Does anyone have a picture of the Board showing where these diodes go ? Thanks, Dick, W1KSZ
-----Original Message----- >From: [email protected] >Sent: Jun 4, 2010 7:14 AM >To: [email protected] >Subject: [time-nuts] Fluke Thunderbolt Monitor Revisited > >Hi All > >As there still seemed to be unanswered questions regarding the circuitry of > these I've separated the two PCBs from one of mine to determine exactly >what is going on. > >Whether or not the regulator circuit is based in any way on the iCruze >original processor board I don't know but it's now quite clear that the >processor circuitry itself is an amost exact copy of Didier's version using >the >20 pin DIP C8051F330 processor. > >The only differences I've found so far are the values of the resistor in >the programming interface and those on the RS232 input but the layout itself >looks to be identical. >I'll go over it more thoroughly later and produce a complete schematic. > >Didier's original schematic, which includes the three series diodes for use > with a 5 volt supply, can be found here ..... > >_http://www.ko4bb.com/Timing/GPSMonitor/Schematic-3.png_ >(http://www.ko4bb.com/Timing/GPSMonitor/Schematic-3.png) > >As commented by Leigh earlier, all the diode positions on the PCB are >occupied by zero ohm links so I think it's reasonable to assume this is >probably > universal and ALL monitors are likely to need modifying to keep the >processor supply voltage at a safe level. > >The absolute maximum rated supply voltage is 4.2 volts, IO port and RST >pins are indicated as tolerating up to 5 volts, but the specified operating >supply voltage range is 2.7 to 3.6 volts so I would recommend fitting all >three diodes as per Didier's original circuit rather than just two. > >The supply to the display is taken directly from the output of the >regulator and not via the diodes. > >For anyone wanting to avoid hardware modification another option would be >to run the unit from an external 5 volt supply, as was originally >suggested, and let the onboard regulator just act as a dropper. >With a 5 volt supply the output voltage from the regulator is 3.6 volts >but of course it isn't regulating and the supply to the display is also >reduced. >I have found that my display at least will run ok at 3.6 volts but the >contrast pot may need adjusting. >However, if this route is followed there's little room for error and it's >important to make sure the external supply is kept below 5.6 volts otherwise >the processor supply will again exceed 4.2 volts. > >Fitting the diodes is a once and for all solution and is certainly the >preferred option. > >regards > >Nigel >GM8PZR >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
