exxos's Atari, Amiga & retro forum

Hello,

From the schematics adressline 21 22 23 from CPU should be connected to the GLUE but what would happen if those lines werent connected? Do you think that would give a white screen? I have one 520STfm that gives white screen and when i measure between GLUE and CPU those adresslines arent connected.

/zChris

If the schematics say they should be connected, then if I were you I'd patch them back in and see if it fixes the issue.

For starters no ROM access will occur!

BW

@zChris the best bet is to consider that everything that's on the schematic is required for a working ST.

It isn't really the case but there is very few bits that don't really need connecting.

@zChris

I'm with @PhilC, If it's on the schematic it's required.

Whist there are variations depending on the specific version of ST schematic you have, the essential logic needed will always be there.

I presume you are using a multi-meter in continuity mode to test? Have you made sure that the contacts on the GLUE and GLUE socket are clean and not oxidised? A layer of oxidisation can be enough to prevent contact with the multi-meter probes, so always worth cleaning with IPA and De-Oxit or Electrolube (Servisol).

Also, I haven't at this point looked at the schematic to check, but if there are any components such as resistors etc in the path between the CPU and MMU, this will affect your results, and you should in those cases check each hop along the way for continuity.

As an aside, you don't need 12V to boot an ST, just 5V will do and if you have PSU concerns, it's best to run this from a bench power supply connected only to 5v to ensure a clean and stable 5V supply.

Thanks for your inputs.

What do you use to remove flux? I use this one https://www.electrokit.com/en/product/i ... ray-400ml/ but it makes everything sticky instead :(

zChris wrote: 06 Oct 2021 18:27 What do you use to remove flux?

Yep, isopropanol (also known as isopropyl alcohol, IPA, propan-2-ol). 90% concentration or higher for electronics.

You can't just spray it on and leave it -- it evaporates and leaves the flux behind. You need to get in with cotton buds or something similar that will soak up the dissolved mess it temporarily creates. Several times, probably, and using lots of buds!

BW