Recent content by gruni

Still no luck. As a last resort: is there anybody located in southern Germany with access to a working Lisa that could help me find the issue by swapping components?

I attached two screenshots of my oscilloscope, one showing an address line, one showing a data line. As you can see the data lines are very jittery. Maybe this has to do with the problem.

I already had a look at the BIOS listing. I agree that the initialisation seems to fail in one of the early steps (MMU initialisation, VIA initialisation, etc.)... One thing i missed: before i took the LISA home, it seemed to start up as it beeped and then accessed the floppy, altough there was...

Reseating the Video PROM solved the missing HSYNC problem, the CRT High Voltage is available now, although the CRT only shows a dark grey screen with some lines scrolling from top to bottom, no matter which ram or if the i/o card is installed... speaker is still clicking if the i/o card is...

Thank you so much! Looks like my ROM is okay. I noticed a stuck LSB in my DUMP, i will have to figure out if it is a problem in the chip or if the connection to my reader using jumper wires was bad...

I found out that the screen most probably stays blank because it does not receive a HSYNC signal and therefore no high voltage is generated. I think i will have to get the Lisa back to the lab to do some oscilloscope measurements...

Hello everybody, in the process of resurrecting an Apple Lisa i am now at the point of inspecting the video prom. Does anybody have a dump of said rom chip that i can compare my image to? Thanks in advance

AFAIK the monitor has to support the uncommon sync timing of the lisa. but at least you should be able to barely make out the lisas screen content, right?  I tried to hook up a PC power supply to the lisa as all my bench power supplies get maxed out by the current consumption (over 3A). Still...

Thanks for your reply. I have two RAM cards and have already tried several combinations of cards and slot but no changes. By now i am running the system stripped as much as possible, removed all drives, removed the video board and all expansion cards. I had a look at the ROM source code and as...

Hello everybody, i recently got a Lisa 2/10 for repair to be displayed in a museum. Unfortunately the computer does not boot. There is no image on the screen, the only signs of life is a repeated clicking noise in the speaker and the Widget drive spinning up. There is no startup beep nor is the...