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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 1:59 am 
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TahoeTV - actually, I used to be near Reno. I lived in Carson City from 1978 to 1982!


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 2:01 am 
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Location: Pewaukee, WI
Reichsrundfunk wrote:
Ummm... please forgive my idiocy but if the owner of this absolutely gorgeous set had a 12” crt around bd such as perhaps a 12KP4 they could plug it in (with a KP4) remove the ion trap and see if they get a normal response?.

Or, if not just check if voltage actually IS varying by adjusting up and down the brightness pot while watching the multimeter response?

I also have a 48-1000 although mine is a preproduction handwired prototype but essentially the same beast. They can be tricky but they are not that difficult to scope out! Just offering a couple thoughts to help you progress forward!

George


The production 48-1000 sets were handwired too.....They did not start using circuit boards in their TVs for about another decade after the 48-1000s were made...


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 2:02 am 
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On the varying voltage - I've used the MM to measure the voltage at the point on the chassis where the yellow wire leaves for the CRT socket - it's a terminal near the back of the set. At that point, turning the Background control *does* change the voltage, in the range I listed above. That charge is getting to the socket, as I've tested the yellow wire with the MM and it is not open - I get a beep with one probe at that point where it connects to the chassis terminal, and the other end stuck into that pin on the socket. So, I believe that the background control is properly varying the voltage, and that voltage is making it to the CRT.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 2:04 am 
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Does anyone know where I can get a replacement picture tube? Preferrably with the metal frame, ion trap and everything attached to it? Do they come in "good" condition, where they will last a long time? Or are all extant examples old and used up and I'll only get a year out of them like I did this one?


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 3:19 am 
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Location: Ann Arbor, MI
The most common CRT failure is a slow (over years) loss of maximum brightness. If the CRT starts out with good brightness it may take 10 years of daily use before it gets too dim to use. A sudden failure does not usually happen. A sudden failure is due to a cracked weld inside the electron gun or a cracked solder joint at the pin. As mentioned above, a cracked solder joint can be fixed by re-soldering the pin. Some tube testers have a function that attempts to fix a cracked weld by applying a high voltage pulse. I don't know how often that works.

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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 5:03 am 
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Location: Crystal Bay, NV
The metal cage holding the CRT is unique to Philco sets of that series. Don't bother looking for that. The 10BP4 tube shows up on Ebay every so often. They can last a long time -- witness the fact that most of these tubes are over 60 year old (but not used most of that time). Try to find one that has been tested on a crt tester. On my tester a good reading (in the green) is 400, but a really fresh crt will test at 600+. The 10BP4 can be rejuvenated (like giving it shot of hormones), but the boost effect will usually wear off much quicker than a good crt will grow weak.

Sometimes it can be a little difficult to remove the crt from its mount, the yoke and the ion trap. With patience you will succeed, just don't drop it! If it proves really stubborn, I'm sure you can find some helpful advise on this forum.

Have you tried the soldering of the pin? You have nothing to lose.
=====
Ron


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Tue 28, 2017 6:26 pm 
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Electronic Memory wrote:
Reichsrundfunk wrote:
Ummm... please forgive my idiocy but if the owner of this absolutely gorgeous set had a 12” crt around bd such as perhaps a 12KP4 they could plug it in (with a KP4) remove the ion trap and see if they get a normal response?.

Or, if not just check if voltage actually IS varying by adjusting up and down the brightness pot while watching the multimeter response?

I also have a 48-1000 although mine is a preproduction handwired prototype but essentially the same beast. They can be tricky but they are not that difficult to scope out! Just offering a couple thoughts to help you progress forward!

George


The production 48-1000 sets were handwired too.....They did not start using circuit boards in their TVs for about another decade after the 48-1000s were made...


Sorry my inaccuracy! I meant to say mine is a pre production prototype for engineer evaluations. Of course all were handwired at that time!


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Wed 29, 2017 4:00 am 
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I have not tried the soldering of the pin, and you are right - I have nothing to lose. So - I have the instructions you guys gave me, and I can try this weekend. Are there any other resources? Web pages, forum posts, YouTube videos, etc.?


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Wed 29, 2017 5:18 am 
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Location: Crystal Bay, NV
Have the CRT horizontal. Apply your iron/gun to the middle of the pin. Use a fine strand of solder - the kind that is about 1/16" in diameter. When the pin is hot, the solder can be inserted into the hole at the end of the pin. Don't go overboard: about 1/2 inch of solder should do. Wipe the pin off while hot to eliminate solder on the outside of the pin.
I have saved a couple of tubes that appeared to be burned out (the filament was open), and the result was a surprise success.
What are the odds? I would say about 1 in 5 or 10 can be saved with the pin re-solder treatment. You may be lucky!
=======
Ron


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Nov Wed 29, 2017 6:58 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 28
I'm sorry I didn't pick this one earlier from the picture off the screen, the grid drive to the CRT threw me. But when you confirmed the cathode pin voltage varies, you nailed it.

