Hi Carl, Well, different meters use different AC measurement techniques. The very cheapest meters just use a capacitor to filter out DC, and then a diode and RC filter to rectify the AC before feeding it to the ADC. These kind often do not have a frequency response much above a few kHz, although depending on what comes before the diode and the filtering, they can have good high frequency response. The better ones directly sample the AC waveform at about 100kHz or 1MHz and then take the RMS of the samples. These have a good response up to about half the sampling frequency. There is a good chance that your meter will pick up SOMETHING if there is significant ripple present. Yes, I would say about 0.1 V would be a good rough threshold. Sean On Sat, Sep 5, 2009 at 12:50 PM, Carl Denk wrote: > I have 2 multimeters, both do AC volts, down to the mv range, one has > RS-232 to the PC, good thought. I'm assuming anything over say 0.1 volt > amplitude would be too much ?? Both meters are what I would call, mid > range quality > > Sean Breheny wrote: >> What about using a multimeter set to AC volts to look for ripple? What >> kind of meter do you have? >> >> Sean >> >> >> On Sat, Sep 5, 2009 at 10:22 AM, Carl Denk wrote: >> >>> Thanks for the quick reply. The closest thing to a o-scope I have is the >>> PC sound card plus Zeitnitz's software >>> http://www.zeitnitz.de/Christian/index.php?sel=3Dscope_en >>> Would have to make a voltage divider to get the 5 volt down below 1 >>> volt, but that's no problem. Do you think that will work. The other >>> quick option is, I have a couple of 1000ufd caps (that's the present >>> value), they are larger, and have leads out both ends (existing ones >>> stand up on the PCB), but I could temporarily solder them in to see what >>> the effect is. Otherwise I would have to order from Mouser or someone. >>> >>> I had previously looked at all caps for bulging, or other deformation, >>> and there is none. >>> >>> ps: will be gone from the PC for a couple of hours, then around for most >>> of the day. >>> >>> >>> >>> >>> enkitec@gmail.com wrote: >>> >>>> Carl Denk wrote: >>>> >>>> >>>>> Disconnected cable from power supply board to video board, and the 5 >>>>> volt supply measured at 5 volts. Used a 20 ohm resistor to create a 1= /4 >>>>> amp load, still had 5 volts, changed to 10 ohm resistor for 1/2 amp >>>>> load, and the 5 volt was back to a couple of tenths volts. I'm assumi= ng >>>>> that some regulator chip is shutting down due to over current, but am= at >>>>> a loss where to go from here. >>>>> >>>>> >>>>> >>>> =A0 =A0 Suggestion: >>>> >>>> =A0 =A0 Verify ripple at 5V output at 20 ohm load. >>>> =A0 =A0 If excessive, replace the 5V filter capacitors. >>>> >>>> =A0 =A0 Mark Jordan >>>> >>>> >>>> >>> -- >>> http://www.piclist.com PIC/SX FAQ & list archive >>> View/change your membership options at >>> http://mailman.mit.edu/mailman/listinfo/piclist >>> >>> >> >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist