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  #1  
Old 01-20-2012, 12:47 PM
Phil Nelson's Avatar
Phil Nelson Phil Nelson is offline
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WTB: 21BSP4 Picture Tube (B/W)

I need a type 21BSP4 picture tube with good emission. This is to replace the tube in my Philco F4646M Miss America TV.

I don't know if there are other 21-inch B/W tubes that will sub for 21BSP4.

Thanks!

Phil Nelson
Phil's Old Radios
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Old 01-20-2012, 01:46 PM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by Phil Nelson View Post
I need a type 21BSP4 picture tube with good emission. This is to replace the tube in my Philco F4646M Miss America TV.

I don't know if there are other 21-inch B/W tubes that will sub for 21BSP4.

Thanks!

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Does that set use a PM focalizer? If so, a 21AMP4 can sub it. Every CRT manufacturer seemed to use their own sequence of numbers.
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Old 01-20-2012, 02:03 PM
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Phil Nelson Phil Nelson is offline
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Quote:
Originally Posted by dieseljeep View Post
Does that set use a PM focalizer?
Don't know what a PM focalizer is. How would I recognize it?

Phil
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Old 01-20-2012, 03:04 PM
tvtimeisfun tvtimeisfun is offline
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Hello Phil I may have a jug that may work on that set I will check and let you know on sunday but let me know if you find one.. thanks Timothy
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  #5  
Old 01-20-2012, 03:20 PM
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Just a guess, but a PM focalizer might be like a permanent magnet focusing setup.
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Old 01-20-2012, 04:40 PM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by Kevin Kuehn View Post
Just a guess, but a PM focalizer might be like a permanent magnet focusing setup.
21ACP4, 21AMP4 and 21BSP4, all the same. Uses a single ion trap. PM focus device is another name for it. You can't miss it. It's right between yoke and the ion trap. Extremely strong magnet. You can also use a self focusing CRT by removing the PM unit.
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Old 01-20-2012, 05:24 PM
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leadlike leadlike is offline
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If it helps, I used a 21CBP4 in place of a 21AMP4. The CBP4 has a pin that needs focus voltage applied to it, but a simple jumper wire took care of that. I had to remove the not-needed focusing magnets as well. Just shows that with a little work, almost any 21" B&W crt will work in your set.
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Old 01-20-2012, 07:42 PM
dieseljeep dieseljeep is offline
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Originally Posted by leadlike View Post
If it helps, I used a 21CBP4 in place of a 21AMP4. The CBP4 has a pin that needs focus voltage applied to it, but a simple jumper wire took care of that. I had to remove the not-needed focusing magnets as well. Just shows that with a little work, almost any 21" B&W crt will work in your set.
Not quite. 21" B&W CRT's come in all shapes and sizes. Large neck CRT's come in 62, 70 and 90 deg. sweep angles. Also screen sizes varied from 221 to 270 sq. in. All 21" CRT's were roughly the same after 1956, as far as physical shape.
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Old 01-20-2012, 10:37 PM
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If you can get your hands on a 21AMP4B you won't need to mess with the Ion trap. Did they ever make 21ACP4 and 21BSP4 in a non Ion trap version?

On another note, I've got a spare 21AMP4B here that tests really good and has great brightness. Problem is I can't get it to focus well at the edges when the center is focused. I don't quite understand it.
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  #10  
Old 01-24-2012, 08:07 PM
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ohohyodafarted ohohyodafarted is offline
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I have a NOS 21dsp4. I compared the specs and the bulb is the same except that the neck is 2 inches shorter. Gun also has a couple extra grid elements but I think if the shorter neck will work mechanically in your set, it may be a possible sub.
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  #11  
Old 01-24-2012, 08:19 PM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by ohohyodafarted View Post
I have a NOS 21dsp4. I compared the specs and the bulb is the same except that the neck is 2 inches shorter. Gun also has a couple extra grid elements but I think if the shorter neck will work mechanically in your set, it may be a possible sub.
That 21DSP4 is a low G-2 CRT. E-stat focusing and straight gun. No ion trap. Used in later RCA's and a sub for a Zenith type 21CXP4. It would require circuit changes.
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  #12  
Old 12-28-2012, 01:14 AM
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Eleven months later, I'm still looking for a good 21BSP4 (or 21ACP4 or 21AMP4).

Phil Nelson
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  #13  
Old 12-28-2012, 01:42 AM
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Eric H Eric H is offline
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Phil, I have an unknown 21" CRT I pulled out of my 1952 Wilcox-Gay (which now has a new 20" Silver-Glo tube), I know that's way earlier than your Philco but it was also the incorrect tube for the W-G and it may be from a newer set.

Does your tube have the typical large neck with the standard 12 pin bakelite base?

The length seems like it would be close based on measuring the TV cabinet but I do know it's an Electrostatic focus tube because they had removed the magnet to install it, but it's easy enough to focus it using B+.

It also has a hack repair to the base where one of the wires broke off flush with the glass, it was rebuilt in 1977 and tests like new. You can have it for shipping if it'll work.
I'd have to get it out of the attic and do some measuring to see if it's physically right.
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  #14  
Old 12-28-2012, 10:37 AM
dieseljeep dieseljeep is offline
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That's probably an old 70 degree CRT. Won't work and won't fit.
Check that E-bay listing. They'll probably sell one at a time.
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  #15  
Old 12-28-2012, 11:11 AM
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baursam baursam is offline
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Hi Phil

I don't know if this will help but I stumbled on an auction last night on eBay for a load of NIB picture tubes. Lots of 21 inch tubes but nothing identical to what you are looking for

http://www.ebay.com/itm/Huge-Lot-Vin...-/300838989095

Good luck

Ross
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