32-bit acorn hardware • Re: My A3000 is dead

The A3000 schemaics that are available are marked 0180,0000 so I assume its not one of the very first.

There's precious little differences, and they're all listed in the TRM.

I've removed the battery and repaired the area around it. The zero ohm resistors were falling apart and the ROM sockets and keyboard sockets were very green so I've replaced the ROM sockets and cleaned up the keyboard ones as best I can since they are becoming unobtaineum. I have tried making my own by cut and shut on smaller connectors but not confident enough in my work to put them in yet. There were also a couple of broken traces which I've fixed.
The PSU seems fine, chucking out about 5.2V so I tried firing it up ... and ... nothing, not even a beep.

I have a Postbox so hooked it up using IanJeffray's suggested connections but no joy, I just get a succession of READ statements with just one byte read.

Those aren't outputs. That's just POSTbox.

Do you have a scope? Have you done the address bus walk? Hold reset, and ARM toggle A<2> at 4Mhz, A<3>at 2Mhz and so on all the way up to A<21> Check this at all four ROMs and their links.

I assume the ROMs are RiscOS 2 as they are 28pin 831000s. Does the Postbox work with OS 2?

No. No POST in anything less than 2.01 which came with the A540. Get/make RISC OS 3 - and note you need to change the ROM link positions for the bigger parts.

I'd like to upgrade to OS 3.11 but reading "RISC OS 3 software upgrade fitting instructions" it says no hardware mods are required for an A3000 but that machines with cardboard covers over the PSU

"are not suitable for user upgrading. It is therefore essential that the upgrade be undertaken by a recommended Acorn Dealer or Service Agent".

Does anyone know what this means and what else has to be done to these early machines to upgrade to OS3?

That's FUD. ignore it.

I've checked power to the major chips and they seem fine at around 4.85V except for the ROMS which came in at about 2.4! That's not going to help.
Could some of the decoupling caps be bad?

That makes no sense - you'll see from the schematics that the ROMs go straight to the power plane. It's basically impossible that decoupling caps can have such an effect. I suggest you may be measuring the wrong pins.

IC28-IC31 regularly get damaged by battery rot, so make sure the address bus walk at the ROMs is working first, proving those latches.

Statistics: Posted by IanJeffray — Sun Apr 06, 2025 7:06 pm

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