Denon AVR 1804 - popping / scratching / noisy

[nazdackster]

Hi all, this is my first post... I have a Denon AVR-1804 and I damaged it the other night. I was connecting speaker level outputs through a line level converter I built (10k in series, 470 ohm in parallel) to a parasound HCA-1500 amp and heard a popping sound, the lights dimmed, and the left front channel of the receiver now sounds just like a blown speaker. All speakers are fine, I switched them around and it's the AVR. Turns out I had a short in my converter, so I essentially shorted the speaker terminals of the AVR1804.

Fixed the converter and hooked it to the speaker front B of the AVR, and with front A off, and B on it sounds awesome and did just what it was supposed to (AVR 1804 doesn't have line level out jacks so I made my own) - the parasound is fine. I'm not sure whether I had it connected to zone 2 outputs or channel B speaker outputs when I shorted it, but in either case I'm surprised I wrecked the A section in the process...

So now the Denon left front channel A seems to be damaged. If I play speakers "A" (connected to a Bose cube 5 channel system) and "B" (connected to the parasound thru converter), then the B left channel sounds bad too. B only is excellent! (stereo mode)

So I'm wondering knowing these clues where to start looking for presumably a bad transistor or some other problem. But it sounds strange to me that B is good, all A is good except left, but A + B left is bad, and why does it sound just like a blown speaker but it isn't? Seems to be at all volume levels, but worse when I turn it up. All other A channels (center, back, etc) seem to be fine.

Any help would sure be appreciated.

Thanks all, sure enjoyed looking through all the posts for similar problems, but didn't find anything quite like this. I have a schematic for an AVR-1803 which is one model down without the B channel, I suppose it will help but I'm not sure what to check first...

Thanks!

Mike

[anatech]

HI Mike,
If you are lucky, you "wasted" the speaker relay contacts. Replace with an original part from Denon.

If you are not lucky, you damaged the output stage and probably the relay contacts as well. This unit should be on a repair bench with a good technician looking at it.

Hint: A good audio technician does not repair TV's and VCR's.

If you are skilled at servicing audio, then you should have some test gear so we can troubleshoot. Otherwise we can only guess.

-Chris

[nazdackster]

Thanks Chris,

I do have a scope and a meter, and with the schematic maybe I can poke around and see if it's the relay or the output stage.

If B speakers sound perfect, and if A and B is driven off the same output (I would think so), your analysis of the speaker relay sounds right... I'll have a look and see if I can find it.

I managed to repair an old JVC amp once that I accidentally watered along with some plants above it (I don't recommend doing that, by the way), so maybe I can trace this one out too... Blew 8 transistors that time! Ooops!

Sounds like relay is an easy check - thanks again...

Mike.

[anatech]

Hi Mike,
Run a sine wave in and monitor the signal on either side of the relay. For this you need a speaker load.

You may be further ahead to simply replace the relay.

-Chris

[Shaun Perez 2]

hi, i may possibly be able to help you troubleshoot this problem. I would need to see the schematic that u have so i can see what circiutry is involved first. if we find that your problem is too in depth then i will let you know to go to a denon tech. however i am a tech myself and an audio lover! my father actually has this same exact model and i would like to see the schematic, as I am possibly going to do some mods/upgrades to it, In return i will attempt to help you out with your problem! I have actually had the same exact thing happen to me as a child when i tried to bridge an amp and didnt understand what i was doing, next thing i know static just as you describe! Its a big upsetting dissappointment

[Leolabs]

Haven't open up any AVR1804 but if the power amp design never change much from AVR16xx series,trouble shooting is easier.As the design is a conventional long tailed pair follow by a VAS stage and the drivers and the output stages.

[Bigred]

I wonder if anyone looks at post dates

I hope after 6 months he has it fixed already

[Shaun Perez 2]

ya, didnt catch that
bit too much