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Early HP35 again: Let's play "spot the difference"
11-18-2016, 04:13 PM (This post was last modified: 11-18-2016 07:30 PM by Harald.)
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Early HP35 again: Let's play "spot the difference"
This is a display PCB as I know it:
[Image: key17ls6e.jpg]

And this one is an early one that surprises me:
[Image: key22xsfi.jpg]


Can you spot the difference?
Ok, yes, the left one is missing a anode drive, I know Smile.
But it is also missing an inductor for the clock generator!
It has 380pF from pin 9 of the anode driver to ground.
Ususally there is a 150pF in series with 330┬ÁH from pin 9 to ground.
However the clock is working fine.

Does anyone know if the anode driver initially had a different design?

Cheers,
Harald
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Early HP35 again: Let's play "spot the difference" - Harald - 11-18-2016 04:13 PM



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