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QDX Rev 4 Only Shows 80M Band After Working Near T2
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After doing some rework on T2 my QDX it only shows 80M in the band config, the other bands do not appear at all. Normally there would be 80,60,40,30,20 with a whole set of options for each but I only see 80M.
I happened to reflash to an older 1_05 firmware and the bands all show up when running that version but disappear again on 1_10. I have done a factory reset with no change. The diodes all go to 0.6-0.7v for the corresponding bands when I test them on 1_05. I'm guessing I did something to an SMT component around T2. The parts are very cheap but I'd like to know what one(s) might be involved and I don't want to attempt to repair something if the fault is elsewhere. I've read through the documentation and I didn't find any mention of band detection/enable aside from the jumper wire if it was a high band model (mine is not) Does anyone know what components or connections would make a Rev 4 QDX only show 80M on 1_10 but be ignored on 1_05? |
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Still looking for what would make the QDX lose 20,30,40,60M. I am sure I did something to the board or a component but I can't figure out which.?
I've been poking around the board for a few days. Haven't made any progress. I see some documentation about jumpering things for different bands but nothing relevant to making it 80M only. Anyone know what short/open/damaged component/trace causes this behavior? 60,40,30,20M should also be in this menu.? |
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Thanks, that was my first thought too. I've done a factory reset, and also reflashed the firmware and then done another reset with no change.? On Sun, Sep 3, 2023 at 4:15?PM Evan Hand <elhandjr@...> wrote: I would suggest a factory reset.? ?It looks like the EEPROM got messed up. |
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Are you sure you downloaded the correct firmware?? There are versions for a single-band QDX.? Try an older version and see if that helps.
Correct multiband QDX is here: Single band is here: I did note that the latest single band is 1_08, and the screenshot you posted lists 1_10, so it's not likely.? Try the prior release: 73 Evan AC9TU 73 Evan AC9TU |
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I'm not quite ready to call it fixed but I got all my bands back!
I found the MOSFET that controls 20M(I think Q5) was faulty. The output from the microcontroller would only come up to 2.1V instead of 3.3V on the 20M band line. When powered off I found less than 100Ohms between the pins on Q5 where Q4 and Q3 would be in the megaohm range. After removing the faulty MOSFET the voltage from the microcontroller reached 3.3V as expected. I then swapped the MOSFET from the 40M filter over to the 20M position. I put firmware 1_10 back on and all the bands stayed!?? I'm not sure what caused the issue and I'm not convinced there aren't still other problems but I have a clear path forward now. I'll be ordering some BSS123s. If I find anything else which might be helpful I'll post back here for anyone who might see something similar in the future. |
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Hello Evan > Are you sure you downloaded the correct firmware??? > There are versions for a single-band QDX.?? > Try an older version and see if that helps. No, firmware is the same... It's just a documentation error, the QDX-M web page should have been updated. The firmware for QDX and QDX-M is the same. I have corrected the QDX-M page now.? 73 Hans G0UPL On Mon, Sep 4, 2023 at 12:35?AM Evan Hand <elhandjr@...> wrote: Are you sure you downloaded the correct firmware?? There are versions for a single-band QDX.? Try an older version and see if that helps. |
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Take a loot at the surface mountt MOSFETS that switch in and out each band. The documentation in the assembly guide is very good but it still took me a while to completely translate that into what I was seeing on the board, especially since something wasn't working correctly. It is possible I am remembering something incorrectly, so take this with a?grain of salt. See if the?bands come back on 1_07. If they do, check if the voltage changes across the diode for each band. You should only see one active at a time.? For me when 80 was on, 20 was also. I don't know why it was different when 40M was on. Q5 was damaged and it was leaking current when it shouldn't. If you find something on when it shouldn't be, check the three pads for the bands.? You should see 3.3V(or really close) on one of these at a time. This is the signal from the microcontroller controlling the MOSFET.? If you find the signal from the microcontroller is working correctly but you're not seeing the bands switch in and out then the problem is probably?here: Ignore the junk on the board in this image. I?cleaned it before I started troubleshooting. These are the MOSFETs controlling the bias for the band diodes. It is a little more complex than this but they're working in conjunction with those resistors. I believe when the 3.3V from the microcontroller goes in on one lead, the mosfet pulls the voltage down to ground. Normally when the band's filter is switched out one of the legs would be near the supply voltage. Not sure if this helps and there may be an error in my understanding or memory of how it works. This should give you an idea if you're seeing the same issue I was with just a volt meter. On Mon, Sep 4, 2023 at 2:01?PM Darrell Frappier <n3jwj@...> wrote: I seem to have a similar problem. My Rev 4 was ordered assembled and has been working fine for months.? I upgraded the firmware to 1_10 and then found the only band available is 40.? Multiple installs of different firmware and factory resets have failed to make a difference.? |
开云体育Good Morning Lloyd,I found the exact same problem and your fix also fixed mine except it was Q3 on a Rev 5 Highband QDX. The mosfet was showing 256 ohms across it. Install a new one and all bands are back. Thanks for sharing. 73, Cliff, AE5ZA
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