exxos's Atari, Amiga & retro forum

exxos wrote: 22 Jun 2025 21:42 So changing chips id consider a last resort. But there isn't much else to look into at this point.

Well don't do anything in a hurry, you might get some other ideas first. Re-read Uwe's text 10 times first :)


If you do end up with new chip(s), bismuth solder can help get the chips off without heating the board too much with air and lifting pads. Apply with an iron and remove with air then clean the pads very very carefully with lots of flux and wick.

I'm very careful with q-tips/cotton buds when cleaning around pads - the threads from these are not tidy, can catch on pads and rip them.

@dml Yeah I got some low temp melt solder paste. Its what I use to change PLDs on the STE536 etc. So it shouldn't be much difference.

The Intel chip simple(ish) to get at.. The other chip has the IDE & PCI sockets in the way.

My other thought is to maybe try tracing D0 and cutting it in various places to see at what point the fault vanishes.. but as the tracks are so close together.. unless the track is easy to get at.. not so simple either.

I suppose this makes me feel a "little" better.

https://www.ebay.com/itm/176309316914


Not sure what the heck the other chip is yet..

https://www.ebay.com/itm/360226102872


Still no idea what it is :lol: Maybe some PCI / IO thing.

Testing D2 as it measures 1R to GND.

My DMM measures 2.0R (it shows 1.9 in the image but its more stable on 2.0)


2.90R ( basically 0.9R real)

Bodged a wire in a D2 track.


3.7R (1.7R real)

I scratched a bit of the track to get a connection there for D2.


So basically 1R more on the Intel chip. Which leads me to thinking the big chip next to the PSU connector is the one actually causing the short.

exxos wrote: 22 Jun 2025 19:28
It starts heating up from power up.

27c cold
30 seconds 32c
60 seconds 37c
1.5mins 40c
2mins 43c

hotspot 53c neat the simm sockets.

Based on the info here CPU Temps I'd say those temps are relatively normal for a CPU running with no heatsink installed.

I do have questions though. Firstly have you checked the power rails for shorts? Either caps or other components.

I'd be doing that first on an older board like this, and if not shorted, what does power look like around the board.

Secondly, is the clock present where it should be? Well that is if you even have a suitable schematic...

I know you've probably done all this but I always like to check...

rubber_jonnie wrote: 22 Jun 2025 22:59 Based on the info here CPU Temps I'd say those temps are relatively normal for a CPU running with no heatsink installed.

:thumbup:

I do have questions though. Firstly have you checked the power rails for shorts? Either caps or other components.
I'd be doing that first on an older board like this, and if not shorted, what does power look like around the board.
Secondly, is the clock present where it should be? Well that is if you even have a suitable schematic...

There's no schematic that I know of. Uwe did send me a bunch of PLD related stuff but it seems to be stuff on how the PLD logic all works. It's rather indepth.

The power rail I did measure at about 180R which I calculated as 27mA. Nothing gets warm really.

The clock I think I verified 20 years ago. But as data and address bus is changing then the clock is likely good. BUT, the logic is in control at this point. No idea what clock that uses. Though as the address and D0 is changing then that's a good sign.

At the moment the boot ROM isn't doing much. Something is shorting its databus out. I can only find 2 big chips its connected to. So I'll have to try and isolate D2 pin on that chip tomorrow and see if the short vanishes. If it does, I've got a big chip to change where I'll have to take out a PCI slot for starters :roll:

Some time ago I made a shorty device, but I cannot find the schema, it was with a speaker.

This looks about the same but then with a display:
https://www.eevblog.com/forum/testgear/ ... -display)/

Maximilian wrote: 23 Jun 2025 00:30 Some time ago I made a shorty device, but I cannot find the schema, it was with a speaker.

This looks about the same but then with a display:
https://www.eevblog.com/forum/testgear/ ... -display)/

Interesting..

I use this normally https://www.exxosforum.co.uk/atari/last ... /index.htm

exxos wrote: 22 Jun 2025 23:36 There's no schematic that I know of. Uwe did send me a bunch of PLD related stuff but it seems to be stuff on how the PLD logic all works. It's rather indepth.

The Milan schematics are on dev-docs.

Steve