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Diagnosis cart and PC connection
Posted: 17 Jul 2025 10:15
by chakobsa
I have a rev c 520STFM which was upgraded to 1 meg about 30 odd years ago. Just pulled it out of the loft and switched it on (replaced PSU) and it shows Black screen with White border. Reset switch works. From what I have read this indicates ram issues. Obviously I have 32 of the little sods!
I have the diag cart via Sidecartridge and want to try connecting it up to my pc via serial. I know exxos sells the cable but wanted to know what software people use these days on the PC side to read the output from the ST (hopefully it will have an output!). I currently use Win 10. Thanks.
Re: Diagnosis cart and PC connection
Posted: 17 Jul 2025 10:19
by rubber_jonnie
chakobsa wrote: 17 Jul 2025 10:15
I have a rev c 520STFM which was upgraded to 1 meg about 30 odd years ago. Just pulled it out of the loft and switched it on (replaced PSU) and it shows Black screen with White border. Reset switch works. From what I have read this indicates ram issues. Obviously I have 32 of the little sods!
I have the diag cart via Sidecartridge and want to try connecting it up to my pc via serial. I know exxos sells the cable but wanted to know what software people use these days on the PC side to read the output from the ST (hopefully it will have an output!). I currently use Win 10. Thanks.
All you need is a terminal on the PC side, I use Teraterm peronally, but Putty should also work.
Re: Diagnosis cart and PC connection
Posted: 17 Jul 2025 10:28
by chakobsa
Brilliant thanks. Just noticed I will probably need to get a serial to USB lead.
Re: Diagnosis cart and PC connection
Posted: 17 Jul 2025 15:48
by jwd
remember to use a null modem cable (cross over cable) not just a normal serial cable for ST <> PC
Re: Diagnosis cart and PC connection
Posted: 17 Jul 2025 16:11
by olivier.jan
chakobsa wrote: 17 Jul 2025 10:28
Brilliant thanks. Just noticed I will probably need to get a serial to USB lead.
Be careful to get a USB to RS-232 and not USB to Serial. ST Serial port is RS-232 which uses +12v/-12v. The cheap USB to serial are only using 0-5v, if you connect one to RS-232 you will most likely fry it.
Re: Diagnosis cart and PC connection
Posted: 17 Jul 2025 22:25
by chakobsa
That is really useful thanks. Just what I needed to know.
Re: Diagnosis cart and PC connection
Posted: 18 Jul 2025 10:17
by chakobsa
I've not been able to find a USB to Null modem USB232 to DB25F. Found some with DB25M.
My PC motherboard has a COM1 header pins so I'm going to try and use that unless anyone has a link to a USB version. Annoyingly I had all the header pc backplates when they were common but now can't find them. I can just use the normal DB25F to DB9F lead.
Thanks again.
Re: Diagnosis cart and PC connection
Posted: 18 Jul 2025 11:10
by Steve
It's strange how something which was working can go into a loft for years, then come down not working. It makes me think environmental factors and whether there are ram-chips in sockets, and if there are, then that's usually a very easy fix.
Re: Diagnosis cart and PC connection
Posted: 18 Jul 2025 11:21
by rubber_jonnie
Black screen with a white boarder usually means a RAM issue.
I'd suggest you have a look at the GLUE, MMU etc, remove them from the sockets and give them a spritz with contact cleaner and reassemble.
Also, it may be necessary to do this:
PLCC contact tweaking., but try just cleaning first.
Re: Diagnosis cart and PC connection
Posted: 18 Jul 2025 11:47
by chakobsa
All the ram chips are soldered. I added the extra 512Kb myself so long ago. I was very poor with a soldering iron then and had to add a few bodge wires but it worked 100% until it went into the loft.
I'm just getting back into the ST. I have serval but this machine is very special to me as it was my 1st ST. case and keys already cleaned and magic of retrobright applied.
I will pull and clean all the ics in sockets shortly.