The Family DuMont

[Kevin Kuehn]

I've found switches where the contacts are stuck open simply from setting too long and hardened grease. Sometimes a squirt of tuner cleaner/lube into the switch and cycling several times will free things up. One the other hand the contacts may be badly burned, in which case you'll need a replacement switch.

Edit - just seen you're already on the right track in you last post.

[CaryLee]

O.K., no luck trying to get the on/off switch to work, so I soldered in a jumper and am working the set off a switched power strip.

I remember saying early on that if I didn't get a TV out of this DuMont, at least I'd have a heck of a big old mono FM radio...and that's what I've got so far!

I'm wondering though, since I've never seen this set do anything (including play FM radio, so I have made progress), exactly how is it supposed to act?

It has a three-position switch which switches from FM to TELEVISION to PHONO.

I'm getting FM radio on both the FM and TELEVISION settings, and when I switch to PHONO, the sound kicks off. On PHONO, I can plug in a phono cord and get a buzz if I touch the center conductor on the other end of the phono cord, so that seems to be working (I must have SOMETHING around here I can plug into that jack! Man, has technology changed! Curse you Optical Audio and HDMI!). On all settings, the heater filament in the picture tube glows. At no time, on any setting, does it sound like the picture tube is firing up..no static electricity sound, etc. No noise from the HV section.

I get a VERY dim eye tube, barely see it, but there is some action there while tuning through FM if I look close enough. Could be a wore out eye tube.

It appears I have a balky FOCUS control. When I turn that control, there is a "dead" spot in the middle where the sound drops out, but it picks up at either end, far left or far right. What the FOCUS has to do with that I have no idea at present.

My first though is that the FM/TELEVISION/PHONO switch isn't working correctly. Should I be getting FM sound on either TV or FM settings? Should the picture tube heater be lit at all times, on all settings? I would assume that switching to FM, the picture tube should shut off, but is that handled through the HV section alone?

Thank you for any thoughts/advice.

[earlyfilm]

Originally Posted by CaryLee

It appears I have a balky FOCUS control. When I turn that control, there is a "dead" spot in the middle where the sound drops out, but it picks up at either end, far left or far right. What the FOCUS has to do with that I have no idea at present.

Check your schematic. Your B+ is fed through your wiper on the focus pot. I assume that is a wire wound. You might see if it is open in the center as that could be causing part of your problems.

Originally Posted by CaryLee

. . . . . (I must have SOMETHING around here I can plug into that jack! Man, has technology changed! Curse you Optical Audio and HDMI!).

I would be cautious about plugging in anything that uses transistors or chips into the record player jack, because this set has a semi-hot chassis though a 100 K resistor. Not enough to current there to hurt a person, but it might be terminal to a transistor circuit that was not buffered against a little AC.

James