Dead AV receiver TEAC AG-V3020

[PeterLeest]

My old TEAC AV receiver AG-V3020 couldn't power up any more.

There is a PCB behind the front control panel with a large processor (MPU). I found out that the power supply to the MPU is 8V. This 8V DC is feed from a small standby transformer (6V AC) in the standby board.

Other feeds in the ribbon cable are 2 x FL, -30V, Standby and Gnd. The 8V DC also used to turn on a relay to power on the main transformer.

Is the 8V DC to the processor too high? I try to connect a separate 5V DC to the MPU. When standby switch is depressed, the Standby pin will drop from 0.5V to 0.2V, do you think the processor is already damaged?

Also, on the board, surrounding Q901, capacitor, resistor and PCB, there are some black mark. I took out the 3 transistors and its associated resistors and capacitors, they measured ok.

Any help of the problem or a schematic will be very much appreciated.

[jaycee]

8V probably should have been regulated to 5V somewhere on the MPU PCB, probably by a zener diode or a transistor referencing a zener diode. If there is 8V to the MPU IC itself, it'll probably be stone dead.

[ROVSING]

i powered up my teac ag-v3020 yesterday, and it played well, by accident i switched of the 230v mains and couldn't power it up again, this morning i powered it up again and it was working - is there some kind of securitycircuit that swiches it of ? and what should the purpose of that be ?
I tried to switch the 230v mains of again today - same problem can't power it up again.

[jeffro]

I have a Teac AG-3020 that has the same symptoms. If I unplug the amplifier for awhile it will sometimes operate normally for a short time and start acting up again.

What happens with mine is all the buttons become inoperative. Sometimes if I unplug it and plug it back in, it will power up but no sound will come out, in addition none of the buttons will operate, including the power button so that I can't turn the unit off either.

Sometimes if it was plugged in and I try to power it up it will not turn on, because I'm assuming, that none of the buttons are operating, including the power button.

Sometimes if left unplugged for a bit, it will operate normally. I wish I could make this thing work. I really like the unit and new ones are so expensive. I like that this unit will drive A+B speakers at 2x8 ohms. Not all new AV receivers will do that.

Have you had any clues as to what is wrong with yours?

[lgouel]

if you are still looking info on AGV3020, you will find everything you need and more on: Download the TEAC AGV-3020 service manual for free - Hifi Manuals

good luck