Problem after installing minerva

[Fred de Boer]

After installing Minerva the QL didn’t boot anymore, before the selection F1/F2 it halted and showed big black and white horizontal stripes, 9 black and 8 white and after inserting the JM ROMs again it is still the same, see attachment.
Does anybody have an idea whets wrong?

Thanks Fred

[belg4rion67]

I think a ram fault… even if I well remember the minerva rom test the ram and display location of bad memory, but in this case probably the bad ram is the video ram

[janbredenbeek]

After installing Minerva the QL didn’t boot anymore, before the selection F1/F2 it halted and showed big black and white horizontal stripes, 9 black and 8 white and after inserting the JM ROMs again it is still the same, see attachment.
Does anybody have an idea whets wrong?

How did you install Minerva exactly? The original Minerva is on a PCB with extra chip for the address decoding; you cannot just replace the Sinclair ROMs with EPROMs.

The stripes on the screen look like a ZX8301 failure, I hope you haven't blown it Do they appear immediately after switch-on or can you see the tweed pattern before?

[Fred de Boer]

I can’t see anything before

[Chris_68]

Did it boot normally before you inserted Minerva? If so I would go back and test with original ROM.

Have you bought the Minerva or built your own?

[Fred de Boer]

I bought the Rom and when it didn’t work I placed the old roms back but the result is the same, almost directly after switching on the strpes.

[martyn_hill]

Halo Fred!

From what you describe, either something was 'disturbed' when removing/replacing/switching back the two ROMs, the legs weren't seated correctly in their sockets or, (hopefully not), the 8301 ULA has died coincidentally with your upgrade attempt.

Unlikely to be a DRAM failure, though the Bus Transceiver IC ('245) or either of the 2 Address line multiplexers (2x '257) might have popped.

What that striped display indicates is that the ROM is not being read to run the boot-up code, so the default ULA pattern stays in view. Usually before you even see the first default frame displayed, the ROM routine to test the DRAM has updated the contents of the video RAM with what we know as the 'tweed' pattern...

Out of interest, when you bought the Minerva EPROM, was it mounted on its small PCB/daughter board, or just a lone EEPROM IC?

Also, what version QL motherboard (Iss 5, or Iss 6/7) do you have?

It's all fixable, but we'd need to dig a little deeper to know how best to do so...

You might start by posting a photo of the original ROMs and then with the Minerva daughter board fitted.

[Chris_68]

Hello,

Follow the advice from Martin, I had a similar issue when I replace my CPU. Proved to be the logic circuitry so upload photos. Could be a bad soldering joint underneath the pcb.

I’m not sure if you will get this behaviour with the jumper on the Minerva pcb wrong but make sure you have it set in one position.

[Fred de Boer]

I toke out the roms again and cleaned the connectors and we are one step further, we now get the start-up screen but without the text in it and no reactions on the keyboard
The board is an issue 6 and the pics are attached

Fred

[Chris_68]

Hi

Shouldn't the Rom ICs be the other way around?
Edit, they are pointing in the right direction but the one marked 23356 should be in top position and vice versa, or?