Quote:
Originally Posted by Alex KL-1
With 0V on pin 11 of these IC, indeed we can have low voltage in the V_POSI.
So the command for this IC can be wrong (like wrong scan detect or some fault, or false protection detection maybe). If the IC is good.
But then, Q203 must follow it and then this emmiter voltage needs to be low, or it is inoperative.
|
Thanks Alex
I measured Q202,203 and I found that the Base-Emitter was very higher, like 1.5V which is way to high, so I assume it's toasted and that would explain the lack of 8.3V.
I am wondering if this situation can be responsible for the lack of 6.5V on Pin 1 of IC604?
There's supposed to be 25V on Pin 11 of IC250. This is missing because the 8.3V is missing on the Base of Q255 and the Anode of D257.
Maybe the 25V on Pin 11 of IC250 closes the transistor input at Pin 6 (of IC250) and bring it to zero. That closes anodes of D255 and then zero volts appears at Collector of Q612. This causes 6.5V to flow through Base of Q612 and to the collector of Q613 and Pin 1 of IC604. Possibly make sense?
In this explanation I am suggesting that the input of IC250 (Pin 6) is being pulled high because of the lack of voltage on its output (Pin 11)
I traced out the voltage path to look at how it's flowing and maybe how it should flow:
