DuMont RA113 saved from becoming an aquarium! - Page 5 - Videokarma.org TV - Video

tvdude1 · #61 10-04-2010, 08:59 PM

Hi did you use the transformer I sent you for your set?

holmesuser01 · #62 10-04-2010, 09:09 PM

It was the one you sent me. It happened fast.

Reece · #63 10-05-2010, 06:36 AM

If you decide to replace the two line-to-ground caps, use type Y2 safety caps, designed to fail open. Those caps are there to reduce RFI coming in over the power line. One source is justradios.com.

*Bill Cahill* · #64 10-05-2010, 11:16 AM

Yes, but, that was primarily from sources such as Car generators, who has one now?, and, diathermy machines. Used yours lately?
I find I have virtually no problem without my caps. And, if the resistor is still there, remove that also.
These line caps only make the chassis more of a shock hazzard.
Bill Cahill

jeyurkon · #65 10-05-2010, 05:41 PM

Quote:

Originally Posted by Bill Cahill

Yes, but, that was primarily from sources such as Car generators, who has one now?, and, diathermy machines. Used yours lately?
I find I have virtually no problem without my caps. And, if the resistor is still there, remove that also.
These line caps only make the chassis more of a shock hazzard.
Bill Cahill

We have a new source of RFI that will eventually be forced on us. Compact Fluorescent lamps. They're not too bad, but they do bother some of my radios.

John

Reece · #66 10-05-2010, 06:03 PM

There are many sources of RFI today, CFL's as mentioned, light dimmers, phone chargers, computer power supplies, not to mention garbage that comes in over the line from the neighbors. I generally put one cap from each side of the line to chassis, after the switch, so they're not working when the set is off. No resistor involved. Granted, interference may be more noticed on an AM radio. TV with FM sound may not be as affected, but possibly AM video could be?

holmesuser01 · #67 10-15-2010, 05:27 PM

I ordered 20 electrolytic caps for the DuMont just now. Planning to order Sprague Atoms, but didnt. I did buy 105 degree C capacitors, though.

I have found the HV caps for the doubler circuits, too. Not a bad price, either.

And now, we wait...

My other projects, the Maggie twins, are next!

holmesuser01 · #68 10-23-2010, 07:24 PM

I started the afternoon by carefully oiling the shafts of the inductuner with turbine oil. I gently rocked the tuning knob shafts and they let go suddenly. Now, the tuner is turning smoothly.

I replaced the majority of electrolytics in the power supply. Installed the 5U4G, and pulled the horizontal output tube. Brought the set up slowly over 2 hours this evening. At around 80 volts, I was hearing noise from the speaker!

At 90 volts, I could hear the signal I was feeding into the phono plug through the speaker! I continued to bring it on up. Started seeing gas glowing in some of the small tubes. The tuning eye is green. Nothing wrong with the power supply. The new transformer is not getting hot.

Finally, at 110 volts, I tried feeding a signal from a VCR to the antenna input. It took a few minutes of adjusting the tuner around ch3 before I suddenly heard the video tape I was playing! Adjusting the fine tuning brought the sound in loud and clear.

I dont have the HV caps, yet. I was feeling brave, and installed the horizontal output, and turned it back on, slowly. Heard a couple of arc pops while taking a fast reading at the anode of the CRT. 3KV. Turned it back off, and pulled the hz. output again, and turned it back on. It has been sitting here playing audio for about 2 hours now, total. I think I will have video, because when the video is playing on the VCR, I can see the brightness of the slight gas in the video output tube change as the picture changes on the movie.

I've been running the chassis for the last week or so without the 5U4G installed just to help the set dry out a bit. With the tube installed, the whole chassis warmed up and I was treated to some dampness smells that I havent noticed before.

I need to rig up a stand for the chassis so I can pull it out enough take readings with everything connected.

I'm not going further until I get the HV caps replaced. During the very short time that the hz. output was installed, I could see the filaments in both of the 1X2's glowing, and touching a screwdriver blade to the caps of them produced a tiny arc.

In the meantime, the electrolytics that remain are not overheating. I will replace them, but I've got other things to look at until I get the HV parts.

I sure didnt expect to hear sound thru the antenna input this fast!

Bruce

holmesuser01 · #69 09-18-2012, 11:05 AM

It's been a long time since the last post. I'm trying to clear out my house, garage, and workshop of unnecessary clutter, and I'm making some progress. I also aquired the RCA CTC-7 set, and got sidetracked with it for awhile.

I've replaced more electrolytics in the DuMont, and a few of the wax capacitors, so far. Also, got and installed the 3 HV capacitors. I've now got 12KV!! It's slow going, though, as I've not seen anything on the CRT screen, yet.

I'm seeing that I'm not getting anything from the brightness control, which is on the -55v line from the power supply. Gotta pull it back out to check. I'll also check out the selector switch to be sure everything is working at the TV setting. FM works, as does the phono setting.

The CRT voltages are mostly there... 300v, filaments, but nothing on the 65v cathode, or the -32v line at the grid. When I pulled the CRT socket completely, nothing changed, so I'm sure the CRT isn't pulling things down.

All I had to check the CRT on is my Sencore TC-109 tester, which shows the tube emitting at 96%, and takes almost 40 seconds for the emissions to start dropping after cutting power to the filament.

Any comments are always welcome. I've done just a few repairs on tube televisions. I made my loot on solid state!

Kevin Kuehn · #70 09-18-2012, 01:35 PM

Do you have the both -55 and 75v supplies on the outside terminals of the brightness control? Make sure V209-B(DC restore) tests good. Check the 100k resistor on the CRT cathode?
I'm referencing from the Riders schematic.

Phil Nelson · #71 09-18-2012, 01:58 PM

I would not expect it to work normally until you replace all of the wax paper capacitors and electrolytics.

Trying to troubleshoot problems while it's still full of bad capacitors is not a good use of time.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Kevin Kuehn · #72 09-18-2012, 02:02 PM

Agree with Phil on replacing caps first. I'd overlooked that you hadn't done all the papers.

holmesuser01 · #73 09-18-2012, 02:06 PM

I'll be checking more things here when I get it pulled back out of the cabinet. I'm not expecting a crisp perfect picture, here. I'm just hoping to see something.

I cant leave the set apart when I'm not working on it. It's not in the workshop.

V209 6AL5, is new.

Kevin Kuehn · #74 09-18-2012, 02:29 PM

I'd check all resistors and caps around V209B, including the brightness control. You do need to have the correct DC bias voltages on the CRT first. Then provided your horizontal and vertical circuits are working, you should see some sort of a raster. You did mention you have 12K of HV, so apparently you have horz drive and your flyback is working...

holmesuser01 · #75 09-18-2012, 03:26 PM

I've got to see some kind of a raster before I can truly continue. My older CRT tester got hit by lightning last summer, and I'm going by what I can find with the CRT function on my tube tester. I have no B/W tube sockets for my B&K color CRT tester.

I'm in no way going to junk this DuMont. I'm suspecting an open somewhere.

Vertical and horizontal are both working. I can hear the vertical pulses in the yoke, and when I adjust the vertical hold, I hear the pulse rate raise up and go down. I have all intentions to replace every capacitor that needs it.

I'll check around V209 and let you know what I find.

Getting the electrolytics done was the first priority after I replaced the power transformer.

I truly appreciate everything said here.