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Discussion Starter · #1 ·
I have repaired many of these units (the HDMI switching problem) and have usually installed a slim but very large 12v DC 250MM case fan at the top of each unit to keep them cool.

Each time I have modified and tied in a standard AC adapter that produced about 10V DC to under-drive the fan to ensure silent operation. I have always picked up power from the 110 input side of the transformer (Yellow and White wires) and this has allowed the fan to start and stop with the unit operation.

Now I have another Onkyo TX-SR606 and that point stays hot at ll times!
Furthermore I cannot locate a switched power source ANYWHERE in the unit!
I have tried just about everywhere I can think of, but even abandoning the AC adapter route and deciding I could use an existing voltage to drive the fans hasn't panned out either.

Why is the 110V AC input pair on the transformer work on all the other switched, and this one not?
I cant find any difference in this one over the others.

In the end, I need a way to drive the fan when the unit is on.

And yes, I have the schematic and have considered using the factory supplied fan driver circuit by installing the parts, but the surface mount resistors make that project too time consuming when a switched power source driving a fan is so easy - usually.

I may have to resort to driving a 110/240v relay from the power amp board relay trigger line, but that means I have to gut the whole unit to get to it.

Anyone know how I would do this?
 

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Can you send the schematic? Or at least post the power supply section?
 

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There is a secondary transformer (T902) that is always on, but it looks to me like the main primary of T901 at P911 on page 15 should be switched as you say. I would check the coil voltage of RL901 on page 15 to see if it is always energized, and see if the voltage across the relay is 0 V (if it is on or shorted) or 120 V. Both sides of the coil should be at +12 V if it is off; when it is on, one side should be at 12 V and the other at ground. If it is always on, the relay may be bad (note the actual relay contacts may have fused so it does not matter what the coil voltage says), the microprocessor board may be bad, the driving transistor (Q9002 page 13) may be bad, or it could be a FW/SW glitch.

HTH - Don
 

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Discussion Starter · #5 ·
I agree with all of this, however that would leave the unit on all the time, yes?
Wouldn't i never be able to turn it off?

It turns off and on just fine however.

And, yes, the relay is always closed once the power is plugged in and 2 seconds have elapsed.
 

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Sorry, I thought that was the problem, always on... If not, and the relay is always energized 2 seconds after plugging it in but the rest of the AVR is not live, there must be another power circuit someplace. Or, something is turning on the relay when it shouldn't but the rest of the AVR does not turn on. I agree it seems odd the main transformer would always be on...

There are some B+ relays over on page 9, RL6901 and RL6902, that might help. Fundamentally you're probably going to have to print out the schematics and/or spend time on the computer tracing through it to find potential switched rails that you can use. Since the receiver powers on and off normally they have to be there, somewhere...
 

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Discussion Starter · #7 ·
Again, Agreed.

However, why does the other unit main transformer energize/de-energize when the AVR is switched off and on?

That is how I am turning off and on the fan I install, (ARGH!)

The units are identical numerically, and there is no provision that I see in the schematics that would indicate an alternate method of construction.
 

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That's why I wonder about a FW glitch. Or some sneaky network setting that leaves more of the AVR on? I don't own an Onkyo, sorry.

Could still be a bad transistor driving the relay, maybe the delay is not really related?

There are lots of options in the "LIST" tables in the schematics but I did not try to wade through them all. No idea if one might explain the difference.

I do not think I am adding value; hopefully somebody might know more and will chime in.
 

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Discussion Starter · #9 ·
I went through the list and found no alternate set up components or circuits that would account for the change in behavior.

It's nuts.
 

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Discussion Starter · #10 ·
Hey DonH50...

I could use some additional assistance.

I think you're onto something with the stuff on the video PCB.
Can you verify for me how to test for bad components on this board without removing them?

I have a Fluke Scopemeter and can do tons of modes for testing and I have tested many of the diodes while installed and I get readings in one polarity, but not the other, as I would expect on a good diode.

However my concern is with Caps and Transistors.

Can they all be tested on-board?

If you could give me some rules of thumb on how to ensure i'm not testing these improperly, that would be helpful.
 

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Discussion Starter · #11 ·
I figured it out and I feel so stupid for not realizing this sooner.

It turns out that there is some setting in the unit that you can set that holds power to the HDMI board and keeps the main transformer hot all the time.
I don't know what that setting is, but once I factory reset the unit, the transformer switches on and off with the standby mode.

This is the expected behavior and I have never seen this before.
I would guess it has something to do with holding power to the HDMI board and/or some other area of the unit to allow for continued operation of some aspect of the receiver.

I found this out AFTER replacing the ENTIRE SVIDEO board from a spare on eBay.
It was VERY hard to desolder the band cables that are soldered to the board, (two), but i got them transferred to the replacement board.
To make matters worse, the spare was much older and was scorched a bit more than my pristine original board.

Anyway it works now and I have a pristine spare SVIDEO board.

IfI had simply factory reset the unit at the start, I would have had this completed a week ago. :(
 

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Sorry, I missed your previous question. The answer is that yes, there are a few things you can test, but it depends upon the circuit, natch.

As it is, glad you figured it out! FW can do the darndest things... There's probably an HDMI passthrough mode and/or scheme that lets e.g. the TV turn on the AVR via HDMI that requires HDMI always be on. A better design probably would've same some power by using a simpler sensing scheme, but perhaps that is what's needed for the HDMI protocol (I don't know the HDMI protocol well at all).
 
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