Seeking Help

[chiu@ucsee.Berkeley.EDU (David Chiu)]

Recently I've run into a bit of odd problem with the old //e I have.
Every attempt to download from varies different system fails regardless
of speed, transfer protocol, or file type. Specifically file transfers
are aborted after excessive errors after approximately 20 - 25k of
material has been downloaded; files smaller than 25k downloads without
problems while file larger than 25k will fail and abort soon after 25k
"limit".

Typically errors reported by the communication programs are 'Data Failure',
'Header Failure', 'Checksum Failure', etc. as if it is losing characters,
although interrupt on the serial card is enabled.

Problem appears to be hardware related since several communication programs
I have all shown similar problem (ProTerm 2.1, Z-Link, and ASCII Express 4.2)
However the fault is no related to the serial card, cable or the MoDem.
(I have several spares, and the problem persists with different combinations)

On board diagnostic reports no error (System Ok), and varies diagnostic
programs also report no error.

For the life of me I can't figure out what component failure could cause
this rather unusual (if not unque) problem.

My system is consists of the following:

Apple //e Enh.
w/4MHz ZipChip
						Speed
Super Expander E w/1024k	(Aux. Slot)
AI InnerDrive 40		(Slot 1)	Fast
Apple Super Serial (2400 BPS)	(Slot 2)	Normal
[EMPTY]				(Slot 3)	Fast
Practical Periphral ProClock	(Slot 4)	Fast
[EMPTY]				(Slot 5)	Normal
Disk II Controller		(Slot 6)	Normal
AI OverDrive 20			(Slot 7)	Fast

Any pointers that might shed some light on this problem is sincerely
appreciated.