Apple Lisa 2/10 no Boot, clicking speaker

[gruni]

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 floppy drive accessed. When connecting an external monitor there are random patterns that flicker sometimes, on a first glance the flickering is related to the ticking noise of the speaker, but i am not sure about that. I already checked the voltage rails using an oscilloscope, they seem stable. When holding the reset button, the ticking stops and when pushing the NMI button somtimes it misses a tick.

Any ideas on that? I don't know where to look first...

Thanks in advance

 

[bibilit]

Hard to say.

I will have a look at the PSU first.

Considering is a 2/10, no battery was present, so no damage either.

How much Ram cards have you got ? (more than one, try to boot with one, then another)

I will try to boot with a minimal setup (no Widget nor Floppy drive) and see what's going on.

 

[gruni]

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 far as i understand is it should beep even with faulty ram. is that correct?

Edit: i just cleaned all card edge connectors, makes no difference

 

[lisa2]

When connecting an external monitor there are random patterns that flicker sometimes

While connecting an external monitor may be helpful in determining if the the system is outputting any video signal, be aware that the Lisa does not output a standard composite signal and requires a very specialized monitor.

 

[PB145B]

be aware that the Lisa does not output a standard composite signal and requires a very specialized monitor.

Did not know that! What all monitors will work with the Lisa?

 

[gruni]

Did not know that! What all monitors will work with the Lisa?

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 no success...

 

[gruni]

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...

 

[gruni]

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 installed. The clicking is produced by the Keyboard VIA toggling the TONE pin. any further suggestions?

 

[gilles]

maybe we can find something on the bios listing. The sram for the mmu may be faulty (on the cpucard). 

 

[gruni]

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 no picture, which could be because of the badly seated video prom. now i have a grey screen but the LISA doesnt start. So the problem that prevents the Lisa from booting could be a mechanical one, altough i already disassembled and reassembled the machine completely.

One more thing i noticed: when the I/O card is present, the bus data lines DB0-DB7 are very "ugly" on the scope, as opposed to them being very clean when the i/o card is removed. but this could also be due to more bus activity and my scope not being able to display this correctly (it's just an old 20mhz one).

 

[gruni]

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.

 

[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?

 

[falen5]

Have you checked the power supply volatges