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Old 7th Sep 2020, 10:47 am   #33
Buzby123
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Join Date: Oct 2011
Location: Culcheth, Cheshire, UK.
Posts: 637
Default Re: I found it !. A very sorry looking MK14

Hi,

The display driver looks like it uses a ULN2007 darlington array for the segments, and some kind of 1-transistor circuit for the anodes. The darlington has a 150R resistor array to the segments, that's not going to help !.

So it looks like I just need to change the resistor array for a start, and maybe replace the darlington with a MOSFET equivalent. Neither of these changes would need rewiring, just replace socketed chips. I'll investigate this later, I've got bigger fish fry at the moment.

Some of the 8 IO switches are a bit dodgy, I remember this from way back. I'm hoping I've still got a few spares, if not I'll have to replace them with a modern equivalent. I don't really want to do this, as I can't find any with the same toggle design. Those perfectly cylindrical covers are so 70's.

Anyway, I'm still working on replacing dead BC109s, all the while cursing my younger self for building such a servicing-unfriendly machine.

Cheers,

Buzby
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