520STM vertical lines yellow and grey, no hi res

[russellnash]

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.

[rubber_jonnie]

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.

[DoG]

...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?

[rubber_jonnie]

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 :)

[russellnash]

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.

[DoG]

So C070243 rev.H right?

[russellnash]

Yes, that is the right one.