On 10/07/2012 8:15 PM, Polymorph wrote:
On 10/07/2012 6:30 AM, Michael J. Mahon wrote:Good luck!OK, after testing I do appear to have a short somewhere. Both the -5V and -12V lines appear to be shorted - using the continuity tester, I get a continuous beep between these lines and ground. When testing the +5V and +12V lines, I get no beep at all (which is what I would expect for all lines). So I guess I'll need to trace back through the -5V and -12V lines and find whatever it is that is causing the short. I hope it's something fairly obvious, as I'm a software guy by day - and whilst I'm comfortable enough with a soldering iron and multimeter, its certainly not my area of expertise. ;-)
OK... I don't think my previous testing was valid (which I'm sure someone will tell me why soon). If I test the +5 and +12V lines with the multimeter probes reversed I also get a continuous beep out of the continuity test.
I checked the voltages, both +5 and +12 were very low - about 0.8V. The -12V and -5V were about half of what they should be (i.e. -5V was measured at about -2.5V and 12V was measured at about -6.5V). So it sounds like the fault might actually on the positive side somewhere.
Am I right this time, or am I still barking up the wrong tree? -- Cheers, Mike Find my Apple II projects online at: http://apple2.sytes.net/