prime

The problem with the 130XE is deffo the EMMU, removing it and wiring A14->FA14, A15->FA15 and /CAS->/CASMAN (and removing the second bank of 64K) produces a machine that boots to basic. Cheers. Phill.

Right I got the 800XL going, turned out to be a problem with the OS ROM, though oddly the OS ROM would read correctly in my Wellon device programmer Anyway it's been replaced with a 27256 and the machine is working now. Cheers. Phill.

Hi all, I'm attempting to repair a friend's 800XL, and 130XE The 800XL symptoms are very dull red screen when switched on, and no other activity. I've desoldered and tested (in my 800XL) all the major chips except the PIA, I'll check that too but I need to socket the PIA in my machine first. These all work fine in my machine. Scoping the Data and address lines I'm getting activity which seems to indicate that the CPU is running, I also get activity on the ROM chip selects which suggests that the decoding logic is OK. I'm also getting valid activity on the 4164s, /RAS and /CAS are strobing as I would expect, I have tried a couple of sets of good RAM chips, so I'm pretty sure these are OK too. I get the same results if I plug in a known good cart. Does anyone have any idea what could be the problem, I'm probably going to try putting the chips from my fiend's machine in mine to see if they run OK in there, as that should indicate that the fault lies elsewhere. Also can a Motorola 6821 be used as a replacement for the 6520 if needed as the chips have the same pinout and functionality ? The 130XE, I think the problem is the MMU, I'm not getting a valid /CAS strobe on either bank of RAM, however the /CAS into the MMU on pin 6 is ok, but /CASMAN and /CASBNK don't toggle at all. I have the facility to program a PAL so I'm going to try replacing the MMU with that and an LS95. I'm finding it hard to source these however, is there a suitable replacement that is known to work, even if it needs a little patch board Cheers. Phill.

Hi all, Does the source code for the SD2SIO firmware exist anywhere for download, I'd like to try using the hardware SPI on the AVR to communicate with the SD card. Cheers. Phill.