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Old 21st Mar 2021, 12:01 am   #181
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: I found it! A very sorry looking MK14.

That mod is for the addition of the single-step feature (as you have said) because the revised / new OS has the support firmware for it built in. The memory hole mod may coincidentally have needed similar mods. If you don't fit the SS hardware but you do fit the 'new' OS, you need to take SENSE-A to 0V otherwise programs will not run.

Right back at the beginning of Slothie's epic 'Schematic Revisions' thread I posted the instructions SOC sent to me when I enquired about how to add extra memory - they don't explain how to add extra memory but they do explain how to free up the memory hole. Not sure if it has also been posted in this thread, if so I could not find it.

https://vintage-radio.net/forum/show...13&postcount=6

Problem is they only explain it from a practical / hardware level (cut this, join that) rather than at circuit diagram level, so I can't say whether the IC pin numbers referred to are correct for an issue II PCB. I actually never did the mod, instead, I removed the VDU which was chewing up nearly all of my memory and didn't use it again until Slothie's issue VI PCB rode to its rescue.

Agghh, just noticed Tim reposted it a few moments ago.
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