Apple ][ Europlus Fault?

[tezza]

Hi Guys,

Re: C2, I’m almost 100% certain this was a result of me messing around pulling chips in and out in a desperate attempt to get it going.

I probably pulled it out and then stick it in the wrong way round, as before I touched this chip the computer booted up and you could type (but not see any characters).

I wish I had just left it alone…

Easy to put ICs in the wrong way. I've done this myself to the accompaniment of a burning smell and an IC that within seconds you can fry an egg on.

It's something you only tend to do once Like any thing, learning occurs most effectively when you make mistakes.

Tez

 

[chuckcmagee]

The SQUARE CPU chips can be put in 90 degrees out! Ask my 2nd degree burned finger how it knows that. This occurred around 1994. Do I still remember the incident? You had better believe it.

 

[Druid6900]

Position C2, contains, as I mentioned, a long-legged wirewrap socket with a small PCB on top of it with a soldered on 7400 and a 74195 from the original socket mounted in a socket on the PCB.

Since the WW socket has notches at both ends, it would not be difficult to put it in wrong way around.

 

[Druid6900]

UPDATE;

Checked all the rest of the TTL chips and they were all good.

BTW, if you are troubleshooting an Apple ][+, the 9334 chip can be replaced with a 74LS259 while the 8T97 chips can be replaced by 74LS367s.

I'm going to be changing the frequency pads and crystal to convert the to a 60Hz board next so I can check the ROM/RAM and linear chips against a known working board.

I will also, of course, replace those two bad chips and I have put a black indeliable mark on those mod sockets that indicates which side goes towards the BACK of the computer.

 

[mwillegal]

74LS367's don't have the quite the same drive capability as the 8T97, however MC6887 are available and equivalent.

8T97s can still be found, but it isn't always easy. Anchor Electronics appears to still have them: http://www.demoboard.com/anchor.htm

The 74LS259/9334 part is an interesting case. Original rev0's motherboards actually labelled the location for a 74LS259, but later revs used the 9334 label. I wish I knew what prompted the switch. Note that 74LS259s are not the easiest 74LS part to find.

Regards,
Mike Willegal