ASEM AM-64 restoration (Apple ][ italian clone)

Saturday October 6th, 2012 asbesto

This computer was recovered about 14 years ago from a Catania junkyard; it was laying into the grass and it was exposed to sun and rain for a long time. It was never working, and followed us from Catania to Palazzolo Acreide; now is time to put hands on it!

List of service we made (documented with pictures):

Check of initial state of the piece, with pictures
Disassembly of all parts: cover, power supply, motherboard, keyboard, printer board, floppy drive board, inferior panel, case.
System / Keyboard / Printer EPROM dump
Visual inspection of power supply, check of components, cleaning, voltage check & correction; reassembly.
Keyboard disassembly, dust removal, key washing, quick drying, contact clean using WD-40, reassembly.
Motherboard cleaning, washing, drying, WD-40 application, drying, integrated circuits reassestment into sockets.
Inferior panel cleaned with WD-40
Case washed with special products
Power on Test

All chip datecode is around the end of 1984; one of them is dated the first week of 1985. 3 or 4 SGS chip are dated 1989 and they are different from the others, that are Texas Instrument and National, so we think they were changed some year after. Considering that, we can date this board around the first months of 1985.

The computer react to power on with his peculiar BEEP!, but video shows repeated stuff. It boot from disk, so it works! 🙂 Keyboard react only to CTRL-RESET, making a beep, but after a while the BEEP goes loop and a lot of SYNTAX ERROR and weird stuff were printed, as you can see in pictures below. Video problem was solved changing the chip D14 near the speaker connector, an SN74LS283.

Keyboard still doesn’t work; we think his controller is burned. It’s a C33294E, we can’t find any info on it. Alessandro Polito brought us a chip labelled TK-10 from his similar Apple clone, and the keyboard was back working again! So we’re sure our chip is burned. Pinout seem similar to a TMP8048 but using it as a replacement we see weird stuff printed in a loop. Maybe a problem of internal programming of the 8048?

Connecting an Apple ][ keyboard, giving correct voltages, we obtain a working keyboard but with erratic key mapping.

Our friend Xad sent us an identical TK-10 from a spare keyboard he had in his collection, so now our ASEM is back working again! 🙂

We was able to read the internal programming of this TK-10 chip as an INTEL 8049H, so we strongly believe we can program a fresh 8049 to clone this kind of chip! 🙂 The BIN program is available in the following link among with other EPROM’s.

EPROM of this computer are:

ASEM AM-64 system EPROM, 27128

ASEM AM-64 Keyboard EPROM, 2716

ASEM AM-64 Printer board EPROM, 2716

Internal TK-10 programming,. read as INTEL 8049H