5AHP7A Vintage SSTV The Deep image

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5AHP7A Vintage SSTV The Deep image

Postby Harry Dalek » Mon Jan 04, 2016 8:16 pm

Still Wishful thinking in my title but this is the next 2016 build after my 3BP1 NBTV monitor is finished .

I checked the Heater pins for conductivity this is fine next finding a B/W TV CRT yoke that will fit this thing ,best i have found vintage wise 1956 TV yoke ,problem was the 5AHP7A plastic plug ,have to have a good look if its lined up with the tube size or not it would be a good reason the 60s yoke doesn't fit .

Bit of a conundrum the 50s yoke fits but the 60s would i think be better suited if i could get it other side of that plug but still might not fit anyway on the neck of the yube

First picture the 2 yokes i had lucky i had something large enough for the plug and neck...

Have to scrounge around for a few bits i still need a case of some sorts being one but no rushing my minds still on the 3BP1 monitor ...
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a 50s and 60s b/w tv yoke
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The 60s yoke that is right for the tubes neck but not for the plug it would have to fit over
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the 50s yoke fits thank goodness
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Last edited by Harry Dalek on Sat Feb 06, 2016 5:00 pm, edited 2 times in total.
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: 5AHP7A Vintage SSTV lives

Postby Klaas Robers » Sun Jan 10, 2016 9:00 pm

I expect the black ring to be a plastic box around the connection of the wires, and not a magnet? I have there a magnet, but the 5AHP7 should not have a magnet there.

If the deflection coil fits around the neck of the tube, it will be a 70 degree deflection coil, and that is what you need. It looks promising to me.

The two thin turnable rings at the very back are two magnetised rings, that are used to place the picture in the centre.
- When the tabs are on each other the magnetic field is zero.
- When you turn them in opposite directions the magnetic field is increasing and
- the picture centre moves in a certain direction.
- When you turn both rings together the direction of displacement rotates accordingly.
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Re: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Tue Jan 12, 2016 9:18 pm

Klaas Robers wrote:I expect the black ring to be a plastic box around the connection of the wires, and not a magnet? I have there a magnet, but the 5AHP7 should not have a magnet there.

If the deflection coil fits around the neck of the tube, it will be a 70 degree deflection coil, and that is what you need. It looks promising to me.

The two thin turnable rings at the very back are two magnetised rings, that are used to place the picture in the centre.
- When the tabs are on each other the magnetic field is zero.
- When you turn them in opposite directions the magnetic field is increasing and
- the picture centre moves in a certain direction.
- When you turn both rings together the direction of displacement rotates accordingly.


I don't think its a magnet but i will test ! ......wise to find out now for sure ,it just seems like a plastic housing to me a very old one at that .
I am reassured you think it has promise .
I was thinking the plastic thing that makes the yoke look longer was more a wiring cover and length wise to position the rings for old CRT it was used on once well i hope i am right.
Thinking still about a housing at the moment and tossing up should i have a square or round hole for the tube ..tube is round but picture is square the dilemma ! :lol: i was looking at these old sstvs i like the look of and might like to copy in a way .
I was going to reuse a case but i think i can make some thing simple i have been working on my cnc machine more a manual version with AC motors but it could very easy make a circle or square cut out of aluminium plate for the crt hole...so i am still thinking about this.
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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: 5AHP7A Vintage SSTV lives

Postby Klaas Robers » Wed Jan 13, 2016 8:13 am

As you have seen, I have a square with rounded corners. The picture is slightly smaller, it just touches the inner sides of the rounded corners. Any way the picture is not always at the same position, I think the magnetic field of the earth deflects it slightly. So a real sharp square is not a good thing.

But I should make the hole in the front plate circular any way. Then you may make a cadre with the squarish aperture before it. Look at the pictures that you have found. As well the wooden chassis with the 7BP7 (7 inch) as the "Heathkit" casing of the SB500 has this.
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Re: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Wed Jan 13, 2016 9:08 am

Klaas Robers wrote:As you have seen, I have a square with rounded corners. The picture is slightly smaller, it just touches the inner sides of the rounded corners. Any way the picture is not always at the same position, I think the magnetic field of the earth deflects it slightly. So a real sharp square is not a good thing.

