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[sigma7]

Do you have advice where good test points for each voltage rail is?

I think this is still "current"  ...

https://lisafaq.sunder.net/lisafaq-hw-pwr_checking_voltages.html

[sigma7]

Anyhow, grateful for any pointers how to further troubleshoot this poor Lisa!

An attempt was made ....

Debugging Bus Errors: https://lisalist2.com/index.php/topic,266.0.html

[sigma7]

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?

There's no such extender board, sorry. You might be able to create one ...

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]

Do you have advice where good test points for each voltage rail is?

I think this is still "current"  ...

https://lisafaq.sunder.net/lisafaq-hw-pwr_checking_voltages.html

...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. 
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]

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. 
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!?

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!

[dmark]

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. 
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!?

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!

You're right, when measuring off the negative side of C47 I get -12V and +12.9V (the latter seems high!)
What tripped me up, and this may betray how little I know about electronics, is that I thought pin 119 (as well as 115) on the I/O edge connector socket was ground, because when I test continuity between that pin and ground (i.e. the chassis), I get a dead short. But now I do see the 5V on pin 119 under operation. How can this be?

Anyhow, lesson learned that testing continuity with the chassis when the machine is turned off is not a reliable way to identify ground.

[sigma7]

... when measuring off the negative side of C47 I get -12V and +12.9V (the latter seems high!)
What tripped me up, and this may betray how little I know about electronics, is that I thought pin 119 (as well as 115) on the I/O edge connector socket was ground, because when I test continuity between that pin and ground (i.e. the chassis), I get a dead short. But now I do see the 5V on pin 119 under operation. How can this be?

With tremedous thanks due to Al Kossow, the "original" Lisa schematics are available on Bitsavers.org, eg. the Lisa 1 or 2/5 I/O is at http://www.bitsavers.org/pdf/apple/lisa/hardware/050-4008-H_IO.pdf

Page 1 shows the card edge pinout, with pin 119 designated as /PWRSW, which will be tied to ground while the front panel power switch is pressed... possibly explaining your observation.

Pin 115 is +5V, which may show initially a low resistance to ground as there is a lot of capacitance that needs to be charged before reaching a steady state; after a few seconds of measuring resistance to ground, it should be more than a few ohms.

If you measure continuity using the "diode test" feature of a DMM (typically the feature that beeps when there is continuity), note that it can be misleading if one isn't paying sufficient attention to what you are measuring and how that feature works when not used to test diode junctions. Sometimes reversing the leads when using the diode test will quickly reveal that the connection isn't a direct one (since it beeps in one direction but not the other), but this may depend on the meter and circuit. Especially when troubleshooting mysteries, it may be preferable to stick with (or verify with) old fashioned resistance measurements, particularly when the difference between 1 ohm and 100 ohms makes a difference.

Your 12V supply may be a bit high due to minimal load on that rail. Since it is within 10% of 12V, it is probably fine.
+5V should be within +/- 5%, ie. 4.75V to 5.25V, so the power supply should be adjusted to that range.

HTH

[Lisa2]

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.

Using a spare wiring harness, ribbon cable ( including the  power switch/ KB jack assembly ), and external monitor is how I run the card cage outside the chassis for debugging.
Rick

[blusnowkitty]

Using a spare wiring harness, ribbon cable ( including the  power switch/ KB jack assembly ), and external monitor is how I run the card cage outside the chassis for debugging.
Rick

What model of monitor is that? Looks like a Conrac 38V44IOCA1?

https://www.ampronix.com/conrac-38v44ioca1-ivtm15a-15v44ioaap

[Lisa2]

What model of monitor is that? Looks like a Conrac 38V44IOCA1?

Mine is a Conrac 38-V44IOA-A2.  Be careful before you buy one, there were many variations of this model and not all versions will support Lisa's scan rate.

Here are the specs:

Industrial Series #V44 - 15
technical data
High Resolution Monochrome Monitor V44 - 15
(15" = 381mm)
Category   Monochrome (CRT)
Format   Cabinet (Metal)
Model   V44 - 15"
Part Number   38-V44IOA-A2
Screen size   15" (381mm)
Max resolution   1000 TV lines center
800 TV lines corner
Phosphor   P4 (white)
Horizontal frequency   15-40kHz
Vertical frequency range   45-90Hz
User controls   Front: A/B Switch, Brightness, Contrast, H Position, H Size, Power, V Position, V Size, VTR Switch
Input voltage   100-240VAC 50-60Hz
Power consumption (max)   65W
On screen display   No
Video connection   BNC loopthrough, channel A/B
Dimensions (WxHxD)   Inch: 15.8x11.7x16.6
mm: 400x298x421
Operating temperature   0-40°C
Weight   30.8lb/14.0kg
Warranty   One year parts and labor
Approvals   UL1950, CSA22.2 950, 89/336/EEC, FCC Class A, FDA CFR21, EN55022 Class A, EN60950
Options   Rack Mounting Kit
Accessories   AC Power Cord
Operators Manual

[dmark]

Apologies all; inbetween catching Covid-19, and then trying to catch up on work after recovering, I haven't had much time for vintage computing projects.

I busted out the Lisa today just to see how she was doing. One new thing that I tried, which might be worth mentioning, is that when she boots with only one of two known good memory boards (tested both separately), she errors out at a different point during the boot process and with different errors. For instance, when loading Lisa Test 3 with only one memory board, the computer just hangs after about 1 min of reading from the floppy drive. No error 45.