What were the results of the PLL Reference Oscillator test - especially
the high frequency at TP3? - the frequencies please.
The 5 volts on the SCK signal is normal.
Do not wear out the slug in L30!
Is this a new build or the result of upgrades to an old K2?
Do you have an oscilloscope with a 10X probe?
73,
Don W3FPR
On 1/27/2021 6:59 AM, M Bak wrote:
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
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
