Howdy everyone.
I got a non-working denon avr2801 from ebay. Since it was (almost) for free I just changed the fuse, powered it up and I got a pretty good bonfire from one of the "non-burning" resistors
. OK, I have another blown amplifier.. cool, change the blown parts and I'm good.. at least that's what I thought back then 
.
While I was waiting for the parts, I removed the blown transistors, assembled it and hooked it to my home audio setup... maaan this denon sounds great!
I got the parts ( the power transistors, the diodes and the zener diodes were all substitutes ). Soldered everything on the pcb, checked it for any visual damage ( after the fire ), crosschecked the resistance of every component with the same on a working channel.. everything was good to go. Powered it up and.... bang! another bonfire from a brand new "non-burning" resistor.
Removed the new set of blown transistors and just left it for a resident amplifier.
A week ago I was out of things to repair and decided to finally fix that receiver ( I also wanted to try a new music setup for which I needed one more working channel ).
Alrighty.. got new transistors, new resistors, new diodes.. well pretty much the standard thing. This time I also thoroughly checked the pre-amp board and the output circuitry for faulty elements. I also tested out of the board TR540 and TR528 together with a set from a working channel.
This time I was totally sure that everything should be fine... and while I was brushing out the flux residue I noticed that there was something wrong with the path between R614 and ZD506. The path is less than 1mm wide / ~10mm long and was interrupted right in the middle of its length. So I guess this explains the enormous amount of damage the channel had ( indeed this is the first time I'm changing that many elements on a blown channel ). Made a bridge, checked again all paths for interruptions and assembled everything back.
Power.. bang!... only smoke and a flash from the fuse this time.
At first glance, this time, it blew only the power transistors and few resistors ( R622, R620, R624 and most likely the emitter resistors ). The pre-stage ones ( tr534/532 ) seem to be fine and currently the receiver is working with them on the board ( but with removed R620 ).
So I already purchased the emitter resistors ( turned out those are hard to find ) and in the next days I will also get the power transistors, but... damn, I do not want another fire.. I almost have paid for transistors what I paid for the whole receiver.
How do you proceed when fixing blown channels?
Are there any procedures you do before powering up the unit?
From the damage, do you see an element which might be faulty?
Any advices are welcome!
Also, with what standard parts would you substitute ZD506/508 and D534/536?
The first picture is with the damage after the first repair attempt ( before I discover the broken path b/n r614 and zd506 ) and the second one - after the second ( with fixed path ).
specs:
https://www.hifiengine.com/manual_li...avr-2801.shtml
I got a non-working denon avr2801 from ebay. Since it was (almost) for free I just changed the fuse, powered it up and I got a pretty good bonfire from one of the "non-burning" resistors
. OK, I have another blown amplifier.. cool, change the blown parts and I'm good.. at least that's what I thought back then .While I was waiting for the parts, I removed the blown transistors, assembled it and hooked it to my home audio setup... maaan this denon sounds great!
I got the parts ( the power transistors, the diodes and the zener diodes were all substitutes ). Soldered everything on the pcb, checked it for any visual damage ( after the fire ), crosschecked the resistance of every component with the same on a working channel.. everything was good to go. Powered it up and.... bang! another bonfire from a brand new "non-burning" resistor.
Removed the new set of blown transistors and just left it for a resident amplifier.
A week ago I was out of things to repair and decided to finally fix that receiver ( I also wanted to try a new music setup for which I needed one more working channel ).
Alrighty.. got new transistors, new resistors, new diodes.. well pretty much the standard thing. This time I also thoroughly checked the pre-amp board and the output circuitry for faulty elements. I also tested out of the board TR540 and TR528 together with a set from a working channel.
This time I was totally sure that everything should be fine... and while I was brushing out the flux residue I noticed that there was something wrong with the path between R614 and ZD506. The path is less than 1mm wide / ~10mm long and was interrupted right in the middle of its length. So I guess this explains the enormous amount of damage the channel had ( indeed this is the first time I'm changing that many elements on a blown channel ). Made a bridge, checked again all paths for interruptions and assembled everything back.
Power.. bang!... only smoke and a flash from the fuse this time
.At first glance, this time, it blew only the power transistors and few resistors ( R622, R620, R624 and most likely the emitter resistors ). The pre-stage ones ( tr534/532 ) seem to be fine and currently the receiver is working with them on the board ( but with removed R620 ).
So I already purchased the emitter resistors ( turned out those are hard to find ) and in the next days I will also get the power transistors, but... damn, I do not want another fire.. I almost have paid for transistors what I paid for the whole receiver.
How do you proceed when fixing blown channels?
Are there any procedures you do before powering up the unit?
From the damage, do you see an element which might be faulty?
Any advices are welcome!
Also, with what standard parts would you substitute ZD506/508 and D534/536?
The first picture is with the damage after the first repair attempt ( before I discover the broken path b/n r614 and zd506 ) and the second one - after the second ( with fixed path ).
specs:
https://www.hifiengine.com/manual_li...avr-2801.shtml
Attached Files
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