Swapping CRTs: what do I need to know?

[oktology]

I have a Tandy Model 4P with the white-phosphor tube, and I think I may have found a suitable donor green-phosphor medical monitor.

Is this a "a CRT is a CRT" situation, or is individual monitor circuitry tied to individual tubes?

 

[daver2]

Could be either.

You require the data sheets for both tubes.

Check the pinouts for the tubes, the heater voltage and current (and whether it is AC or DC) and then check the expected operational voltage ranges for the various electrodes within the CRT.

Also, check the mechanical mounting arrangements.

It is a similar issue to finding an equivalent IC...

Dave

 

[oktology]

Man, finding datasheets for CRTs is a real pain in the neck. I found the datasheet for the Philips OEM tube that's currently installed, but I can't find datasheets for any of the potential replacements--mainly out of HP logic analyzers.

 

[daver2]

Perhaps post some numbers and see if we can help?

Dave

 

[oktology]

The original is a Philips M24-302W/P. Also used in the Commodore PET 2k/3k series as M24-302G/H, the green phosphor version that I want to install.

I'm looking at a Hitachi 230CYB31, which looks physically similar to the Philips tube.

Original OEM Philips:


Hitachi:

 

[bzotto]

The Sencore (and other brands) CRT testers had info books that listed key specs of filament and bias voltage information for all sorts of tubes so they could be setup correctly for testing. I didn't find exact matches to either of your tube types in the big spreadsheet, but two very similar listings look like:

CRT # Adapter Type Filament Voltage Bias Direct Heat
230CYB4 6 Video 1 12 36V No
M24-302 6 Video 1 11 52V No

The pinouts at the tube necks appear equivalent (good) but the voltages may be a bit different-- the Hitachi tube probably expects a little more juice (12V) for the filament than the original (11V) although I suspect you would just compensate with the brightness control a bit. More notable is the fifth column above which is bias voltage, which is different. I'm not a CRT expert, so I can't tell you whether this is a nonstarter, or whether it's a "maybe it will work but maybe less well" kind of situation. HTH

 

[bzotto]

...bias voltage, which is different. I'm not a CRT expert, so I can't tell you whether this is a nonstarter, or whether it's a "maybe it will work but maybe less well" kind of situation. HTH

FWIW this also doesn't speak to the color gun grid stuff that Dave mentions above-- color tubes have more variables than B&W sets do.

 

[oktology]

HTH

Thanks for the info. It’s more steps in the right direction.

FWIW this also doesn't speak to the color gun grid stuff that Dave mentions above-- color tubes have more variables than B&W sets do.

Fortunately these are monochrome tubes, which does simplify things a bit.