I've got good news. I had the wrong Capacitor in the BFO section and just happened to have a replacement for C169. Whoops I told on myself! Any way at TP2 +4917.74 and -4911.90 for a difference of 5.84. Don struck again. Hi Hi.. I'll check the voltages on RP6 tomorrow.
Ed.. AB4IQ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of K2bew Sent: Saturday, January 19, 2019 5:35 PM To: [email protected] Cc: Elecraft Mail List <[email protected]> Subject: Re: [Elecraft] K2 VCO Alignment T5 L30 Don et al, I tried a 15pf cap ( what I had on hand) at the source of Q19 to ground and I got .025v on R30 that did not change with the adjustment of L30, essentially no voltage. So, I took it off and it went back to 4.5 volts. So, then I tried Vicenç, EA3ADV's suggestion and I put 17 turns on the red wire of T5. That got me a voltage of 8.5V on R30 with L30 bottomed out that I was able to easily back off to a stable 6 volts. I went ahead and did the voltage tests on the other bands and had a nice range of 1.844 to 6 volts as my low and high on the VCO. So, that's all set. However, new problem. I went on to the test the BFO and I have 0000.04 kHz. on TP2, so it's not working. I went to the trouble shooting guide and I have 0.058 Vrms on pin 6 of U11 with the RF probe. Looking at the archives of the reflector that would indicate that U11 is bad and I need a replacement, correct? or are there other things I should look at first? The good thing is I'm becoming very accustomed to the radio and enjoying the trouble shooting. Thanks for all the help, I really appreciate it. 73, Tom Bewick, K2BEW On Fri, Jan 18, 2019 at 10:33 AM Don Wilhelm <[email protected]> wrote: > Tom, > > Normally I would say to spread or compress the turns on T5, but > Elecraft encountered a batch of J310 FETs that do not work very well > at Q19 - the PLL reference oscillator. These troublesome FETs have > now been purged from the Elecraft stock, that the problem should go away > going forward. > I am not sure that is your problem, but it is worthy of checking. > > First question is - did you get good frequency readings for the PLL > Reference Oscillator range? If it fails, you see a strange frequency > reading at the high frequency end (when BAND+ is tapped). > Now, the other "funny" thing is that it sometimes checks OK with the > internal counter probe plugged into TP3, but fails when the probe is > removed. > > Under those conditions, the PLL and VFO do not lock together > > So the first thing to try is to solder a 10 to 15pF capacitor between > the source of Q19 and ground. Then between a combination of adjusting > the red turns on T5 and L30 see if you can obtain the correct R30 voltage. > > If that is successful, then all should be well. > > If not successful, get a replacement Q19 from Elecraft. Send the part > number and description to [email protected] and ask for a replacement. > > If that does not correct things, then email me and we can go through > some other checks to determine the source of the failure. > > 73, > Don W3FPR > > On 1/18/2019 8:48 AM, K2bew wrote: > > Don et al, > > > > Since I know Don monitors the reflector as well as the support > > emails, rather than email Don directly I thought I would ask the > > question on here because I know I always find it helpful to read > > other peoples questions > on > > here and Don's answer. > > > > Building the K2 I am at the VCO Alignment voltage check on R30 and > > adjusting L30. > > VFO frequency set at 4000.00 kHz > > I initially got 3.5 volts and bottomed out L30 to get it to 5.5 > > volts, > and > > then I over screwed it to try to get that last half a volt and ended > > damaging it, so, then I carefully took out L30 and put in a new one. > > > > I also took out T5 and rechecked all the ends for continuity, > > rewound the green wire to space it exactly in the middle of the red > > winding and > spaced > > everything evenly. I confirmed it is the large yellow core, I have > > 16 on the red wire and 4 on the green (by the way the illustration > > shows 14 > turns > > of red) . I verified I have R30 as Br-R-Br 120 ohms with both my DVM > > and > by > > color, and I verified C72 is 271, and I reflowed the solder on both. > > With a new 4.7 inductor (large slot, no red mark) in L30 I now get > > 2.75 volts on the left side of R30 to start with and it bottoms out > > at 4.5 > volts > > (I was very careful to not bottom it out too hard this time and > > damage > this > > one, and I have already ordered a couple new ones from Elecraft). > > > > What else can I do to increase that voltage? Would changing the > > number of windings on T5 change it enough to get to 6 volts? > > > > Thank you and 73, > > Tom Bewick K2BEW > ______________________________________________________________ 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] ______________________________________________________________ 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]
