Requesting Help for repairing Macintosh XL and restoring to 2/10

[bmwcyclist]

To use System 6.0.8, you must also be using MW+II.

Sun's MW+ only supports up to System 6.0.3

GTK

I need a Frequency Generator also right?

[bmwcyclist]

Update. ROMs ver H copied from my other LISA, installed and a VROM from Vintage Micros. Now just waiting on my PFG kit to arrive.

Still using my backup PSU.

The one that came with it is not producing 5v on pin20, testing under load with the home made load tester from FB.

Fuse is good and I replaced the ugly caps. Still no love. I wish I had the experience to produce a troubleshooting guide for the PSUs.

Mac works under 6.0.2 looks crisp and no burn in on the CRT. Different tint from the other LISA though, I didn't expect that...


Previous owner drilled a big hole in the back panel, I guess to cool the XLerator , I acquired a new back panel, not sure if I should just throw the other one out? I pulled the slot covers off and noticed they have different part numbers inked on them. So many odd things different between the two 2/10s!

I assume no one wants the MacXL ROMs?

[stepleton]

The one that came with it is not producing 5v on pin20, testing under load with the home made load tester from FB.

Fuse is good and I replaced the ugly caps. Still no love. I wish I had the experience to produce a troubleshooting guide for the PSUs.

Pin 20 is the +5V standby power, which is basically a separate, smaller, very simple linear PSU inside of the Lisa PSU. You can basically ignore the entire schematic and focus on just this bit:



(I'm assuming you have the 1.8A DataPower PSU; the 1.2A Apple PSU has essentially the same circuit at the top of this schematic.)

There are basically only ten components, and you can do common-sense checking on most of them with a multimeter. Check whether the capacitors are shorted; check whether the diodes have sensible voltage drops in their forward direction and whether they block current in the reverse direction; check that the transformer has continuity through each of its coils (note that you will want to temporarily remove the E6/E7/E8/E9 jumpers before you do this).

If everything looks reasonable, then the voltage regulator Z1 starts to seem like the most likely culprit, and is what I suspect may have gone wrong. This part is easily replaced. Good luck!

Mac works under 6.0.2 looks crisp and no burn in on the CRT. Different tint from the other LISA though, I didn't expect that...

Greenish or whiteish? My two Lisas have different phosphors as well. The Lisa 1 is whiteish, the 2/10 is greenish.

Previous owner drilled a big hole in the back panel, I guess to cool the XLerator , I acquired a new back panel, not sure if I should just throw the other one out?

If you're just inclined to toss it: I'm missing some slot covers and would love to buy some spares from you.

I assume no one wants the MacXL ROMs?

Check to see if they are backed up anywhere first (they probably are); if you have a ROM programmer you can read the contents that way, otherwise BLU may be able to dump them for you. Then, assuming they are EPROMs, store them in an ESD-safe way so that you can use them for something else later?

[bmwcyclist]

If you're just inclined to toss it: I'm missing some slot covers and would love to buy some spares from you.

Oh my gosh, with all the invaluable help that you've given me over the past couple years I could never dream of charging you for them. The cover only came with two slots, but I'm happy to send them to you. Just message me your address!

[bmwcyclist]

Mac works under 6.0.2 looks crisp and no burn in on the CRT. Different tint from the other LISA though, I didn't expect that...

Greenish or whiteish? My two Lisas have different phosphors as well. The Lisa 1 is whiteish, the 2/10 is greenish

Yep, one of each see photo!

Also, this is perfect troubleshooting information for the PSU. Thanks again.

[stepleton]

Oh my gosh, with all the invaluable help that you've given me over the past couple years I could never dream of charging you for them. The cover only came with two slots, but I'm happy to send them to you. Just message me your address!

That's very kind but shipping to England may make you think again :-)
Either way I will send you a message offline.

Reflecting a bit further on my PSU advice: checking the diodes CR6-CR9 is a little trickier than I let on because they are arranged in big loops, thus you will never be able to test a single diode in complete isolation unless you pull out at least one of its legs. So if we think about it a little bit more...

Before starting, pull out the daughter card: I think this ensures that the Line Sense line doesn't connect to anything; otherwise it is basically connected to ground through a resistor, and that will complicate measurements.

Diodes CR7 and CR8 have their anodes and cathodes tied together (on the anode side it's through the transformer, but that doesn't matter for diode testing). Testing in the reverse direction we should still see that current is blocked. In the forward direction, you should see a voltage drop in the 0.7V-1V range, but you will not be able to tell if both diodes are working or if one of them might be open.

With CR6 and CR9 it is the same story.

If you lift a leg of a diode out of the circuit, then you can test it individually, of course!

If your measurements around the diodes are as they are "supposed" to be, and if the other components look good, I'd still be inclined to suspect the voltage regulator, despite the ambiguity.

I also forgot to say explicitly that all of the measurements I'm recommending are with the PSU unplugged! Note that if the PSU is EVER plugged in, there is +340V of rectified DC energising various components in the PSU, even if the PSU appears "off", even if the interlock switch is open, even if the daughter card is removed. This can cause you a lot of harm. Beware!