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ISO Amp help

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slipstream(at)wavecable.c
Guest

Posted: Sat Dec 11, 2010 5:45 pm Post subject: ISO Amp help

Well, my first attempt at the Isolation amp has fizzled. 

 I've pretty well resigned myself to starting over from 

scratch, but I want to make sure I don't repeat the same 

mistakes again.



Here's what I get:  A lot of distortion when the amp is 

powered up.  With no power, I can hear the radio softly 

through the headset.  Power on the amp, it's all 

distortion.  I removed all inputs from the amp -- radio, 

intercom, nav, etc, same thing.  All it needs is power. 

 The d-sub connector is mounted on the solder side, per 

the illustrations, so power is pin 8.



I can't find any spots where solder might have jumped 

terminals to create a short.



A mistake I did find was that I didn't understand the 

polarity aspects of the capacitors, and some were 

installed backwards.  Once I figured that out, I removed 

them and reinstalled them in the correct orientation, but 

there has been no change to the distortion.  Either the 

damage had already been done, or that mistake wasn't the 

problem.



Any input would be appreciated.



One bill of materials question:  Parts 6 & 7, A24794, do 

not appear anywhere in the plans aside from the bill of 

materials.  Is that the solder-in ic socket that was 

replaced by the new machined-pin socket (revision H), or 

have I missed something else here?



Brooks

RV-7 details details

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 11, 2010 7:24 pm Post subject: ISO Amp help

 	  Quote: 	
		  One bill of materials question:  Parts 6 & 7, A24794, do not appear 

anywhere in the plans aside from the bill of materials.  Is that the 

solder-in ic socket that was replaced by the new machined-pin socket 

(revision H), or have I missed something else here?


	


   No, those were optional and used under the amplifier

   chips. They weren't on the boards I photographed and

   as a result, did not get tied to the BOM tags.



   This kind of trouble shooting is very difficult

   to do by remote. If you're interested, mail the

   assembly to me. I can probably figure out what's

   going on in a few minutes. I'll share the process

   by which the discovery was made.



   Bob Nuckolls

   Bob 130

   Medicine Lodge, KS  67104-0130



   Bob . . .

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