Doesn't write floppies #3
Description
I just finished assembling my Quapple card and installed it into a Victor VPCII (8086 4.77MHz) 640k RAM / 1 floppy 360k / CGA adapter / ST225 Hard Drive with MSDOS 3.3.
After lots of test to arrange the right placement of the CGA / Quapple / HD CTRL cards into the computer (yes, some arrangements work and some no, go figure) I got a stable config to load and run QUADLINK.EXE and booting Apple II software.
This is AMAZING, fantastic job to reverse engineering and produce such a great ISA device!
But there are a couple of problems I've been struggling over and over to try to fix but can't...
First: the sound is very, very faint from the speaker in Apple mode. In PC mode everything is OK. I've been checking signals with a multimeter oscilloscope on UC41C pin 9, the sound signal is clear and nominal, but on pin 8 it's barely there, only a few mV. So I checked U41 and even replaced it but no change. I don't have a background in electronic, so I may just plug a simple speaker on UC41C pin 8 to get the Apple sound. Any advice?
Second, and most annoying issue is WRITING to floppy disk doesn't work. I mean I can read 5.25" floppies in PC and Apple modes, but there is no way to format a new floppy or even write on already formatted ones. The floppy works well when connected directly to the motherboard. Formatting, reading and writing on disks is fine, but when the straight cable goes from the motherboard to Quapple with the floppy cable from Quapple to the disk drive, no way to write anything on any disk. I checked U41 and U44 a lot, and they both fine when tested with my TL866 programmer.
Anyway, I would appreciate if someone can point to some areas of investigations here.
I understand Quapple is intended to work only on genuine original IBM 5150 but I am curious why I experience those 2 issues.
I have some time to check all ICs, verifying all PALs and the EPROM to make sure no obvious mistake was made when building this great card.
Thanks.