Alignment and Test, Part II
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Hello,
just completed my K2 to the Alinment and Test Part II. Here i have some problems... With the VCO test I always measure 8v at R30. The voltmeter reading does not change at all i tune L30 or the VFO. Thus I have thought T5 am wrongly wound. But no change after rewound it... The Troubleshooting in the manual was not a big help. I measured there the following voltages: Reference Oscillator Output, Pin 1 of U4: 1.1V VCO Output, Pin3 of U3: 0.4Vpp with an DC offset of 4v VCO Buffer output, Pin6 of U3: 0.8Vpp with an DC offset of 4v R30 left side: always 8V Can someone help me? 73 Peter - HB9DUT _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
Re: Alignment and Test, Part II
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Peter,
A probable cause is a soldering problem on the thermistor board. Examine it VERY closely, and if nesessary, remove it and re-do all the soldering. Remember that this little board does not have thru plated holes, so soldering on this board is more critical that for the rest of the K2. Also check all other components in the PLL reference oscillator area for proper values and proper soldering. Look at the schematic to identify the components (RF Board sheet 1 of 4, upper left corner). 73, Don W3FPR ----- Original Message ----- > > just completed my K2 to the Alinment and Test Part II. > Here i have some problems... > With the VCO test I always measure 8v at R30. > The voltmeter reading does not change at all i tune L30 or the VFO. > Thus I have thought T5 am wrongly wound. But no change after rewound it... > > The Troubleshooting in the manual was not a big help. > I measured there the following voltages: > > Reference Oscillator Output, Pin 1 of U4: 1.1V > VCO Output, Pin3 of U3: 0.4Vpp with an DC offset of 4v > VCO Buffer output, Pin6 of U3: 0.8Vpp with an DC offset of 4v > R30 left side: always 8V > _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by HB9DUT
Hi,
thank's for all the good pieces of advice. Unfortunately up to now without success... I accomplished the following steps: - checking all parts of correctness and correct value: -> ok - checking each solder point: -> ok - checking solder points of T5 and the thermistor board with an DMM -> ok i have also checked all DC voltages from the IC's in the PLL section: Ref. Pin VDC my K2 -------------------------------- U3 6 4.3 4.2 7 8.0 8.0 8 0.0 0.0 U4 1 2.1 2.1 2 2.4 2.3 3 0.0 0.0 4 2.3 2.3 5 5.0 5.0 6 5.0 5.0 7 0.0 5.0 ** 8 0.1 0.6 ** 9 0.0 0.0 10 0.0 0.0 11 0.0 0.0 12 0.0 0.0 13 4.0 0.0 ** 14 5.0 5.0 15 5.0 5.0 16 5.0 5.0 U5 1 0.0 5.0 ** 2 5.0 0.0 ** 3 5.0 5.0 4 5.0 5.0 5 0.0 0.0 6 2.0 2.0 7 0-4 4.0 8 5.0 5.0 U6 1 0-8 8.0 2 0-4 4.0 3 0-4 4.0 4 0.0 0.0 5 4.0 4.0 6 4.0 0.0 ** 7 0-8 8.0 8 8.0 8.0 ** this values are outside of the specification The 12 MHz Reference Oscillator is working with an range of 12.3 kHz. Does someone have still further tips where I to search could? 73 de Peter _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Hello Jim,
yes i have a O'scope. I mesured the following Signals: U4 Pin 4: 1.2Vpp sine form U3 Pin 3: 0.8Vpp sine form U3 Pin 6: 1.6Vpp sine form is this ok? 73 de Peter k4zm schrieb: > Peter: > > Do you have an O'scope? It appears that you have no input to Pin 4 if > U4 which is the output of the VFO that mixes in the Synthesizer. With > a scope you could trace back to see where the signal stops. Look at > Pin 6 of U3 and Pin 3 of U3. The synthesizer is not in a locked > condition so that means that the chip is not getting one of the > required signals. Since the Ref Osc is ok and has the proper range I > thing the problem lies in the VFO or Buffer circuit or maybe even the > VFO ALC circuit. > > 73 > Jim Younce K4ZM > K2 SN:18 > Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by HB9DUT
Hi Peter,
The significant voltage could be the PLL chip PDOUT, U4 pin13. Check for shorts on this pin that would give a zero reading. Not sure if the PLL chip itself would support such a low voltage whilst working normally. Have seen reported of odd effects with RFC15 the DC feed to the PLL chip U4 pin16, so check for actual DC continuity with this component. What you do not appear to state and this is very important, is the VCO oscillating or not?. Checks with the K2 frequency counter at TP1 would at least help as an initial test. The frequency read depends on the band in use and reference to the table at the beginning of Appendix B gives the range of VCO frequencies to be expected. Tests with the RF probe/DMM at TP1 should give a reading between 600mV and 750mV according to the Elecraft trouble shooting guide. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by HB9DUT
Oh my god - shame on me :-)
I found the problem, i use the wrong core for the T5. All was ok, the parts the windings on the core... but it was the wrong one.... Now with the correct core the voltage at R30 can be adjusted with L30. Thank you to all for the assistance. But i have another question: The internal frequency counter work, i have calibrated on TP3 with an externel counter. But on TP2 (BFO) i read only nonsens on the Display. My external counter reads the correct frequency at TP3. Maybe the level at TP3 is low or i have a problem with the RF-Probe. 73 de Peter _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by HB9DUT
See Elecraft Builders Alert #21, October 19, 2004.
The frequency counter input transistors Q9, Q10, 2N5179 on the K2 Control board can be low gain if the blue faced type. This gives similar symptoms to what you have on the BFO TP2 which has a lower RF level than TP1 or TP3 consequently can cause randow readings. Was discussed a few days back. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
Re: Re: Alignment and Test, Part II
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In reply to this post by HB9DUT
Peter,
For your BFO problem. Look at Q9 and Q10 (MPS5179) on the control board. If they are colored blue, they may be weak - Elecraft will replace them with the black ones. In the meantime, 2N2222s may be substituted. The signal level at TP2 is much lower than at TP3. Your probe must work since you were able to measure the PLL/VCO frequencies at TP1 and TP3. If I recall, you have a 'scope (if not, use an RF Probe) - you should see 0.025 to 0.070 volts RMS at TP2 (K2 menu must be in CAL FCTR or no rf voltage will be seen). On your 'scope this will be 70 mv to 197 mv peak to peak. If you have OK RF voltage on TP2, all should be good, but if not, check the level at U11 pin 6, that should be 0.20 to 0.70 Vrms (0.56 to 1.98 Vp-p). Since your external counter shows the correct BFO frequency, I suspect Q9 and Q10 on the control board. 73, Don W3FPR ----- Original Message ----- > > The internal frequency counter work, i have calibrated on TP3 with an > externel counter. > But on TP2 (BFO) i read only nonsens on the Display. My external counter > reads the correct frequency at TP3. > Maybe the level at TP3 is low or i have a problem with the RF-Probe. > _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by HB9DUT
Hi,
ok i think builder alert #12 describes exactly my problem with the frequency counter. I have ordered a pair of new MPS5179's for replacement of Q9 & Q10. As soon as the parts arrive I will again report 73 de Peter - HB9DUT _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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