But I should make the hole in the front plate circular any way. Then you may make a cadre with the squarish aperture before it. Look at the pictures that you have found. As well the wooden chassis with the 7BP7 (7 inch) as the "Heathkit" casing of the SB500 has this.


I very much like your SSTV case Klaas but alas not easy to find a Heathkit to scrap these days even so i did track down 2 empty cases on the net and the price wanted for them was not worth it for me .

From what you say better go with the first idea of the round cover hole be the easy for me to cut out as well, OK i will go with that when i buy some Aluminium Sheet round hole it is .
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: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Thu Jan 14, 2016 3:52 pm

HI Klaas i checked my deflection yoke its just a plastic cover as i expected thank goodness . some more scrounging today i found a a plug that will fit it and also by luck i had a very large computer like power supply fan that when i remove the fan motor the housing will let the picture tube rest in it as i did on the 3bp1 crt front panel /
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: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Wed Jan 20, 2016 7:22 pm

Searching around i found something just big enough to mount the CRT so cut the hole out and might just work .

With the Crt and plug in it just fits in the case by luck more than any thing .

I have been thinking about the EHT power supply problem ,i have to do some testing here and measure that it does what it says it does but did buy 2 DC 3V to 7KV 7000V High-voltage Generator Boost Step-up Power Modules and another that gos up to 10,000 volts these are small and would need a diode.

I like the idea its small but i can always make some thing like the (ZVS) flyback driver with a small flyback transformer if that doesn't work out .http://www.fusor.eu/HV.html

The data sheet says it runs from around 5kv to 7kv maximum 10kv

Still putting stuff together i have to clean up the yoke a bit the old plastic wire cover at the end is a bit cracked i wouldn't worry about it but the yoke rings are held there as well..

Last picture my first pictures :wink: Uv Light is fun ...when i finish this i would like to put it up against my mechanical sstv monitor .

AncientBrit wrote:Has anyone tried directing a scanning laser beam onto the external face of an unpowered CRT?

This would of course need both X and Y deflection of the laser beam.

Would the phosphor glow or does it only get excited by an electron beam?

EDIT.
For a quick test just use the existing polygon line scan and holding the CRT (in lieu of the phosphor drum) move it sideways and see if a raster is left behind.

Graham


A long time to answer this question Graham from my other topic but noticed this reviewing a circuit.

I didn't have a crt with the right phosphor not using a laser this time but that uv light frequency is the same so the answer must be yes.
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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: 5AHP7A Vintage SSTV lives

Postby AncientBrit » Wed Jan 20, 2016 11:58 pm

Hi Harry,

Two great demos.

Not sure I'd care to hold those two wires though!!

Cheers,

Graham
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Re: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Thu Jan 21, 2016 8:24 am

AncientBrit wrote:Hi Harry,

Two great demos.

Not sure I'd care to hold those two wires though!!

Cheers,

Graham


Thanks Graham no i was not the one holding the HV wires I am not that brave either ! :shock: its the same picture that sells it on ebay and aliexpress BTW you can some times find much better deals on aliexpress great for electronic parts love the free postage .I noticed some of the other high voltage modules on other sellers posts have no idea of the voltages saying stuff like it does 40 or 50kv 100kv and such, i am sure they are adding a zero by mistake i would be very worried it they do looking at the spark distance in their photos i doubt it.
Any case stuff i want to do is under 10kv i am not to interested in making X rays :wink:
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: 5AHP7A Vintage SSTV lives

Postby AncientBrit » Fri Jan 22, 2016 7:25 pm

Hi Harry,

A couple of things to watch out for on those cheaper models is that they don't recommend continuous opearion and the output current is fairly small and probably would be insufficient for use as a HV supply for a CRT.

Cheers,

Graham
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Re: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Fri Jan 22, 2016 11:16 pm

AncientBrit wrote:Hi Harry,

A couple of things to watch out for on those cheaper models is that they don't recommend continuous opearion and the output current is fairly small and probably would be insufficient for use as a HV supply for a CRT.

