Advise needed for buying a oscilloscope CRT

[Learner]

Hi guys,
I am looking to buy some used CRT from old CROs off ebay, the problem is that there is no manual or data sheets on any of these old bits. Is there any way/methods that I can test to find out the pin connections for these CRTs? also the biasing voltages?

Any adivise on what I should watch for? or is this just a bad idea thats not worth pursuing.....

Thanks!

 

[lavenatti]

If you knew what the CRT was meant to be used in, I'm sure you could find a manual.

If you just want to build your own oscilloscope, why bother? They are so cheap on ebay that it isn't worth the trouble.

 

[stevez]

It would seem that you ought to be able to get a part number of the tube that would lead you to some specs. Certainly there have to be books in print that have that information even if it's not on-line.

You might take a look at amateur radio oriented publications. I know a number of guys who use old CRTs to make modulation monitors - apparently something relatively simple to make. I passed along several non-working scopes (from early 60's) to a friend who was going to do just that.

 

[Learner]

You might take a look at amateur radio oriented publications. I know a number of guys who use old CRTs to make modulation monitors - apparently something relatively simple to make. I passed along several non-working scopes (from early 60's) to a friend who was going to do just that.

Hi Steve,
That's exactly what I am looking to do!!!

I am trying to build amplifiers which using the CRT to display the signal not only in amplitude but also aiming to display the frequency spectrum if I can pull that off, also synthesizers and being able to see the VCO modulation etc...

However, I donno if it is possible to find the specs of these odd cheapie CRTs.... they are usually very small like this one here....

**broken link removed**

any thoughts?

 

[lavenatti]

**broken link removed**

This place may be helpful.

 

[Learner]

Wow!!!

Those are beautiful!!!!!!

I wonder if he has the data sheets for the one he is selling........ I am actually looking for those CRTs on the old bomber planes because of the marking on the screen, they just looks absolutely AWSOME but they seem to be very rare to find....

 

[lavenatti]

You could mimick those markings with some fancy artwork and the clear printable sheets for your laser or inkjet printer.

 

[mechie]

Old oscilloscopes ?

It sounds to me like you are trying to scratch-build an oscilloscope, possibly with reduced functionality.

If space isn't a problem you could start with a normal 'scope and just mod it.
If space is a big concern then consider a Thandar SC110A oscilloscope (seen for about £25 on EBay), these are cute little tubes about 1.5" square. The entire scope can run from batteries and the circuit diagram is (as are most old 'scopes) available from all over the place.

Producing a frequency analyser is easy if you only want audio and you have a voltage controlled band-pass filter and an oscillator capable of sawtooth (or, at a push, triangle) waveforms (you mentioned synthesisers!).

 

[Learner]

Wow....thanks a lot mechie!!!!!

You guys ROCK!!!!!

If I can just find a monolithic IC VCBF that is if there is a such piece!??

 

[efren sabio]

Hi Learner,

I know how you feel! In fact, I have 3 scopes! My 1st is 26 yrs old and
still working. Then I saw another like it for peanuts so I bought it. Then
I found out that both weren't working after long unused. What to do?
You need a scope to troubleshoot a scope! You have to see those
waveforms, like the sawtooth that brings the dot back to the left of the
screen! Luckily, I found a simple (uncalibrated) scope, again for peanuts,
so I bought it just to fix my 2 other.
With just basic math you can design your own circuits, preamps, power
amps. Then if you have a scope you can see the waves you create!
You can even watch a guitar pick-up output- without amplification-
with your scope.

Efren

 

[Learner]

Re: Old oscilloscopes ?

Producing a frequency analyser is easy if you only want audio and you have a voltage controlled band-pass filter and an oscillator capable of sawtooth (or, at a push, triangle) waveforms (you mentioned synthesisers!).

Hi mechie,
I haven't been able to find a VCBF monolithic chip, so I guess my option would be to find a circuit with highest Q possible for good resolution and a VCO chip that can putout ramp wave at 44Khz and above with the peak to peak voltage set to modulate the bandpass filter from 20 to 20Khz.

Howeve, the problem I am encountering is that I dont think there is any VCO chip that puts out ramp wave form???

Also, I am having diffulty finding a high Q VCBF eg >200 or even 100.....
Where do one start?

Thanks a lot!!

 

[spuffock]

Take a look at the datasheet for the lm13700 from national semiconductor.
You may well end up buying a lot of the chips........

 

[Learner]

Take a look at the datasheet for the lm13700 from national semiconductor.
You may well end up buying a lot of the chips........

Hey spuffock,
That is really COOL!!!!

Thanks a lot!!!!!!