Unusual TV - Videokarma.org TV - Video

csingle · #1 04-30-2007, 12:37 PM

Hello.

I have posted a couple of times about this set, but I didn't have good pix until now. This is a Mitchell set, and I am having a difficult time trying to find any information about it. I obtained a new pix tube (21MP4) from El Predicta on Saturday, but am at a loss on the rest of the set. A dligent search (3 years) has not led to anything made by Mitchell except for a few radios. I hope that someone has an old Sam's or Riders in a dusty corner, or information of any kind for this otherwise unknown set. Here are some pix, hope they help.

-Chris

kbmuri · #2 04-30-2007, 07:32 PM

Sometimes SAMS indexes by the chassis number, not the model number. Is there a chassis number stamped (or inked) on the back of the chassis anywhere?

Tubejunke · #3 04-30-2007, 08:45 PM

That record player/radio looks curiously like similar vintage Zenith. I don't see the typical "cobra arm" tone arm though. Not that this observation helps in finding info on this set. I have heard of Mitchell as far as radios and WWII bombers but I've never seen a TV.

Steve K · #4 04-30-2007, 09:15 PM

Chris:

I have the Riders info for your set. PM me with your address and I will copy it and send it off to you tomorrow.

Steve

csingle · #5 05-08-2007, 11:00 AM

Hello.

The Rider's information seems to be rather accureate as far a tube layout/ etc. I haven't really dug into the TV, but will soon.

-Chris

csingle · #6 05-11-2007, 02:09 PM

Recapped the TV Section last night, plan to do the radio/phono tonight. I bought a good selection of HV caps, and it sure seems to be helpful. Thanks for the Rider's manual! The Schematic is spot-on perfect, although the radio section isn't there, but it should be fairly simple, condsidering it is just an AM/Phono.

csingle · #7 05-13-2007, 08:02 AM

Hello.

I powered up the Mitchell set last night after recapping all except for (2) .1uf 600V caps that I couldn't source. The trouble now is that I can't get any High voltage or raster. I do hear the flyback whining, and it may be my misunderstanding, but I thought that the sound of a flyback and good tubes would indicate High voltage present. I unfourtunately do not have a HV probe, and can't clearly think of a way to measure the voltage without one. Any assistance would be appreciated. Thank You!

Steve K · #8 05-13-2007, 10:19 AM

Chris:

Do you have audio? If not you need to start back from the high voltage. Also it is possible that those .1 caps are bad. In what circuit are they? Don't overlook the obvious, tubes could be bad. Check the horizontal output and the 1B3. Assuming all that's good a quick check to see if the horizontal section and flyback transformer are working is to take the top cap off the 1B3 and wrap the leads of a small neon bulb around the wire. Turn on the set and if the bulb glows everything up to the 1B3 is working and the problem is between that and the CRT. I think you can still get neon bulbs at Radio Shack.

Steve

csingle · #9 05-19-2007, 06:38 PM

Hello.

I got the new Pix tube in the set, after recapping, etc. Definitely have HV and raster. (Found out the hard way, then checked with an HV probe I borrowed) Am getting good reception on a local TV station. The trouble is that the image is displayed 3 times across the screen, and the Vert. Hold isn't holding at the right position, but more like 70% from the bottom of the screen. I've tried adjusting every control on the set, both independently and in combination, with no improvement. Any suggestions would be appreciated. Thank You, -Chris

trinescope · #10 05-19-2007, 07:08 PM

If it's doing what I think it is, the vertical oscillator would be running at 20Hz instead of 60Hz. Double check your capacitor values in the vertical circuits and also the resistors for having drifted out of spec. I had that happen to me once on an old RCA.

Steve K · #11 05-19-2007, 07:38 PM

Chris:

Are the three images across the screen (side by side) or on top of one another. If they are side by side your horizontal is off frequency.

Steve

csingle · #12 07-07-2007, 08:43 AM

Hey all.

I just wanted to update on this set. Last evening, I spent several hours chasing the horizontal section after finally finding and ordering a 3900 pF 400V cap. That didn't fix it directly, but required replacing a resistor that was 28% out of spec. Seems a liitle more than a silver band should allow lol. Anyway, got that changed and messed with the hor. frequency control and got a beautiful horizontal sync. Vertical is another story. The raster fills the screen, with a compressed pic in the top 3 inches with various tracings in the rest of the screen. I suspect more bad resistors, but it was 12:15 PM, and I had to work at 6 AM. I'll do more tonight if I have time.
-Chris

Celt · #13 07-07-2007, 08:52 AM

Mallory makes the .1uF 600+V caps you are seeking. Antique Electronic Supply has 'em @ http://www.tubesandmore.com

csingle · #14 07-07-2007, 09:33 AM

Thanks,

I did have some new .1 uF 400V caps, and after I really looked at the circuitry and schematics last night, I believe they will work alright.

wa2ise · #15 07-07-2007, 11:59 AM

If you have a pair of 0.05uF at 600V caps, use them in parallel to make 0.1 at 600V cap.

As for the wrong horiz frequency, you probably are locking at some simple fraction of the correct frequency. Say 3/4 or 4/3, or such.