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.
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.
520STM vertical lines yellow and grey, no hi res
-
- Posts: 114
- Joined: Fri Mar 26, 2021 2:46 pm
- rubber_jonnie
- Site Admin
- Posts: 10605
- Joined: Thu Aug 17, 2017 7:40 pm
- Location: Essex
- Contact:
Re: 520STM vertical lines yellow and grey, no hi res
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.
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.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Re: 520STM vertical lines yellow and grey, no hi res
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.russellnash wrote: ↑Wed Apr 28, 2021 2:52 pm ...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...
What motherboard revision did you have?
- rubber_jonnie
- Site Admin
- Posts: 10605
- Joined: Thu Aug 17, 2017 7:40 pm
- Location: Essex
- Contact:
Re: 520STM vertical lines yellow and grey, no hi res
I agree that's a good place to start.DoG wrote: ↑Wed Apr 28, 2021 4:53 pm Or change the ram chips that are hot to touch first of all.
What motherboard revision did you have?
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
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
-
- Posts: 114
- Joined: Fri Mar 26, 2021 2:46 pm
Re: 520STM vertical lines yellow and grey, no hi res
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. When I next update the thread I will try to post a photo. Thanks.
-
- Posts: 114
- Joined: Fri Mar 26, 2021 2:46 pm
Re: 520STM vertical lines yellow and grey, no hi res
Yes, that is the right one.