5BP1 CRT

[Terry S]

Just happened across a NOS 5BP1 green phosphor CRT. Still in the
original military marked cardboard carton, never removed, one end of
the carton unstapled, but the CRT is still secured in the box. I no
longer have a CRT tester so can't test this beast.

Any interest?

Terry

[threeneurons]

No, I have 2 5BP4s (white phosphor), and they are rather large animals. I don't know what I'm going to do with mine either. On top of that I also have 2 5UP1s.

But, I did make a little tube checker, to at least, light them up, and do rough deflection tests.

http://threeneurons.files.wordpress.com/2012/09/crt_tst01.jpg

It doesn't have a socket, but individual socket pins, so it can be hooked up to just about any electrostatically deflected tube, that can be lit up with ~1700V. The 5BP1 can be operated at 1500V. The tester is small, so if you're interested I could loan it to you.

[John Rehwinkel]

> But, I did make a little tube checker, to at least, light them up, and do rough deflection tests.
>
> http://threeneurons.files.wordpress.com/2012/09/crt_tst01.jpg

That's cute - do you have a schematic for it? I'm guessing it's a variant of your 34063-based nixie supply with a voltage multiplier and resistive divider.

- John

[Terry S]

Interesting offer -- now the dilemma -- do I open the box and test the
tube, or leave it in the box untested, where it is perhaps worth more
to a collector?

I'm really interested in building a scope clock with the tube. Trying
to find a kit I like is the problem.

Any recommendations?

Terry

[Oscilloclock]

Not that I'm biased (!), but if you are able to roll your own, you can see two nice designs employing circle graphics at Grahame's site and at Oscilloclock.com . These are based on David's original design at cathodecorner.com .

 

There are many other raster graphics based designs, which have kits available. Dutchtronix must surely be the most common, but a google will show more.

 

Aaron

[Nick]

On Wednesday, 28 November 2012 15:39:43 UTC, Oscilloclock wrote:

Not that I'm biased (!), but if you are able to roll your own, you can see two nice designs employing circle graphics at Grahame's site and at Oscilloclock.com . These are based on David's original design at cathodecorner.com .

 

There are many other raster graphics based designs, which have kits available. Dutchtronix must surely be the most common, but a google will show more.

 

Aaron

No disrespect to David, but the original idea comes from old examples of character generation for RADAR & ATC (air traffic control) screens etc. when everything was analogue.

R. L. White, Forming Handwritten. Like Digits on CRI Display, Electronics,32:11, p 138-140 

Nick

[threeneurons]

Here's the checker schematic.

It uses 2 MC34063 chips. One for the HV, and the other for the 6V heater. 10 signals go to the CRT tube.

[Charles MacDonald]

On 12-11-28 02:59 PM, threeneurons wrote:
> Here's the checker schematic.
>

> <http://threeneurons.files.wordpress.com/2012/11/crt_tstr.gif>

>
> It uses 2 MC34063 chips. One for the HV, and the other for the 6V
> heater. 10 signals go to the CRT tube.

A lot of the old scope circuits used to run the cathode at a negative
voltage. (this required a well insulated filament transformer.) but
meant that the defection plates were almost at ground potential. One
could create a test signal that would draw an pattern on the screen.


--
Charles MacDonald Stittsville Ontario
cm...@zeusprune.ca Just Beyond the Fringe
http://Charles.MacDonald.org/tubes
No Microsoft Products were used in sending this e-mail.

[threeneurons]

> <http://threeneurons.files.wordpress.com/2012/11/crt_tstr.gif>

>


A lot of the old scope circuits used to run the cathode at a negative
voltage.  (this required a well insulated filament transformer.) but
meant that the defection plates were almost at ground potential.  

 Yes, If I ever made a real circuit, to use them, I would use the negative cathode voltage approach. But the heater/filament has to be close to the cathode voltage. Less than 100V off. For the simple test circuit, a high positive voltage was just more convenient. Deflection test, is just done by clipping on a test lead, and connecting the individual deflection plates to +1800V or +1400V. It's quick-n-dirty.

If you use the negative cathode voltage, then the heater has to have a filament winding that's galvanically isolated from every other supply, except maybe the cathode. The secondary and primary need to have some very good separation, such as a split bobbin transformer. Not a problem back in the old days of analog scopes. They had transformers made just for this purpose.

[John Rehwinkel]

> A lot of the old scope circuits used to run the cathode at a negative
> voltage. (this required a well insulated filament transformer.) but
> meant that the defection plates were almost at ground potential.
>
> Yes, If I ever made a real circuit, to use them, I would use the negative cathode voltage approach. But the heater/filament has to be close to the cathode voltage. Less than 100V off. For the simple test circuit, a high positive voltage was just more convenient. Deflection test, is just done by clipping on a test lead, and connecting the individual deflection plates to +1800V or +1400V. It's quick-n-dirty.

Thanks for posting the schematic! Any suggestions on inductors?

> If you use the negative cathode voltage, then the heater has to have a filament winding that's galvanically isolated from every other supply, except maybe the cathode. The secondary and primary need to have some very good separation, such as a split bobbin transformer. Not a problem back in the old days of analog scopes. They had transformers made just for this purpose.

After some poking around, I settled on the Hammond 183F12 for floating the heater at a high negative voltage. It's isolated to 4000V, which is plenty for the
CRTs (and monoscope) I'm playing with.

- John

[Grahame Marsh]

Another technqiue is to overwind a torriodal transformer with an auxillary winding.  The isolation is set by the wire you overwind with.  I wind on 10 turns, measure the voltage under 0.3A (or whatever) load and calculate the number or turns and required length.  Not very elegent but it works Ok.  The proper windings on the transformer are then supply the rest of your circuits.  The VA for the core must be respected obviously.

Grahame

[threeneurons]

Thanks for posting the schematic!  Any suggestions on inductors?

My personal favorite, right now, is the Bourns SDR1806 series. I get 6W out without too much trouble. Its a surface mount part, but its pretty big, so tacking on leads is pretty easy.

All Electronics use to have a great little 220uH coil. I could get 8W out of those. It got hot, but whatever insulation they used, held up at that temp. Unfortunately, they sold out of those a couple of years ago. I used ~500 of them, and they only cost 20 cents (in 100 qty). Nothing specs that good, at that price, right now.