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Re: Need Help setting the PA Bias Current for sBITX
Aaron, Sounds like ur making headway. reverse polorizing a unit sometimes takes patience to work out all the weakened components or some that wont fail unless its under load. I dont own the SBITX yet, but it seems from the info you provided its now isolated to the transmit sections. I would start by looking at the si5351 area and where the Pi connect since you actually witnessed some smoke. where there is smoke, there is char, or holes in something or burnt traces. check driver transistors, and anything feeding the finals. Also check your interconnecting wires for any burn marks or punch thru holes .Since you are actually receiving stuff, i would say your si5351 and PI are good, unless the si5351 had one osc crap out .It has 3 outputs. order a si5351board asembly which are cheap, and replace the one in your Sbitx. . Also look for any interconnecting components leading to these items on the board such as traces burnt, resistors discolored, etc. You are doing great. you got the receive up and running!!!!!! . recheck ur fets and also any driver transistors and pre amp transistors.Also check ur biasing resistors for opens. Good luck on ur repair Aaron. You have made alot of headway since u are receiving stuff and power is flowing back into the unit. might check your voltages on your finals , and anything up stream from the finals. Sounds like ur getting very very close. GOOD JOB!!!!!! 73 David ac9xh
On Tuesday, June 11, 2024 at 10:42:15 PM EDT, Aaron K5ATG <aaron@...> wrote:
Hello All, Yup still trying to get my sBITX working again. Here is a recap.? Back in March I accidently cross polarized the transceiver First thing I did was to replace both IRF510's? Q16 & Q17 That didn't work so I found that D7 Needed to be replaced. I replaced it with another 1N4007 Diode ( I think that this is intended to protect the circuit in case of cross polarization. It didn't work that in my case.? I then replaced the voltage regulator with the suggested Drok Voltage Regulator I then would turn it on and would get wisps of smoke and the smell of burning electronics. I could not locate the source of the smoke but it was coming from the area around the SI5351 and RPI. A couple of days later I pulled the SI5351 out to look at it and returned it and powered up the transceiver and there was no smoke or smell of electronics burning.? I hooked it up to an antenna and it was receiving very good, 'Next I hooked up a dummy load to it and put it in transmit and it would completely shut off immediately Next I was told that I need to set the PA Bias since I replaced the IRF510's? in order to do that I had to follow these steps:
No idea on how to measure the current with a digital multimeter so I had to do some cinematic research on how to do it. I basically had to put the DMM probe in the right socket on the DMM and put the DMM in the circuit. Here is a pic of what I did (i apologize for the crudeness of the image, I just rushed through it)? When the sBITX is in Receive the DMM displays a 0.43, when it goes into transmit it jumps to 0.86. Before I hooked up the DMM to start adjusting the? ? ? ? ? ?PA-BIAS1 I set it to zero (full counter clockwise.) When I adjust PA-BIAS1 there is no change to the DMM readings in either receive or transmits.? This is where I'm at now and I'm unsure what tunnel in this never ending maze of tunnels to take in eventually getting this radio back on the air. I'm starting to wonder if it ever worked in the first place and my recollection of me enjoy using it is just an illusion within the confines of my cerebral carnival.?? -- '72 Aaron?
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Need Help setting the PA Bias Current for sBITX
Hello All,
Yup still trying to get my sBITX working again. Here is a recap.? Back in March I accidently cross polarized the transceiver First thing I did was to replace both IRF510's? Q16 & Q17 That didn't work so I found that D7 Needed to be replaced. I replaced it with another 1N4007 Diode ( I think that this is intended to protect the circuit in case of cross polarization. It didn't work that in my case.? I then replaced the voltage regulator with the suggested Drok Voltage Regulator I then would turn it on and would get wisps of smoke and the smell of burning electronics. I could not locate the source of the smoke but it was coming from the area around the SI5351 and RPI. A couple of days later I pulled the SI5351 out to look at it and returned it and powered up the transceiver and there was no smoke or smell of electronics burning.? I hooked it up to an antenna and it was receiving very good, 'Next I hooked up a dummy load to it and put it in transmit and it would completely shut off immediately Next I was told that I need to set the PA Bias since I replaced the IRF510's? in order to do that I had to follow these steps:
No idea on how to measure the current with a digital multimeter so I had to do some cinematic research on how to do it. I basically had to put the DMM probe in the right socket on the DMM and put the DMM in the circuit. Here is a pic of what I did (i apologize for the crudeness of the image, I just rushed through it)? When the sBITX is in Receive the DMM displays a 0.43, when it goes into transmit it jumps to 0.86. Before I hooked up the DMM to start adjusting the? ? ? ? ? ?PA-BIAS1 I set it to zero (full counter clockwise.) When I adjust PA-BIAS1 there is no change to the DMM readings in either receive or transmits.? This is where I'm at now and I'm unsure what tunnel in this never ending maze of tunnels to take in eventually getting this radio back on the air. I'm starting to wonder if it ever worked in the first place and my recollection of me enjoy using it is just an illusion within the confines of my cerebral carnival.?? -- '72 Aaron? |
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Re: sBITX 64Bit Pi Image Available
#sBitx
Ashhar, that's your reward for producing such a finished and professional looking transceiver. The uBitX, the -40, etc, were clearly experimental and not all done so no surprise.
