Denon amp that I am trying to repair. It was working fine suddenly it stopped. No more sound. Once in a while comes on , if the receiver is on for sometimes. I am not sure what to change. I guess it is in output stage. Do I have to change the output transistor or it just some kind of relay?
when I turn the receiver on, the power/standby light blinks 7 or 8 times and ralay clicks. But no sound. Please give some input so that I can fix the amp. I am really into it. Any help would be appreciated.
when I turn the receiver on, the power/standby light blinks 7 or 8 times and ralay clicks. But no sound. Please give some input so that I can fix the amp. I am really into it. Any help would be appreciated.
Check for DC on outputs.
One of the channels has DC due to some faulty component.
AV receivers tend to get very hot and some resistors get open-circuit.
One of the channels has DC due to some faulty component.
AV receivers tend to get very hot and some resistors get open-circuit.
so problem might be because of resistor? The thing it is just intermittent. Sometimes if I keep it on for a while sound comes back. And than sound becomes scratchy...like skipping cd and than cuts off ..no sound.
I learned to always check potentially faulty resistors and capacitors...
You may also have problems with any transistor..
Can you measure the voltage at output? Ant DC present?
Try this:
use a 'spare' speaker with a >20 Ohm resistor and a large bipolar capacitor in series. this way any DC will be blocked to the speaker.
If possible, get an cold air spray and put a little of it on each transistor. If there is no difference, spray on resistors starting from output.
Another thing to check: connect a working amplifier to the input of the amp modules of your AVR. If the sound is there and clean, the problem is the module, if not, you can have problems with other part: digital volume control.. maybe not 🙂
If you have the service manual, send me a copy and I'll show where to start.
You may also have problems with any transistor..
Can you measure the voltage at output? Ant DC present?
Try this:
use a 'spare' speaker with a >20 Ohm resistor and a large bipolar capacitor in series. this way any DC will be blocked to the speaker.
If possible, get an cold air spray and put a little of it on each transistor. If there is no difference, spray on resistors starting from output.
Another thing to check: connect a working amplifier to the input of the amp modules of your AVR. If the sound is there and clean, the problem is the module, if not, you can have problems with other part: digital volume control.. maybe not 🙂
If you have the service manual, send me a copy and I'll show where to start.
does the display stay lit? if so, have you tried changing surround modes. if you want to bypass the DSP, put it in EXT IN mode and feed signal in through the EXT INPUT jacks on the back. if it works fine that way, you probably have a problem with the DSP board or one of the power supplies feeding it. +/-15V regulators are a common failure item in Denons
I have one with the surround & center channels not producing any output. I checked and all outputs transistors have negative and positive rail voltage (+/-52vdc) but am only getting sound/output from the two front channels.
Any ideas?
Any ideas?
my have solved the issue. Now both channels work. My receiver was dusty , so I cleaned all the knobs and put some lubricant on the balance knob. Now both side had output. I bought the received used and I think it was sitting for a long time collecting dust.
check the setting from the menu. I think the receiver is set not for two channels, stereo mode. Put it on dolby digital or any other mode. It should work. Check also if the receiver is set to bypass on or off.
I've gone through the Dolby Digital and the other setting and still no sound from the surround and center channels. I don't have the user manual so its a little difficult understanding which setting to use, but I've used pretty much all and same results.
All the outputs tested good, so don't know if its the DSP board that's not processing the surround and center channel.
I sure don't want to trash it, especially knowing its repairable. I sure wish I could find a free service manual for this model.
All the outputs tested good, so don't know if its the DSP board that's not processing the surround and center channel.
I sure don't want to trash it, especially knowing its repairable. I sure wish I could find a free service manual for this model.
Found the problem!
Thanks for the tip - the denon AVR-2800 doesn't actually have 15V regulators but I found that the 5V regulator (IC903 as shown)
This seems to be a common problem and the 7805 used by Denon - over time and with heat the IC loses the ability to regulate and the 5V line sags to about 3V, usually the voltage will slowly rise to about 4.5V and the DSP board starts working again.
Replace this with another 7805 IC and the Amp works flawlessly. Do not be tempted to replace with an 'equivalent' 5V regulator as the 7805 forms part of a tuned and cascaded regulator and any mismatch in characteristics causes the entire 5V rail to oscillate.
Thanks for the tip - the denon AVR-2800 doesn't actually have 15V regulators but I found that the 5V regulator (IC903 as shown)
This seems to be a common problem and the 7805 used by Denon - over time and with heat the IC loses the ability to regulate and the 5V line sags to about 3V, usually the voltage will slowly rise to about 4.5V and the DSP board starts working again.
Replace this with another 7805 IC and the Amp works flawlessly. Do not be tempted to replace with an 'equivalent' 5V regulator as the 7805 forms part of a tuned and cascaded regulator and any mismatch in characteristics causes the entire 5V rail to oscillate.
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