5AP7A ?

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5AP7A ?

Postby Harry Dalek » Sun Mar 26, 2023 4:50 pm

Troy from the forum donated a beautiful P7 CRT to me a while back and looking at the original CRT box its marks 5FP7A but on the CRt Neck its marked i think 5Ap7A looking for data what's on the neck nothing is coming up my last SSTV used a 5AHP7A .
I don't plan on using it just yet but have in mind a low frame rate monitor for it in time .
Wonderful looking thing might be able to do the same and better these days with little panel displays and the PC its self for sure but the point is keeping history alive here otherwise you could just use one pc as a transmitter an the other as a receiver and be done with it and there go's any electronics pride left in your soul . :?
Its one of those things electronics never stays still and you can either ride the train and pass every that's gone by or get off the train at stops and enjoy what was . :P
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Re: 5AP7A ?

Postby Steve Anderson » Mon Mar 27, 2023 11:20 am

I don't have full data on the 5FP7A, only abridged, but I do on the 5FP7B. The difference is usually minimal and in most cases can be ignored.

As you'll note, it's again magnetically deflected and focused, more than likely developed for long-range radar applications as noted in the datasheet.

To eliminate some possible types, how many pins are on the base? (Including any missing ones, common on CRTs)

Steve A.

5FP7A.pdf
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5FP7B.pdf
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Re: 5AP7A ?

Postby Harry Dalek » Mon Mar 27, 2023 4:02 pm

Steve Anderson wrote:I don't have full data on the 5FP7A, only abridged, but I do on the 5FP7B. The difference is usually minimal and in most cases can be ignored.

As you'll note, it's again magnetically deflected and focused, more than likely developed for long-range radar applications as noted in the datasheet.

To eliminate some possible types, how many pins are on the base? (Including any missing ones, common on CRTs)

Steve A.

5FP7A.pdf


Yes the big pain on this one is more the focus coil which would have to be made i have some data on this in an old magazine ,the SSTV i made in the about 1990 i was lucky enough to be given a focus coil long gone now ..but i recall after some use the coil would warm up and and defocus a bit . Wonder if you could get a ring magnet big enough for some thing like this mmmm
Steve i had another look at the CRT markings in day light and it is marked 100% 5AP7A on the glass so do you believe the marks on the Tube or the box it was in ? If there were data for a 5Ap7A it would be easy
The pins there are 8 pins and no gaps
And thanks for the data i see the pins are similar spaced need to check the connections.
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Re: 5AP7A ?

Postby Steve Anderson » Mon Mar 27, 2023 5:35 pm

I would forget what's on box, and if you are sure that the markings on the tube itself are clear enough, go with those. The box probably has simply been re-used. Not uncommon with older stuff generally. Obliterate the existing box makings and add the correct one(s) when you are sure. Or find/make a new unmarked/correctly marked box and throw out the old one....so there's no confusion in the future.

The fact it only has 8 pins is also a pointer in the direction of it being at least a magnetic deflection CRT, possibly focus too. The datasheet I have for the 5AP1 and 5AP4 indicates it has an 11 pin base, all electrostatic, so I don't think you have a 5AP7(A) there. The 'A' suffix usually makes little difference...

5AP1.pdf
(80.82 KiB) Downloaded 239 times


A 5AP1 will be the same (usually/more often than not) as a 5AP4, 5AP7 and so on...

When you add up the pins required for an all electrostatic CRT eight isn't enough..

2-Heater,
1-Cathode,
1-Grid (Intensity),
1-Grid (Focus),
1-Grid/Anode (Accelerator) - but not always, but usually on CRTs of 3" or more.
4-X & Y deflection plates,

So a reasonable minimum of 10 pins, usually more...

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Re: 5AP7A ?

Postby Steve Anderson » Mon Mar 27, 2023 6:07 pm

Here's a CRT I would love to have, excellent for demonstrations. you can see all inside...

DG16-1.jpg


In this case the deflection plates are brought out on dedicated terminals to reduce capacitance in the deflection circuits. In this case around 8 pins, maybe less, on the base should be enough...this is a Philips DG16-1 with a medium persistence green phosphor, for general oscilloscope and demonstration use. Its construction is just as the textbooks show, it's then those invisible electrons can be easily seen (well, they can't) doing something...producing a result on the screen...

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Re: 5AP7A ?

Postby Harry Dalek » Mon Mar 27, 2023 7:51 pm

Steve Anderson wrote:I would forget what's on box, and if you are sure that the markings on the tube itself are clear enough, go with those. The box probably has simply been re-used.


I would agree but some thing is up if the markings on the CRT give no data coming up could the crt be marked wrong and placed in the corrected box ?
The Box and CRT is the correct size shape for what it was to hold and time period which i think is 1947 so either way the CRT and the box are from around the same time .
Not uncommon with older stuff generally. Obliterate the existing box makings and add the correct one(s) when you are sure. Or find/make a new unmarked/correctly marked box and throw out the old one....so there's no confusion in the future.


