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Compatible CPU for Kaypro 2X?

Z80As were about 0.75 each back in the day for OEMs.

Note that Z8400(NMOS) is the "official" family name, with variants, such as Z84C00 (CMOS part). Also, Zilog suffixes the part with the speed rating, so that Z840004 is an NMOS Z80 rated at 4MHz, while a Z84C0008 is a CMOS Z80 rated for 8 MHz operation.

If you're really desperate, I'll got a few "pulls".
 
For the fun of it I tried the 20 MHz Zilog Z84C0020PEC in my Kaypro and it works fine (at original speed ofcourse)

They came form an UK seller for about 7 Euro's a piece
 
I ended up trying the 6MHz part I linked for now, as Jameco's extra charge for orders under $15 meant I'd be paying just as much if not a little more to order one from them. I'm hoping changing the CPU might change the symptoms of my machine so I can get closer to fixing it.
 
Chuck(G) said:
FWIW, I've found that replacing the CPU in most cases accomplishes little. I hope your case turns out better.
Click to expand...

Yeah, agree with Chuck.

In my 'kaypro' experience, I've had a bad CPU but it wasn't the only bad part.. Whatever killed the CPU also killed a few custom, and irreplaceable, IC's. The Z80's don't generally die on their own without something causing it, and whatever that was, probably killed other things along the way. If you're lucky, they didn't take out the Custom Gate Arrays, but if they did, it's pretty much game over (unless you have the knowledge to reproduce those with custom chips, I guess). Luckily the Z80 is cheap (and socketed) so it's not a big deal to swap it out.
 
Unfortunately swapping the Z80 didn't change anything (but I'm still glad I did as the old Mostek Z80 was pretty gross looking). However, I noticed that a chip seems to be straight up missing from my board, after looking at images of other very similar Kaypro boards online.

The chip is above the WDC branded chip, marked "Z80A PIO":

http://www.nightfallcrew.com/wp-content/gallery/non-linear-systems-inc-kaypro-484/IMG_1693.jpg

I don't have a clue what this chip does but could its absence be causing me issues?
 
The PIO provides an interface to the RTC and modem, and usually it's absence doesn't prevent CP/M from running (boards were left with PIO, RTC, and modem un-populated for the "economy" versions).

I don't think I have a description of what problems you are seeing. Can you describe what's wrong?
 
If you're talking about the 40 pin DIP above marked PIO (on your photo as the MK3884), it's a Z80 SIO chip, otherwise known as a Z8440, or in CMOS, as a Z84C40. The Mostek part number is a second-source ID.
 
durgadas311 said:
The PIO provides an interface to the RTC and modem, and usually it's absence doesn't prevent CP/M from running (boards were left with PIO, RTC, and modem un-populated for the "economy" versions).

I don't think I have a description of what problems you are seeing. Can you describe what's wrong?
Click to expand...

I just get a blank green screen with diagonal lines going down it when I turn the machine on, the same problem I had with a TRS-80 Model 4 I briefly owned actually. I don't even know where to start with that.
 
That sounds like either the video (analog) or else the CRT controller IC(s). Hard to say which without seeing the pattern. The analog circuitry is probably repairable, and CRT controller chip might be replaceable, but the custom-LSI CRT chip is probably only replaceable by cannibalizing another Kaypro.
 
durgadas311 said:
That sounds like either the video (analog) or else the CRT controller IC(s). Hard to say which without seeing the pattern. The analog circuitry is probably repairable, and CRT controller chip might be replaceable, but the custom-LSI CRT chip is probably only replaceable by cannibalizing another Kaypro.
Click to expand...

It's really hard to see because the CRT is so dim (and doesn't respond to the brightness knob) but there's kind of a big green box with lighter horizontal lines going across it.

D1j6LblWoAETfgt.jpg
 
I'm no expert in the area of video, but that could almost just be the normal raster of a blank screen, with brightness set to maximum. Still, blank screen means nothing (software) is running. If the brightness knob does nothing, that might imply something wrong with the video circuitry. It's probably going to take old-fashioned detective work, and an oscilloscope, to track down what is wrong. I guess the good news is that there is a raster, so some clocks are still working.
 
durgadas311 said:
I'm no expert in the area of video, but that could almost just be the normal raster of a blank screen, with brightness set to maximum. Still, blank screen means nothing (software) is running. If the brightness knob does nothing, that might imply something wrong with the video circuitry. It's probably going to take old-fashioned detective work, and an oscilloscope, to track down what is wrong. I guess the good news is that there is a raster, so some clocks are still working.
Click to expand...

I don't own an oscilloscope, time to find someone who does I guess...
 
durgadas311 said:
I guess the good news is that there is a raster, so some clocks are still working.
Click to expand...

I don't know how good the news is though. If I recall, I was also getting this screen on my 2/84 which turned out to be the bad custom chips. Hopefully it's not that on his, but I'm not sure if this is enough to know if it's bad or good news yet. :)

Generally I find that computers that don't power on at all make me the most optimistic that they can be fixed since it's usually just a power supply issue... Things like this (similar to the Commodore "black screen") could be just about anything.
 
I do have a multimeter at least so I could probe the custom chips and see if they're getting correct voltages and such, granted, I don't know what said custom chips are...
 
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