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wharfspider

D-75A IOC activates when amp powered up

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Sometimes upon amp power on, one channel IOC light comes on whether there's a signal or not. The signal will distort regardless of level. Swapped inputs and problem stays with same channel. Power cycling the amp several times will clear the problem. The IOC also sometimes kicks in on its own... power cycle will clear it up, usually takes a few cycles. Ideas? Thanks!

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If the level pot itself has one of it's solder connections making contact with the front panel it will cause this symptom. You need to remove the top cover and make sure the pot hasn't moved. Other then that is could be a leaky cap or small signal transistor causing the IOC condition. The best way to tell that is place it on a bench and run a signal and when it acts up see if the positive or negative side is missing. This could lead to a leaky or defective last voltage amp transistor, pre-driver or even a bias transistor. Since it appears to be some what intermittent it could be tricky to locate. I would suggest the amp come in for service to be checked out.

Thanks,

Kip Whitehead

Crown Technical Support

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A follow up... The level pots were so nasty that no audio would pass except at a few positions, so replaced them and all has been fine for a week of solid 'on' time, no mysterious IOC activation.

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