Worth fixing? Denon DRA-550... - diyAudio
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Old 2nd September 2010, 08:16 AM   #1
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Default Worth fixing? Denon DRA-550...

I have an old Denon DRA550 receiver in which the right channel has died. Is it worth fixing this thing or do I just pilfer it for parts. They are 50W p/c so I thought I might be able to use the transformer for my chip amp.

I tried to find a service manual for it to see what size the transformer is and only found one at servicemanuals.net but they want 17.00 for it and I don't want to pay for one if it is going to the big graveyard in the sky....

Cheers
Bruce
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Old 2nd September 2010, 11:57 AM   #2
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the specific amp worth working with... basically is well made as is it will need recaping and some service and generally this is something worth doing in an allready well made machine

cost of upgrading such a machine can be very low if done diy but will cost a lot if done by expert .In any case there is a very good potential for this machine to be repaired and upgraded and with a life expectancy of at least 30 years .

on the negative side of this amp is the internal wiring that will produce crosstalks if more than one active source is conected and the preamp section that complicates signal a bit more

schematic is available if you wish to have it just e mail me
and here is some info regarding repair procedures and trouble free start up vintage amplifier repair/upgrade manual

kind regards sakis
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 2nd September 2010, 12:42 PM   #3
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Hi sakis

Thanks for the insight.... I think there is a possible better future for this amp yet. I am definitely up to giving it a go, heck, if I stuff it up I'll use it for parts

The circuit diagram would definitely be handy, will have to try and source a service manual to see how to pull it apart safely (read put it back together afterwards ).

I cracked it open just now and found some blackening on the board, focused around cap C564 & resister R586 (or could be 566). The resistor has come away from the board which wouldn't help much plus it is blackened.

I'll send you a PM re your email and give you mine too. Thanks again for the offer.

Cheers
Bruce
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Old 2nd September 2010, 12:53 PM   #4
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service manuals talk about what is inside your amp but will tell you nothing about the procedure ...

if you are not familiar with that and/or the vintage amplifier repair/upgrade manual is not fully understandable ...simply dont even start ...

i could help you up to a point but it canno be done without the basics
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 2nd September 2010, 01:00 PM   #5
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Hi again

The service manual would be purely for pulling it apart in the right order so I can get the board out safely.

I am reading your other thread now to get a handle on the task.

Cheers
Bruce
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Old 2nd September 2010, 01:48 PM   #6
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hmmmm not in this service manual i think ... but see for your shelf check your e mail in a few minutes
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 2nd September 2010, 03:26 PM   #7
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Thanks for the email, got it and have been looking through the docs.

Have run into a roadblock at the moment. I have confirmed that resistor R566 is toast but cannot find it on either the parts list or in the schematic. It and it's neighboring cap C564 shows on the board layout diagram however which I find strange. It's 1:22am now so I am going to get some sleep and look again tomorrow.

My plan was to replace the resistor and then do some measurements to see what is happening as a starting point but until I find the value of the component I am stuck!

Cheers
Bruce
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Old 7th February 2013, 02:56 PM   #8
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Default Tone Control - Frequency Response

I am looking for a test review, where I can find a diagram of the frequency response by various positions of the baxandal tone control.

Stereophile dosn't release this diagrams of that model.

For me the most important thing is the center frequency, from where the high frequencies are enhanced by boosting the treble.

Thank you for an advice to such magazines, where this model was tested.
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Old 7th February 2013, 03:10 PM   #9
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Hello T

+-8db at 100Hz for the low +-8db at 10khz for the high

Quoted from the service manual
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Old 7th February 2013, 05:26 PM   #10
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Quote:
Originally Posted by sakis View Post
Hello T

+-8db at 100Hz for the low +-8db at 10khz for the high

Quoted from the service manual
sorry for my not perfect phrasing.
I write:
..."from where the high frequencies are enhanced by boosting the treble"
but I mean:
..."from where the high frequencies and low frequencies are enhanced by boosting the bass and treble"
This frequency is those, where is not any increase/decrease (center/pivot frequency).
The lowest and the highest cut-off frequency isn't important for my case.
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