Steenamaroo
...
Hi all.
I racked eight wbs m490 modules last christmas and then went to uni until now.
When i left they all worked, and now that i'm back only seven of them work.
I've done the usual go to troubleshooting (new mic, new lead, etc etc)
I've also done module switching and opamp switching and can confirm that the fault is in the one specific module.
The module powers up but does not pass audio.
I've also ensured that the switches for input and output selection are not at fault.
I've tested the resistances of the input transformer and they check out fine.
What i've discovered.
Testing the power section of the module showed that i'm getting +18 as i should, but the -18 is coming through as -12.
I've replaced the relevant resistors/diodes/caps (c51 c53 r148 cr17) for the -18v and it's still -12.
Full schemo is at www.steenaudio.com/m490.pdf
Can anyone take this problem a little further?
Thanks in advance.
I racked eight wbs m490 modules last christmas and then went to uni until now.
When i left they all worked, and now that i'm back only seven of them work.
I've done the usual go to troubleshooting (new mic, new lead, etc etc)
I've also done module switching and opamp switching and can confirm that the fault is in the one specific module.
The module powers up but does not pass audio.
I've also ensured that the switches for input and output selection are not at fault.
I've tested the resistances of the input transformer and they check out fine.
What i've discovered.
Testing the power section of the module showed that i'm getting +18 as i should, but the -18 is coming through as -12.
I've replaced the relevant resistors/diodes/caps (c51 c53 r148 cr17) for the -18v and it's still -12.
Full schemo is at www.steenaudio.com/m490.pdf
Can anyone take this problem a little further?
Thanks in advance.
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