Your CRT has an O/C cathode. Most likely internal, i.e. a weld in the gun itself.

This used to be a stock fault back in the day (60's in Australia). We'd see it most commonly in Thomas 23HP4s, expensive tube to replace because the 23HP4 was a laminated faceplate tube. Never (as I recall) in AWV or Philips CRTs.

Good news is, there's a fix for it. Bad news is, it might not work, or the fix might not last for very long.

With the TV running and while watching the screen, tap the neck of the CRT with the handle of a large screwdriver. One or two taps is often all it takes. Not so hard as you might break the glass, it takes some judgement.

With the Thomas 23HP4s this would sometimes result in a permanent fix. Sometimes it would last a year, sometimes a few seconds. It might not work for you, but it's sure worth trying.

Oh, do try resoldering the base pins first. The 23HP4 had an all-glass base so that was never an option.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Fri 01, 2017 2:22 pm 
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I will try this weekend to do the pin soldering, but I may need to get some thinner solder. Thank you for all of the detailed instructions.

In the meantime i am looking for a replacement picture tube. I have a couple of people who say they have a “good” one, but I’d like to know exactly what to look for. What is hot he scale on which “goodness” is ranked? Is NOS better than used? Is anyone out there doin rebuilds? In other words:

—> what do I need to know so that I get the best tube that will last a long time? I’m less concerned about the price, quality is more important.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Fri 01, 2017 4:52 pm 
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Location: Pewaukee, WI
I've seen good and mediocre NOS, I've also seen dud tubes placed in the box that their replacement came in sold as NOS by uninformed sellers. I've seen used tubes that beat the few NOS specimens I've encountered. What you need to look for is a good/strong testing tube with no face scratches, phosphor discoloration/black spots....You also want the aquadag to be in good shape (unless you feel like dropping ~$20 on a spray can of dag).

If you plan to be a serious TV collector I recommend you get your own CRT tester...I pretty much don't buy sets or CRTs unless I can test them, or they are cheap enough that I can live with a dud tube.

EDIT: Also there are no active rebuilding opperations that will simply take on a TV CRT....The only ones left are military sector only, and the ETF rebuilding project, that while capable of a rebuild is not offering it as a service (at least not yet, and their progress is slow so don't hold your breath).


Last edited by Electronic Memory on Dec Fri 01, 2017 11:46 pm, edited 1 time in total.

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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Fri 01, 2017 9:56 pm 
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Location: WI 54812
Unfortunately the only 100% guarantee is in seeing a CRT operational in a chassis. We now know that if a used CRT has previously been operated for an extended period with the ion trap maladjusted, that there could be a shadow cast on the phosphor that only becomes visible when the CRT face becomes operational. This is caused by the electron gun aperture having been vaporized by the electron beam being incorrectly aimed, which in turn deposits that material on the back side of the phosphor. This phenomenon is often mistaken by many in the TV collecting community as ion burn, which it is not.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Tue 05, 2017 4:26 am 
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What are your thoughts on this CRT on ebay: https://www.ebay.com/itm/332352685701?ul_noapp=true
He posted a picture of the test reading, which is at the low end of "good". Are there tubes out there with better readings? If so I can wait and would pay more. Or is this as good as it gets these days?


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Tue 05, 2017 5:25 am 
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Honestly, it all depends on the individual tester and it's calibration (or lack there of). I've seen two testers of different makes and models (I think I've seen two of the same model do this too) test the same tube and one scores it mediocre while the other tests it as strong.

Someone else's tester will only tell you if it is fit to make a raster. To understand how to interpret relative quality reading of any tester you have to use that exact example of that tester on several CRTs of varying quality and observe how those CRTs work in working sets... If you want the best example you need to have your own tester and go test it before you buy, or find a seller who knows their tester and attests that it is a strong reading.


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Tue 05, 2017 6:06 am 
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But if you re-solder the cathode pin on your CRT, you may well find that you don't need another CRT.

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Tom


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 Post subject: Re: Philco 48-1000 - Brightness Failed
PostPosted: Dec Tue 05, 2017 9:34 pm 
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I’m just checking out the CRT market in case I need to get one.


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