Hi all,
I've been trying (in vain) to repair a Vortex SP512 (512K RAM expansion for the CPC464) for the last few days, but I'm getting nowhere because I don't have schematics and it's nothing obvious. I've tested the CPU, GA, EPROM, RAM, connectors and the general function of each logic IC. All seems fine, but it still doesn't work. Very frustrating.
Has anyone ever done any reverse engineering on this device or know where any (even unfinished) schematics are available. I fear I may have to give up on this if I can't find more info.
Bryce.
It may sound quite obvious but... might the problem resides in the CPC rather than in the Vortex SP512 board?
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The 464's (I have two to test with) both work perfectly without it.
Bryce.
Bryce,
Is the connector on the 512K expansion okay?
When you connect the board does the 464 still operate okay? If it does not then there is likely to be short somewhere.
If it does then are the passives okay? These may be damaged due to age.
Did you try a continuity check on the IC connections from what you can see connected. Those going under the chips would be hard to check of course.
Are you able to check the RAM in a different board (I understand there is 2 banks of 256K just like the one used in DK'Tronics memory expansions).
rpalmer
Power = 5V present and typical voltage drops seen.
CPU = Tried several known working CPUs.
GA = Tried known working GAs.
RAM = All tested externally (in DKTronics RAM expansion) and working.
EPROM = Tested and working.
Logic = Power and "reasonable" active output values seen on all chips.
When connected to the 464 I just get a black screen, however, the CPU is running normally and reading RAM. All connections (81 of them) to the mainboard were continuity tested and are fine.
Bryce.
I can see how this is a real doozie of an issue to resolve.
@Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225)
Is it possible to remove the RAM from the Board, and see what happens ?
Ray
Yes, and it does exactly the same - Black screen.
Bryce.
Quote from: Bryce on 08:33, 06 December 17
Yes, and it does exactly the same - Black screen.
Bryce.
The SP512 has the ability to force all the ram off through a software switch. This could be forced on - the IC that holds this information may be broken?
Or try disabling it's onboard rom, that will stop it from running the self test.
Alternatively see if this port is being activated:
FBBD port is decoded as: xxxxx0xxx0xxxx0x
The program could be attempting to activating the ram and that is then failing and it's gone black screen.
I wrote a test for it to check my emulation of it and to check it's working, but you can't get it to boot yet so it's a bit useless :(
Valuable information. The only IC that holds information is the EPROM and that's good. However, if I disable the EPROM I don't think the board will work at all? With the EPROM and/or RAM removed the device will most likely still give me a black screen, but I'll give it a go anyway.
Bryce.
Well, I own a CPC464 with Vortex SP512, it has the latest BOS providing 288 KB RAM for BASIC programs. The other RAM can be used for machine code or as printer spooler. It works like a charm.
If somebody wants to have the unit please PM me. I ask for 200 Euros including shipping cost. BTW: It was used by Vortex Computersysteme until they closed. This unit would be perfect for retro engineering.
Didn't you sell that with the 464 on ebay a few days ago??
Bryce.
Nope, didn't get high enough. And since I have to pay my bills I can't afford to give it away for nearly free. I know 200 bucks is kind of brazen faced, but one can see how much other guys ask for just a CPC464 or CPC6128.
I also have a SP512 - I am not going to sell it, but if you should need the EPROM or the like, let me know!
Bryce, I would also lend you the SP512 if that helps.
Thanks. I have arranged to hold on to the broken SP512 first, to see if I can reverse engineer some of it. A working one would be useful, but not worth the expense of sending it a few times around the world.
Bryce.