Replacing 90 degree crt with 70
 

Hello everyone. I am desperately thinking of replacing a broken AW 53-80 picture tube with a 21YP4 which I found online for sale. Is there any possibility of it working, even with mediocre picture, or should I give up? The original picture tube is very rare.

The first thought is that it won't fit in the cabinet. A 70 degree tube is longer than a 90 degree and will stick out of the back. Otherwise it may work, though it will be overscanned and linearity may be poor.

Compare the data sheets and check:

Same basic electrode structure?
Same neck diameter?
Same focus method? (magnetic or electostatic. The AW53-80 is electrostatic)
Same heater voltage and current? (this can be accommodated if necessary)
Is EHT voltage rating sufficient?

https://frank.pocnet.net/sheets/127/2/21YP4.pdf
https://frank.pocnet.net/sheets/030/a/AW43-80.pdf

Since the AW53-80 was relatively common in the UK it may be better to post on a UK based forum.

Thank you very much. The voltages are almost identical. I just posted on a UK forum. Thanks again.

If all else is doable except deflection angle, you could conceivably use a 'width sleeve' to reduce horiz deflection. That's a cylinder of thin brass shim stock, slid inside the yoke, between the CRT neck and yoke coils, and insulated (provided there's enough clearance). Slide it in just far enough to give desired H deflection. The vertical could probably be done with just height and lin adjustments.

I've successfully reduced width with a few turns of wire on a ferrite rod in series with the H scan coils. The sleeve mentioned in the previous post is normally used to correct H linearity rather than reduce width.

The AW53-80 has a 6.3V 300mA heater. The suggested replacement has a 600mA heater. If the set has a series heater chain you will need a small 6.3V transformer to run the heater.

Thanks everyone for the information! Yes, I keep in mind that I will need a separate filament transformer because it's a chain tv set.

Small nit, but back in the day, some BW sets actually came with a 'width sleeve' pre-installed. Idea being, it could be withdrawn as needed to increase width as the set aged or for low line voltage.

https://www.bunkerofdoom.com/crt10sp4/index.html
Example of 110 degree vs 70 degree attempt