Re: Help with strange audio fault #qcx
Just a quick update.toggle quoted messageShow quoted text
I am still struggling to track this fault down but I do now have some data from my latest investigation.
Do note that this QSX40 set aligned perfectly and was working fine for 2 weeks.
The fault is no receiver output. However if I turn it off for an hour, it fires up again for about 5 seconds and then fades out. This is repeatable. If I fire it again instantly, the fault hasn't cleared and stays silent.
I have been around every solder joint with the iron, not very scientific but sometimes it is a quick fix.
So I though I would start at the beginning with a factory reset and realignment.
8.7 Peak BPF worked fine and produced its normal deafening output.
However 8.8 I-Q Bal, 8.9 Phase Lo and 8.10 Phase Hi are all at 0
Given this alignment needs audio from the output stage, this I think is a fairly good pointer.
And now IC10, these voltages are clearly wrong
I have been over and over the PCB looking for shorts and dry joints around IC10 and IC09 to no avail (that doesn't mean they don't exist)
The weird part is that after leaving the set off, after time it will always fire up for a few seconds before fading away.
I am going to get my supper and then have another bash but any pointers at all would be most gratefully received.
73 Ted M7ECH
On Thu, Jan 10, 2019 at 02:13 PM, <qrp@...> wrote:
Just before I remove the QCX40 from its enclosure to fault find, I thought I would share it in case anyone else had ever experienced a similar issue.