Yep that's a good idea another reason i wanted to check here and have on the forum for when i use this but reading all your post again could it be possible the crt was marked wrong and put in the corrected box at the factory ? it is strange the CRT has no data or even any thing coming up with those markings as a know CRT i will keep looking but i should ask Troy he might know more of the story as it was he's crt and knows at least where he got it .

The fact it only has 8 pins is also a pointer in the direction of it being at least a magnetic deflection CRT, possibly focus too. The datasheet I have for the 5AP1 and 5AP4 indicates it has an 11 pin base, all electrostatic, so I don't think you have a 5AP7(A) there. The 'A' suffix usually makes little difference...


So that's Strange what's marked on the glass that's got me confused i will double check with Troy he might know .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: 5AP7A ?

Postby Harry Dalek » Mon Mar 27, 2023 7:55 pm

Steve Anderson wrote:Here's a CRT I would love to have, excellent for demonstrations. you can see all inside...

DG16-1.jpg


In this case the deflection plates are brought out on dedicated terminals to reduce capacitance in the deflection circuits. In this case around 8 pins, maybe less, on the base should be enough...this is a Philips DG16-1 with a medium persistence green phosphor, for general oscilloscope and demonstration use. Its construction is just as the textbooks show, it's then those invisible electrons can be easily seen (well, they can't) doing something...producing a result on the screen...

Steve A.


I think Chris long has some thing similar a while back was asking if any one was interested. Beautiful things now that's a light globe !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: 5AP7A ?

Postby kd2bd » Tue Mar 28, 2023 1:21 am

Harry Dalek wrote:Yes the big pain on this one is more the focus coil which would have to be made i have some data on this in an old magazine ,the SSTV i made in the about 1990 i was lucky enough to be given a focus coil long gone now ..but i recall after some use the coil would warm up and and defocus a bit . Wonder if you could get a ring magnet big enough for some thing like this mmmm

Harry,

As the temperature of the focus coil increases, its resistance increases and the current flowing through it decreases, changing the CRT focus. Since the coil's magnetic field (and level of focus) are based on current flow rather than voltage, it might be worth trying to drive a focus coil through an adjustable constant current source rather than an adjustable voltage source. With the coil being fed by a constant current source, the current flowing through the coil will remain at a fixed value, as will the level of focus, regardless of the coil's temperature. Many of the popular 3-terminal DC voltage regulators (LM317, etc) can be configured to serve as adjustable constant current sources.

When my interest in SSTV first developed in my teen years, I liked the idea of using a fixed magnet for focusing much better than having to supply DC power for a coil (or a high voltage for electrostatic focus). I was lucky to come across what I believe is an old Quam Focalizer permanent magnetic focus assembly that worked well with my 7BP7. It would be interesting to see what might be constructed today using an array of small modern neodymium magnets.

73 de John, KD2BD
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Re: 5AP7A ?

Postby kd2bd » Tue Mar 28, 2023 3:27 am

I found some additional information on the 5AP7 CRT here: https://frank.pocnet.net/other/docs/PHBrans/PHBrans_Vademecum_TV&SpecialTubes_15th_1959.pdf. It further confirms that the 5AP7 is an electrostatically focused and deflected CRT with an 11-pin base. I was able to piece the following together from the PDF above:

5AP7-data.png

5AP7-base.png
5AP7-base.png (29.98 KiB) Viewed 7020 times

10 of the 11 pins on the base are used. However, your CRT, unlike what is shown on the 5AP7 datasheets, has an 8-pin base AND a second anode connection on the bell of the CRT. So, even if the 5AP7A were simply a 5AP7 with the second anode connection moved to the bell, there still wouldn't be enough pins on the base for the focus anode and the deflection plate connections.

You might be able to find more clues by carefully examining what you can see of the gun structure. Comparing the physical dimensions of your tube versus the 5AP7 datasheets might help determine if your tube is indeed related to a 5AP7, or is something else entirely. I'm beginning to think your tube may have been manufactured to specifications of a specific client and application, and may not have been available for general use.

73 de John, KD2BD
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Re: 5AP7A ?

Postby Steve Anderson » Tue Mar 28, 2023 2:36 pm

kd2bd wrote: I'm beginning to think your tube may have been manufactured to specifications of a specific client and application, and may not have been available for general use. 73 de John, KD2BD

Entirely possible. The radar CRTs that Decca used (9", 12" and 16") where made by someone (I've forgotten who) to their specification. The phosphor was P7-like, but also to their own 'special brew'. The type designation was nothing like what we're used to, 5BP1, DG7-32 and so on, but a unique 'house number'. (Also forgotten). I wish I had 'borrowed' a couple while I worked there. I also regret not 'spiriting away' a bunch of circuit diagrams.

