working like it was before. Five minute fix after five days of fruitless troubleshooting over work that "obviously I must have messed up"! Well, technically I did mess it up but I lost an unbiased approach to the troubleshooting. Lesson learned...maybe. Can't make any promises on that one! More updates on progress, I hope, in the days to come now that I'm out of the self-induced quicksand.

In fact, this hobby sometimes is very challenging in various aspects... sometimes I found myself re-opening several times TV's due to several reasons...

The gear on he back of the TV dial makes setup easy. I used the signal generator to output a crosshatch pattern on channel 4 and when it was perfectly tuned, I slipped the dial onto the shaft engaging the dial gear teeth with a lower reduction gear on the tuner and channel 4 illuminated by the dial light and the tuning bar through the opaque portion. I tried checking the accuracy moving the generator to channel 7 output and rotating the dial towards it and that's when I noticed the dial mismatch. I'm curious to know how the FM tuner works. Both dials spin in the same direction but at different rates, the FM dial turning much faster than the TV dial. There's a wide, opaque region on the TV dial labeled "FM" and my guess is by the time that area traverses the dial light, all of the FM stations on its dial will spin through the opening allowing tuning across the broadcast FM band. But none of this is going to happen until I find the appropriate dial or...dare I say...swap out the tuners. That's a daunting prospect for sure.

Sound and picture aligned. I'm going to install the 12QP4 later tonight and see if it's any better but this is performing well. Soon I'll turn my attention to the cabinet. It has all the original brass screening on it and it's in pretty good shape. I have an original hinged metal back on the parts chassis and I got a decal set from RadioDaze.

https://imagizer.imageshack.com/v2/1024x768q70/924/umPZ7O.jpg

Started on the cabinet. The lacquer on the cabinet is so thick! I hate strippers and the mess they make so I used my scrapers to get the bulk of the finish off. Slow going but this is going to be a collection showpiece so I’m taking my time.

Image deleted...see below

Great progress. It can be tough along the way but if you persevere you will get there! If you go to page 21 of this Dumont Service News it shows the different dial configurations and part numbers. https://www.earlytelevision.org/pdf/dumont_service_news_vol23-11.pdf

Sorry for that gigantic picture. I uploaded it from my phone and I guess it chose the biggest version available. Here's a more reasonably sized group of photos.

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Great progress. It can be tough along the way but if you persevere you will get there! If you go to page 21 of this Dumont Service News it shows the different dial configurations and part numbers. https://www.earlytelevision.org/pdf/dumont_service_news_vol23-11.pdf

What a great resource Tim. I thought I had downloaded everything the ETF had to offer on Dumont TVs from this era. Thanks again.

I'd switch to lacquer thinner at this point to get the last traces of finish off and even out the color. You don't want to sand through that nice veneer.

I'd switch to lacquer thinner at this point to get the last traces of finish off and even out the color. You don't want to sand through that nice veneer.

Will do. I made a vow… no power sanding!

Swapping tuners on these isn't too hard...3-4 wires and some screws. I had to pull the tuner on one in the last year to get in and fix the antenna coupling cap that had went open... Until I did that I was wondering why the tuner was so darn snowy.

I favor lacquer thinner and steel wool for stripping...Seems to be the best combination of cheap fast and minimal cleanup.

Swapping tuners on these isn't too hard...3-4 wires and some screws. I had to pull the tuner on one in the last year to get in and fix the antenna coupling cap that had went open... Until I did that I was wondering why the tuner was so darn snowy.

I favor lacquer thinner and steel wool for stripping...Seems to be the best combination of cheap fast and minimal cleanup.

I got just about everything off the top and I've gone as far as I'm going to go. No sand throughs.

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My big concern, for both stripping and finishing, are the angled vented sections that transition the top from the sides. I said earlier the brass screening here and on the bottom of the cabinet are pristine. When I do the front, I intend to remove the safety glass and surround and the brass ring around the tuning 6AL7. The screens are another matter. I can't see removing them (just the vents) but how in the hell am I going to spray a finish on this without getting lacquer all over these screens? Masking them would be very difficult but an option.

How are the screens attached? Stapled on the inside? If so, pry they off with a screwdriver.

Very small staples maybe 1/8th of an inch across the top. I’ll give it a shot

Sometimes you can pull staples with a good pair of needle nose pliers...

Got them out. They were closer to wire brads than staples. Trying some CitriStrip so I don't stink up the house!

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Quick update...CitriStrip didn't do squat in 30 minutes but I'm not giving up on it. As per instructions, I spread it on thick all over the cabinet side and covered it with Saran Wrap so it doesn't dry out overnight. We'll see in the morning how it does. If it's not up to what I want, I bought a can of the real stuff full of neurologic toxins but guaranteed to strip off the finish!

I'm really surprised. Shold start dissolving that lacquer finish immediately. 30 minutes should be more than enough. I wonder if it's old? Works on everything including poly, but is a bit of a mess to clean up. Assuming that is original finish, acetone or lacquer thinner should work very well. No need for strippers.

I removed the stripped out gear attached to the dial that came with my tuner. I discovered these gears are not brass but a hard phenolic. Perhaps Dumont chose to do that to protect the tuner from over rotation as the teeth would strip out before damage was done to the ceramics in the tuner? I don't know. Through some grinding, drilling, prying and a bit of epoxy, I was able to get the broken gear off my dial, the good gear off the counterclockwise dial and mounted on my dial. We'll see if it works once the epoxy cures. Phenolic gears...that's a new one for me!

