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ProFile post fails with 5 flashes

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  • 68kMLA Supporter

I have two ProFiles. The drives and PSUs from both work okay with one of the controller boards. Combining either PSU/Drive with the other controller results in 5 flashes within about 30 seconds of power-on. The stepper motor moves around back and forth a few times at the same time the light flashes.


I took out each IC and cleaned with contact cleaner. In that process there were a few chips with corroded pins some of those pins broke off in the process. 

U28 - SN74S86N

U37 - 341-0067

U39 - SN74S74


I replaced U28/U39 and soldered a pin onto U37 where one had broken off. The symptom did not change after replacing those chips. 


The PSU and controller board have been recapped and both rails test okay under load.


Does 5 flashes indicate a specific failure?

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I'm not aware of it having this meaning, but it's possible that I haven't run into this sort of problem before.


I hate to advise it, but study of the 247-page ProFile Level II Service Manual might shed some light on what's happening here. Page 142 and onward seem to describe what the ProFile firmware attempts to do during power-on, so if you can relate that narrative to what you're seeing, you might make some progress in your troubleshooting. This is a lot of work, but it probably beats reading the reverse-engineered firmware, which you could do instead :-) 


I haven't read these resources carefully, but I did search the service manual for "flash" and "blink" and didn't really find anything that would suggest to me some kind of error code that manifests itself as blinks. If that's the case, then it could be that the five blinks just means that whatever hardware error there is is manifesting when the surface scan reaches a certain early point in its progress over the disk.

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  • 68kMLA Supporter

I read through that Service Manual last night and it just leads down a path that recommends replacing the controller board. I guess I'll start carefully swap testing with the ICs from the other board. Thanks for the tips!

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Since you also have a working board, you may be able to do some side-by-side comparisons between what the electronics do on both. Do you have equipment you can use to take measurements of signals on the board? An oscilloscope or a logic analyser would be especially helpful, but not everyone has these to hand.

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