Onkyo TX-NR616 exploded, transistor cross reference help

[illegible]

I have an Onkyo TX-NR616 that has expired loudly.

It was bought new in December, 2012, and used lightly. In early 2017
some of the audio stopped working. We found out about the DSP issue
and that Onkyo would fix it, which they did - it came back with the
DSP tagged "REPLACED".

About a month later, some of the surround dropped out, with a brief
message about an output short (there was none). I poked buttons
randomly and was rewarded with a series of bangs and flashes from
inside the unit, then silence and smoke.

The SBL channel on the driver board and associated output
transistors have gone to meet their maker. A 22uf cap on the driver
board (C5445) blew with enough force to wrap metal shrapnel around a
nearby power transistor, and the power transistor (Q6065) has a crater
in it.

Needless to say, Onkyo was no help, since it's out of warranty. It
sounds like this exact failure isn't uncommon, so I can't really blame
Onkyo for messing something up during the DSP fix.

So, first question - does anyone know why this happens, and if I fix
it, why won't the same thing happen again?

I found a replacement driver board for $25 with free shipping, that's
below my pain threshold for not having to deal with cross referencing
parts and hoping I don't get counterfeit/out-of-spec parts.

I haven't put the curve tracer on the other transistors yet, but I'm
assuming that all the main board transistors on the SBL channel are
blown. Digikey has the power transistors - 2SC4469 and 2SA1695, but
the others - 2SC1740S and 2SC2229 are proving harder to find. I can
buy them off ebay, or type "2SC1740 replacement" into a search engine
and go with whatever's recommended. Does anyone have any better
advice than that?

And, do I have to do any calibration after replacing the power
transistors and any other components that are out of spec?

Thanks for any help!

[mmartell]

Re: Onkyo TX-NR616 exploded, transistor cross reference help

You can probably go with whatever Digikey recommends as they came through in a few 636 and 646 threads here and no resulting problems.

After the repair you should adjust the idle current at least for the repaired channel. DL the service manual for more info likely available at Elektrotanya.

As to the "why" I dunno but not totally out of the norm for an amp to blow a channel occasionally and take a few good parts with it. It has been noted by myself and others that the finals don't seem snugged up to the heatsink on some models so there's a possible thermal issue there. Wouldn't hurt to have a look.

[tibimakai]

Re: Onkyo TX-NR616 exploded, transistor cross reference help

When I had issues like this, I have sent an Email to them and they recommended some other transistors for me.
Sometimes, I have found the finals at Frys Electronics as NTE components.
One set for example(for 636/646 NTE36/37), comes paired in one bag(!).
I have repaired quite a few Onkyos already and on all of them, all the finals were just snug. This is my theory, that they are not tightened properly and the heat is not transferred properly.
Most likely, that big white .22 Ohm ceramic resistor, is open as well. Not to easy to find one in 5W.
Usually, I find the two final transistors blown, that .22 resistor and maybe one or two very low resistance resistors are blown.
The biggest damage, is on that pre-amp board. Most likely, you have at the bottom some SMD transistors blown, the pre-final one(maybe both), capacitor, some 2.2, 33, 120 maybe 10 Ohm resistors.
You should check everything, at that channel.
When is all replaced and checked, at least on the models that I have worked on, 636 and newer, I had to use, a 100 Ohm resistor on each lead going to the DMM, when measuring idle current. You will have an initial measurement and then a burn in measurement after like 5-6 minutes. You should have a variable resistor, at each channel and you should adjust it accordingly to the SM.
If the values are rising way to fast, you still have a problem.
On the latest models, this adjustment is not required (yeahh).
That $25 is probably is a good idea. But, how can you be sure, that board is all good?

[dobrykamil]

Re: Onkyo TX-NR616 exploded, transistor cross reference help

This is my theory, that they are not tightened properly and the heat is not transferred properly.

I reckon that most of the problems like this, is caused by fricking pre-amp which runs very hot, even when idle.Next time, take a really close look at the solder joints of the faulty channel.
In case like this, I always check that small transistor near the finals, it's Q6005 in SBL channel.

[tibimakai]

Re: Onkyo TX-NR616 exploded, transistor cross reference help

I don't have the schematics in front of me, but it is that transistor, between the final transistors?
If yes, then for me they were always good. I have never had one blown.
I agree, that everything is way to hot.
I used to install a laptop cooler fan, with adjustable speed and power it, from the TV's USB port. This way, is always on.
The latest receivers, don't have fans anymore and they run pretty cool.