Harman Kardon AVR1700 won't power up

[tom66]

Re: Harman Kardon AVR1700 won't power up

No. Don't just check them. REPLACE them, even if they test good. Reason is, audio transistors are very sensitive, and a minor performance degradation can lead to you blowing up your new transistors in short order. It might work for a few days... it might blow up straight away.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

Do you mean to replace the transistors? That is what I will do.

[tom66]

Re: Harman Kardon AVR1700 won't power up

Both transistors, plus the driver and sub driver transistors at minimum. That is 6. Sometimes the bias transistors fail, make it 8.

Be VERY careful with eBay transistors. About 50% are fake. They will blow up again in short order.

Did someone say amplifier repair is easy? It's not...

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I could use your help identifying those transistors. This is the first time working on an audio receiver.
It seems that the FL-Channel has the shorted transistor.
The shorted transistor is Q653.
I need to replace:
Q653
Q659
Q852
...

[tom66]

Re: Harman Kardon AVR1700 won't power up

BLUE: Test and replace it failed or out of nominal specification.
RED: Replace regardless of test result.

Edit: C852 should be BLUE.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

OK, I have ordered all those transistors, almost $25(!). It will take a while since they are from China.
I still have to check the resistors on that PS.
Going back to the other PS which partially works.
All the voltages are there, except the +/- 45V.
This, most likely suffered from that shorted 2SB1560 transistor.
The secondary diodes are fine.
I don't know what else can I check. I'm surprised that there is no protection between the amp and PS(or I can't see it, if it's there).
If that transistor got shorted, the damage can be only in the secondary part of the PS or can get to the primary side also?

[tom66]

Re: Harman Kardon AVR1700 won't power up

Umm, Chinese transistors are just as bad as eBay ones, did you not read the link on counterfeits? If you can't find them from REPUTABLE suppliers like DigiKey, Newark, Mouser, then let us know the part so an alternative can be sourced. OK to change transistors as long as they are matched pair and close or identical in specification.

It's so easy to counterfeit transistors you can do it in your garage.

[tom66]

Re: Harman Kardon AVR1700 won't power up

If that transistor got shorted, the damage can be only in the secondary part of the PS or can get to the primary side also?

Likely not, there is current limiting.
AMP VCC ON?
Check voltage across C947, primary side.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

Unfortunately I haven't read that article. Where it is?
They claim that they are original Sanken transistors.
The power transistors are sold in pairs.
Actually these were available at Digikey, but I tried saving some money.
I guess the power amplification should be as close as possible(hfe if I remember well). This can be measured with some multimeters, right? I have a BK which has that. I will measure them to see how match they are.
I have checked the rest of the marked components. Two 0.47 Ohm resistors were open, R729, R730.
R891(next to the VR) showed only 79 Ohm, but I guess the VR is causing that value.
R668, R698 are showing 0.3 Ohms. I haven't un-solder them yet. Maybe the inductance is causing this reading.

[retiredcaps]

Re: Harman Kardon AVR1700 won't power up

Unfortunately I haven't read that article. Where it is?

Seriously????

The picture of the "Supplier Reaction to Counterfeit Claims" alone is worthwhile.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

So at that point, the voltage is 19.16V.
I couldn't find that capacitor, though. I have used D931 instead.

Where can I find that article?

[Khron]

Re: Harman Kardon AVR1700 won't power up

Both transistors, plus the driver and sub driver transistors at minimum. That is 6. Sometimes the bias transistors fail, make it 8.

Be VERY careful with eBay transistors. About 50% are fake. They will blow up again in short order.

Did someone say amplifier repair is easy? It's not...

See the underlined "About 50% are fake"? If you slide your mouse cursor over it, you'll notice it's a link

[tom66]

Re: Harman Kardon AVR1700 won't power up

It's irrelevant if the gain and external specifications match. The die ("silicon chip") is typically fifth to a tenth the normal size, which means the transistor is liable to failing quickly. Just hope eBay will refund you money when you find out they are fakes (you will probably be able to compare labels between the existing devices and the new devices and play "spot the difference".)

[tom66]

Re: Harman Kardon AVR1700 won't power up

IC93 has good supply voltage so I wonder if it is bad like IC92 and this is causing your loss of ±45V.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I have ordered that IC too, hopefully they are good ones.
I will get the power transistors from Digikey and I'm thinking of replacing the capacitors as well.
What kind of electrolytic capacitors would work in these amps?

[tom66]

Re: Harman Kardon AVR1700 won't power up

Panasonic FC are best for audio, though you'd struggle to hear the difference. FR and FM work well too.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I'm seeing "Audio" when I'm selecting the capacitors at Digikey. They shouldn't be those for the amp section?
I think that I will hold off on replacing the caps for now, until I learn more about audio devices.
What could be the difference between a capacitor for a SMPS or one for an amp?

[tom66]

Re: Harman Kardon AVR1700 won't power up

Amplifier capacitor have a slightly higher ESR and lower internal inductance, which reduces ringing (high frequency noise introduced by sudden changes in amplitude... BAD.)

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

I have transferred the IC93 to the partially working PS, and the the AVR started right up.
Yeahhh!!
Now I have already a set of Onkyo speakers ordered refurbished from accessories4less, for $229 shipped with one year warranty. It's a 7.1 system!
Now on to playing with it.
Thank you all for helping me with this receiver.
I still have the other one to repair, but I'm still waiting for the parts to arrive.
I'm thinking of buying other ones like this and sell them after I have repaired them.

[tibimakai]

Re: Harman Kardon AVR1700 won't power up

Second receiver.
Got all the parts in and replaced them.
Haven't connected the amp part. Wanted to see if unit powers up at least, and it did. Display it was on and all the other lights.
When I plugged the amp connector and started it up, I have just heared a big pop coming from the PS. I think that the same IC92 blew up. I can't even read the part number from it.
I will have to do more measuring tomorrow.
I'm wondering what else was shorted in the amp section?