LisaList2

One of the principal motivations for buying my LISA was so I could actually do some writing on it for work and networking on GlobalTalk. In order to do what I want, I need a working XLerator with the RAM upgrade installed.

(abbreviated timeline)

I purchased an Xlerator, and in the original configuration, it worked well for several months.

I felt it was time to do the upgrade. A friend of mine put in a socket so it might be easyer to do the upgrade and troubleshoot.

I am NOT an experienced board-level repair person. However, the upgrade instructions seem straightforward, well-written, and include excellent diagrams.

I have completed the upgrade and checked the modifications according to the manual and to the best of my knowledge.

The Xlerator is now not working.

Any and all help is greatly appreciated.

My information is that the original RAM that worked in the Xlerator should still work and could be used to troubleshoot. It is not working.

As soon as I choose RAM ONLY MODE at startup it resets (see video below)


I purchased a SECOND LISA WITH XLERATOR CARD just to troublshoot this issue.

The second Xlerator card (unmodified) works great in both LISAS. I tried its RAM in the MOD card, and no change.

NOTE:

I can, at boot, turn the Xlerator OFF, and the Xlerator control panel will correctly identify the original RAM in the SIMM slots, but only sees BANK 0 of the 8 Meg RAM (2x4).

I have tried just installing RAM in BANK 0, still no luck.

More NOTES:

Due to concerns that my friend might have damaged the U3 Chip when inserting it into the socket, I bought a replacement to use in its place.

LISA resets on RAM MODE @ Startup after Mode Selection screen

OFF MODE, boots to MacWorks II+, control panel correctly displays 1 or smaller SIMMS in both banks

4 MEG SIMMS mouse behavior was odd, jerky. (OFF MODE) in MacWorks II+

I will include a few photos of my modifications. Please don't make too much fun of my skills, but constructive criticism is always very welcome.








Videos:

1. Fast Mode Selected at startup reset:
2. OFF Mode Selected boot into Mac Works II+ and checking control panel: https://youtu.be/76yy6UnWtTY

Quotethe upgrade instructions seem straightforward, well-written, and include excellent diagrams.

Thanks!

QuoteMy information is that the original RAM that worked in the Xlerator should still work and could be used to troubleshoot. It is not working.

Yes, the RAM should still work; sorry to hear that you're having difficulty...

You could send me high resolution photos of the various connections to review - there might be a visible problem. However, I suspect you'll need to send it to me for investigation/repair.

QuoteYou could send me high resolution photos of the various connections to review - there might be a visible problem. However, I suspect you'll need to send it to me for investigation/repair.

Thank you so much!

I'm so glad you're able to help!

I'll get you the photos you want posted but I'm going to assume I need to send it to you. I believe I still have your email to get your address.



Again, thank you very much.

Close ups.

I have double checked continuity back through each step of the modification.

I'm stumped.

IMG_9602 shows two parts, a 74LS132 and a 74F253... what is this picture communicating?

QuoteClose ups.

Can you show more detail of the connections between the two piggyback chips under the short red and blue jumpers?

Normally when this modification is performed, U3 is not removed and replaced with a socket, but instead the PAL is soldered directly on top while still attached to the board. Is it possible that when removing the chip, a trace under U3 was damaged/disconnected, or was it inspected/checked carefully to affirm that removing the chip did not disturb the connections?

Quote from: sigma7 on Yesterday at 11:10:44 PM

QuoteClose ups.

Can you show more detail of the connections between the two piggyback chips under the short red and blue jumpers?

Normally when this modification is performed, U3 is not removed and replaced with a socket, but instead the PAL is soldered directly on top while still attached to the board. Is it possible that when removing the chip, a trace under U3 was damaged/disconnected, or was it inspected/checked carefully to affirm that removing the chip did not disturb the connections?

I did check the pads to make sure there was connection from the top of the socket. I will try to work out the traces.

The picture of the two chips was posted by accident, but basically was a reminder for me to try and check out the possibility of putting the wrong U2 chip in.

I've got two projects going on at once. I'm also building a Vintage chip tester. And it occurred to me another chip on my desk may have been picked up by mistake.

I remember before starting the piggyback that I checked the name on the back of the chip to make sure it was correct, but now that things are not working I'm questioning everything.