Hi all! Reigniting an old thread, but thought I'd see if I can gain any insight here. I also have an AVR-2807. I, too, am repeatedly blowing the 125v/8A fuse on the board nearest the AC input. No speakers, no equipment attached to the unit. When I turn on the unit WITHOUT that fuse, it powers on, full green light, but no display. Does this help narrow down where the fault might be? I'm not an electrical engineer, but fairly competent with a soldering iron and fairly savvy in electronics, when I've got the good old internet there to educate me. Thoughts? Thanks!
You can download a
service manual here.
We are very reluctant to provide service advice, as it is dangerous, especially if you have no training.
For your protection no attempt should be made to service the unit without a Variac. This is a variable voltage transformer, which can lower the voltage to the unit under test, to make servicing easier. This stops fuses blowing right away. More importantly it isolates the unit from the AC mains, and makes servicing much safer.
DO NOT muck around in this unit without one of these devices.
Now you will need an amplified meter. Using an non amplified meter just does more damage.
You may well need a signal generator and o-scope.
First find out what the blown fuse supplies.
There are a lot of power supplies starting on pages 97.
When you see which part of the unit the blown fuse supplies, disconnect the board or boards that power supply is supplying. If the fuse blows with the boards disconnected then that power supply needs service.
Now connect boards one by one and see which one is drawing the excess current. Unless it is the power amp board, then you will need to replace that board if it is available, and it probably isn't. With modern service mounting you will not repair the board.
If the problem is in the power amp, and it very likely is, then you have a chance of servicing it.
You will need a signal generator and o-scope.
Now the power amps are on one board and the power transistors are discrete.
Now disconnect the rail voltage from all the output stages, and reconnect one by one, to see if there is one or two blown output pairs.
Be prepared when you find the culprit to check out the driver stage. Often but by no means always the driver stage is damaged as well.
There are thyristor crow bar DC off set protection circuits I see. These frequently need service especially when fuses have been replaced multiple times. If you don't check this carefully then you will blow the new power transistors right away.
If there is a major board blown then the cost will not be worth it, and as I said the board may not be available.
The only areas were you might come out ahead is if there is a power supply you can repair or a set or sets of power transistors that can be replaced.
This is a complex unit, with a service manual 130 pages long.
This will be a very steep climb for you if it is the first unit you have serviced.
