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General Category => Your projects => Topic started by: Kunkel on October 13, 2014, 02:47:04 AM

Title: Denon receiver dead - incorrect antenna may have caused this?
Post by: Kunkel on October 13, 2014, 02:47:04 AM
Hadn't turned this one On in a couple of months. Picked it up again, fixed the broken antenna connector...connected an AM loop antenna... worked for 15min and it turned itself off.

The male connector already had the central prong broken when I found this unit in the trash. Today I removed the rest with the Dremel and soldered another prong.

https://i.imgur.com/t31lakm.jpg (https://i.imgur.com/t31lakm.jpg)

https://i.imgur.com/VhnGA92.jpg (https://i.imgur.com/VhnGA92.jpg)

I only had an AM loop antenna around but connected it anyway like this:

https://i.imgur.com/nQC5F37.jpg (https://i.imgur.com/nQC5F37.jpg)

I dont know if this might have caused the damage or not. The unit worked perfectly for 15min (finally had FM reception) but just shut down and it doesnt turn on anymore.

Havent tested anything with the multimeter yet. I'd just like to ask first if the incorrect use of antennas might have been the problem.

Here is teh service manual:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAA&url=http%3A%2F%2Fwww2.aerne.com%2FPublic%2Fdok-sw.nsf%2F0c6187bc750a16fcc1256e3c005a9740%2F0ca2b7730109733bc125706d0024caf3%2F%24FILE%2FDRA345_all.pdf&ei=TxA7VPTtB4nraMzngogG&usg=AFQjCNHNxyOnO8e3Jgaj65LVM4mfh3JUPQ&sig2=_8olpLzr1rWjbWi9txosrA&bvm=bv.77161500,d.d2s&cad=rja (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAA&url=http%3A%2F%2Fwww2.aerne.com%2FPublic%2Fdok-sw.nsf%2F0c6187bc750a16fcc1256e3c005a9740%2F0ca2b7730109733bc125706d0024caf3%2F%24FILE%2FDRA345_all.pdf&ei=TxA7VPTtB4nraMzngogG&usg=AFQjCNHNxyOnO8e3Jgaj65LVM4mfh3JUPQ&sig2=_8olpLzr1rWjbWi9txosrA&bvm=bv.77161500,d.d2s&cad=rja)

https://docs.google.com/file/d/0B6fu025jFteZaHAzZHVndDlWdUk/edit?pli=1 (https://docs.google.com/file/d/0B6fu025jFteZaHAzZHVndDlWdUk/edit?pli=1)

http://www.hifiengine.com/manual_library/denon/dra-345r.shtml (http://www.hifiengine.com/manual_library/denon/dra-345r.shtml)
Title: Re: Denon receiver dead - incorrect antenna may have caused this?
Post by: kam on October 13, 2014, 08:54:46 AM
Hello Kunkel,
Judging from the technology i see and the photos, i can tell that this is a rather old equipment. I mean older than 10 years old. Right? So:

Job #1: Replace all electrolytic capacitors, good or bad, just replace. They have a lifespan of around 5000 hours, that is 7 years of use with 2 hours a day.
Job #2: Check for the power supply unit. This is where you r problem begins. Find and measure the outputs. Follow the tracks from the transformer down to the PSU output. The service manual does not provide a schematic so you may have to make one yourself just for the power supply.


Title: Re: Denon receiver dead - incorrect antenna may have caused this?
Post by: Kunkel on October 13, 2014, 20:36:07 PM
Kam, thank you for your patience :)

Are capacitors sensitive to heat? My devices only work during the weekend and I never push them hard but the truth is my room gets very cold and humid in the winter, hot and dry in the summer. I'm asking this because I have another receiver (AKA AA930, vintage) with similar symptoms: stopped producing sound after  a long time without use (it turns on but there's only a low frequency noise). No rough use, no high volume, no dust, working perfectly since 1968 and then puff, no sound.

The Denon was found in the garbage with a dead right channel and broken antenna connector. I was able to revive it by replacing some transistors, resistors and bypassing burnt copper traces. It work perfectly for 3 years until now.

First inspection after it was found:

http://i4.photobucket.com/albums/y107/Valdispert/800800Imagem050.jpg

http://i4.photobucket.com/albums/y107/Valdispert/800800Imagem049.jpg

http://i4.photobucket.com/albums/y107/Valdispert/800800Imagem048.jpg

Fixed:

http://i.imgur.com/PjaUE.jpg

http://i.imgur.com/Pq47R.jpg

The manual includes a schematic in the end, would this be enough?

https://docs.google.com/file/d/0B6fu025jFteZaHAzZHVndDlWdUk/edit?pli=1

PS: I can get a new receiver for cheap in an auction site but I wouldnt like to trash this one, at least not before understanding what went wrong. I hope you understand this and excuse my beginner questions.


Title: Re: Denon receiver dead - incorrect antenna may have caused this?
Post by: kam on October 13, 2014, 22:03:30 PM
oh yes, this schematic is perfect for the job. You begin bottom right with the power supply. Measure the transformer outputs.  Orange-orange is one output, blue blue the next, and then you have a +- between red red and common is black. Then go ahead check the outputs of the bridge rectifiers. better use an oscilloscope to see how smooth the output is. The IC605 provides a 6 volts output.

You get the point... Somewhere the power should be missing...
Title: Re: Denon receiver dead - incorrect antenna may have caused this?
Post by: Kunkel on October 14, 2014, 17:50:40 PM
Ok, I'll study the schematics in the next few days and will give it a shot. Thank you!