LisaList2

Quote from: berskyboy on Yesterday at 09:55:59 AMT4:5 - T4:6. in ohms mode 0 ohms
T5:5 - T5:6. in ohms mode 0 ohms

Ok, good.

Quote from: berskyboy on Yesterday at 10:00:15 AMDo I connect CR18 again?  I would presume so.  I also took out the heatsink and screws for T3, and T4.  And should the daughter board be placed back in before testing?

You can reconnect CR18 or leave it disconnected at your convenience.

The daughterboard should be in place.

T3 and T4 don't have a heatsink or screws. If you mean Q1 & Q2, at a minimum, the screws should be removed, if the heatsinks are then loose, removing them too is wise.

Quote from: sigma7 on Yesterday at 04:15:38 AMNormally, with Q1 and Q2 out of circuit (either completely, or with the 4 phillips head mounting screws removed such that their cases are disconnected), the main transformer will not receive any switching current.

In this state, the only output voltage will be +5Standby.

With the high power circuitry inactive, we can (hopefully) check some of the control circuitry without having a fault in the high power circuitry blowing the fuse.

Double check that Q1 and Q2 are disconnected (4 screws removed) or completely removed from the circuit board.

Ensure a good fuse is installed.

Connect the test jig load circuit to the card edge, and turn its small switch "off".

Do I connect CR18 again?  I would presume so.  I also took out the heatsink and screws for T3, and T4.  And should the daughter board be placed back in before testing?

Quote from: sigma7 on Yesterday at 03:38:33 AMRefer to the drawing, and measure the resistance between each of these pairs (Q1 and Q2 still removed from the circuit):

T4:5 - T4:6
T5:5 - T5:6

In each case, the resistance should be close to 0.0 ohms.

T4:5 - T4:6. in ohms mode 0 ohms
T5:5 - T5:6. in ohms move 0 ohms

Quote from: TorZidan on September 21, 2026, 07:31:39 PMare you a human?

Ah, the eternal question.

Thanks for your kind words; I'm hoping that describing this example of the process will be useful to others someday too, but 'are you not entertained' is sufficient reward.

A computer that can still be repaired at the component level by moderately technical users is, I think, a fortunate anachronism.

Normally, with Q1 and Q2 out of circuit (either completely, or with the 4 phillips head mounting screws removed such that their cases are disconnected), the main transformer will not receive any switching current.

In this state, the only output voltage will be +5Standby.

With the high power circuitry inactive, we can (hopefully) check some of the control circuitry without having a fault in the high power circuitry blowing the fuse.

Double check that Q1 and Q2 are disconnected (4 screws removed) or completely removed from the circuit board.

Ensure a good fuse is installed.

Connect the test jig load circuit to the card edge, and turn its small switch "off".

Connect the line power and turn on the power strip; there should not be any smoke, flashes, odours, blown fuse or other dramatic evidence of something happening. If something does, stop here, disconnect the power and report what you observed.

If Q1 is still mounted on the board, measure the DC voltage from its case to ground. If the voltage exceeds 1 Volt, immediately remove power and stop here.

The small switch should still be in the OFF position, and the power strip will be on. Check the DC and AC voltages from pin 3 of the daughterboard connector to ground. This should be about 16 to 18V DC, and should have an AC voltage of less than 1V; if the DC and AC voltage are in that range, continue with the next step. If not, stop here, remove power, and report what you observed. If the DC voltage is about half or double, investigate whether the 115/230V jumpers are not installed correctly or damaged or not making proper contact. If the DC voltage was zero, check the fuse.

Remember to set the meter back to DC volts after measuring the AC volts.

Check the DC voltage across R33 (from one end to the other, not to ground) & across R2. (These are two large resistors beside the large black capacitor C8.) They should be about 150-170 V each (positive or negative, depending on which way you probe them): if so, continue with the next step. If not, then the primary rectifier, line filter, and associated components are suspect - stop here, remove power, and report what you observed.

Check the DC voltage at pin 12 of the daughterboard connector to ground. This should be about 5V: if so, continue with the next step. If not then Z2 on the daughterboard is suspect - stop here, remove power, and report what you observed.

Make sure the interlock switch has been engaged. Set the small switch (on the test jig connected to the card edge) to the ON position. There should not be any smoke, flashes, odours, blown fuse or other dramatic evidence of something happening. If something does, stop here, disconnect the power and report what you observed.

Collect measurements from the following steps A - H and report what you observe. As before, stop, disconnect power and report observations if anything happens that isn't expected.

These measurements are much more easily done if the black lead of the DMM can be secured to ground, freeing up a hand to operate the switch. eg. clip the black lead to the grounded side of a load resistor. If nothing else is available, inserting the black probe into the grounded mounting hole near the card edge connector and leaving it leaning against the edge may work. Be careful to not dislodge the probe while power is on; you might want to tape it in place. Turn off the power strip if you need to fiddle with this connection.

