SYMBiFACE edge connector issues

[redbox]

Is it the fixed version of Firmware 3.1 (i.e 3.12)...?

The old version could cause a boot cycle error on a real CPC.

[Munchausen]

Arg! Well, I'm pretty sure it's a connection problem. I've resoldered the IDC connector about 5 times. It will then sometimes start, but if I move the cable around it stops working. I've tried different cables. I've also tested all the connections from the LowerROM to the edge connector test points (well, not really test points, I think they are the holes for connecting a centronics connector). I tested each connection while waving the cable around, and they all came through fine.


In short, I'm at a bit of a loss. It's clearly a connection problem, but I'm now guessing it must be in the CPC itself... though I don't quite know how... apart from anything, the CPC looks as though it could have been made yesterday, it's so clean and new.


Indeed, it is FW3.12. The standard firmware will not boot from the LowerROM either.


Any ideas?

[Munchausen]

Just tried the LowerROM on my 464, and it works beautifully


So I plugged the symbiface into it, and FW3.12 reports "RAM: 560K"!


I didn't even know extra RAM would work with the 464, because it lacks the banking mechanism - what's going on there?? And why does it not report 576K?


The only thing is, I don't get the symbos ROM boot logo. So I tried the symbiface back on my 6128 afterwards (without LowerROM), thinking the ROMs weren't being initialised for some reason on the 464, and I don't get it there any more either. Could it have become erased somehow? Could the LowerROM have caused it? I hope I haven't damaged my Symbiface at some time 


So now all that remains to do is:


1) Figure out what on earth is wrong with my 6128 (suspect bad connection in the CPC somewhere).
2) Get the ROM manager/other ROMs on to floppy disc or tape, so that I can actually boot some stuff, and test that the symbiface is definitely working 100% (most worried about this as it costs a pretty penny and is hard to replace).


Can rom manager and stuff be run from a 464 with the tape deck? Not that I have any way to make tapes, but I have one of those tape->3.5mm jack adapters, so I could plug it into my PC and play tapes to the 464 (I just got a replacement tape drive for my 464). Is there a tool to convert .dsk to .tap?


I STILL have no way to make floppies (3.5"). Don't suppose anyone wants to volunteer to make me a couple and post them to me? I'll happily pay for the discs/postage/time.


Thanks for your help guys!

[Bryce]

Are you sure you haven't just disabled the SF2 ROMs while you were experimenting?
As they are stored in a battery backed RAM, you may have also shorted the supply by mistake which would also erase the RAM-ROMs. The LowerROM Board wouldn't erase anything on the SF2.

Bryce.

[Munchausen]

They weren't disabled no, I double checked. A short is much more likely though - I think I accidentally shorted 5V to GND at some point for a split second (though the symbiface is on the 12V line of the same supply), and I'm not sure if it was before or after testing (I do remember that it was while the CPC was off though), but would that do it?


I didn't even know a short will erase the RAM... hopefully that is the cause. I could have shorted it accidentally at another time and not noticed (my PSU setup is a bit of a mess ATM).


Bryce, do you have any particular suggestions for checking the expansion port lines inside my 6128? I don't know where they all go, but I think some are direct to the z80 and some to the gate array? I guess I'll have to get the schematics and trace each line individually.

[Bryce]

No, the only way to properly test them is to test each one individually with an oscilloscope or a Logic Analyser.

Bryce.

[Munchausen]

Hmm, that's a bummer. I have a 1MHz scope, but that's too slow, right? I guess the scope/logic analyser is needed because the fault is intermittent and hard to trace?


I will try using the continuity tester on my multimeter, to see if that can find anything. If I don't I guess I can re-solder all the joints and hope I catch the problem. Does that sound reasonable?


Thanks.

[Bryce]

A 1Mhz scope is fine, you're not trying to read the pulse lengths, only their levels. Connect it to one of the data lines, set it to trigger on a positive edge with a trigger level of about 2V. When it triggers measure the voltage of the positive level. It should be 5V of course. If it doesn't trigger or the level is lower than about 4.75V then that's the pin giving you problems. If all is ok, move on to the next one. Do this for all Data and Address lines.

Bryce.

[Munchausen]

Great, now there's a plan! But it's back to waiting again, until I can retrieve my scope in a few weeks time


At least I can play with the 464 in the mean time I'm going to make some tape images and convert them to wavs

[Munchausen]

I only just thought this through enough to realise that I can't do much testing of the symbiface with only a tape drive anyway, because even if I load the ROM manager I'll have nowhere to load ROMs from without a disc drive! D'oh!