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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Sun 04, 2018 2:03 pm 
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Joined: May Sun 17, 2009 10:08 pm
Posts: 329
Location: Massachusets, 02019
I have brand new Philco crt in the original early Philco box still sealed if you want original. Also have rebuilts from Hawkeye 4 of them if you dont trust people with used ones. I do have good ones no junk.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Sun 04, 2018 2:29 pm 
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Joined: Jan Sat 31, 2015 10:06 pm
Posts: 408
I would be interested the tubes, tvdude11. The new-in-box philcos sound interesting - do they have the magnets and metal frame and cables and all? I'm certainly interested in a good tube that will hopefully last a while. Even if I can get the current tube working again, it would be good to have a spare as these will only get rarer. Let me know what you have and how they test, and the price, and we'll see if we can make a deal.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Sun 04, 2018 6:27 pm 
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Joined: Mar Sun 01, 2009 10:27 pm
Posts: 4357
Location: Ann Arbor, MI
sdyer wrote:
After a couple of months of being very focused on my new job, I took some time tonight to work with pin 11. I tinned some 30 gauge wire, heated the pin - which was indeed very hollow - and inserted the wire. I soldered the end up. When it was cooled I snipped off the wire and sanded of some bits of excess solder. I'm not sure my tinning technique was adequate - the 30 gauge wire is very thin, and I ended up with solder along it for an inch or more - the length it fit into the pin. It was not even, more globby. The end of the pin, though, is soldered over as before. The 30 gauge wire definitely made contact - before I soldered up the end I pulled on it and it was anchored deep inside by the solder in there.

I turned the set on, and no change. The set runs. The sound is good. The picture is there, but very dim. Contrast and tuning etc. knobs all function. Brightness knob does nothing.

While it was running I tried rapping on the end of the picture tube with a screwdriver handle as someone suggested above, but no change. The picture didn't even flicker.

Next I may re-try the tinned wire to see if I can do it better. I'll let you know.

While you are at it, do the other pins too. It does not sound hopeful, but it's not going to take a lot of time to try it.

_________________
Tom


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Sun 11, 2018 8:46 pm 
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Joined: Jan Sat 31, 2015 10:06 pm
Posts: 408
Today I did the following:
- replaced R101, which was reading atop 70% or more high in circuit.
- tinned/wired/soldered the remaining pins on the CRT (see picture below). I used 24 gauge wire, had used 30 on pin 11. I stuffed another 30-gauge wire not pin 11 for good measure.
- banged on the picture tube with a screwdriver handle, in a variety of locations, while the set played
None had any effect. Still very dark picture, Background has no effect everything else functioning normally.
Next up is to get a new picture tube.


Attachments:
File comment: Of course, the wires were trimmed and excess solder cleaned up before I hooked it back up.
Tinned, soldered.jpg
Tinned, soldered.jpg [ 99.78 KiB | Viewed 182 times ]
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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Mon 12, 2018 3:52 am 
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Joined: May Sun 17, 2009 10:08 pm
Posts: 329
Location: Massachusets, 02019
I may have a spare frame also


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Mon 12, 2018 4:59 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 684
Location: Crystal Bay, NV
What is the crt cathode current? You can measure the voltage drop on the cathode resistor (R344, I believe). A current of 80 microamps (typical) will cause a voltage drop of 8 volts, using a FET voltmeter or a VTVM. Not sure where this will lead, but knowing the crt current is useful knowledge. The main thing is to make really sure the CRT is bad before you buy another. Perhaps there is somebody nearby (where are you?) who could loan you a test CRT or put your CRT in their set.
=====
Ron


Last edited by TahoeTV on Feb Sun 25, 2018 9:03 pm, edited 1 time in total.

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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Mon 12, 2018 5:47 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 151
You could use my tester:

viewtopic.php?f=3&t=331576

But frankly, looking at the symptoms, i.e.

The picture on the screen, i.e. very poor LF response
The fact that the set uses G1 not the usual cathode drive,
The brightness control has no effect even though its voltage varies, and
Looking at the circuit,

I can be pretty darned certain that the CRT has an O/C cathode. The only reason you can see any picture at all is because of heater-cathode capacitance/leakage.

My tester will reveal a very low cathode current, if anything at all.

Use clip leads to connect direct to the pins, as in the diagram. That at least bypasses the tube socket. If it still reads close enough to zip, then it's bad like I said.

Pity the neck tapping didn't help. It doesn't always work in my experience.....

Oh BTW, the Thomas tubes that I used to see with O/C cathodes in the 60's, when you looked closely at the gun through the glass, there were TWO connections to the cathode. They must have been expecting trouble!


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Sun 25, 2018 8:12 pm 
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Joined: Jan Sat 31, 2015 10:06 pm
Posts: 408
Does anyone still rebuild CRTs? Hawkeye and Clinton Electronics are names I've seen come up when I search the forums.

I'd be happy to pay to have the one I have fixed up.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Feb Sun 25, 2018 8:21 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5196
Location: Woodinville, WA USA
The last CRT rebuilders in the world went out of business years ago. This part of the ETF website details their project to start rebuilding CRTs again:

http://www.earlytelevision.org/crt_rebu ... useum.html

CRT rebuilding is complex, requiring skill as well as the right equipment. Until the ETF project ramps up, collectors have few options -- either use what you have, or find a replacement. Fortunately, your TV uses a 10BP4, just about the most common vintage CRT, so replacements can be found if you need one.

Regards,

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


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