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Kenwood Kr-v9090 is in protect

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michaeleleanor

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My friends Kenwood kr-v9090 receiver is in protect. I checked the circuit and re-flowed the board and checked for any buldging capacitor but did not find.
I have downloaded the schematice, can anybody assist me finding the fault. Thanks in advance.

Hello,

One of my friend has given me his Kenwood Kr-v9090 receiver for repair.
The problem with the receiver is that on switching on, everything works fine the display and i can hear the relays clicking but only for 5sec, then it goes into protect.

I have downloaded the Service manual. Kindly advice what should i be checking to find out the fault.

Thanks in advance

I have merged your posts.. Please don't double post! Moderator
 
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I use to work on many of those gener kenwoods many years ago and can only guess that you are posting from overseas with limited resources as it would not be worth the trouble. While they were considered as"higher end" units at the time, NONE were known to be "service friendly" as they were crammed with circuits galore and a rats nest of wirings---try following some of the wiring on schematico_O--

The dreaded shut down issue could be caused by many different things; anything from the overloaded speaker lines all the way up to blown output(s), missing voltage(s), bad connection(s), open filter caps, biasing runaways, relay control...etc. And there is always a possibility of a bad processor but it is very rare.
While the forum is certainly not a place to cover everything, I'll try to give you some pointers and leave it at that;

The key point to remember is the fact that you have a monitoring microprocessor with a dedicated protect line pin that is tied to many sense circuits. Anything from too much DC offset on any of the channels OR too hi/lo level of various DC levels or current draws would trigger the protect line. While I do not remember the exact values, if I remember correctly, you should have a low at protect line All the time---you can verify that with a VOM at the protect pin. Biggest challenge is to determine what circuit is causing the trouble on the protect line?-- yes it can be very time consuming not counting the unforseen possibilities of "Man made" issues. Also I think there was a test mode that would allow you to keep the unit ON for further troubleshooting. Just make sure NOT to have speakers connected.

Good Luck:)
pin35.jpg
prt line.jpg
 
I think it will be difficult for me to fix it as i am not that good in repairs, have manged to fix few but this seems to go over my head, will try with the pointers given from you, appreciate your help on it. Will post if i am successful so that anybody else have a similar problem can benefit from it.
 
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