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Re: 5AP7A ?

Postby Harry Dalek » Tue Mar 28, 2023 3:03 pm

kd2bd wrote:I found some additional information on the 5AP7 CRT here:


Hi John Thanks for also taking an interest i have not heard back from Troy who i got the Tube from but as i mentioned to Steve It says its a 5Ap7A problem with the 5ap7 data that's got me stumped is its only got 8 pins as you know also its a what the hell moment !


You might be able to find more clues by carefully examining what you can see of the gun structure. Comparing the physical dimensions of your tube versus the 5AP7 datasheets might help determine if your tube is indeed related to a 5AP7, or is something else entirely. I'm beginning to think your tube may have been manufactured to specifications of a specific client and application, and may not have been available for general use.


I have had to do that a bit of late looking at what go's where in the CRT its not really a problem getting it going just be nice to check with the data ,i would think like most of these its last anode is at 7KV focus and cut off can be worked out .
The idea the CRT is a one off is very interesting i will have to be very careful i will look into pin connections later in the week
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: 5AP7A ?

Postby Harry Dalek » Tue Mar 28, 2023 3:07 pm

Entirely possible. The radar CRTs that Decca used (9", 12" and 16") where made by someone (I've forgotten who) to their specification. The phosphor was P7-like, but also to their own 'special brew'. The type designation was nothing like what we're used to, 5BP1, DG7-32 and so on, but a unique 'house number'. (Also forgotten). I wish I had 'borrowed' a couple while I worked there. I also regret not 'spiriting away' a bunch of circuit diagrams.



Yes grab it while you can i say ! Sounds like i am very lucky to be the owner of this CRT
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: 5AP7A ?

Postby Harry Dalek » Tue Mar 28, 2023 3:16 pm

kd2bd wrote:
As the temperature of the focus coil increases, its resistance increases and the current flowing through it decreases, changing the CRT focus. Since the coil's magnetic field (and level of focus) are based on current flow rather than voltage, it might be worth trying to drive a focus coil through an adjustable constant current source rather than an adjustable voltage source. With the coil being fed by a constant current source, the current flowing through the coil will remain at a fixed value, as will the level of focus, regardless of the coil's temperature. Many of the popular 3-terminal DC voltage regulators (LM317, etc) can be configured to serve as adjustable constant current sources.


That's great advice John i will take that in when i end up using this if i going down the electromagnet path .

When my interest in SSTV first developed in my teen years, I liked the idea of using a fixed magnet for focusing much better than having to supply DC power for a coil (or a high voltage for electrostatic focus). I was lucky to come across what I believe is an old Quam Focalizer permanent magnetic focus assembly that worked well with my 7BP7. It would be interesting to see what might be constructed today using an array of small modern neodymium magnets.

73 de John, KD2BD
[/quote]

Its crossed my mind John i suppose adjusting the focus might be adjusting each magnets distance from the CRT neck and work out the correct position then it could be in a fixed position ...some thing to think about also when i get around to using the CRT ...........have to look if i can find any thing on the Quam focalizer new to me .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: 5AP7A ?

Postby kd2bd » Sat Apr 01, 2023 6:21 am

Some information on the Quam "Focalizer" and its use with a 5FP7 and similar CRTs can be found here: https://labguysworld.com/5FPn_CRT_Tester.htm

Either a ring magnet or a series of small bar magnets can be used to build your own. The tough part would be to construct an adjustable magnetic "shunt" between the magnet(s) and the tube to simultaneously confine the magnetic field to a narrow "gap" of maybe 10mm or so, and to adjust its amplitude for proper focus. The article referenced above explains how this works.

73 de John, KD2BD
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Re: 5AP7A ?

Postby Harry Dalek » Sat Apr 01, 2023 8:05 am

kd2bd wrote:Some information on the Quam "Focalizer" and its use with a 5FP7 and similar CRTs can be found here: https://labguysworld.com/5FPn_CRT_Tester.htm

Either a ring magnet or a series of small bar magnets can be used to build your own. The tough part would be to construct an adjustable magnetic "shunt" between the magnet(s) and the tube to simultaneously confine the magnetic field to a narrow "gap" of maybe 10mm or so, and to adjust its amplitude for proper focus. The article referenced above explains how this works.

73 de John, KD2BD


There's more on it than i thought John its very interesting seeing one constructed ,i will for sure look into it once i start to look into using the Tube .
Comes down a lot to what i have handy cheapest way easiest way to do it either the coil or the passive way or both just to see ?
I like Richards labguys CRT power supply idea to test the tube .
At the moment my minds been fully on working on the power supply for the MBTV and our little friend is in its box safely packed away for while.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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