Hi All, With thanks to exxos for helping me source the parts I now have working units built, cleaned and assembled. Unfortunately my costs have gone up so I'm going to put the price up a little. 27C400 USB programmable EPROM emulator/kickswitcher. Photo0948.jpg Quantity Price each 1 £22 2+ £21 5+ £2...

I finished soldering the batch today and programmed the firmware. All good... one short under a CPLD cleared but everything else ok. I'll clean them tomorrow and then they are ready to ship :D The low profile pins I bought have a bigger diameter on the side that would go into the socket compared to ...

Digikey parts arrived yesterday and Mouser parts arrived today. I built up one panel to check everything seems OK and so far so good. I paid more for parts than I'd hoped because of the global chip shortage. The CPLDs for example were out of stock so I bought the next speed grade up which are 30% mo...

rubber_jonnie wrote: ↑Mon Apr 26, 2021 11:39 am Are there any other ULAs I should know about?

Nope. Everything else is discrete logic and off the shelf ICs.

The serial/cassette ULA (SERPROC IC7) never had heatsink & never needed one. Only the Ferranti made main ULA (VIDPROC IC6).

The original Ferranti ones need a heatsink. The later VIA ULAs do not.

I have now found a troubleshooting book that describes my problem exactly, and goes into more detail, so I will follow that. It's also possible one of the chips is dead as it is supposed to have a heatsink and it's missing. Video chip I think. I don't think that should stop it booting though. The U...

If a B doesn't boot then you should get the low drone from the sound chip AKA "long beep". If you don't get that then there is either something wrong with the sound chip/amp or perhaps you are missing clocks - they all come from the ULA derived from the 16MHz crystal circuit. Power, clocks...

OMG! Look what Parcelforce just delivered.


All credit to exxos for finding the supplier. It was a bit of a saga ordering with some supplier hurdles and confusion!

If interfacing though a PLD (or CPLD) you can route through a spare pin to get extra delay. e.g. an ATF22V10 pinnode is ~10ns IIRC