gjw@clyde.UUCP (Gregory J. Wroclawski) (04/10/85)
A week ago I submitted the folowing query. Although I got no response from the net through some leg work I was able to figure out the problem: Problem: I have an Atari 400 with 48K, a Trak AT-D2 disk drive with printer port and 4K buffer connected to an Epson MX-80 printer. The problem is when printing large files, large portions of the files are lost. It seems as if the 4K buffer in the Trak gets filled the Atari does not stop sending data to the Trak. Small files, < 4K, print with no problem. I believe I have all the DIP switches in the Epson and on the back of the Trak set properly. Has anyone had a problem like this? I am hoping it is a setup problem not a problem with the printer interface in the Trak. Solution: After asking a local dealer about the problem he informed me that Trak was shipping disk drives with one of the printer buffer memory chips missing. I opened the disk drive myself and after some poking around saw an empty 28 pin dip socket. There was another 28 pin DIP socket with a 24 pin DIP IC plugged in. Upon checking the numbers on the chip I found that it was a Misubishi 2Kx8 static NMOS RAM. I happened to have 2Kx8 CMOS static RAMs and I plugged one of those in the empty DIP socket in the same manner as the existing RAM. That is lining up pin one of the 24 pin RAM to pin 3 of the 28 pin DIP socket. The printer interface works beautifully now. Further investigation of the data sheets of 2Kx8 static RAMs and and 8Kx8 static RAMs revealed that they are practically pin for pin compatible with the additional address lines placed at pins 1,2,27,28 of the 28 pin package. Therefore expanding the TRAK's printer buffer to 16K requires substitution of the 2Kx8 RAMs with 8Kx8 devices plus cutting a jumper wire to tell the controller how much RAM is in the buffer. It's amazing that TRAK was selling known bad disk drives with only half of the printer buffer installed hoping that people wouldn't notice till the 90 day warranty was up. You wouldn't notice the problem unless you overflowed the 2K buffer in the disk drive printer interface. Now I know why TRAK went out of bussiness!