Quote:
Originally Posted by Heatercathodeshort
Great write up and what an epic journey!
The CRM91 pre war tube is an odd one and was certainly 'wide angle' at 64 degrees, compared with it's post war replacement the CRM92 57 degrees listed as a replacement for the CRM91.
It is a short stubby tube and considerable difficulties could be experienced attempting to squeeze the 92 into a 91 chassis. Mazda gave very little information stating only that the bulbs physical dimensions differed from the original..
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Thanks HCS for the nice comments.
I noticed that Mazda gave very little information about the physical dimension differences, and how to accommodate them
Luckily, I did have the broken CRM91 to take measurements and compare against a CRM92, plus I obviously could put a CRM92 in and measure the differences (i.e. discover what is different and why it is different). It doesn't only differ in length, but also in breadth along the length, and given the circular hole in the CRT mount was designed for the CRM91 breadth, it ends up sticking out above the mount by about 10mm too much and sticking out below the CRT mount by about a bit too.
Which means it hasn't enough clearance when the chassis is swung into the "presentation mode" as it hits the glass. Obviously fixing the 10mm sticking out there impacts on the deflection/focus coil mounts as the 10mm has to go somewhere.
I spent some time working out how to accommodate the extra differences, as I wanted to do this in a completely non-destructive way, without modifying any of the existing parts.
Also if I ever do get a CRM91, it is important to be able to put it back to the original.
I'll cover the work I did at the appropriate place, as I want to keep things in chronological order.