Found a Philco

[andy]

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[andy]

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[Chad Hauris]

You could supply a signal from another tuner into the IF stages to rule out any problems in the tuner, provided the Philco uses the modern IF frequency...also have you checked all screen voltages on the IF tubes, maybe a shorted cap burned out a resistor, also could be a bad video detector diode? What is the negative AGC voltage...you may need to bias the if stages with adjustable negative voltage from a power supply to check how they respond.

I'm hoping to get that far as to get any kind of picture, but your story gives me hope. At least I know the history of my DuMont, that it worked until around 1980 or so and hasn't been moved or plugged in since.

I'm just waiting for the caps to arrive from JustRadios in Canada.

[andy]

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[andy]

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[andy]

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[Dave S]

Originally Posted by andy

I also added a DC restoration diode. It was really easy to do

Andy,

As a self-taught "shade tree" engineer, there are so many things I am really, really good at being ignorant about. I've been pretty good at diagnosing and repairing many of the common problems since I was a kid, but I've never had the luxury of a comprehensive education on the subject, so certain things still leave me scratching my head or other parts of my anatomy. I have NEVER been able to fully grok the mechanics of DC restoration. Can you (or anyone else) point me to a reference that serves as "DC Restoration for Dummies", or maybe be kind enough to try to explain it either here or privately in a way that my aging and deteriorating brain cells can understand?

I'm actually not TOO stupid, I mean I know why we use DC Rest., but I have some sets in which it's not working and I can't seem to get my head into the circuit enough to home in on the problem. Also, the concept of simply "adding a diode" to improve an existing circuit as you said you did is something that is definitely outside my ability to cook up.

Thanks in advance if you're up to making me less ignorant on the subject!

--Dave

[bgadow]

Looks great! Its still cool to watch an old set "paint a picture" like that. That could not have been a real common crt, it doesn't look familiar to me.

[andy]

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[andy]

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[old_tv_nut]

Originally Posted by andy

I'm having a problem getting it to focus after I disassembled the focus magnet assembly to clean out the old sticky grease and lubricate it. I'm sure I put it back together exactly the same way, but now the focus knob has very little effect and the picture is always very blurry. It's so blurry that 1" high text is completely illegible. I've tried adjusting all the CRT neck adjustments with no improvement. Has anyone run into this before with a permanent magnet focus assembly?

Here's a close up picture of the focus assembly before I dissasembled it. It uses 3 magnets located 120 deg. apart around the CRT neck. The focus is adjusted by moving a metal sleeve in, or out.

Random thought:
Is it possible you have one or more of the 3 magnets installed in reverse?

Magnets are a strange thing.....striking, dropping or smacking them can cause them to lose their field or at least measurably reduce it. Magnets left unused (without any ferrous material nearby) tend to lose their strength----as a matter of fact, some magnetic base micrometers that I have use a metal plate that connects the free ends of the magnets (in the base) so that while in storage the strength of the magnets remains intact.

I suspect that some magnets that had been in a fixture or formation in combination with other magnets might present anomalies upon their removal of said arrangement, and this may be what occurred when you took the focus assembly apart. Bottom line, you had a weak magnet (or magnets) that sorta kinda worked in unison, but once you disturbed their positions then they went flooey.

That's my story and I'm sticking to it!

Anthony

[andy]

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I wonder what, if any, effect that may have upon the guns.....if there's any chance that this might harm them in any way. Dunno.

Anthony