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Good gear off the wrong dial
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Gear transferred and glued to my TV's dial

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I'm really surprised. Shold start dissolving that lacquer finish immediately. 30 minutes should be more than enough. I wonder if it's old? Works on everything including poly, but is a bit of a mess to clean up. Assuming that is original finish, acetone or lacquer thinner should work very well. No need for strippers.

CitriStrip is new. Just bought it. I don't want to use lacquer thinner in quantity on this unless I can do it outside. If I need to go to the killer stripper, I'll do that outside.

CitriStrip overnight worked OK but it was a real mess to clean up and even out the color. Just not worth it to me. Went back to the scraper. I wouldn't say it's quick work but it gets it off safely. This finish is THICK!!!

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Got 89% of it stripped and lightly sanded. As far as I can tell there's no sand throughs of the veneer. There's some pretty tough glue holding in the dial glass. Yes, it's the same laminated safety glass the CRT has in front of it. The CRT safety glass was held in by the same glue that had lost its adhesion but the dial glass is on there to stay. I'll try some heat first I guess.

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Finished the weekend by putting color on the Dumont. It'll lighten up once it's dry. I'll give it 5 days then move it into the spray booth. Best thing I did for my guitars, furniture builds and now, vintage TV cabinet restorations was building one in my shop. Filtered air in and overspray out. Eliminated dust as a concern in my finishes.

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And what could be better than watching the final round of The Masters on my 1950 Admiral while working on it?

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Looks like you used stain? Old school way is shellac sealer, toner lacquer, grain filler then clear coat. Opaque toner on the trim to get even color and good contrast.

Not meant to criticize just giving some advice.

Looks like you used stain? Old school way is shellac sealer, toner lacquer, grain filler then clear coat. Opaque toner on the trim to get even color and good contrast.

Not meant to criticize just giving some advice.

No no problem. Appreciate the advice!

It won’t need grain filler. Scraping the finish left behind a surface with the grain filled. This is just first color application. I’m going to wool it down with 0000 steel wool and then hit it with a waterborne lacquer I use with a water soluble red mahogany dye mixed in. If that gives me what I want with color and tone, then I’ll spray on 2-3 coats of clear. I’ll probably put the decals on before the clear coats. You ask 100 woodworkers how to put color and finish on you’ll get 100 different protocols! One question Bob, what level of gloss did these TVs have coming out of the factory? I can’t imagine a high gloss finish but what’s left of the finishes on most of the wood cabinet TVs I’ve gotten look pretty glossy!

High gloss nitrocellulose lacquer but the higher end sets would have a hand rubbed finish which knocks down the sheen. I use rottenstone or fine pumice and a felt block followed by wax.

High gloss nitrocellulose lacquer but the higher end sets would have a hand rubbed finish which knocks down the sheen. I use rottenstone or fine pumice and a felt block followed by wax.

Got it...thank you so much!

Added red toner to the finish after lightening up the stain but it's still too brown. I'm not going to sand it clean (don't want to risk sand throughs) but I'll remove the majority of the brown off so the lighter mahogany striping in the grain takes in primarily the red color. Bob, you're right, I should have sealed it with shellac first to control the depth of the staining. The stain soaked in like a dry sponge soaks up water and made it too dark and too brown.

Yep either pre-stain conditioner or sealer.

I think I got the color right. This is the one pic I took that shows the red highlights best. Lousy light in this corner of the shop.


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My finishing materials showed up yesterday. I'm only posting this to provide information about an available product that solved a finishing dilemma for me. The wonderful advantages in quality and ease of application of nitrocellulose are, for me, more than offset by the issues around its use. I have a dedicated spray booth I use for spraying finishes on my guitars but it is not vented to the outdoors. It is a particulate filter and doesn't address the solvent fumes that come with spraying traditional lacquers. Besides quick drying and the grain enhancing characteristics of nitro, it has what's called "burn in" meaning each coat sprayed on melts the previous coats and becomes one solid finish. Shellac does this too but if you need to spray water based finishes like I do, burn in isn't a property they have had. It's an issue for any finish that gets wet sanded and rubbed out to a high gloss because when multiple, individual layers of a finish are sanded through, the layers show in the form of "witness marks".

About 10-15 years ago, due primarily to tightening VOC restrictions, waterborne finish manufacturers started to step up their game. The finishes got clearer, harder and popped grain better but they still went on a surface as distinct layers. Some products claimed burn it if recoated during a limited window but I found none of them satisfactory,

Target Coatings was a small startup company around this time and they developed a line of waterborne finishes including a lacquer claiming burn in if recoated within 48 hours, a time window considerably longer than the open recoat time for products like Resisthane, another claimant of burn in and water based. I tried their product line and I have never used anything else since. Their custom formula EM 6000 product is as close to nitrocellulose as you can get in a low VOC product. It is amazing. It cures rock hard, clear and has 100% burn in.

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I only mention this because I struggled with finishing schedules, solvent fumes and other issues for years. This single product solved all of that. Every bit as good as nitrocellulose with the same properties but no solvents. It can be sprayed indoors with little concern. Of course, you need spray equipment. It's not a finish in a can. HVLP, self contained units are available. Instead of a compressor, they essentially use a fan to provide air flow and they are very good for spraying water based finishes.

Got the finish sealed with dewaxed shellac, put on the decals and sealed them in and then applied the lacquer. Starting working on the knobs as well.

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That looks very nice!

Wow, excellent!

Thank you both!

I need to pull the chassis because I need to tweak a few more things but once the cabinet was done, I had to see what it all looked like.

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Beautiful!