SE/30 INTERMITTENT FLOPPY FORMAT PROBLEM

[Rjp663]

Would someone be helpful and take a voltage reading with your O'scope for me?

I need to know the voltage amplitude of the External Floppy Jack J6- pin 19 (Attachment refers), while formatting a floppy. My O'scope is reading 3.6vpp. 

Thank you

Rick

View attachment EXTERNAL FLOPPY J6.docx

 

[Rjp663]

Solved.

I'm posting the results of my troubleshooting should someone else have this error.

Symptom was intermittent floppy disks write errors while trying to format, or during floppy disk apple diagnostics.

The write signal (WR) voltage level was low (~3.6vdc square wave) vice the proper 5vdc; thereby causing intermittent errors to occur. You could see the WR signal on the external floppy jack J6 pin 19 using an o'scope.  I traced the signal back to the output of U7 pin 16. Removing and reinstalling the PAL16L8D chip returned the output to proper voltage levels (~5vdc). 

Hope this helps someone else in the future.

RickView attachment uh7.docx