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integrated amplifier SONY TA-AV490

I have an intregatad amplifier sony TA-AV490 that is without sound, it turns on the power, from standby, it switches all the functions, and when connecting it makes the connection of the protector of the audio output, it has 65volts negatives and 65 positves in the transistors amplifiers of outgoing, everything is as normal, but does not have accurate sound help for repair, thank you.



Re: integrated amplifier SONY TA-AV490

Is this a new problem and the unit used to be working? Or is this a new to you and has never worked? In other words when did this problem start?

Make sure that there is a jumper between the Left Pre-out jack on the rear panel and the Left Main-In jack. And similar on the Right channel. If the jumpers are missing or lost, a spare rca cable can be used to connect these together. If there is an equalizer installed in these jacks, remove it and try the rca cable.

-bob

Re: integrated amplifier SONY TA-AV490

Thanks for collaborating, but I have already done this, I forgot to say, that the output transistors are cold all the time, there is no heat in the heat decoder, once again I thank for the possible collaburation.

this amplifier worked, but it has been a long time out of use.

Re: integrated amplifier SONY TA-AV490

Hi,

There isn't a Service Manual available for me to look at. So all that I can suggest is that you read the viltages on the output transistors. And see what is missing or wrong. For a "standard" amp with "normal" NPN and PNP resistors you should see rail voltages on the collector pins and less than 1 volt positive and negative on the bases and very little on the emitters. That will tell you where the problem might lie.

-bob

Re: integrated amplifier SONY TA-AV490

hi bob, I read the voltages on the output transistors, all voltages are correct 65+ and 65 - on collectors, and on the base it is 0.2volts and on the emitter 0 volts.
then I took the manual service because it has here in HI-FI ENGINE. https://www.hifiengine.com/manual_library/sony/ta-av490.shtml
hen I measured the voltage in the preamplifiers, and then it was at zero, I did not have the 61 volts + and the 61volts -- in these ICs i following the circuit I found a circuit regulator that powers the preamplifiers, and in that circuit I found the R-807, opened,and the trasistor 2SD1312 on short-circuit colector-emitter.
now I will buy the components and repair, again thanks for the collaboration.

Re: integrated amplifier SONY TA-AV490

Hi,

The voltages on the bases are too low. They should be closer to 0.6 or 0.7. So it does point to a problem in the driver circuit that lookks like you have identified.

Just in case you didn't find all of the faults, you might want to connect the AC input to the amplifier in series with a standard filament bulb. This will limit the amount of current that the amp can draw. The higher the wattage bulb the more current it will let flow to the amp. If everything looks good as far as voltages go (and no smoke!), you can then connect the amp directly to the ac power.

Let us know if you get it working! We love to read a success story.

-bob

Re: integrated amplifier SONY TA-AV490

Hi, Bob, I think when I have the voltage in the two I.C. UPC 1342V Power Amplifer, 59volts neg. and 55volts posi. That the base volts goes to the 0.6 volts, because these two I.C. are the divers. Now it is difficult for me to buy the transistor 2Sd 1312 here in Portugal, I live in the islands of the Azores which still makes it harder but I hope to succeed.

thanl you JMMBorges

Re: integrated amplifier SONY TA-AV490

Thanks, I'll do it, then I'll say something.