exxos's Atari, Amiga & retro forum

Not sure if it was a side effect of the move, but I recently pulled out one of my STEs to see if I could help somebody on the forum, only to have the machine die on me, just giving a white screen on boot.

Annoyingly I can't boot from the diag cart either.

The problem seems to come from the dual TOS switcher, but may go deeper than that.

So far, the current draw is about normal and compares to my working machine well, and I'm powering via 5v from a bench PSU, since 12V in not necessary to boot, and I can keep an eye on power.

An initial quick look at this, and comparison to my working machine shows no activity on the switcher address/data lines, or on the /CE /OE lines either, bar an initial pulse when the machine is powered on.

The good machine shows typical TTL type activity on all of the above.

I have tested the ROM itself in the good machine and know it's not a problem, so that's something in itself. I think it's time to look at the schematic and firstly see if I can see what's wrong with the /CE signal.

I'm worried that one of the SMD ICs has died, but let's follow the evidence and see where it leads.

Did you solder in or use sockets ? As the sockets are normally to blame ordinarily . I end up reseating the ROM board like 20 times sometimes before it works.'I have the same problem with STFM boards. Only have to look at the things ...

exxos wrote: 26 Nov 2021 01:32 Did you solder in or use sockets ? As the sockets are normally to blame ordinarily . I end up reseating the ROM board like 20 times sometimes before it works.'I have the same problem with STFM boards. Only have to look at the things ...

I used sockets since they were already there, and it has worked for ages, and my 2nd one is the same, and works fine. It stopped working when I unplugged the switcher as it goes, so sockets are not ruled out.

What I may do is get some turned pin socket strips and replace the sockets with those as the two 6850s are also in sockets (looks like factory fitted sockets too, I didn't do it) so they are in the way of soldering it onto the board straight and level.

At least then the connection will be decent, and a round pin in a round hole, rather than a round pin in a flappy double wipe hole!!

Actually I disagree. Those round pin sockets actually potentially have less contact as there's no active force pushing the contacts together, unlike the spring mechanism of the wiper sockets. With the round pins you're holing that the tolerances are poor enough that the surfaces are forced together.

The only sort of guaranteed connection with round pin sockets with round pin headers is at the top of the pin/whole where the cone and anti-cone meet.

I've had a few cases where I've had to replace the round pins as they'd become too smooth for a good contact in a turned pin socket.

stephen_usher wrote: 26 Nov 2021 09:45 Actually I disagree. Those round pin sockets actually potentially have less contact as there's no active force pushing the contacts together, unlike the spring mechanism of the wiper sockets. With the round pins you're holing that the tolerances are poor enough that the surfaces are forced together.

The only sort of guaranteed connection with round pin sockets with round pin headers is at the top of the pin/whole where the cone and anti-cone meet.

I've had a few cases where I've had to replace the round pins as they'd become too smooth for a good contact in a turned pin socket.

That's a fair comment..

The double wipe sockets on round pins don't really work. True they push up against the ROUND pins, the contact area is tiny hence contact problems. Round pin square hole...

I've been though all this many times. If you use a quality turned pin socket, again I always recommend 3M the fit is tight and contact area is a lot more, hence better connection.

Arrrgh, contrasting opinions!!

I will have a think on it.

3M wipe sockets will hold better than others as the metal is stronger.

But on all my boards, every one which has wipe sockets is iffy. Even the sockets I've changed for new wipe sockets don't last. The only STE which has been reliable is the one with turned pin sockets. If you use a cheap socket you will still have contact problems as the tollerences are bad.

If turned pin stuff was that bad, why would it even exist ? Wipe sockets are better for ICs as you have 2 flat surfaces pushing in both sides of a flat area. When you stick a round pin in a socket, you have a round contact point on the outermost edge only. Draw a circle on some paper and draw 2 line each side then see how it just doesn't even look right.

Though having dealt with all this stuff for knocking 30 years and fitting stuff to 100s of machines and tested thousands of ROM boards over the years, I know what works in the real world.

OTOH just solder it in and don't bother with sockets at all.

exxos wrote: 26 Nov 2021 11:20 3M wipe sockets will hold better than others as the metal is stronger.

But on all my boards, every one which has wipe sockets is iffy. Even the sockets I've changed for new wipe sockets don't last. The only STE which has been reliable is the one with turned pin sockets. If you use a cheap socket you will still have contact problems as the tollerences are bad.

If turned pin stuff was that bad, why would it even exist ? Wipe sockets are better for ICs as you have 2 flat surfaces pushing in both sides of a flat area. When you stick a round pin in a socket, you have a round contact point on the outermost edge only. Draw a circle on some paper and draw 2 line each side then see how it just doesn't even look right.

Though having dealt with all this stuff for knocking 30 years and fitting stuff to 100s of machines and tested thousands of ROM boards over the years, I know what works in the real world.

OTOH just solder it in and don't bother with sockets at all.

I think, all things considered, I will remove the old double wipe sockets that I left there for convenience sake. I have some suitable turned pin stuff I can use, so I will do that.

rubber_jonnie wrote: 26 Nov 2021 11:41 I think, all things considered, I will remove the old double wipe sockets that I left there for convenience sake. I have some suitable turned pin stuff I can use, so I will do that.

The problem is what brand are they.. If you have cheap sockets in particular ones sold by rapid etc, you likely will have contact problems anyway.

This is why I only went for branded sockets on the H5 and only recommend 3M. because pretty much every other socket has been garbage which I have tested over the years.. Of course you probably remember the PLCC nightmare etc.