On/Off in the following refers to the small switch on the test jig attached to the card edge. The power strip can remain on (the behaviour of some of the following measurements is different if the power strip is turned off/on instead of the test jig's switch).

A. Turn off, locate pin 13 of the daughterboard connector (at the CR15 end), then while watching the voltage at pin 13, turn on: the voltage should rise from a low voltage about 0.5V to about 4.8V over a few seconds.

B. Turn off, then while watching the voltage at pin 8 of the daughterboard connector, turn on: the voltage should rise briefly, from near 0 to near 5V, then return to 0. This takes less than a second but should be visible. If it is stuck at 0, double check the interlock switch has been bypassed.

C. Turn off. Carefully (be careful the probe does not slip and cause a short circuit) hold the red probe to the lower end of R30 on the daughterboard (R30 is at the left edge/corner). The voltage should be near 4V.  Then while watching the voltage, turn on: the voltage should drop immediately to near 0. If the voltage remains high (around 4 VDC) then the soft-power circuit is suspect.

D. Turn off. Carefully (be careful the probe does not slip and cause a short circuit) hold the red probe to the + (plus) side of C14 on the daughterboard (not far from R30). Then while watching the voltage, turn on: the voltage should rise over a few seconds from near 0 to near 4.8V. If stuck (around 0 VDC), then the brownout circuit is suspect.

E. Turn off, then while watching the voltage at pin 10 of the daughterboard connector, turn on: the voltage should drop from about 2.4V to about 1.4V for a noticeable but brief period (less than a second). If you don't see the brief drop, turn off, switch the DMM to AC Volts and when you turn on again, you should observe the AC voltage briefly rise from 0V to perhaps 1V (the value will depend on the DMM), then return to 0 before you turn off again. If no activity is observed, then Z2 on the daughterboard is suspect. Set the DMM back to DC Volts.

F. Turn off, then while watching the voltage at pin 11 of the daughterboard connector, turn on: the voltage should drop from about 2.4V to about 1.4V for a noticeable but brief period (less than a second). If you don't see the brief drop, turn off, switch the DMM to AC Volts and when you turn on again, you should observe the AC voltage briefly rise from 0V to perhaps 1V (the value will depend on the DMM), then return to 0 before you turn off again. If no activity is observed, then Z2 on the daughterboard is suspect. Set the DMM back to DC Volts.

G. Turn off, locate R7 on the main board. R7 is on ceramic standoffs beside a silvery heatsink plate. One end should measure around 16-18V. While watching the voltage at the other end, turn on, the voltage should rise briefly, from about 1.6V to 5-15V (varies depending on the speed of your DMM), then return to 1.6. If no activity is observed, then Q4 or T5 is suspect.

H. Turn off, locate R5 on the main board. R5 is on ceramic standoffs near the center beside R4. One end should measure around 16-18V. While watching the voltage at the other end, turn on, the voltage should rise briefly, from about 1.6V to 5-15V (varies depending on the speed of your DMM), then return to 1.6. If no activity is observed, then Q3 or T4 is suspect.

The short circuit of Q1 and Q2 would result in a current having most of the available energy from the main capacitors (plus more from the power utility until the fuse blew).

This current goes through windings of pulse transformers T4 and T5, so we need to check that there is still continuity through those windings.

Refer to the drawing, and measure the resistance between each of these pairs (Q1 and Q2 still removed from the circuit):

T4:5 - T4:6
T5:5 - T5:6

In each case, the resistance should be close to 0.0 ohms.

Yes I know for sure I'm 100% grateful!! Plan B would be this clone PSU,

https://68kmla.org/bb/threads/lisa-1-8a-psu-clone-by-warmech.47154/page-2

but I am still hopping to get the old gal running.  LOL.  Lisa would be a girl right?

Piling on to say the same. What a heroic effort!

@TorZidan There's a few mechanisms at play here and they require a patched LisaEm to make it work. I don't think I've pushed those patches yet. I added some test hooks that watch a file and push its contents through the COPS as if it were typed on the keyboard. There's also the automatic screenshot and mouse mover. The AI tools appreciate screenshots of errors (and it's hard to copy/paste out, anyway).

For Minix, specifically, the console also directs output thru the serial port, and using 'expect' we can wait for particular output and act on it. There should also be tests that dump to file and open the profile image after to compare.

Have not tried it, but this picked my interest:

"The make lisaem-* targets boot the images in LisaEm without anyone at the emulator, type commands and check the output."

I could not figure out how this works. Are you sending these commands over a serial port or somehow "typing them in LisaEm" (similar to the "paste host clipboard" menu item)?

Why is this important: if you are developing something for the Lisa using AI, it would be extremely useful to "tell" the AI how to launch LisaEm and how to compile and run and test your new app by moving the mouse, clicking, typing text, inspecting the Lisa screen, etc. This way the AI can run in a close loop, without your intervention, until it completes the task.