Onkyo reciever, exessive ripple on +12V? how much is acceptable?

[amelbye]

I'm troubleshooting this onkyo surround reciever. It's old, but high quality. (Integra A-SV810Pro)

The problem is bad contact in the main speaker protection relay.

My first thought was to replace the relay. However, I measured the ripple on its' coil voltage to be about 5V, which seems quite a lot on a 12V line.

What to you think? Is this a normal amount of ripple of this application, or should I investigate the PSU board? (the reason I'm asking is: I'll have to disassemble the whole chassis and probably even cut a few wires to get to the PSU board. This amp is not service friendly at all)

[b700029]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

FIVE volts?!?!

In other words the voltage is oscillating between 7 and 17V?

That doesn't sound normal at all.

[dood]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

I believe it would mean 5VAC on a 12VDC line.

[Toasty]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

>>However, I measured the ripple on its' coil voltage to be about 5V...<<

Measured how? With what? Meter? Scope?

Service manual; available at: www.elektrotanya.com

Just type in SV810 in search box.

The 2 main supply filters are 12,000uF @ 63v. It is a split supply with +45v and -45v.

Toast

[amelbye]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

I measured the ripple with a scope.

I've attached a picture of the readout.

It is not on the +50 or -50 lines though. This amp also has +12, -12 and +5, and this was measured at the positive side of the coil in the speaker protection relay (schematic page 2, part RL601).

As a start, I had a look at the board called DC Power supply (schematic page 3), and replaced a bunch of 10uF Sanyo caps that had an ESR of about 3-6. Put in new parts measuring about 1.5. All the major capacitors seem fine, at least when I measure their ESR in-circuit.

The result is... no sound. I must have broken something on the way. I'll post back with more information when I've made some more measurements.

[Toasty]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

Output of pins 12 & 14 from Q929 µPA81C drives both RL601/2.

http://www.alldatasheet.com/datashee...EC/UPA81C.html

JL761 just below and to the right of the relays are C775 & 776 --> 2 - 6800uF @ 50v caps.

I hate scanned schematics that are at a poor resolution.

Toast

[Toasty]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

EDITED above.

[amelbye]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

Thanks for your input.

You're right, Q929 controls the relays.

C775 & 776 are smoothing caps for +/- 33V, which as far as I can see is only used for driving the rear power amplifier. I've measured their ESR, and they look fine

Q929 is on the PSU board, and it seems that my fiddling with that board has either broken that chip, or at least caused it to stop opening the relays for whatever reason. And not only that. I no longer have signal on the main power transistors.

I do however have signal at the board called "auto input balance". That's as far as I've got

[amelbye]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

I measured the DC voltages on Q929.

pin 1-6: 0V
pin 7: 4.4V
pin 8: 0V

The other side of the chip is unaccessible unless I take the board out, which will also mean powering off.

This makes sense though. DC input on pin 7 means DC output on pin 10, which will switch the relay on the power board.

pin1 and 16 is the rear relay
pin3 and 14 is the center relay
pin5 and 12 is the front relay

these pins connect to the front display panel through p007

p007 connects on in the upper right corner of schamatic part 4. In this schematic the front relay control line is labeled "PROTRL", center "CENRL", rear "REARL". This goes into a large chip with 80 pins.

http://www.alldatasheet.com/datashee...4074719FS.html

How do we determine why this thing has decided not to turn on the speaker relays?

[b700029]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

That's a microcontroller, and if it's defective there's no easy way to replace it.

However you may want to check how the protection circuit works, and make sure its inputs to the microcontroller are OK.

[Toasty]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

I'd like you to go back over what you've done and see what has caused the change in function or loss thereof.

I keep pointing at these various large uF caps because they would be supplying any other subsystems with power. You should be checking the power across them -all- for ripple. Because the ESR -looks- good, does not necessarily mean they are working correctly. They could have easily lost capacitance and are not providing the filtering necessary. This unit does not use a switching power supply, rather a linear. The ripple you are seeing is 60 cycle, and is correct for a bridge or 1/2 wave rectifier.

What is wrong, as you noted, is the amplitude. 99-44/100% of the time, it's a bad main filter cap or two. That must be coming from the main power supplies connected to the transformers, not any subsequent ones.

So, start at the main supplies and their high uF value caps, and check for ripple.

Once you get that cleaned up, the microprocessor and subsequent circuits may come back to life and act properly.

Toast

[Scenic]

Re: Onkyo reciever, exessive ripple on +12V? how much is acceptable?

Don't know if it helps, but this might apply to this model as well.
http://www.youtube.com/watch?v=q_ypk0sbt5I
http://www.youtube.com/watch?v=mwWTSq-5IH0