voltage display problem
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I have some problems with my K2 transmitter section, but first would like to clear up a problem with the voltage display. After giving the correct value for several days, it suddenly began to read 23.3 volts no matter the input voltage. This persists even after resetting both the relays and the whole system (4-5-6). The volltage at the Vsense of U6 (control brd) is correct; I.e. about 2.1 volts for 11.9 in or 0 for 0v in but the display only reads 23.3 v. The current display is correct. Any hints of where to look next?
joe carney KB3FBR _______________________________________________ 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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Joe,
Check the VSENSE signal path from U3 pin 7 to U6 pin 5. The easiest way to check is to measure the voltage at both points. On the U6 pin 5 end, measure the voltage directly on the chip pin rather than the socket. If the voltage is different, there is some break in the path - check the socket and be certain pin 5 is securely in contact with the socket. If you find the voltage going into U6 pin 5 is the same as at U3 pin 7 and your voltage display still says 23.3, the only cause can be a bad input on U6 (in that case, you need to replace the firmware chip). 73, Don W3FPR MARY HAYS CARNEY wrote: > I have some problems with my K2 transmitter section, but first would like to clear up a problem with the voltage display. After giving the correct value for several days, it suddenly began to read 23.3 volts no matter the input voltage. This persists even after resetting both the relays and the whole system (4-5-6). The volltage at the Vsense of U6 (control brd) is correct; I.e. about 2.1 volts for 11.9 in or 0 for 0v in but the display only reads 23.3 v. The current display is correct. Any hints of where to look next? > > joe carney KB3FBR > _______________________________________________ > 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 > > > 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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Don:
Thanks for the quick reply. Indeed the voltage at pin 5 of U6 is as expected (2.31 for 11.9 v in). To be sure: the firmware chip is U6, on the control board?? I'll replace that and see what happens. If I may continue with my litany of problems since they may well arise from U6(ctrl brd): The receiver works well but problems show up on transmit. On initial test, it indicated excess current even at lowest power setting. After several trials, it would no longer switch to transmit. (The voltage at D6 anode rises to about 4 v then drops in spite of having 7.9 v at the emitter of Q1 (ctrl brd)). Pin 2 of U8 (ctrl brd) remains at 0 v though there is 0 v at the rf det on the rf brd. Right now I'm not ruling out a problem from Q5 through Q8 on the rf brd, which may have fried U6 (ctrl brd), so I'm still looking. Are these problems compatible with a faulty U6 or do I need to continue looking? joe carney KB3FBR If you find the voltage going into U6 pin 5 is the same as at U3 pin 7 and your voltage display still says 23.3, the only cause can be a bad input on U6 (in that case, you need to replace the firmware chip). 73, Don W3FPR _______________________________________________ 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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Joe,
These symptoms are possibly (but only indirectly) caused by a defective U6. The firmware is the major element in the power control system, but from your other conditions, it is difficult to pinpoint - if indeed the power control circuits were the cause for low power, that would not cause a high current draw - in fact the current draw would be low rather than high. Your D6/Q1 statement is a bit confusing. Check the 8T and 8R voltages at D6 and D7 anodes as well as the collector of Control Board Q1 and Q2 for both the receive and transmit conditions. The voltage at the anode of D6 is 8R (through RFC12) and CB Q1 is the 8T control transistor. 8T is at a high voltage (8 volts nominal) during transmit and 8R is at a high voltage during receive - they should never be on at the same time. High Current is usually a problem associated with the low pass filters or T4, but resolve the 8T/8R situation first because if both are active at the same time, high current could result. 73, Don W3FPR MARY HAYS CARNEY wrote: > Don: > Thanks for the quick reply. Indeed the voltage at pin 5 of U6 is as expected (2.31 for 11.9 v in). > > To be sure: the firmware chip is U6, on the control board?? I'll replace that and see what happens. > > If I may continue with my litany of problems since they may well arise from U6(ctrl brd): > The receiver works well but problems show up on transmit. On initial test, it indicated excess current even at lowest power setting. After several trials, it would no longer switch to transmit. (The voltage at D6 anode rises to about 4 v then drops in spite of having 7.9 v at the emitter of Q1 (ctrl brd)). Pin 2 of U8 (ctrl brd) remains at 0 v though there is 0 v at the rf det on the rf brd. Right now I'm not ruling out a problem from Q5 through Q8 on the rf brd, which may have fried U6 (ctrl brd), so I'm still looking. > > Are these problems compatible with a faulty U6 or do I need to continue looking? > > joe carney KB3FBR > > > If you find the voltage going into U6 pin 5 is the same as at U3 pin 7 > and your voltage display still says 23.3, the only cause can be a bad > input on U6 (in that case, you need to replace the firmware chip). > > 73, > Don W3FPR > > > _______________________________________________ > 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 > > > 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 MARY HAYS CARNEY
Joe,
I might point out that the most likely cause for failure of Control Board U6 is static damage. When handling it (or other static sensitive devices), follow good ESD practices. Most modern active devices *are* static sensitive to one extent or another. An antistatic mat and a wrist strap are a good investment. For inexpensive antistaric measures, look for a mat a bit bigger than a computer keyboard size at those places dealing in computer components - TigerDirect (www.tigerdirect.com) is usually my first place to look, but there are many more - search on 'antistatic' at the site. 73, Don W3FPR MARY HAYS CARNEY wrote: > Don: > Thanks for the quick reply. Indeed the voltage at pin 5 of U6 is as expected (2.31 for 11.9 v in). > > To be sure: the firmware chip is U6, on the control board?? I'll replace that and see what happens. > > _______________________________________________ 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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