emusonacid! legacy

hi,
i'm new on here, i have just had a look on all the topics but i cant see one relating to my current problem.
somtimes in fact most times when i power up it will not boot up correctly and comes up with a fatal rom error message on the screen with loads of different map addresses,
somtimes it loads up fine, but then comes up with the message at any point from a few minuets after power up to a few hours after power up
other times it crashes at the eos splash screen & sometimes it crashes before it gets to checking floppy drive,
it seems quite randon in nature, tonight it took 16 power up's before it started corectly, that was 6 hours ago and so far it hasnt crashed.
it is running eos 3.0b, it's has 64mb ram, imb flash, 1mb cpu ram,

i have another e64 that runs fine, it has the same specs as above,
i have swapped the 64mb mem over still the same, i have swapped the boot rom over, one isv06 one is v07, but still the same fault,
i havent swapped anything else over yet

has anybody got any ideas or could it be a board fault, hope not as it will just end up as spares for my other machine,
i havent swapped the power supply over yet that may be worh a go, after all the machines are over 25 years old, 5 years older than my toyota lucida, and that still runs great.

any help will be realy appreciated

thanks

I suspect the power supply to be unstable.
If so, it can be fixed by a radio technician.

BTW:
The e64 has been built between 1995 and 1996. So your e64s are not that old.

hi

many thanks for your reply, and appologies for my cofusion with the age of the e64s i meant 15+ years old, my only excuse is it was the early hours of the morning and i was tired.
i relised my mistake after i had sent the post,but for some reason i have not been able to get back into the web site until tonight, i think my isp had a routing problem.

anyway since then i have swapped over the power supplies and the problem is still there, one thing i did notice by accident was that when the e64 started up and was running great, if i tapped on the front anywhere i could get the fatal error message to come up, so i decided to swap the complete front panels over,
i thought great the problem was solved, so after rebuilding the machine back up, i switched on, the machine was just going through the start up splash screen then it again locked up and i got the fatal error message on the screen, so my next step is to take the main board out and try to look for any bad solder joints & hairline cracks in the print, if all else fails i shall look out for another machine and keep this one for spares,
i can still read all the data on the hard drive with my other e64 even if the first machine has crashed as soon as it is switched on,( both machines linked via cd rom) so it's not all bad news.

I see an issue in the changing time until the error occures.

It makes it hard to isolate the error, even because you checked the mainboard with Sample Ram, Control Face Plate and Power Supply from a working machine. Therefore it seems obvious that the error has to be on your mainboard.
Your assumption that there is a bad solder joint might be right.

The error can be related to a defect memory-address in the CPU-RAM, so that every time this memory address is accessed by chance the
system crashes or to a bad circuit path on the mainboard.

I think that you need a service manual, an oscilloscope and all available datasheets for the common components to isolate the error.
Maybe you should check if there is a service for the EMU products available that has the technical documentation available.
This is an issue for an experienced technican.

hi thanks again for your input and help,
i have several scopes,and a host of electronic test gear, i am an electrician by trade but over the years i have got more and more involved in the electronics & repair side of things,
so i guess i am realy looking now for as much information as i can find regarding corect circuit voltages & waveforms etc, and some free time to fully check it out

i was hoping for an easy fix, i thought just maybe it's a common fault and someone could point me right to it but i guess not, just my luck.
intermitent board faults or address mapping faults are never the easyest to locate

thanks again for all your help
if i get it sorted i will post back on here, it may be help to others.