C105 and 106 have a 1000 volt rating in the Damper circuit, the one is your pic looks way underrated, the snap you heard could have been one of those

That's actually C103. But as far as the SNAP goes, my God....

I stopped counting at 12 badly soldered connections. And I KNOW I checked them before powering up, but maybe not well enough. This wasn't my recap job, so I'm also in the habit of giving each cap a good tug at each end before moving on to the next.

The cap connected to the focus pot was TOTALLY disconnected. What a mess, everything was falling apart. I'm just scratching my head as to HOW. I don't end up buying a recapped set very often, so I guess as long as it's fixed, that's what matters.

Well, we'll give her another go and see what happens....

Powered up. Lost audio, raster, and the tuning eye. Fuses are both good, all tube filaments are lighting, including the picture tube. Dammit.

I'll admit that I'm at a loss as to where to even start from here.

1) Get a bright light and look for a solder bridge or burned through insulation during the resoldering.

2) Measure B+.

3) If no luck, download the Sams on ETF and check socket resistance measurements.

Jas.

Kind of what I had in mind. I was hoping to find a common component for an easy fix, but I should know by now that never happens :)

My assumption that the snap I heard was coming from the loose end of the cap that should have been going to the focus pot with voltage finding its way to chassis ground, though it wasn't grounded out.

Time to start from scratch.

OK
Calm down
Drink a beer or 5
Have Volt/Ohmmeter probe in hand
check all Wire wounds, check Voltages on power supply Caps for a Start
Have another Beer
Visually Check the Caps in the Damper and audio output to make sure they are correct Values and VOLTAGE Ratings
Also Remember that soft Start Circuit with Relay does it operate? I just sent someone here a good one

I was thinking about Candohm resistors. Does the 110 use them? They were all bad in my RA-113.

Well, when I say "start from scratch", I don't say that in a panicked way, just basically means that I pull the chassis and start testing some components. First on my list are the candohms. I replaced them all in my RA-113 as well. Even if they're not bad initially, I've had them fail or drift badly after time.

Still want to shake this guy's hand?:D

Sure, with a charged capacitor tucked neatly between my fingers :D

I know what happened here. DuMont caps are the gooeyest things in the world, and my bet is that he didn't realize that the goo on the wires isn't exactly something that promotes solder adhesion. The filter cap connections are fine, along with anything that had a wire connection. When reconnecting everything, I just sanded the old chassis wires with some folded 400 grit paper pulling it forward over the wire, and used some flux. All of the connections are nice and solid now.

With the BANG I heard, I would have guessed that the result would be obvious, but it's not.....at least not to the extent that I've examined it. The chassis is on the bench now, but attending a wedding and getting the old van ready to pass state inspection took precedence this weekend :)

Well, made *some* progress......

It missed my attention the first time around, but C3A was somehow disconnected. The previous tech used these funky bits of waferboard with copper coating on either side to turn the old positive terminals on caps into mounting points. Not exactly what I would do, but it is what it is.

I saw this pair of filters sitting near the terminal, and they didn't LOOK as if they were disconnected, but apparently they were. They're each 1000 uF 50V. What made me scratch my head is the values on them. I traced out the entire circuit and decided that it must be the replacements for the values that are stated on the Sams, which I can't make heads or tails of. See for yourself.

Anyway, it's connected now and no change in the set. Onward to the candohms.

You can plug those numbers from Sams into this reactance calculator.

http://www.sengpielaudio.com/calculator-XLC.htm

1.5 ohms @ 120 Hz is about 884 uF which you could round up to a standard value of 1,000 uF. They are used as filter caps on the horizontal and vertical centering controls.

Checked all the candohms and larger resistors (wirewounds). All in spec.

Brought me to thinking about the power relay under the chassis.

When I was cleaning up the mess of connections I discovered, there were 2 terminals on the relay that were bridged with a couple pieces of wire from the multistrand wire going to the relay. Thinking that it was just a sloppy job, I separated the wires, but now I find myself wondering if that was what caused the set to actually work in the first place.

One of the wires that was connected goes to pin 8 of the 5U4s, the others I can't see where they go, but I assume that those two complete that particular circuit. From what I can find, the relay should show 5000 ohms across the coil, I have 3800.

If this relay were dead, and with those strands of wire connected, could this have caused the set to work before, and not now?

Those caps still look under rated to me. Anything less than 1KV is trouble waiting to happen. One may have blown.
Further, I doubt very much it's the flyback.
Is there a high voltage paper cap across the caps of hv rectifiers? If so, replace. I believe they are rated at 10KV.
Bill Cahill

Makes sense, if the relay or driver circuit were bad, the connection might have been bridged on purpose to provide B+ to the set.

jr

Yep, that was it :)

Had the chassis on the bench, so on my lunch break I jumpered the connection, and used the variac to power it up.