Cheers,

Graham


OK Graham better i know now than work with it ,so on to plan 2 with using a small fly back transformer .
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: 5AHP7A Vintage SSTV lives

Postby Klaas Robers » Sat Jan 23, 2016 8:50 am

The current that a CRT needs from the HV is very low. I guess for a 7BP7 and the like 100 uA. These generators can easily supply that. A colour CRT has a beam current of 0.5 mA per colour, so 1.5 mA in total for a white screen. However this is at 25 kV. But then the amount of light that it gives is enormeous. And you should take in account that the shadow mask absorbs at least 75%. So an SSTV picture tube will need no more than 0.1 mA.

In my 7BP7 / 5FP7 monitor the 5 kV is generated by a fly back converter, made from a 88mH ring core with two extra windings. It runs from about 15 volts. The advantage is that it supplies too +250 volt for the focussing and +100 volt for the video driver stage.

An important thing is, Harry, that the HV should be stabilised. The drawn current changes between black and white, and then the voltage should be stable. If not, the picture size breathes between black and white areas. That will be very well visible.
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Re: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Sat Jan 23, 2016 10:44 am

Klaas Robers wrote:The current that a CRT needs from the HV is very low. I guess for a 7BP7 and the like 100 uA. These generators can easily supply that. A colour CRT has a beam current of 0.5 mA per colour, so 1.5 mA in total for a white screen. However this is at 25 kV. But then the amount of light that it gives is enormeous. And you should take in account that the shadow mask absorbs at least 75%. So an SSTV picture tube will need no more than 0.1 mA.

In my 7BP7 / 5FP7 monitor the 5 kV is generated by a fly back converter, made from a 88mH ring core with two extra windings. It runs from about 15 volts. The advantage is that it supplies too +250 volt for the focussing and +100 volt for the video driver stage.

An important thing is, Harry, that the HV should be stabilised. The drawn current changes between black and white, and then the voltage should be stable. If not, the picture size breathes between black and white areas. That will be very well visible.


So it would be possible for the little generator module to work my original idea was a flyback transformer but i saw these and that would save me building something ..

I do have 2 or 3 round core 88mH hand wound they were used in the first sstv monitor the monitor was given to me it didn't work i replaced the circuit and used 741 ics instead of a passive filter using those.

on the module I was thinking of using an lm317 on the low end of use to supply the voltage to this module ,using either and old micro wave oven diode or 7 in4007 1000 volt diodes in series.

Graham mentioned they might have a problem working in continuous use ,i have to test them but seeing what they are being sold for a spark gap show ! i would think this would be the problem i have lost many a high voltage transistor using the power supply like this for to long .

Since i have had a week off the 3bp1 project really with nothing to do i used my time to look into the circuit for the monitor ,I liked the look of the SSTV monitor circuit in the old Hamradio magazine CQ December 1975 issue .
I had all the ic's to this one handy its a bit more complex than most monitor circuits my luck more fault finding when i test the stages :roll:
Has a free running scan with no signal which i would rather as well ,see how it gos.
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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: 5AHP7A Vintage SSTV lives

Postby Harry Dalek » Sun Jan 24, 2016 6:50 pm

I have finished the last circuit board...3 days work there think i spend more time looking for a part at times than soldering it together .

Now i have to check stage by stage what works what doesn't / :roll:
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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: 5AHP7A Vintage SSTV lives

Postby Klaas Robers » Mon Jan 25, 2016 11:37 pm

Oei Harry, I never work in that way. I always build stage by stage and first checking the just built stage. Then I always have a working circuit, or the fault is in the last built stage. Even when I rebuilt the old working monitor on a wooden frame onto the aluminium frame of the Heathkit SB500, I assembled and tested it small PCB by small PCB.

It is extremely difficult to find faults in the large circuits that you have built. At least for me..... Good luck. You'll need it.

For the 5 kV, I think that you can use the small module. However, you should make a voltage stabilization for it. That is the input voltage should be dependent of the output voltage.

Do you have the ability to measure high voltages to say 10 kV? The first thing then is to connect the module to a variable input voltage and measure the output voltage. Find the input voltage that gives you 5 kV of output voltage. For my self built fly back inverter with voltage multiplication this was about 14 volt. Two very high ohmic and long resistors in series bring this high voltage to an opamp circuit that regulate the input voltage of the inverter circuit by feed back. This circuit is fed from a voltage of about 24 volt. Then the 5 kV becomes a stable 5 kV, which is what you need.
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