Good morning, I have this unknown Parallel Printer interface card "Type 2" that seem not working properly.
I identified all signals to pinhead printer connector and made a cable to connect to a standard centronics parallel printer.
Only two signals are read from printer, at the pins 19 and 20 of pinheader. Only pin 20 however seem to be taken in consideration.
I also tested all chips with a xgecu tester, all ok, and I attach the eprom image.
I think that eprom could be corrupted. The card work in some ways, but outputs corrupted characters (also on the screen) in both Apple ][ and Apple //e. The system never hangs when I type PR#1 and I print some things, but the output is totally corrupted despite some sort of coherency seem to exhist from expected screen output, actual screen output and printed chars.
I see that only first 192 bytes of eprom are effectively addressed as firmware, the remainings 64 bytes are used to read inputs from printer through a 74LS251 that output the two signals to data bus bit 7 (pin 19 at C1C0h and pin20 at C1C1h)
The first bytes of eprom coincides with the original Apple Printer Card (but these addresses all 256 bytes as firmware and input signals from printer is read in other ways).
The rest of the eprom at C800h is addressed in a way similar to Grappler, but there are no other similarities.
The latest version of MouseDesk recognize the card correctly as "Printer Card" but I made no test under this SO.
Various utilities for hardware test do not recognize the card.
I tryed to replace original 74LS373 with a 74LS374 but nothing changes.
There are some things that I can try to get this card working? If someone could has the eprom image would be a nice chance. Or maybe someone can recognize some similarity with known original cards?
Regards
The circuit board was made with very wide openings in the solder mask layer, resulting in an absence of solder mask dams between adjacent pins. This can result in forming solder bridges between pins, and there appears to be at least one here, between pins 1 and 2 of the 74LS00.
Looks like an identical clone to the card that came with my Apple II+:
PrinterCard.jpg
I have tested it and it works with a Commodore MPS 1230 configured as a parallel printer:
Printer.jpg
Here is the contents of my 2716 PROM:
PrinterCardROM.zip
Thanks but bridge between pins 1 and 2 of the 74LS00 was made by me because that gate is used as inverter and pin 1 was leaved floating (!)
TTL see a logic 1 at unconnected input, but I dont'like it.
Regards
Wow, super! Thank you for eprom image and for testing.
Do you can tell me where pins 19 and 20 is connected to printer?
Now I check all.
ALso thanks to applefritter forum!
On my cable pin 19 on the card goes to pin 10 on the Centronics (Acknowledge) and pin 20 goes to pin 11 on the Centronics (Busy).
Perfect, thanks.
My eprom differ only in one single bit. I burned a new eprom with your image and now my card work well.
Thanks again, best regards.
I am happy I was able to help!
Yes, it looks like a single bit flipped from 1 to 0 (0xBD --> 0xB9) and broke it.
This is the EPSON original, and the ROM is dumped and available there for a decade:
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Parallel/Epson%20APL%20Printer%20Interface/Photos/Epson%20APL%20Printer%20Interface%20v2%20-%20Front.jpg
Epson APL Printer Interface v2 - Front.jpg
The ROM from there differs by a lot more than a single bit though:
Diff.png
Many thanks, very interesting. Within few days I will try the original eprom then I will report the results.
I have a couple different variations of the APL card made by Epson with slightly different board layouts, and although I haven't dumped the EPROMs on any of them I wouldn't be surprised at all if there were different versions. It is obviously also not uncommon at all for clone cards to differ from the originals. But if there is a single bit difference, that seems like it could be bit rot. The significant differences shown in that image would seem to be unlikely a chip failure but more likely some different version.
Yes, probably the original Epson rom will not work in my clone because the Epson rom show code in the entire first 256 bytes space (boot firmware), where the clone put the printer state input circuit reading in the last 64 of 256 bytes space.
I just want to add that yesterday I acquired this Bulgarian clone printer interface card from 1987. It had a damaged Soviet EPROM chip, so I simply burned the ROM from Post #3 above into a new chip and it worked like a charm!
APC-01.png
Fun fact:
This card could be used to house a custom ROM to perform other tasks than a printer interface.
For instance, back in the 80s, clock cards were expensive, and the cheapest one, tne AE Time ][ was not ProDOS compatible.
Since then someone's writted a ProDOS driver for it, but in the 80s someone wrote a custom ROM for this Epson card which had some sort of software glue logic so that the Time ][ could be used as a generic "ProDOS compatible clock". Cool hack. Don't know where it came from, but in my stash is a clone card like this with a ROM that's inscribed "Time][" on it that I burned long long ago.
Of course, a modern day hack is the SmartPort SoftSP ROM that can be used in cards similar to this to get smartport capabilty through a regular Disk II card.