As I crawl through all my tests on my V2 with TVS and V3 software plus the fixes I'm finding a better and better unit. The receiver is outstanding as have been your past designs. I expect in a year or so, all the issues will be done and a ham not so interested in experimenting, will find a fine transceiver. Since a separate computer is not needed for logging, digital modes, QRZ lookup, and web access, it is an impressive compact radio+computer. 73, Bruce, W4BRU |
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Re: sBITX 64Bit Pi Image Available
#sBitx
Remote ssb hf? On Tue, Jun 11, 2024, 2:19?p.m. JJ - W9JES via <w9jes=[email protected]> wrote:
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Re: How hot is too hot?
It's interesting, isn't it, as long as you don't know what the CPU temperature is, it doesn't bother you. You just use it.
Google says: "What is the maximum temperature a CPU can handle? How hot should my CPU get? The safe temperature range for most CPUs is between 40¨C65¡ãC (or 104¨C149¡ãF). At the highest loads, your average CPU temps can go up to 80¨C85¡ãC (176¨C185¡ãF), but consider this the absolute limit. Sustained CPU temps above 80¡ãC (176¡ãF) can do long-term damage to the CPU and its silicon." And my experience is that it depends on the modes in which I use it and how long (continuously). For me, the external heatsink is at room temperature, and the CPU temperature would be high for my usage if I hadn't done internal cooling. I cool the outer rib with a 92x92x25mm silent fan. I use it in FT4, FT8 and sstv mode, which use the CPU in continuous operation. One time I saw that I was close to 80C degrees, then I had no CPU cooling and I made a screenstream of the process I used. When I noticed the higher temperature, I immediately stopped recording. I am currently cooling the CPU with a 50x50x10mm silent fan and heatsink. Thus, the maximum CPU temperature is around 40-50 degrees Celsius. I'm still using the first RPi4 and I changed the output FETs once because I was testing on battery and had no current limitation. I'm getting close to 4300 QSOs with these FETs I replaced and 6.3A current limiting at 12.5V with the IRFZ24N fets. These are my experiences. From the beginning, I constantly make sure that I am able to cool the heat-generating parts. I have been using the device since the release of the v3 alpha. (Nov 2023) -- Gyula HA3HZ |
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Re: sBITX 64Bit Pi Image Available
#sBitx
Here is a sneak peak on another project currently in development.
-JJ ? |
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Re: How hot is too hot?
So as long as it's in the grey it's okay. Thanks JJ, I'll stop worrying now or find something else:-) BTW, it seems to be working quite good. I don't know if this is possible, but the waterfall seems better looking with less noise in it, maybe it's just the band is more quiet today, but the overall feeling is smoother operation.
Joel N6ALT |
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How hot is too hot?
I never worried about my sBitx V3 temp until yesterday when I upgraded to JJ's 64 bit OS, now the temp stares at me all day long making me worry. I run my V3 all day everyday. it's been on almost three hours now and it says it's at 68C, does that seem hot too hot? The case doesn't feel any hotter that it did with the 32Bit OS. What do we think?
Joel N6ALT |
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Re: Scratch building
Thank you Gary, now everything works @5Vcc ( but no more touch screen, of course!) I can probably save energy at 3.3V, but I use the 5351 board from Cina, working @5V. There is always something to learn, for example? not all BAT54 are the same.....I need BAT54SL, not a common BAT 54, or 54A or 54C, and of course I buyed the wrong ones... :-))))) C81 on emitter of Q90 must be 100nF, and not 470pF as indicated on V6. Still a lot of fun, also at 68 y.o. paolo ? |
Aaron K5ATG
Bruce W4BRU
HA3HZ
Joel Caulkins/N6ALT
Paul Allison
Bob Benedict, KD8CGH