I recently acquired a Laser 128EX, and populated the memory card to 1MB. I tested out Henry Lowe's Card Cat and RAMWerks programs, and I'm seeing some odd display issues that I'm trying to figure out if my Laser is having issues, or it's some odd bug in the program that affects Lasers. So if any Laser owners would be willing to check out these programs, I'd appreciate it.
In Card Cat, the display issue I see is when it first starts up and says "scanning x of 7", once it hits slot 3, it starts incrementing numbers after the 7. So it will say 3 of 71, 4 of 72, 5 of 73, etc.
With RAMWerks, it's failing the first bank of memory. And all the other memory says OK, but has a question mark next to it. I've shifted the ram banks, and bank 1 always fails. Additionally, the percent completed is also showing extra digits. Like "Test Progress 76%7" and "Testing RAM bank 10 of 129".
I did reach out to Henry, but hoping to get some additional data points from other Laser owners. Links to the programs are below.
Our forum colleague skate323k137 also has a Laser 128 (you can see it in this post). If you PM him, I am sure he will find the time to give Card Cat and RAMWerks a try on his machine.
Thanks for the lead. Looks like he hasn't been active in a little over 5 months, but I'll give a PM a try.
Henry said using MAME he was able to duplicate the first bank failure with RAMWerks, but only when using ROM 6 or 6.1. I'm running 4.5, as 6/6.1 seems to have broken Smartport and even "dumb" 3.5 drives. My concern is MAME maybe isn't exactly emulating the hardware correctly, they may have just hooked up a clone of the IIc to the laser ROM and called it a day. And there could be some slight hardware differences.
Henry believes that Laser didn't impliment the RAM Factor functionality exactly as AE intended, and thats why the first block fails with RAMWerks. But so far, other programs that use said RAM, like Copy II+ and Appleworks seem OK with it.
Unfortunately, I think I've found that this unit does have some kind of display issue. I was running the official Apple Diagonistics, and noticed erroonious/extra characters on the screen as I moived through the menu. I ran the character generator test, and it was not good. Basically, it just alternates between these two screens where one looks normal, and the other, not so much. Both the base and aux RAM have passed multiple testers, so I don't think it's a RAM issue. Anyone have any ideas what to look at?
Edit: Looking through the technical manual, I'm guessing either I need to flash a new charachter rom, or possibly replace a 74HCT175 that is involved in the circuit. Does that sound right? Unfortunately netiher are currently socketed, so it will be a bit of work to get them out. Once out, I could dump and verify the hash on the ROM (and burn a new one if needed), and I have a backbit tester to check the logic chip. Thoughts?
Cargen 2.JPG
Chargen 1.JPG
I have several Laser 128's, EX's and EX/2's with different ROMS and memory cards (populated differently). I'd be glad to help. Henry is great to work with, we worked together on proper identification of the Franklin Ace 100 (not 1000). I'll be a little hit and miss for the next week, then I should be more available. Hit me with next steps in your testing protocol.
Thanks. I think my display issue is local to my unit. I desoldered the 74hct175 in the char gen circuit and it initially failed in my BackBit chip tester pro, but passed every time since. I have new ones coming from DK tomorrow. Along with some 28C64s, incase it turns out the rom is bad. But I'm sure your data points on testing the extended memory would be interesting to Henry (and me) whenever you have time.
Well, it's not the 74HCT175. And it's not the video ROM itself. I'm starting to run out of ideas. The EX does have two 41464 RAM chips installed for the video circuit. I wonder if maybe one (or both) of those could be bad?
I'm somewhat out of my waters here, so if anyone has any ideas, I'm open to them. Service manual with schematics and descriptions is here.
Edit: for grins I just tested some of these issues in MAME and see the same graphical glitches. So, at this point I'll just wait till 8bitHeaven has time to check things out.
Sounds like the main ram (128 on board) may have a bad chip. Best to find a tester that tells you which byte is bad so you can swap that chip.
Chiming in here from the MAME side of the equation: I noticed this same odd display problem (in Apple IIc Diagnostics 2.0 > Video Patterns Test > Character Generator Test), when emulating las128ex with the 4.5 firmware, and a similar problem on las128e2 with the 6.1 firmware.
However, after updating las128ex to the 6.0 firmware, this particular problem is fixed (although there are still odd stray characters when navigating through the diagnostic menus.)
Since MAME doesn't emulate bad RAM (on purpose, anyway!) this indicates to me that the problem is with Laser's text firmware not being entirely faithful to the original Apple II behavior.
Maybe your RAM is fine, and you should get a second opinion running the same test on another Laser 128EX, with the same firmware?
I'm pretty sure my RAM is all good. It has passed a couple different test programs. I also pulled the video ROM and a LS chip associated with it, and they tested fine. Even burned a new ROM and tried a new LS chip for giggles, same issues. And yeah, I noticed when I was checking out the 6 and 6.1 ROMs in the machine, the CG test looks better, but there are still other display issues. Working with Henry Lowe, he managed to fix all the display issues in beta copies of Card Cat and RAMWerks he sent me. After all of this, I believe everything is fine, I just ran into a 1% case of where the Laser isn't fully compatible with some kind of display method available for use on A2 machines.
Vtech did at some point revise the Laser EX motherboard. Mine had a "VTC Version A" sticker on it. I have seen pics of boards with a B sticker on them as well. And the schematics don't exactly match my board. For example, VTECh shows clamping zeiners on the RGB lines in the schematic. But are completely absent from mine. But I have seen pictures of boards that have them. Who knows, maybe they made some changes late in the model to fix these issues. Unless someone with a later B revision board can test, won't know for sure. But more than likely, this is just an edge case.