On Sun, Apr 20, 2025 at 10:29 PM, Kai Bouwman wrote:
IC403 pin2 to ground shows 0.015V and pin 14 to ground shows 0V?
I think this is not so typical. It would mean
- IC403 is broken or
- IC204 is (half) dead or
- IC406 is broken (low probability).
For a broken IC403 I had expected the voltage at pin 7 and / or pin 9 are different from 2.5V. But you told early all pads from T401 are at 2.5V. Should IC204 be the culprit?
?
Please inspect the area around IC403 and IC406 and around all the components connected to these elements using a strong magnifier. Maybe there is a small solder bridge / a tiny tin ball or solder whisker.
?
Did you ever test the TX? If IC204 would be broken no signal would be produced for transmitting. But take care, one side of the PA is switched on all the time if you try to transmit in this status. Lower the supply voltage to 7.5V, connect a dummy load and try to transmit only for a short time, not more than some seconds and wait 30 seconds until the next test. Check the output and the supply current. The current should be not higher than 0.5 ... 0,8A. If you see an output of at least some mW IC204 should work at least "half" (CLK2). And check the voltage at the G of the BS170 when transmitting. For this please read
QMX QMX_plus PA problems, broken BS170 section Diagnostics No. 5 to see which voltage should be found. If no signal is generated by IC204 you will find 0V at two gates and 5V at the other two.
but on IC406 I¡¯m getting 0V on all of those pins
This looks like a result from voltages at IC403 pin2 and pin14.
?
73 Ludwig
?
