Hi everybody,

I just bought a Cyclone that is not working and I wanted to see if anybody has tips on what to look for.

No LED's light up when I turn on the Cyclone. If I wait a few seconds and toggle the on/off switch quickly one or more times, the right-most LED comes on but nothing else. No reaction to button presses.

I checked the power and it looks fine, reading about 4.92V at the '+5V' test point. Battery also reads well over 4V.

I should mention that my Cyclone has a peculiar (to me) power supply mod. At the bottom of the PCB there are three capacitors soldered over the ceramic disk capacitors that seem to be the original filters/buffers for the 7805. What I find odd is that there are three caps, not one, and that one is tantalum, one axial electrolytic, and one boxed where I presume that means a film capacitor.

I have tried resetting the 80C31 CPU by shorting pin 9 to 5V, no effect.

I pulled both the ROM and RAM chips from their sockets because I know that that can 'fix' contact corrosion. No effect. I think this means I have also effectively erased the RAM chip.

I just used my EPROM programmer to read the ROM chip. It is bit for bit identical to the v1.0 'Cyclone.BIN' file in the files section of this group.

The only other fix I have seen discussed on the internet is replacing the 80C31. What I can also consider is replacing the retro-fitted power supply caps.

Ideally I would like to have some 'evidence' that something's broken before I start randomly desoldering things. I have a digital oscilloscope but I don't have the experience to know what to look for. How do I see, with the scope, if the CPU is behaving well

Any ideas are welcome. Cheers!

Jacob