Don, Your first suggestion seems possible. 12 uH is fitted as supplied with the thermistor mod kit.
All components D16/D17 etc checked and are OK and there are no bad joints or shorts. John G3NYX. ----- Original Message ----- From: "W3FPR - Don Wilhelm" <[EMAIL PROTECTED]> To: "John Heaviside" <[EMAIL PROTECTED]> Sent: Wednesday, November 24, 2004 8:54 PM Subject: Re: [Elecraft] KS PLL Reference Oscillator > John, > > In my experience, you will find one of 3 things wrong. > 1) The inductor on the bottom of the board below the PLL crystal (L31) is > too large. If you have a 12 uH inductor there, request the 10 uH from > Elecraft. OTOH, if it is already 10 uH, look elsewhere. Elecraft is > currently shipping the 10 uH inductor with the kits which should match the > PLL crystal supplied. > 2) There is something unsoldered, poorly soldered, or shorted on the > thermistor board. > 3) R19, or parts of RP2 are improperly soldered or have an incorrect value. > > The BAND+/BAND- measurement points are the extremes, and your voltages at U6 > pin 1 are correct. Normal operation will not cause the varactor diodes to > be left at zero volts - this is NOT the cause of your problem. > > Be certain you have the correct varactors at D16 and D17 - looking from the > top of the board, D17 (1SV149) should be smaller than D16 (MV209) > > 73, > Don W3FPR > > ----- Original Message ----- > From: "John Heaviside" <[EMAIL PROTECTED]> > To: "elecraft reflector" <elecraft@mailman.qth.net> > Sent: Wednesday, November 24, 2004 3:09 PM > Subject: [Elecraft] KS PLL Reference Oscillator > > > K2 PLL Reference Oscillator Range. > > Further to my previous posting: the problem was not insensitive counter but > was in some way connected with the RIT/XIT control. The low frequency > reading BAND- is now stable but is too low. BAND+ is 12099 and BAND- 12078 > giving a range of over 20kHz which is outside specification. > > I have checked the circuit and all seems to be OK. > U5 pin7 (U6 pin3) is 4.06 at BAND+ and 0.01at BAND- which seems OK according > to the circuit diagram. > U6 pin1 is 7.48 and 0.00. This again seems OK as U6A has a gain of about 2 > with a small -ve bias resulting from the thermistor mod. > D16 and D17 are unbiased at the low end. (They actually self bias from the > RF ro a small +ve voltage at R19/C100). This seems to be bad practice as > the capacity will vary widely from component to component and result in > widely varying reference oscillator range. Hence my 20kHz range? > > Am I mistaken? Is there a fix for this? > > John G3NYX > _______________________________________________ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
