The elusive Indextron

[jhalphen]

Hi Again,

To further the topic of the beam-index micro-crts, here are some pictures given to me in 2004, courtesy of Charles Osborne (thanks!) who sometimes posts here.

The CRT is a Hitachi H-6289 single-beam "Indextron" CRT and at 1.5" screen diagonal it is truely a technology wonder.

Hitachi developped the CRT to bring color viewfinders to cameras and camcorders at a time when shadow-mask CRTs were deemed too dim and power-hungry to be acceptable in equipment running off batteries.

The "Wizard of Oz" pictures is courtesy of John Folsom Jr, Thanks! John.

The last document is from RCA cameras CC-030 and CKC-021 Theory of Operation section in the services manuals and describes the screen structure of the H6289 CRT.

One nuisance about repackaging the color viewfinders for use as micro-NTSC monitors is that there are 2 photocells for the indexing system, one sensitive to UV and the other to green (aside from the Green phosphor there is also a Green Index Phosphor) and both must face the screen and be shielded from outside light or the index sync goes haywire and the screen reverts to monochrome.

Another info learned from experience with these viewfinders is that obtained a constantly correct Red is near impossible. Depending on color content, Reds vary from having a purple tone to a dull brown, so flesh tones remind the user of the early days of NTSC - "stop twidling that Tint control!"

This is not the H6289's fault, i suspect some cost-cutting was done in the complex matrix processing required to produce the RGB/Y signals to keep component count and cost acceptable.

OT:
The Sharp 3.5" 3LS36 TV mentioned in this thread (sold in pink, black, white) uses an ordinary shadow-mask color CRT, a 100HB22.

Best Regards

jhalphen
Paris/France