exxos's Atari, Amiga & retro forum

The C104 470 microF and the L29 Inductor I had already changed from my STF donor board in the hope it might help.
Yes I find it no fun with a multimeter, but I have enjoyed the learning experience. I cannot detect the high low transition, assuming it is there. I will get a logic probe. I am very fond of STM's because of the lower profile and Mouse port is not in a stupid place. I assume there will never be a new board from Exxos that will fit in the smaller case., so will have to fix em.
I have no idea what an oscilloscope costs but my new Atari ST hobby had had me gripped for a few months now, we will see. Yes I checked the continuity through the whole set of rams chips, it made me dizzy at first following the schematic. :shock:
The layout I certainly found difficult to understand at first.
As far as what Frank said, that is what I did first because it sounds unlikely having 8 dead lines, but I can't find anything, but I haven't changed the chips. Anyway, part of the ram is damaged regardless of what other things are not right. I follow every suggestion that I receive.
Thanks.

I have a 520ST, so like yours but no modulator, and had a lot of memory problems.

In the end I just removed all of the chips and fitted an exxos 4MB MMU/Shifter RAM adaptor and it runs just lovely.The problem with mine was damaged tracks due to a very old piggyback RAM expansion.

You can do an awful lot with a multimeter, but the minute you try to get TTL levels it gets harder.

A logic probe is a very cheap middle ground between a multimeter and a 'scope. My basic scope was £150 and I use it a lot for repairs, but I didn't get one until I was doing a lot of repairs.

It takes time to build your repository of knowledge, and I started off with just a multimeter and a soldering iron.

The more you do, the more you enjoy it, the more tools you want to help you out.

russellnash wrote: 28 Apr 2021 14:52 ...As far as what Frank said, that is what I did first because it sounds unlikely having 8 dead lines, but I cant find anything, but I haven't changed the chips...

Just desolder the 74LS373 and/or the 74LS244 and solder in a new one. Or just sockets to see if test with diag cart does anything. I don't think it is any tracks on the board that is broken. Start by changing the two mentioned chip previously first (U23/U27). Then, check with diagcart again. Then start changing ram chips if needed. Or change the ram chips that are hot to touch first of all.

What motherboard revision did you have?

DoG wrote: 28 Apr 2021 16:53 Or change the ram chips that are hot to touch first of all.

What motherboard revision did you have?

I agree that's a good place to start.

One thing I would add is that a picture speaks a thousand words and this thread is very short of them.

If you can add some of things like the board etc it would help us to help you :)

The board is revision H. I will desolder the chips when my braid arrives.I know people take photos all the time, mostly with their phones. I do not have such a phone, which I think is a wonderful thing. I borrowed a camera to take photos for another thread and before I was finished all the photos disappeared from the card and I got to spend the rest of the day trying to recover the many photos on it. :D When I next update the thread I will try to post a photo. Thanks.

So C070243 rev.H right?

Yes, that is the right one.