Issue. Unable to undertake VCO alignment. Voltage at R30 fixed at 24mV.
The VCO oscillator test (Alignment and test Part II p 63) has passed. Well the frequency is 7.98MHz rather than 8->10 but that conceivably could be within the bounds of measurement error. In the VCO alignment test a DMM (Keysight U1271) clamped onto the left side end of R30 reads 24mV no matter what the setting of L30. I have looked everywhere over the appropriate circuitry but can see no issues. Including triple checking T5 which is 100% wound and fitted properly. I made the measurements from troubleshooting (PLL Reference Oscillator and VCO P 10) and got:- Reference Oscillator Output 0.72 VCO Output 0.24 VCO Buffer Output 0.59 All measurements are at the low end of the acceptable range but just in spec. I measured voltages in the area and have noted the following:- 1. U4 (MC145170) pin 7 CLK/SCK is at 5v as against the specified 0v. 2. U4 pin 13 PDOUT is at 5v rather than 4v. This feeds the inverting input of U6B causing the output to be low. 3. The gate input of Q18 is 0 rather than -1. I am at a loss as to what to check next and any suggestions would be most welcome. BTW I also have a ½ decent scope so can probe with that assuming I can figure out what I should be seeing. The K2 is a brilliant kit but seriously different to tube amps. which is my usual playpen. Thanks -- If you are afraid you are living in the future. If you are sad you are living in the past. If you are content you are living in the now. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