It's sure an improvement from where I was when I had a picture last, but it's still not right. Contrast control does nothing, and neither does width. I can get it wider, but then I have to max out the horizontal drive and the whole picture darkens up in the center. Focuses fine. Not very bright, but I did notice that the picture is getting better just with tweaking and use, as everything is beginning to "wake up".

Getting there, getting there :) . Think it's time to re-test tubes before I go further. One candohm was working but was out of spec, so I'll place that on my next Mouser order.

After tubes, the first thing I'd check would be the cathode resister on the horizontal output tube.

If your other checks do not find the problem. . . .

I notice that the Sam's that you are using lumps the 12 inch RA-103 with the 19 inch RA-110 chassis. I see that Rider keeps them separate.

I have no idea what Du Mont changed (other than the yoke) for the bigger CRT, but there is a slight chance that the person who recapped your set used the more readily available Sam's instead of either Du Mont or Rider diagrams and accidentally created an image size problem.

Jas.

This is the relay that was retrofitted under the chassis. Look like it should work?

http://www.digikey.com/product-detai...Q15-1t1-VQ16-c

The P&B relay is within specs on amperage, under specs on voltage, but probably is OK. (Switching 440 + DC with a 120V RMS AC rating.)

Apparently Du Mont did not publish the pull-in current requirement :no: and that makes it impossible to answer without a test.

What should be a safe way to check the relay is to remove both 5U4's but leave the two 6X4 bias rectifiers in. Unsolder both switched leads. * (The lead going to the 5U4 will have 440 AC on it, so cap it.)

Put a battery and same voltage test lamp in a loop circuit with the switched relay contacts. Power the set up, still with 5U4's out, and remove and replace the 6AL5 power delay tube. The relay should click with each operation, possibly with a slight delay. Test lamp should be on with tube in, and out with tube out.

If relay clicks, but does not light the lamp, the relay is bad. If relay does not click, the trouble probably is in the switching circuit, but there is also a slight chance it could be a bad relay, or the relay coil pull-in rating is incorrect.

With that said, I've never done a relay test on a Du Mont, but have used similar methods on other industrial equipment when I did not have component information or a spare relay. If anyone sees anything I just wrote potentially harming the set, please holler now!

Jas.

* Oops! Clearly an oversight above, hope there are no more.
Before someone points it out, with the 5U4's removed, the only voltage on the socket filament pins is 5 V AC since the 440 AC is on the plates. I would still cap the hot wire before running the test.

Was suggested by a member in PM a while ago (honestly don't recall who) that suggested that I look at the yoke for the problem. Bought a new yoke for the set, and it's sat since about 2 weeks after my last post on this.

Now that I've got a yoke tester and have learned how to use it (very easy BTW), I tested both the new yoke and the old. Looks like that's (at least some of) the issue.

Here's where I'm at. Aftermarket yokes always make me scratch my head, but with the supplied diagrams usually I can figure it out. This one's confusing me a bit.

Below are the pics of both the new and the old yokes. The old yoke has colors red, red/black, green, and tan/black. The new yoke's wiring is green, green/black, tan, and tan/black.

As well the new yoke has caps in it while the old doesn't. Resistors are the same.

Appreciate a little advice :)

Looks like the green are your vertical and the red (faded to tan*) are your horizontal.
I'd try it with the caps first and snip them if they are causing any issues. On yoke swaps I usually do the first power up with clip leads so I can quick turn it off and swap them if I got a winding connected backwards.

*I recently repaired a 50's amp for a guy and one of the tan wires had a stripe of black letters running along it that consisted of the word RED repeated over and over...I had my self a good laugh when I noticed it.

Probably best to follow the wires to the actual coils to identify H vs V. The H coils consist of two closed loops, one above and one below the neck. The V coils are on the sides. If the picture ends up upside down or left-right mirrored, all you have to do is swap the leads of the particular deflection coil that is producing the problem.

(Edit: I didn't see Tom C's post before I replied - there is some duplication in our responses.)

The good news: Looks like I got it right!

The bad news: HV faded out. Stops at the top of the 1B3. Next is a doorknob cap and a resistor, so one of those is shot.

Not giving up yet :)

Is the 1B3 filament glowing?

I'm pretty certain it was, actually.

i would try the doorknob or doorknobs if it has more then one , that is if your not too buried in the snow, and you do now have a fly tester , simple to use , remove these tubes , the horz out , the hv rect , the damper , one wire goes to the plate cap wire of the horz out and the other to the plate cap wire of the hv rect , before connecting the wires you turn it on , set it to shorts , adjust the needle to the iron core line on the meter , hook wires up to the plate cap wires without touching and you will get your results , the fly will probably sing too.

