Crown D-150 series II IOC light on

Mikelg · 1st April 2005, 08:53 AM

It has been quite a while since I have done any bench work. I have ordered a service manual for a Crown D-150 series II Amp I bought. Channel 2 seems to work, channel 1 does not. When I power up the amp the IOC light is on for channel 1. The serial number of my amp is: 056605 Any suggestions on where I should look first? Any help would be greatly appreciated. Thanks Mike

6502dude · 1st April 2005, 09:02 PM

I think I have service manuals for D150A Series I and IC150A.

I don't recall seeing much for trouble shooting tips.

IOC stands for "Input Output Comparator"

It is intended to turn on led when input differs slightly from ouput based on distortion (clipping of output waveform). Circuit has pulse stretcher to allow flashes to be visable on short transients.

D150A design is supposed to be short circuit tolerant.
However, with no output I would check output transistors first, followed by drivers.

amplifierguru · 1st April 2005, 09:28 PM

This was a chip (I think LM833) driven amp whose greatest design weakness, in my opinion, was an unbiassed output stage. I repaired a few used for PA systems way back. Always the power transistors and sometimes the drivers.

Were they 2N3584 and 2N6421 both TO66.

moamps · 1st April 2005, 09:55 PM

on-line service manual

http://www.crownaudio.com/gen_htm/legacy/legacamp.htm

1st April 2005, 08:53 AM	#1
Mikelg diyAudio Member Join Date: Mar 2005 Location: Tifton, Georgia	Crown D-150 series II IOC light on It has been quite a while since I have done any bench work. I have ordered a service manual for a Crown D-150 series II Amp I bought. Channel 2 seems to work, channel 1 does not. When I power up the amp the IOC light is on for channel 1. The serial number of my amp is: 056605 Any suggestions on where I should look first? Any help would be greatly appreciated. Thanks Mike

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1st April 2005, 09:02 PM	#2
6502dude diyAudio Member Join Date: Apr 2005 Location: Toronto, Ontario	I think I have service manuals for D150A Series I and IC150A. I don't recall seeing much for trouble shooting tips. IOC stands for "Input Output Comparator" It is intended to turn on led when input differs slightly from ouput based on distortion (clipping of output waveform). Circuit has pulse stretcher to allow flashes to be visable on short transients. D150A design is supposed to be short circuit tolerant. However, with no output I would check output transistors first, followed by drivers.

1st April 2005, 09:28 PM	#3
amplifierguru Account Disabled Join Date: Aug 2004 Location: Earth	This was a chip (I think LM833) driven amp whose greatest design weakness, in my opinion, was an unbiassed output stage. I repaired a few used for PA systems way back. Always the power transistors and sometimes the drivers. Were they 2N3584 and 2N6421 both TO66.

1st April 2005, 09:55 PM	#4
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	on-line service manual http://www.crownaudio.com/gen_htm/legacy/legacamp.htm

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