uBITX v6 Low Audio - Back at it again
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Hi Richard,
Really sorry, my mistake, I have measured C10 again to the ground and this is also ~823 ohm.
But don't bother with C10, nor C30. This is the same as measuring resistance from base of Q10 and Q30 to GND.
In both there is ~823 ohms. Your measurements brings confusion as I was thinking we have only trouble at 2nd RX chain,
are you sure its not 0.82 kOhm? If this is 0.82k then its OK.
?
Anyway 50 ohm on base of Q30 is NOK.
Can You de-solder C30 and measure voltages on Q30 before replacing Q30?
?
Regards
Tomasz |
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Sorry, my bad. It is 0.82 kOhm, not 0.82 as reported. Thanks for catching that. Base of Q30 is in fact 50.8 ohms. i rechecked. OK, C30 will get removed and voltages checked on Q30. 73, Richard AG5M On Friday, February 28, 2025 at 12:38:02 PM PST, tomekdm sp7etd via groups.io <tomekdm@...> wrote: Hi Richard, Really sorry, my mistake, I have measured C10 again to the ground and this is also ~823 ohm. But don't bother with C10, nor C30. This is the same as measuring resistance from base of Q10 and Q30 to GND. In both there is ~823 ohms. Your measurements brings confusion as I was thinking we have only trouble at 2nd RX chain, are you sure its not 0.82 kOhm? If this is 0.82k then its OK. Anyway 50 ohm on base of Q30 is NOK. Can You de-solder C30 and measure voltages on Q30 before replacing Q30? Regards Tomasz |
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C30 removed. The end closest to the display came off when desoldering. PCB looks OK. With C30 removed, voltages on Q30 are: E = 1.74, B= 2.41, C=7.76 Pretty much as you mentioned. C30 will be replaced with 100nF, Evan was so kind to send me one snail mail. So until then, 73, Richard AG5M On Friday, February 28, 2025 at 12:53:23 PM PST, tomekdm sp7etd via groups.io <tomekdm@...> wrote: If after de-soldering of C30 voltages on Q30 will be near voltages of Q10, so: E= 1.6, B= 2.4, C= 7.9 Then You need to replace C30 with any 100nF (0,1uF) ceramic capacitor. If voltages will be still low as before: E= 0.0, B= 0.28, C= 11.00 Then Q30 needs replacement. Regards Tomasz |
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Unknown. I heated the end closer to the back of the PCB, and the cap fell right off the board, with a end still on the PCB. A check of the cap shows it is open, not surprising with the end missing. Anyway, I found a 0.1uF cap in the junk box, just a tad too big, Hi Hi, to put in on the board, but connecting it to the board gives me LOTS of audio again. When replaced with an appropriate cap I'll be back in business. Then to calibrate the BFO, frequency, etc. And have it on the air again. 73, Richard AG5M On Friday, February 28, 2025 at 02:25:59 PM PST, tomekdm sp7etd via groups.io <tomekdm@...> wrote: Interesting why it cracked/failed... due to mechanical stress, like bent of PCB... temperature shock...? or was it already bad since new... |
tomekdm sp7etd
Richard AG5M
