Re: Sbitx finals replacement
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So my problem I suspect is in the transmit section of the Sbitx. I got out the schematic and measured dc voltage on the source and gate of Q9 IRF4905. They are both the same 13.79 volts. So perhaps the PAs I bought are suspect. My thought is that when q10 turns on to allow Q9 to switch something is still grounded at the PAs. ? If someone here has their open I would like to get a voltage reading off Q9 and the PAs. ? ? Art N2AJO If I am not learning I am not having fun ? ?
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From: olson339@... <olson339@...> Sent: Monday, August 15, 2022 12:33 PM To: 'Art Olson' <olson339@...> Subject: RE: [BITX20] Sbitx finals replacement ? Farhan ? Ok I got my amp meter out rather then look at the one on the power supply Initial power up .603 amps Sbitx operating in receive .0709 Call CQ via FT8 no sudden spike current drops to zero and then after bootup back to .603. ? I am going to try another rpi ¨C not sure it that make a difference. Will let you know ? Art
N2AJO ? ? Farhan The Sbitx draws about 2 amps the shuts down N2AJO? ?Farhan Will check current and get back to you.? Screen doesn¡¯t go weird. It just goes blank.? Yes it reboots as if power is reapplied I have the basic kit - minus lcd and rpi Art ? Art,? 4 questions. can you monitor the current at shutdown? Does the screen go weird before it shuts down?? Does it try rebooting or does it just goes inti a shutdown? Are you using the full kit ? ? On Mon, Aug 15, 2022, 2:23 AM Art N2AJO <olson339@...> wrote: Farhan ? Ok have installed a LM2596 and preadjusted it for 5.4 before I installed it. I still have the same problem with the Sbitx shutdown within 1 or 2 seconds, reboots with the main display screen again.? tT receives great but can¡¯t transmit at all. Not sure what is next top look at. When I first? got it and ran FT8 I got about a 6 to 7 second output and then it shutdown ¨C blown regulator and finals. ? art ? ? I had this problem with fake LM338s. Most of them are simply relabelled LM317 that give up on current peaks. We, unfortunately, wiped the LM338s cleab from Mouser for our own production. The switching regulators that I mentioned in a earlier email work best. - f On Sun, Aug 14, 2022, 2:15 AM Art N2AJO <olson339@...> wrote: back again. Replaced the LM338 and the 2-IRFZ24N finals. checked to ensure the final and the LM338 tabs to ensure no ground connectivity and in contact with the heat sink. Measured the DC voltage of the LM388 tab 5,4 volts. Final tabs 13.8 volts. Put it all back together and receive works fine. Tried FT8 and within a second or 2 the rig shuts down and reboots. I also updated the firmware. So any suggestions on what next to check.?
I did order the voltage regulator Farhan suggested awaiting their arrival.
Art
N2AJO
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