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denon dra 685 issues

 
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Dirk54
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PostPosted: Fri May 26, 2006 11:38 pm    Post subject: denon dra 685 issues Reply with quote

I need a service manual for a Denon DRA 685. It is in the protection mode and nothing seems to change, no matter what parts are replaced. Rolling Eyes Razz
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blakeraptor
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PostPosted: Sun Jun 11, 2006 7:11 am    Post subject: protection Reply with quote

did you ever get the unit fixed? My stays on Protection and I have tried everything I know. Any help is much appreciated.
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friscotexas
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PostPosted: Sun Jun 11, 2006 7:13 am    Post subject: Denon DRA 685 Reply with quote

My unit says Protection immediately after its turned on. I have tried all the remedies explained in the service manual to no avail. Is there any secrets here or am I toast?

Any help is much appreciated.
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DVS
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PostPosted: Tue Jul 18, 2006 12:06 am    Post subject: Protection Light Reply with quote

Strangely enough I have to repair one of these amps now. Protection circuits are kicked for a couple of reasons depending how the circuit is set up like for example if the high and low rail voltages differ from channel to channel it will trip a comparitor circuit which will disable the amp or if there is a low impedance load on the output. When I start working on it I will post my results here.

Since I have no schematic this may be irritating. Check all of your Rail voltages on both channels, check DC bias on output transistors etc etc.
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mdtipton49dyahoo.com
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PostPosted: Thu Aug 24, 2006 2:51 am    Post subject: Re: Denon DRA 685 Reply with quote

My unit says Protection immediately after its turned on. I have tried all the remedies explained in the service manual to no avail. Is there any secrets here or am I toast?

Any help is much appreciated.[/quote]
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mariafer
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PostPosted: Thu Nov 30, 2006 4:02 am    Post subject: Denon DRA-685 Protection Reply with quote

I have the exact same problem. The unit goes to Protection mode even without any inputs or outputs connected. I replaced several parts but nothing seems to work either. If any of you ever solve the problem, I'll thank you any help you can give me.
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ipod



Joined: 04 Jan 2007
Posts: 8

PostPosted: Thu Jan 04, 2007 1:24 pm    Post subject: Re: Denon DRA-685 Protection Reply with quote

mariafer wrote:
I have the exact same problem. The unit goes to Protection mode even without any inputs or outputs connected. I replaced several parts but nothing seems to work either. If any of you ever solve the problem, I'll thank you any help you can give me.


Try to contact [email protected]
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martinique
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PostPosted: Thu May 10, 2007 7:27 pm    Post subject: Denon DRA-685 Reply with quote

I had the protection fault also on above model. Here's what I found. Measure +15 and -15vdc at CN1 connector near front of chassis. One of these is probably missing. Mine was the +15.(Yes you can measure these even during protect mode). Now being very careful with power still on, check outputs at IC1 and IC2. These are mounted near the front of the large heatsink. +15 is from IC2, and -15 from IC1. Even though you may again measure both +/- 15, check the actual copper pads under chassis if (with power off and unplugged) you get no continuity from IC1/2 outputs to corresponding pins at CN1. On the unit in my shop, the output leg of IC2 had completely severed from the copper pad. It was very difficult to even see it.

If in big hurry, could probably go back to beginning and just press down on top of pcb with something non-conductive. Then power on to verify.

Note, chassis back must be attached and some screws reinserted especially at the tuner, to prevent a different protect mode symptom.
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