Hi everybody,

 9vozand and 

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 turbn 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 mods   . 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.oz

z

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 Y,, d  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