LisaList2

Quote from: AlexTheCat123 on April 23, 2026, 06:35:53 PMI made a Lisa PSU tester PCB a while back that plugs into the PSU edge connector and has all of the power resistors onboard as well as test points and LEDs for all the rails. And of course a big toggle switch to turn the PSU on and off.

Very so cool! Appreciate the verification as well as everybody else chiming in - I thought that that's something that I had heard about - did you published this description before because my description is so similar to what you're talking about.

Anyway so the issue is it just gets too hot and so we need to find a convenient load - I think someone else where said that a 100 watt aluminum chassis resistor (~$10US) would be good for burst testing.

An for good measure (and safety) some basic 555 timer on there probably would be a smart idea to limit it 10 or 15 seconds at most the idea is just to get a nothing formation off of the power supply to determine whether it's dead off the go or it's working - as for long term stability. well we know the problems with old caps.

Anyway, something new for me to learn, always something more to learn. 

I made a Lisa PSU tester PCB a while back that plugs into the PSU edge connector and has all of the power resistors onboard as well as test points and LEDs for all the rails. And of course a big toggle switch to turn the PSU on and off. The issue is that the power resistors got really hot really fast, so I can only leave the supply on for maybe 30 seconds at a time before getting worried. It does work though!

Quote from: TorZidan on April 22, 2026, 03:49:07 PMTo complement stepleton's answer above

Ha, thanks! I'm so disorganised with my photos that I basically gave up on finding that one before I started.

Once a friend and I were in a "what's getting hot?" bind while diagnosing a PSU without having a thermal camera handy. We had a suspicion of the culprit but didn't want to touch the part to confirm it. So we poked it with a hot glue stick and sure enough! And given how fast it melted we were glad not to have tried a finger first.

That is so cool! Want

Edit #2: So this little thing switches out the CPU ROMs, video state ROM, and also bypasses the screen mod transformer with the flip of one switch. Neat!

I have it, too. It came unexpectedly with my 1st Lisa (2/10) that my neighbor placed on a trash collection pile in front of his house ~ 15 years ago.

It basically switches on/off a Square Pixel Modification Kit.

The board is plugged in place of the two ROMs and also via ribbon cable into the video ROM on the CPU board.
The flip switch (Mac <-> Lisa) engages/bypasses the small transformer that is located near the video board, and also (via 2 separate pins) is connected to the board to turn it on/off.

Here are some photos that I just took. Enjoy.

It's not for sale, but if someone wants to reverse engineer it, I will "cooperate".

1, 2/5, and 2/10 mother board, I/O, and CPU boards are available unpopulated.

Anyone know where I can find a working ROM Switcher?

Quote from: anotherLISAguy on April 22, 2026, 02:13:30 PMI don't think that the anticipated use would be a hell of a lot just enough to get a decent read - in my head I kind of imagine that edge connector plugging with that push button - While I fancily imagine this device why not put in some digital readouts to get numbers - inside of a minute you could get a health check with nothing more than the grandchild of your LISA O card, a power cord and a plastic doohickey to set the Reed switch. 

To operate the PSU, you need some minimum loads on the supply rails. At least 3-4 A at +5 V and 0.5 A at +12 V. An old spare bulb box from a car or a set of power resistors would be suitable for this.

Without a load at +12 V the crowbar will trigger and shutdown the PSU. You will hear a ticking sound.

Connect +5 Vsense (pin N) to +5 V and ON (pin X) to +5 Vstby (pin 20).

To complement stepleton's answer above, here is his "Lisa 0": https://68kmla.org/bb/threads/finally-manged-to-acquire-a-lisa-2.43744/post-477609

I am hesitant to post a photo of mine, as it looks much more ugly. I used hot glue on my resistors, and it starts melting if I keep the PSU running for more than 30 seconds. What was I thinking!

IIRC, the 1.2A PSU is much more sensitive about loads on each rail, so you need all the resistors on the picture. The 1.8A PSU may work with fewer resistors.

Hey thanks for charming in I just happened to peek in and see if anybody had any input on it I do recall that there was somebody who had an article on temporary powering on and a resistor as you said is what you used.

I don't think that the anticipated use would be a hell of a lot just enough to get a decent read - in my head I kind of imagine that edge connector plugging with that push button - While I fancily imagine this device why not put in some digital readouts to get numbers - inside of a minute you could get a health check with nothing more than the grandchild of your LISA O card, a power cord and a plastic doohickey to set the Reed switch. 

I'll have to do a better job of scouring the Lisa list it might have been LISALIST 1 to find that magic combo - Like I said at least you're validating that I wasn't imagining things even if my plug and play testing doesn't exist it sounds like it could easily enough - thanks for the info hopefully somebody else can say "I remember that article and have a copy of the thread" or whatever. 

Either way with the information, I can somewhat confidently old school the ps check while fantasizing about my plug and play device .

Again take care and LISA ON!