I built a QMX low band in the summer with no issues. So, I bought a high band kit for Christmas and after building it, I see nothing. No bootloader, no start, nothing on the display. Comparing the two, on the second build, there is nothing at all on the 3.3V rail, it draws about 8.5mA while pressing the left encoder to power up, then nothing when I release the button. Unwisely maybe, I tried substituting all the individual boards from the new build into the earlier main board, and everything works there, so it must be some sort of fault on the new main board. I can't see anyone else with this issue on the forum, has anyone else seen this? Advice welcomed, at the moment it's sitting there useless!

George, M0HLP

开云体育

Can you tell if the 3V3 linear regulator is coming up? If it's not, then the MPU won't come up and turn on power hold.

I built a QMX low band in the summer with no issues. So, I bought a high band kit for Christmas and after building it, I see nothing. No bootloader, no start, nothing on the display. Comparing the two, on the second build, there is nothing at all on the 3.3V rail, it draws about 8.5mA while pressing the left encoder to power up, then nothing when I release the button. Unwisely maybe, I tried substituting all the individual boards from the new build into the earlier main board, and everything works there, so it must be some sort of fault on the new main board. I can't see anyone else with this issue on the forum, has anyone else seen this? Advice welcomed, at the moment it's sitting there useless!

George, M0HLP

-- 
Paul -- AI7JR

No, the 3.3V regulator isn't coming up, at least one the older mainboard it does, but not this one. So PSU modules themselves are working.

Actually, to make this clearer: when I put the new PSU modules onto the old main board, everything works, but new modules on new mainboard, no 3.3V rail on the pins along the top of the mainboard PCB, (or anywhere else).

I recognise, given what I've read elsewhere on the forum (particularly Hans' explanation of the power up sequence) and from reading the schematics, that if the 3.3V linear isn't working, then nothing will, so if the new PSUs work on the old board, then I conclude it must be working. But, I do admit to not having measured the actual node between IC101 and D103...

That's interesting - I have observed the same behavior with my build. I'd earlier built a v1 low band QMX successfully. I ordered and built the v2 high band (for 9 volts) which shows the same behavior - 8 mA when left button depressed, no other apparent activity. Familiar with the boot procedure I checked the power boards and connectors for cold joints or bridges - nothing apparent to me. During the build I'd followed antistatic procedures (antistatic work surface, arm band, grounded iron); however, from the behavior I assumed that somehow I'd fried the MCU. I'd put it away to come back to later (getting ready for a move, so cleaning up the storage area).?

John KI3J

Yes, I'm used to being careful with static too (I work in aerospace electronics), so I don't think I have fried anything on the board either.