ONkyo TX-NR626 Check SP Wire

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

I replaced all transistors and all electrolytics in the R driver. I have triple checked the SMD and discrete resistors as well.

Idle voltages stay within service manual tolerances even as it heats up!
The voltages across the plus and minus sides of the driver match the L and C channels.

I have even tried reducing all channel idle voltages to 1mv and it still overheats and drops the B voltages in half (you can hear the drop-down voltage relay click in). How can the power transistors get so hot when the idle voltages/currents are so low??

When the B voltages drop in half the unit temp drops to room temp (75F) in a couple minutes.

The heat sink gets so hot (135F) you cannot leave your finger on it. And this is with no input, no volume, and no speaker load.

Thanks.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

It could be, that you have missed a component.
Check every(!) component, at channel R on the vertical board, and base board.
Compare measurements, with another adjacent channel.
Idle current is stable, after reaching the amount off time, specified in the service manual?
I don't know how hot is yours, but these receivers run quite hot.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

I received a 626 that was in VPROT. The R channel was blown. I noticed that channel had been serviced before. I replaced the bad channel power transistors and some small parts in it's driver. I set the idle current and it seemed to work fine for about 4 hours when it blew the same channel again. (VPROT) It is ‘repaired' now again but I am reluctant to run it for very long. The idle currents on all channels are normal and stay within service manual limits. But here's the odd part, when it is turned on it starts getting hot with no input, no volume, and no speaker load. It gets up to about 135F in 20 minutes and then the unit switches the +/-B from 60V down to 29V which cools the unit off.
1) Why did it blow the the same channel again?
2) Why is the unit getting so hot with normal idling currents?
Any help would be greatly appreciated.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

It's been a while since I have repaired a 626 and I don't remember. Lately I have repaired a bunch of 636s, 545.
Usually I have found bad SMD transistor at the bottom as well. Sometimes a capacitor was blown near the medium power tranzistors.
If you don't want to blow it again, you will have to check all the components.
It will take like 15 minutes, it's not that hard.

[grunca]

Re: ONkyo TX-NR626 Check SP Wire

Would greatly appreciate sharing your experience, what parts did you replace ?
I found the final power transistors bad and, on the vertical board I had two medium power transistors that were bad and one low power (2sa1037), also a 82ohm resistor on the vertical board and the 2x .22 ohm on the high power finals.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

You will have to check everything on the vertical board, course only the bad channel one.

[grunca]

Re: ONkyo TX-NR626 Check SP Wire

thank you !

my front right front stage power PNP and NPN pair are shorted and the collector resistors are open.

can you save me some time and let me know which preamp parts you found to be bad ? Of course I can check further than that, but it would be a good start.

thanks !

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

After all is done, you will have to check and adjust as necessary the idle current.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

Measure all final transistors for short, mounted on the heatsink. Cut the shorted legs and the receiver should turn on. After that, you have to measure all the components on the base board, around the shorted transistors. Most likely, the Emitter ceramic resistor is open as well.
Than remove the pre-amp board and check all the components that belong to the bad channel. Replace what is bad.

[grunca]

Re: ONkyo TX-NR626 Check SP Wire

I downloaded all manuals linked here and ready to open the receiver for repairs, any advice ? thanks.

[grunca]

Re: ONkyo TX-NR626 Check SP Wire

asking anybody that can answer.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

Who you are asking?

[grunca]

Re: ONkyo TX-NR626 Check SP Wire

Did you end up fixing it ? can you share what you learned ?

thanks.:compy

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

http://elektrotanya.com/?q=showresult
You have to wait like half a minute, to show up below the picture, Get manual.

[commpradeep]

Re: ONkyo TX-NR626 Check SP Wire

BTW, I check the other Onkyo service manual for the TX-NR series, it shows the set point of 6mV on 0.22 Ohm which represents 27mA of current on the output transistor.

This could be something very old to you but very new for me like beginner,

Can you please share the NT626 service manual if you have ... Please

[budm]

Re: ONkyo TX-NR626 Check SP Wire

Oh BTW, you do not adjust for minimum current, the Transistor has to be bias on to reduce crossover distortion, in this case it is Class A-B amplifiers. You can do class A but you will need lots of heat sink and good power supply, Class A amplifiers make good room heater.
http://www.aikenamps.com/index.php/w...ver-distortion
http://www.electronics-tutorials.ws/...ier/amp_7.html

[budm]

Re: ONkyo TX-NR626 Check SP Wire

BTW, I check the other Onkyo service manual for the TX-NR series, it shows the set point of 6mV on 0.22 Ohm which represents 27mA of current on the output transistor.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

Thanks for clarifying.
I remember about that button combination on the 609. That was my first receiver.
I will try it out on these also(I have a 515, 616 and 626). Most likely the 515 will have to go.
I'm thinking about replacing the factory fan, with a much bigger size fan, to cover bigger area and maybe I find one, that the RPM can be adjusted. This way, I could run it at lower RPMs(quiter) and cool everything much better.

[artois7]

Re: ONkyo TX-NR626 Check SP Wire

Always wondered that. Thank you!

[budm]

Re: ONkyo TX-NR626 Check SP Wire

"Quiescent current = the 6mV reading you took from the test points..! (before anyone jumps in and says the current can't be taken in mV and that it doesn't make sense; this is word for word from the service manual!)" Divide the voltage reading by the resistance will give you the Idling current, they are just taking the reading of the Voltage drop across the Emitter resistor of the output transistor, this way you do not have to open the current path to put the DC Amp meter in series with the current path, that is how it been done with many solid state amplifiers and that how I did it it since the 70's when I was working for warranty station for SANSUI, PIONEER, PHILIPS, FISHER, ZENITH, RCA, MAGNAVOX, etc. we had lots of service manuals at that time.