Bruce Griffiths wrote: > Jim Robbins wrote: > >> My SR620 fails in its Self Calibration routine at "Cal Error 07". The Users >> Manual describes this error as a problem with the "Start TAC" (Time to >> Amplitude Converters) and indicate that this flags a Hardware problem in the >> circuits which perform the analog interpolation between the 90 MHz clock >> ticks. Anyone have any experience with this? Is this a repair shop problem >> or user correctable? I am unable to find a "Service Manual" for this unit >> also. Many thanks for any input. Jim Robbins >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > Jim > > The TAC is a fairly straight forward circuit comprising a capacitor that > is pre charged to a reference voltage and discharged at a constant > current during the short time interval to be measured. > At the end of this time the voltage across the capacitor is measured by > an ADC which also measures the STOP TAC output among other things. > Since it uses discrete components and the manual describes how it works > in some detail it should be fairly easy to troubleshoot the circuit even > without a schematic. > > Bruce > According to the parts list the integrator capacitor used in the TAC is a 100pF Z5U unit. If this is indeed correct then its no wonder linearisation of the TAC output is required. However the sample and hold cap is sted to be polypropylene in the text whilst the parts list specifies polystyrene.
Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
