exxos's Atari, Amiga & retro forum

I turn on the machine. ROM0 get fluctuations after i press and release the reset button. ROM1 and 2 does not get any fluctuations after i release the reset button.

What do you get on pin 6 ,10,11,12,13 of the CPU ?

exxos wrote: 18 Aug 2021 21:25 What do you get on pin 6 ,10,11,12,13 of the CPU ?

On pin 6 i have high. Then when i press and release reset there is some activity and then it stays high. Same behaviour on pin 10. Pin 11, 12, 13 is high and there is no changing when i press and release the reset button.

/zChris

Do you have a diagnostic cartridge ? You may get more clues over serial link.

No i dont. I'll see if i can get a hold of one.

/zChris

I also suggest cleaning the ROM chip & CPU with IPA and maybe use a PLCC CPU instead.

Some weeks ago i sent it of to @DoG that did some checks on it. He used a IDE which has its own ROM and it did not boot on that aswell. He also used a diagnostic card and did not get any serial output.

/zChris

I checked it a couple of weeks ago but I didn't do much since I don't have an oscilloscope.

I have tested all chips that was in socket on another computer (not the glue and mmu since they are smd) and all are working (at least to the degree that they are booting it). SIMM was also tested in another computer. Tested with both plcc and dip 68000. I think I tested that all the chip had 5V.

Read the ROM and checked it working in another computer. I'm unsure which roms was on it? I think it was some patched v1.04 UK (by P.Putnik) and TOS v2.06 swe. I have tested with another rom I had but made no difference. I also tested with IDE v1.1 R1C since it it had rom onboard but it didn't work either. BUT I'm a bit unsure if I actually removed the rom on the H4 during this test now that I think about it.

Both smd (glue and mmu) was reflowed with solder and checked if pins was stuck to board. All plcc was cleaned with IPA, both socket and chip.

I have tested to use diag cart and a serial cable (9600,8N1) to another computer but it doesn't run at all.

I think I would be tempted to remove the smt glue and mmu in case one has failed.

However, the mmu can usually be checked if there is activity on the MAD lines as these should pulse regardless of the cpu being halted or not.

The chips are normally pretty unkillable. Though removing it might cause damage... then having to solder the PLCC which may cause more trouble.