Pete Thank you, I will look at its some time in the future, right now I let it cook for a couple of weeks undisturbed and than I may cut the trace that seems not to do any thing. If you have a 100 MHz scope it will trigger on any pulse in this unit unless your scope is defective. I think there are features hardware wise in this unit that can be activated at manufacturing depending on price and demand. I am sure you are aware of instruments that a hardware wise the same and cost any where from $15 000 to $40 000 the only difference is the software imbedded and many times you can buy an upgrade. Bert message dated 11/18/2011 10:26:02 A.M. Eastern Standard Time, bell.pe...@gmail.com writes: All the pins have things connected to them - but pin 6 seems a little strange - it's connected to the 'ACT240 (in fact, it goes through 3 sections of the chip in series!) and finally to the xilinx chip - but none of these signals ever appear to do anything and the output is just constant high. It's possible that this the pulse is just extremely short - the fastest scope I have at home is only 100Mhz - but I would have expected to be able to tirgger on it at least.
Regards, Pete On Fri, Nov 18, 2011 at 9:09 PM, <ewkeh...@aol.com> wrote: > Pete > Thank you for doing all the work. This is great info and will help all of > us that want to discipline the beast. One more question, since you have done > so much testing is there one pin on the connector that has nothing > connected to it? > Thanks again Bert Kehren > > > In a message dated 11/17/2011 9:59:14 P.M. Eastern Standard Time, > bell.pe...@gmail.com writes: > > OK, I just managed to get some spare time to have a look at this, and > here are some conclusions: > > 1) The fine frequency adjust pot is not connected to the c-field > circuit. All the connections to it go across the board to the MAX1246 > ADC chip. The track is wired between ground and the vref output on > this chip and the wiper goes to a little pi filter (ceramic cap, 100K, > 1uF tant) that feeds channel 1 (pin 3) on the ADC. As far as I can > see, it goes nowhere else. > 2) The c-field current is fixed. The circuit is very simple - there > is a 5.1V reference generated using a zener and a 681R resistor to the > 8.8V and this is fed into a potential divider consisting of a pair of > 120K resistors. The centerpoint of this divider is connected to pin 5 > (+ve input) of a TLC27M4BI - the output of this amp (pin 7) is > connected via a 270R resistor to pin 2 of the FPC connector and hence > to the c-field coil. The return side of the coil (pin 1 on the FPC > connector) connects to pin 6 (-ve) of the opamp and via a 620R > resistor to the 5.1V reference. > > If there is any other input to this circuit, I have not been able to > find it, despite probing all over the board. > > Conclusion: > > This version carried out the fine frequency adjust digitally by > changing the reload values on the DDS chip - the reason the pot does > does nothing in this specific model is that the DDS trim is now being > carried out over the RS-232 port and as a result the pot value (if > it's being read at all) is not being used for anything. > > Adjusting the c-field still works, though - if you connect a DC supply > set at about 2.55V via a high value resistor (I used 100K) to pin 5 on > the TLC27M4BI next to the flex cable connector then you can trim the > frequency by adjusting it. > > Regards, > > Pete > > _______________________________________________ > 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. > > _______________________________________________ > 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. > _______________________________________________ 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. _______________________________________________ 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.
