Mitsubishi linear tracking turntable repair

[Shaunh]

i have a 1981 Misubishi linear tracking turntable with photodiodes with code SP254FS. One is damaged and i am trying to source a modern equivalent. Any help would be greatly appreciated.
Thanks
Shaun

 

[rjenkinsgb]

What type of package are they in?

TO18 with a glass end, transparent TO92, some surface mount type etc..

 

[Shaunh]

Hi RJ
They are surface mounted square cells about 2mm by 2mm
I can send a photo if that helps?
Thanks
Shaun

 

[rjenkinsgb]

I'd expect any general silicon photodiode to work reasonably; it's just finding the one with the largest area, that will fit in the appropriate location.

For an infra-red source, these look pretty good:
https://uk.rs-online.com/web/p/photodiodes/7103844/

Or these, for visible light:
https://uk.rs-online.com/web/p/photodiodes/7103847/

Although a lot of the specs for those assume use in reverse leakage mode, they do give an open-circuit voltage figure, which shows they can be used in "photocell" mode which appears to be what that circuit may need.

They are cheap enough to have a go, anyway.

My only other thought is that if they are for the arm tracking system rather than one of the general detectors, replace both with the identical part to maintain the "balance" of the servo system.