Flyback was buzzing ever so slightly :)

Passed the continuity test easy, but the shorts test is not looking so good :sigh:

And I did disconnect half of the width coil as per the tester instructions.

Kinda crispy looking too isn't it?

Yeah, kinda :(

Why is it that sets I fix for other people are easy jobs, and MINE are SUCH a pain in the ass? :tongue:

At least you don't gotta tell folks that X$ of work and caps into it you found some blown part that could be nearly impossible to find...I dread that possibility; which is why I rarely work on other peoples stuff.

And along those lines, neither Stancor nor Thordarson list a flyback for this set.

Welp, looks like I'm gonna pull the picture tube and put it back in the Emerson from which I stole it, and restore that one. I'll stick this one aside until a parts set happens to become available.

Merit lists HVO-90 as the replacement. Possibly one will turn up.

I haven't seen anyone ask this. I generally test the transformer in service by removing the 1b3 cap and see if I can draw an arc. I would take a pointed screwdriver and connect one end of a clip lead to the screwdriver and the other end to ground. If I can pull a 1/2" to 1" arc, I am satisfied the flyback transformer is okay.

I saved myself looking for a transformer on my old RCA 8TC271. The doorknob capacitor had shorted. I did the same later on my Zenith color TV to find the arc was healthy and the rectifier tube was bad. This was only after I had moved and acquired the spare transformer!

Wow. Are you serious about connecting it to ground?
The only way i've ever done it or seen it done is to draw an "air arc" with an ungrounded but well insulated screwdriver.
The air arc is just about as long anyway since it's RF. And it doesn't risk overloading the xfmr as a straight-to-ground current path might.

Tim
that reading isn't the worst , if you lay the fly tester on its back does it show a different reading ? if the meter went all the way down it would be bad , i've seen good flys read what you are getting , i thought i had a bad fly once because of a reading like that and went through the headache of replacing the fly and it had the same reading , the problem was the doorknob
mike

Yes, I'll ground the screwdriver. I just make sure I do not ground the HV Plate lead.

I just want to ensure the current goes to ground and not through me! One should be able to draw an arc when the tip is about 1/2" away. This is a quick test and should harm the circuit if a tube is used

Evidently it doesn't hurt anything. Guess it's just the thought of arcing it straight to ground gives me the willyjeebers.
:yikes:

I test HV with a neon bulb. I was getting HV (although not as much as I'd expect) all the way to the cap of the 1B3, then nothing after. The resistor tests good. Maybe I'll replace the doorknob before I pronounce the flyback dead. Where do I source those, anyway? Or what style do I use? Never replaced a doorknob before.

Without a HV meter, the neon bulb is the best way to check HV, They glow with anything
above 50V, and if you do some experimenting with the bulb and a working set, then you
have an idea how close you have to be to a HV source for it to glow.... A working HV
source will set it glowing X inches from the 2nd anode wire, x inches from the transformer,
x inches from the Horiz plate cap.... It was the first device we in tv repair school made,
and learned to use to measure HV at several spots in a tv.

Electricity will only travel from a positive - negative potential to the oppisite potential..
Same for an arc. If you don't ground the screw driver, then the next lowest potential
is through all high resistance paths to ground.... Like you and the handle.....

Like lightning, very high potential will overcome the high resistance of distance and
the poor conducting properties of air...

The neon tester we made in schooll was to test electrical outlets, It was made out
of a piece of house wire, a resistor, and the neon bulb, which was tucked into a piece
of the wire's insulation... Pretty neat little thing. So we held it by the wire to test for
HV, kinda held it backwards... But you have to be aware that the magnetic field, or
electrostatic field will be making the light glow, and inducing a voltage into the wire
as well.... So if you are not careful you will get a taste of it.... Or get too close and
get a spark to jump and get a bigger shock....

.

Grounding the screwdriver when testing for HV at a rectifier tube plate is definitely a BAD idea.

In most sets, the voltage at the plate of the HV rectifier has a DC component of a few hundred volts, in addition to the high voltage AC pulses. Providing a DC path to ground will take the B+ (from the HOT tube plate), and short it to ground through the HV winding on the flyback (200-300 ohms?) and the (low) resistance of the arc itself. This can easily burn the flyback winding open, as it is not designed to have any appreciable DC current running through it, and it is wound with very fine wire.

A grounded screwdriver should only be used to (briefly) check for DC high voltage at the CRT anode lead, and then only if you don't have access to a real HV meter or probe.