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D-150a SII IOC question


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#1 Tony9409

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Posted 13 June 2012 - 09:17 PM

I have a D-150a series II and was wondering what the sequence the IOC lights follow....when you turn the unit on they both blink then turn off, when you turn the unit off they come on bright then gradually go out. Is this normal ? The amp sounds good and quiet... Are there other sequences that show a problem  other than flashing if the amp is clipping at high volumes?

thanks
Tony

#2 joust

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Posted 28 June 2012 - 11:28 AM

Tony,

The IOC is the Input/Output Comparator indicator. Basically, it compares the output to the input signal and flashes if there exists distortion or clipping conditions. On power up it is normal for the IOC to flash. Also, on power down it may behave as you mention, filter caps are discharging at a slow rate.

Though, to be more thorough, it would be best to have the input and output bias levels (settings are inside amplifier) adjusted for maximum efficiency. Don't forget, this si a DC amplifier! :)

joust

#3 Tony9409

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Posted 28 June 2012 - 07:47 PM

Thanks. I do have the input and output bias adjusted to spec ranges. The amp recently was recapped and sounds great.

On a second D-150A SII in for repairs; I've recapped it and replaced blown output transistors on channel 1. I've measured and adjusted input/output bias to spec, however on turn on channel one IOC doesn't flash nor go on briefly post turn off like channel two does.  Any suggestion where to check ? should I assume when the output blew it took out part of the IOC?

Tony

#4 karlos the dc300a

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Posted 05 July 2012 - 12:53 PM

check the 2961 transistors on the ioc board. and the i.c.

never had any two amps show similar ioc operation, just how the voltages discharge at turn off.

good luck