General Category > LisaList2
Lisa 2 started throwing Error 45
sigma7:
--- Quote from: dmark on May 07, 2022, 07:14:13 pm ---Do you have advice where good test points for each voltage rail is?
--- End quote ---
I think this is still "current" ::) ...
https://lisafaq.sunder.net/lisafaq-hw-pwr_checking_voltages.html
sigma7:
--- Quote from: dmark on May 07, 2022, 02:02:20 pm ---Anyhow, grateful for any pointers how to further troubleshoot this poor Lisa!
--- End quote ---
An attempt was made ....
Debugging Bus Errors: https://lisalist2.com/index.php/topic,266.0.html
sigma7:
--- Quote ---
--- Quote ---how do you test the CPU board in operation? Is there something like an extender board to run the computer with the card cage outside the case?
--- End quote ---
There's no such extender board, sorry. You might be able to create one ...
--- End quote ---
General purpose off-the-shelf commercial extenders tend to be quite expensive, and you'd need two for the different sized connectors, so a home-made one is tempting.
An alternative to using an extender is to use the chassis wiring outside of a chassis; I've been using a home-made extender on the power/video connector for quite some time, and use a drive/keyboard cable removed from a chassis for the other connector (instead of a second extender). I think others have all the wiring outside of the chassis, but maybe that is only practical with an external monitor.
Since the signals in the Lisa are relatively 'slow' (ie. much less than 1 GHz) they tolerate a modest extension without difficulty. The fastest signal between the motherboard and chassis is the B&W video signal (~ 20 MHz) and since it is B&W it would have to degrade quite a lot before the video became unusable. On my extender I used coax for this one signal, the rest are plain wire (~ 18 AWG I think) between a (female) card edge socket and a veroboard with (male) card edge contacts. Extension length is about 8" (20 cm)
Now that one can get inexpensive boards produced in China, that may be a good way to go if someone has time to do the artwork. Perhaps there is enough interest to get some pre-orders here.
If you are tempted I would suggest:
* Make the extender in two pieces (one with 0.100" spacing, the other with 0.156" spacing), as the alignment of the two sizes of connectors is different in the Lisa 2/5 and 2/10
* Break out and mark the power supply voltages
* It may be helpful to have the possibility of headers on the floppy signal extender to connect drives behind the computer. For maximum utility one could have pads for two set of headers, one pair of 26 pins for the 2/5 and one 20, one 26 for the 2/10.
* Consider a potentiometer to reduce the speaker volume and (adjustable?) +12V power for a small fan that draws air through the PSU.
edit 1: Another advantage to using an extender is being able to adjust the PSU voltage in real-time with the actual load.
dmark:
--- Quote from: sigma7 on May 10, 2022, 06:01:27 pm ---
--- Quote from: dmark on May 07, 2022, 07:14:13 pm ---Do you have advice where good test points for each voltage rail is?
--- End quote ---
I think this is still "current" ::) ...
https://lisafaq.sunder.net/lisafaq-hw-pwr_checking_voltages.html
--- End quote ---
...nice one! (the joke, and the voltage measurement guide)
Now, the 5V rails look fine... But the 12V rails seem way out of whack on the I/O board. +7V and -17.5V respectively. :o
Which is weird, because before I measured a clean +12V on the Lite Adapter board, so I assumed that the same rail was ok elsewhere!
Just to make sure, I pulled out the Lite Adapter board again and measured on the floppy header, and am still getting a very neat +12V there.
So... at least I have a concrete issue to track down. It's almost as if 5V is being subtracted (or negative voltage added I guess) to the 12V rails!?
sigma7:
--- Quote from: dmark on May 11, 2022, 06:28:30 pm ---Now, the 5V rails look fine... But the 12V rails seem way out of whack on the I/O board. +7V and -17.5V respectively. :o
Which is weird, because before I measured a clean +12V on the Lite Adapter board, so I assumed that the same rail was ok elsewhere!
Just to make sure, I pulled out the Lite Adapter board again and measured on the floppy header, and am still getting a very neat +12V there.
So... at least I have a concrete issue to track down. It's almost as if 5V is being subtracted (or negative voltage added I guess) to the 12V rails!?
--- End quote ---
Seems like the voltages are probably normal, but suspect one lead of your voltmeter is on the +5 rail instead of ground, perhaps due to an error in the FAQ instructions...
Double check that the ground lead is at ground potential, eg. the end of C47 nearer the edge of the board. If voltages are still wonky, try putting the ground lead on the chassis (voltages won't be as accurate but not off by 5V).
And check the lead connections at your meter aren't reversed (eg. red to common, black to V) ... this sometimes trips me up.
Good luck!
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