Harman Kardon AVR1700 won't power up

[tom66]

Re: Harman Kardon AVR1700 won't power up

I can't see a short on the amp isolated side blowing up IC92. You may have had a solder bridge, or something else on the power supply is bad.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I have turned on the PS with the front display board and the HDMI board and it was fine. It must be something on the amp board. I will look at it later on.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I have replaced again the IC92 and the power supply works again. I don't understand why it shows +/-25V, but the same voltage was showing the other receiver also and that one it works.
I'm not worried about that.
I haven't found anything wrong, that I did, except some pads came off from the PCB, but they all make contact. No shorts.
What else could I check to make sure that I'm not blowing up again the IC92?
At the 45V connector I don't see a short, but the resistance keeps changing, going toward 0 very slowly. I haven't waited it out. It seems like it really slowed down at 17Kohm.
I have checked the final transistors and I don't see any short there either.
On the IC92, I have noticed that it blew out a piece of plastic, between pin#3 and pin#4.

[tom66]

Re: Harman Kardon AVR1700 won't power up

Ah, check if there is a 4 ohm / 8 ohm impedance switch on the rear. If so, try setting it to 8 ohm and see if you get +/-45V.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I haven't seen a switch on the back. The speaker has to be at least 6 Ohm.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

There is a feature "in front of the amp" in the schematics that detects voltages between 25V-38V(4.3A) and 38V-45V(3.9A) and there is a third detect mode Protect(7A). Not sure what it does though.
I see two large capacitors on the Amp's board. Can't those increase the voltage even higher?
It can't be in that area some shorted component?
Right now I'm using the receiver, using some headphones and it's working fine.
I'm scared to connect the 45V supply connector. It would set me back another 2-3 weeks to get the IC.
The is also a connector called Protector Test (Short). Not sure what can be done with this?

[tom66]

Re: Harman Kardon AVR1700 won't power up

It may be an option in the system menu.
If you are using 6 ohm speakers I wouldn't worry.
Lower voltage there will limit maximum output power, but it will still sound fine up to reasonable volume levels.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I don't have speakers connected right now.
It's so tempting to connect the 45V connector, but I'm afraid that it will blow again and it's $6.50 a chip.

[tom66]

Re: Harman Kardon AVR1700 won't power up

I have had this confusion before on a Yamaha AVR. It had a switch on the rear. Yours may be adjusted in the software.

You can insert a lightbulb in series with 45V connector, which will limit current drawn in case of a fault to reasonable levels. You should also be able to get low level audio out.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

That sounds good. Good idea.
I have a +/-45V supply, should I use two bulbs? What kind of bulbs should I use?

[tom66]

Re: Harman Kardon AVR1700 won't power up

Yes, use one on +45V, one on -45V.

40W bulb should work.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

120v/40w?

[tom66]

Re: Harman Kardon AVR1700 won't power up

yep.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

It's working. Not sure what happened the first time.
Thank you very much Tom!!.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I have celebrated a bit to early.
Tonight I have hooked up the receiver to a 5.1 speaker system and I have realized that the front right channel is not working correctly.
I can barely hear it and it doesn't sound clear, it has a gargling sound.
I guess when it was shorted the front left channel, the right one got some damage also.
The final transistors could have an issue?

[tom66]

Re: Harman Kardon AVR1700 won't power up

Check your source. Are you playing 5.1? If so, you may have configured it incorrectly. Try with just stereo, for now. Would be very odd for left channel to kill right -- but it's possible both were bad.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

The left channel place well. I have switched the two receivers and the good one works well at that channel. I have switched speakers between as well, because they are refurbished and I have connected them the first time. Still the same.
Must be something with that channel.
I haven't opened it yet, but soon I will.
I have also see on the schematic, there is a 1.2V/-1.2V that can be adjusted. I haven't even checked that after I have replaced the transistors.
I have found some of the screws holding the final transistors, lose. So, I'm thinking that maybe somebody tried adjusting that variable resistor.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I have just realized that is still the channel has issues that I have repaired, the front left.
So this channel is not blowing anything up, but it still has an issue, low volume and garbled sound.

[tom66]

Re: Harman Kardon AVR1700 won't power up

Did you use cheap eBay transistors? Because that can happen if you use cheap eBay transistors...
Yes, do check you have set the bias point correctly, service manual should have instructions.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

The finals are from Digiey and some are from Ebay, but US sellers.
Some are from China.