On Wed, Apr 2, 2025 at 05:32 AM, Michael Shiplet wrote:
- battery plugged in, radio turned off: 0.00A, ~12.08V
- radio turned on, normal operation: 0.06-0.10A, ~12.08V
Hello Michael, that's fine.
- radio turned on, frozen: 0.18-0.20A
A bit much but no heavy short or so.
?
This case is interesting and the situation is cloudy. Hard to debug from afar. And debugging maybe dangerous for the QMX. There are two reason:
- VDD = 4.5 V is higher than the rating and heavy stress for most of the IC connected to VDD. The controller, the heart of the QMX, is connected to VDD.
- VDD = 4.5 V and a higher current looks like the zener diode D109 is in action. With regard to the characteristic the diode current could be 120 ... 160 mA and the power 540 ... 720 mW. This diode is rated 500 mW and may heat up to much from to much power. If this diode will break the resistance could go to a low value or a high value. For first case VDD would be lower and no problem for the controller and for the second case vice versa bringing more danger for the STM32 and others.
So staying (for a while) in the failure status is dangerous but how to debug not being in this status?
?
And I see one more problem. I don't know is the controller stopping because VDD is to high or is VDD raising because the controller stops? Without a proper running controller no proper running SMPS for VDD and VCC.
?
Could you check please R110 and R112 (good soldered and not damaged). Via this voltage divider a feed back signal from VDD is produced to control VDD.
?
There are some good points in posts before:
?
George wrote:
Also replug the front panel and look at the display connection and while it's out check for a tiny bridge or a whisker that may be in there. That will answer a lot of questions?
And please make a careful visual inspection using a strong magnifier. Look for solder bridges, blobs and whiskers.
?
George wrote:
Also do you have the internal GPS? if so unplug it.
Also is it in a case? If so remove it.?
And when you test for success and you reach the faulty state again please remove the supply immediately.
?
Stan wrote:
I'm wondering if you have a temperature-dependent issue that causes the 5V supply to get shorted to Vdd, pulling Vdd up and Vcc down.
Maybe also take a resistance measurement (with power off) between Vdd and Vcc.
Stan wrote:
When you said you could reproduce the problem by trying to attach the terminal, did it happen when you connected the cable, or when you hit enter in the terminal window to bring up the menu?
I'm curious about your answers.
?
73 Ludwig
?
?
