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[rayarachelian]

The 6504 does get pretty hot, so maybe something is wrong with it.

That doesn't sound good at all. Hope your replacements arrive soon.

[AlexTheCat123]

Hope your replacements arrive soon.

I hope so too! The only place that I could find a replacement 6504 was in China, so it could take around two weeks to get here. The 2732 ROM will arrive on Wednesday or Thursday, though. I'll keep you posted about the results of installing the new parts!

[rayarachelian]

Yeah, it could have gone bad, but, any chance there's a short somewhere on the 6504's socket, or an output being sent to something that only the 6504 itself should output like address lines?

If you pull out the 6504 and put it on a breadboard and give it +5V and GND, does it also heat up? I'd worry about these before replacing the 6504 with another - if something on the I/O board is causing it to fry, it will damage the replacement too.

Sadly, yeah, 6504s are rare. They're just 6502s with extra I/O lines, but ofc you can't easily replace them with a 6502.

[patrick]

6502 and 6504 are based on the same die, they just have different packages. So you could use a 6502 with an adapter socket. Connect A12..15 low and /SO high. Certainly you don't want piggiback boards in a vintage machine, but for a quick check this should be acceptable.

Have you checked the reset signal on the CPU board? Sometimes capacitor C8 gets leaky and the NE556 will stick low. To confirm this, you could disconnect C8 and use the manual reset button on the back of the machine.


For the COP421 I have designed a replacement board a few years ago: http://john.ccac.rwth-aachen.de:8000/patrick/COPSreader.htm. This was intended as a tool for software analysis, but could also be used as a replacement for a defective part.

[AlexTheCat123]

Yeah, it could have gone bad, but, any chance there's a short somewhere on the 6504's socket, or an output being sent to something that only the 6504 itself should output like address lines?

I've checked the socket and there aren't any shorts or any signals going places that they shouldn't.

If you pull out the 6504 and put it on a breadboard and give it +5V and GND, does it also heat up?

Yep. It still heats up on the breadboard.

Have you checked the reset signal on the CPU board?

The reset signal looks good. It goes low for around a second to reset the 6504 and then it goes high again.

For the COP421 I have designed a replacement board a few years ago

I made one of your COP421 replacement boards a few days ago and I have it installed in my Lisa right now. I think I accidentally called it the X/COPS in a few previous posts because I was browsing eBay and saw one that seems to be made by VintageMicros that's called X/COPS and I just got the names mixed up. It doesn't seem to be relaying signals from the keyboard and mouse to the VIA, but it's definitely sending signals to the LS153 mux that connects to the keyboard and mouse and it's sending sync pulses to the keyboard as it should. I'm guessing that this is related to the I/O board error 57 that I'm getting and that it will start sending these signals to the VIA once the Lisa can pass the self-test without any errors.

[AlexTheCat123]

Finally I've got some good-ish news! The disk controller problem is still a thing, but I did get the keyboard and mouse working! I decided to desolder the COP421 from my original I/O board and move it to the new board and that fixed the keyboard and mouse problems. I guess something's wrong with my COP421 replacement board, but I'm not sure what it could be since I have verified that the contents of the EPROM are correct and I've checked that all of the connections on the adapter board are good. With the keyboard and mouse working, I'm now able to enter service mode and I checked the memory location that you specified for where version of the I/O ROM is located. It matches the 00 that is displayed in the upper right hand corner of the screen during the self-test. With this problem fixed, I guess it's just a matter of getting the floppy controller working and figuring out what's wrong with my COP421 replacement board. The COP421 issue is particularly weird because my COP replacement seems to handle soft power-on just fine, making it seem like it's executing code properly, but the keyboard, mouse, and soft power-off don't work.

[Lisa2]

Let it be known that the 6507 CPU is a direct replacement for the 6504 CPU on the Lisa I/O board.   The 6507 may be a little easier to find since it was used in millions of Atari video games. There is a minor difference on one or two of the pins but they are not used on the Lisa.  As already was mentioned the Die is a 6502 on both the 6504 and the 6507, just with different pins brought out in the package.
HTH,
Rick

[AlexTheCat123]

Let it be known that the 6507 CPU is a direct replacement for the 6504 CPU on the Lisa I/O board.

That's good to know! I wish I'd realized that before I bought a 6504 from China...

[AlexTheCat123]

I just got the replacement 2732 I/O board EPROMs in the mail today, but my TL866II Plus programmer won't program the chips because they require a 21V Vpp when programming, but my programmer can only go up to 18V. The weird thing is that I've programmed 2716s that also require a 21V Vpp on this programmer in the past and it has worked fine, but now I'm stuck since I can't write to these EPROMs. Hopefully I can find a solution quickly and get the code into this chip!

[jamesdenton]

Can you read the ROM and compare the checksum? Wonder if that would be enough to confirm.

[blusnowkitty]

I just got the replacement 2732 I/O board EPROMs in the mail today, but my TL866II Plus programmer won't program the chips because they require a 21V Vpp when programming, but my programmer can only go up to 18V. The weird thing is that I've programmed 2716s that also require a 21V Vpp on this programmer in the past and it has worked fine, but now I'm stuck since I can't write to these EPROMs. Hopefully I can find a solution quickly and get the code into this chip!

I'll throw in my two cents here; since I do so much with all kinds of old computers I went and bought myself a Willem programmer. Fairly cheap, supports the really common 27-series EPROMs. Software can be annoying to set up, though, and you need a PC with a built-in parallel port. Probably doesn't hurt to wire up a 5 volt adapter as well, otherwise you'll be trying to step up 5v at 500ma from the USB port (power only) to at most 28 volts...

[AlexTheCat123]

I found a strategy that, while incredibly inelegant, seems to be getting the EPROM to program. I just made a simple shell script that programs the EPROM over and over again and, after letting it run for a couple hours and then reading the contents of the chip, it seems to have successfully programmed around half the EPROM. Hopefully it will be completely programmed within a few more hours. I'm not sure how good these repeated writes are for the chip, but I bought 10 of them, so I'll still have 9 more if this somehow damages it.

[patrick]

So you program 15 minutes at 18 V instead of 50 milliseconds at 21 V? Could work.

You will run into problems if you ever try to erase this chip again. But since your Lisa is supposed to last forever, this will never be necessary 

[rayarachelian]

But since your Lisa is supposed to last forever, this will never be necessary 

Heh, the only immortal Lisa is LisaEm - and some day the only way to run it is running it inside an emulator. Yes, that may happen one day.

[D.Finni]

But since your Lisa is supposed to last forever, this will never be necessary 

Heh, the only immortal Lisa is LisaEm - and some day the only way to run it is running it inside an emulator. Yes, that may happen one day.

Sure, but first you'll have to finish writing the emulator and fix all of its bugs. 

*ducks and runs*