The Sinclair QL Forum

Just to rule out the switch itself (seemed ok though) I made direct wired connections instead but still the same problem with Minerva (JS still works though)

Have decided to go for 3rd (& last) time lucky but have run out of 74ls133 so have to wait for them to arrive later in the week

In the meantime I’m putting the other ICs (eeprom, gal, clock) I’m going to use into the socketed version of the board to at least prove those 3 work ok before I use them in the final board

Can’t get the socketed board to work with any of the spare chips I have left

So this is the end of the road for my JS/Minerva I2C/RTC switcher

I still have the working socketless Minerva MK2 so hasn’t been a complete waste of time, but can’t use it in my main in use QL as I need JS in that

Will have to drop any ideas of I2C stuff and get a ROM switcher sometime

Many thanks
Tony

Jackpot…

I realised that there was something I hadn’t tried with the socketless version where JS was working but Minerva hung with green lines

I fitted the battery and now it works!

Next up will be to test the RTC/i2c are working ok and then I can fit it permanently in my main QL

This is the Switchable ROM waiting to be fitted (cabling is Switch for JS/Minerva 1.98, Battery & I2C 'D' harness to match my BBC B cabling so that all I2C stuff can just be swapped between them)


And the underside showing the 74LS133 installed upside down on the bottom of the PCB, along with the 2 diodes (1 prevents the board trying to charge the non-chargeable battery), so that it will all fit inside the QL under the keyboard


RTC is all tested, but can't test I2C until it's actually in a QL internal ROM socket

Have now fitted it in my main QL and all working (not tried I2c yet though)

This picture was taken before I moved it to the left hand ROM socket

(Don't look too closely at any visible soldering)

Thanks for all the advise

Nice work t0nyt. Great to see you persisted with your efforts. And thanks for the picture.

dilwyn wrote: Tue Aug 19, 2025 12:11 pm Nice work t0nyt. Great to see you persisted with your efforts. And thanks for the picture.

Thanks Dilwyn

And have now confirmed I2C is working ok too