Hey there folks,
I have a strange problem with my Marantz PM57 that I just can't get my head around. It had shorted amplifier chips in the right channel, which had caused the fuse to blow. I replaced them, and fired it up with my dim bulb tester - the tester lit up bright (100w bulb) and didn't dull down, the power light on the front of the marantz lit up and then faded out. I quickly unplugged it and searched for another short - couldn't find it. So, I powered it up again to look for something hot, this time it powered straight up, the DBT lit up and then faded to nothing and the amp worked perfectly. I performed an idle current adjustment, and then had it playing music for 30 mins or so. Then, I switched it off and went out for lunch - came back and now it is turning on with the same symptoms as before, a bright solid light on the DBT and no power on the front. The main filter caps are reading 2.2v when it is like this, as are the main chips. The only thing getting hot is the 3 pin plug from the transformer into the board, which connects directly to the bridge (not shorted), then goes to the filter caps (not shorted, reading within range of capacitance) and then to the amplifier chips.
9/10 times i turn it on it goes like this, and 1/10 times it will start up normally.
What on earth is going on here? can anyone help?
Many thanks
I have a strange problem with my Marantz PM57 that I just can't get my head around. It had shorted amplifier chips in the right channel, which had caused the fuse to blow. I replaced them, and fired it up with my dim bulb tester - the tester lit up bright (100w bulb) and didn't dull down, the power light on the front of the marantz lit up and then faded out. I quickly unplugged it and searched for another short - couldn't find it. So, I powered it up again to look for something hot, this time it powered straight up, the DBT lit up and then faded to nothing and the amp worked perfectly. I performed an idle current adjustment, and then had it playing music for 30 mins or so. Then, I switched it off and went out for lunch - came back and now it is turning on with the same symptoms as before, a bright solid light on the DBT and no power on the front. The main filter caps are reading 2.2v when it is like this, as are the main chips. The only thing getting hot is the 3 pin plug from the transformer into the board, which connects directly to the bridge (not shorted), then goes to the filter caps (not shorted, reading within range of capacitance) and then to the amplifier chips.
9/10 times i turn it on it goes like this, and 1/10 times it will start up normally.
What on earth is going on here? can anyone help?
Many thanks
Maybe try to localise problem ie, Left/right channel, power supply??? Clearly the psu is being dragged down, so remove load by lifting resistors/jumpers and any secondary fuses
