My OSI 610 build - Expansion for the OSI 600

[rubber_jonnie]

Seems like just cutting the WE track and wire to vcc would likely solve the issue then?

Very likely, yes.

I'll wait until my replacement ROMs arrive and make a decision on what I'll do. Tying it to 5v won't hurt it for other ROM types, so probably the best option.

[rubber_jonnie]

OK, so interestingly, my 600D is a Klyball replica and pin 21 is actually already tied to 5V and not GND.

As it goes the original build schematics don't show pin 21 connected to anything, but the service manual shows it connected to GND.

One in the eye for consistency...

It's working currently with a 27C16, which is positive.

[rubber_jonnie]

Sitting here on 7 iterations of the RAM test just fine:

IMG20250721092751.jpg

Will leave it running for now.

I do have more EPROMs on the way, I'm not convinced the 27C16 is good, but it does at least work.

[stephen_usher]

:dualthumbup:

[rubber_jonnie]

:dualthumbup:

It's now completed about 25 test cycles of the RAM with no problems, so I have switched it over to a game to let it run and see how it behaves.

Fingers crossed I'm out of the woods now and can get back to looking at the 5.25" floppies again and to make some more 'real' disks.

[stephen_usher]

Well, the system shouldn't be actively trying to wipe its ROMs now. :-)

[rubber_jonnie]

Well, the system shouldn't be actively trying to wipe its ROMs now. :-)

Fingers crossed!

It'll have a much harder job with the 27C16 :) And it has a label over the window :)

[rubber_jonnie]

OK, so another interesting issue.

I think the SYSMON socket has something off about it as if I leave the machine on for any length of time I get chip creep and have to push the ROM back in again. The 28C16's still don't work, however the 27C16 still seems good, though I do intend it replace it if I can.

The socket has to go though, so I'm going to replace it with a turned pin type to see if that improves matters. Currently its a double wipe socket from the same batch as the BASIC and CHARGEN ROMs, but none of those have had an issue.

I'm not keen on turned pin sockets, but figure I should give it a go on this occasion.

[rubber_jonnie]

OK, so after replacing the SYN600 ROM (Sorry, I've been calling it SYSMON) things still weren't right, so as per my previous post, so I went ahead and changed the ROM socket to a turned pin type, and also eventually swapped out the ROM for a new one.

It seemed to improve, but then after after a few days, I start to get this again:

IMG20250731185326.jpg

Which is almost like no CPU is present since the video RAM will fill up with garbage if this is the case. So I took a look at the CPU socket and that looked off as well, plus by flexing the board a bit, or pushing on the CPU, I could cause the machine to boot again. Also, simply typing cause cause a crash.

So I pulled the CPU socket and it doesn't look great:

IMG20250731190902.jpg

I dropped in a turned pin socket and so far so good.

Anybody else been having socket issues, I know another builder over at OSIWeb has had socket problems too, but they sourced theirs from somewhere else entirely. These were new double wipe sockets, but it seems like there is no springiness in the contacts and they just push away and then the contact is poor.

[stephen_usher]

Are the sockets "special" in any way or just hard to get non-turned pin versions these days?