ONkyo TX-NR626 Check SP Wire

[RJARRRPCGP]

Re: ONkyo TX-NR626 Check SP Wire

The heat sink gets so hot (135F) you cannot leave your finger on it.

More like 160F! If you can't leave a finger on it.

[redwire]

Re: ONkyo TX-NR626 Check SP Wire

Not much has a few days time-constant, aside from a bad connection or a damaged (but not dead) transistor.

The amp might go into thermal runaway, where once it gets hot, the idle current keeps going up (=gets hotter) until it roasts the output transistors. So I would suspect the three transistor VBE multiplier (one on power amp, two on driver board) may not be working properly.

Don't forget Q6001/R6232/R6021, temperature sense on the heatsink. If it goes lazy or open you will lose the bias multiplier and it would wreck the o/p transistors. The resistors (trimpot) nearby might be worth checking. If Q5411 died then an overload could work its way back to Q6001- although the resistors should smoke first. You can always compare readings with other channels.

My experience with the Onkyo TX-NR636 is the idle current tracking is not so great, it's very low when the amp is cold and I can hear a little cross-over distortion. After 10 minutes that goes away and the amp settles into the right idle current.
It's supposed to be the other way around - as temperature goes up, bias goes down. The design is not the best IMHO.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

The thing that keep perplexing me was every time I fixed it, it would work fine for a few hours or even a few days and then blow the channel.

[redwire]

Re: ONkyo TX-NR626 Check SP Wire

Onkyo driver boards are super easy to solder bridge. Close spacing, lead-free solder and teardrop pads. Then the heat from some transistors turns the PCB brown. It's just really fragile, pads and traces lift off easily.
I spend 1/2 an hour under a microscope checking each channel for poor connections or bridges.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

Update: After repairing the R channel several times I finally cut the PCB trace from the power transistor emitter resistors to the output relay and replaced it with a wire and the unit no longer blows the channel. Maybe when the receiver warmed up the PCB trace somehow shorted to ground. There were no obvious signs of a short though.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

I was hoping the point of the other boards was to eliminate the driver board components as possible suspects, thereby narrowing the search for the bad part(s).

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

The only thing I can say is, that you have missed some bad component(s).
There is no point, in buying other boards. You still have to find the bad part.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

I bought a working NR626 and swapped driver boards to try to solve this problem. The old driver board in the working NR626 works fine but the working driver board in the old chassis blew the same R channel components. With no input nor volume this second unit combination has 354mv on the R amp output (before it eventually blows). It also has 254mv voltage difference on the differential pair bases for the R channel while the L channel has only 8mv on the differential pair bases. It also drops to the low B voltages after about an hour.

I'm assuming the swap test points to the motherboard amp section. I believe I have double checked all those R channel components at least twice.

Please help...

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

Replacing the fan fixed the overheating nicely but the unit still failed (VPROT) after threes days running 6-8 hours a day. Failed parts are: Q6051, R6081, Q6061, and R6091 the R channel power transistors and their 0.22 ohm base resistors.
On the driver board R channel: R5351, R5471, Q5461 and Q5411 failed.

Service manual link:


Any suggestions would be greatly appreciated.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

Found another fan assembly from an eBay seller by contacting everybody that is selling or has sold any NR626 parts. No need to reply to my previous post. Thanks.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

If you want to keep this receiver and not resell it, I would suggest to get a 120mm PC fan and mount it to the top case from inside.
When I had these older receivers, I have used a laptop cooler's internals, fan and fan controller. I have ran the USB cable to the TV. When the TV it was on, the fan it was on.
I have adjusted the fan controller to a speed, that the fan noisy did not bother me.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

My fan order on eBay fell through (seller lost the part). Anybody have a Onkyo TX-NR626 or 616 fan for sale? KF1225B1E-33ACD54RB or 4710KL-04W-B10-EA2. Thanks.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

Temperature and output voltage can be confirmed the following operation when the unit is powered on.

[DISPLAY] + [ON/STANDBY] * 2 → [TONE]

e.g. 001 042 F:x S:H

Displayed Fields:
(001)Voltage of VOLH port,
(042)Temperature of thermal sensor,
(x)FAN speed (x: Stop, L: Low speed H: High speed),
(H)Amplifier power Supply voltage condition (H : High-B L : Low-B)

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

I know, there is a way to check the receiver's temperature, with a combination of button presses.
Per artois7. on page #3:
"From memory, I think if you hold down display and the power button, release display and press the tone button, you should get an internal temperature reading. My 609 reads around 23 degrees on first power on and will idle somewhere mid 30s-40s ish (and it's got no ventilation around it..!)"

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

In the 626 diagnostics menu there is a "confirmation of output sensor and thermal sensor" test. It reports the voltage of the VOLH port, the temp sensor, fan speed, and the amplifier power supply voltage condition (High-B or Low-B). The implication is the Low-B may be used for overtemp situations.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

Yes, I incorrectly connected the resistors in the measuring leads.

The schematic shows the drop-down relays are MPU controlled by SEC1H on pin 128. This appears to switch between the +-S1L and +-S1H voltages. It certainly let the amplifier cool down when it switched low. I could hear the click but there was no change in the display. The first time I 'fixed' it, it died after 4 hrs resulting in a reported VPROT fault. (from overheating???)

Warning: I'm strictly an amateur here so I could easily be mistaken about anything I report.

Again, thanks for your help. It is greatly appreciated.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

You are talking about, the 100 Ohm resistors, in the measuring leads?
I'm not familiar, with that voltage drop thing. Why would that happen at all?
The receiver did not show any message, that is in protection mode?
If it was overheating, it should have shown something.
mmartell, was referring to other resistors as well.

[jworthin]

Re: ONkyo TX-NR626 Check SP Wire

tibimakai:
All channels were hot.
The unit did not arrive with a fan but researching further looks like this model should have one. I have ordered a replacement.
I did not have the 100 Ohms resistors installed correctly. Fixing them and resetting the idle current seems to have fixed the overheating and voltage drop back. Thanks!

Could overheating cause the shorting of power transistors before the immediate thermal protect shutdown could protect the unit at 100F?

mmartell:
I checked the two base 0.22 Ohm resistors and the 5W ceramic double 0.22 Ohm resistor.

[mmartell]

Re: ONkyo TX-NR626 Check SP Wire

Did you check the main board resistors near the final transistors as well ? There are at least two there known to go open, one being the dual package emitter resistor.

[tibimakai]

Re: ONkyo TX-NR626 Check SP Wire

Every channel is that hot, or only the R.
The 626, has a fan?
If I remember correctly, at 60C the fan should kick in.
You are using a 100 Ohm resistor on each lead, when measuring the idle current?
I have never replaced all the capacitors, usually only one is blowing, or none.