intermittent sound volume dependent....

[pucho812]

the last of the stumpers. The aux masters are still being sorted but at least there is something to go on.

The problem  is with line inputs  on a channel or two. They behave the same, if the line trim is at unity, and the output fader at unity on a channel I get intermittant signal. What I have noticed is it's dependent input signal level.  So for example if it's working I can measure an input signal of +4dBu and measure the output of the channel at  around +4dBu(within a decimal point) on the AP, this is with both input trim and output fader at unity.  However if I lower the signal generator level,  I can get it low enough too that the line input cuts out  and this is with the input trims and output fader at unity.  to get the channel back. to working, I have to adjust the signal generator, sometimes upwards at +20dBu in order for the channel line amp to come back on.  thankfully I have a schematic for this but it is not a 100% match to the circuit board. 
there have been a few other ways to get around this too,  I can skip the line amp and go into the channel pre eq insert return  and work.  I can also reseat the channel strip in the frame and it causes signal to come back on and off.

I suspect this is cap or transistor related, but this is just a guess as I have yet to run the channel with the extender card.

 

[abbey road d enfer]

I suspect this is cap or transistor related, but this is just a guess as I have yet to run the channel with the extender card.

Indeed you should check voltages between one that works normally and a faulty one, but I suspect it could be an oxydized contact somewhere in the chain.

 

[JohnRoberts]

+1 symptom sounds like oxidized switch or perhaps bad solder joint. Usually they don't drop out that quickly, but fixing it with strong signal is typical (voltage punches through thin insulating oxide layer).

I have seen switching insert jacks that became intermittent. Maybe tap around the board with a pencil eraser to see if anything responds to light percussion.

JR

 

[ruffrecords]

Try also cleaning the module connectors and check them for dry joints. Sounds like the signal exits the module to the insert from which point it is OK. Unless they are fingers, it is usually worth reflowing the pins of a module connector

Cheers

Ian

 

[Bo Deadly]

Are there relays in the faulty path?

 

[pucho812]

There are no relays in path.
Edge connectors were cleaned  already.
Will reflow solder today and see.
Thanks for the advice guys...

 

[pucho812]

well haza haza. I had the  offending channel on the extender and boom got  my drop out.  I then traced with an oscope and found the exact point at which signal is not happening. I re-flowed the joint and now it does not drop out anymore 8)  thanks for all the advice guys...

 

[JohnRoberts]

for the win....

JR