Onkyo TX-NR5007 Protect Mode Repair

[jbkiansiang]

Hi I am having problems with an Onkyo TX-NR5007 going into protect mode.  I have experience fixing a few other receivers but I am struggling to narrow down areas to check. The service manual can be found here:
https://elektrotanya.com/onkyo_tx-nr5007bs.pdf/download.html

Things checked/tested so far:
1. All output transistors seems ok.
2. Fuses are all intact.
3. All 3 Bridge diodes on PC boards seem ok.

Testing observations:
1. If i remove all the vertical amplifier pc boards from BAAMP-0191, does not trigger protect mode.
2. By connecting JL6041B wires individually, the signal triggering protect mode is coming from VPRO line. IPRO does not trigger.

Any help to filter down which areas to check or possible causes is greatly appreciated.

[mzacharias]

The most likely problems involve amplifier channels and power supply issues. Onkyo has once again shown their true colors by obfuscating the part numbers of the output transistors.

Although they are drawn as bipolar in the schematic - they could well actually be Darlington's - it wouldn't be the first time. This can be determined later. Who knows if they even sell parts for these to individuals. If they used normal part numbers (and they are almost certainly ordinary transistors re-labelled) this would not be a problem.

To start with, you should be able to measure DC offset at any of the individual amp channels, measuring from the bias test points to chassis ground. If only one channel has a DC offset, obviously that channel needs repair. If all channels have an offset - it points to a power supply issue - probably a regulator or some bias voltage source.

[jbkiansiang]

Hello mzacharias, thanks for the response.
For measuring DC offset, there are two bias pins for each channel, so while powering on I just need to probe either one of the bias pins and measure to chassis right? (sorry because this is the first time I'm measuring DC offset, hence not sure about the method yet)
FYI, seems the transistors are Toshiba bipolars TTA0002(q) and TTC0002(q).

[mzacharias]

Hello mzacharias, thanks for the response.
For measuring DC offset, there are two bias pins for each channel, so while powering on I just need to probe either one of the bias pins and measure to chassis right? (sorry because this is the first time I'm measuring DC offset, hence not sure about the method yet)
FYI, seems the transistors are Toshiba bipolars TTA0002(q) and TTC0002(q).

Yes just measure DC from either bias test point pin to chassis ground.

What I meant about the transistors - these appear to be "house" numbers or custom parts. I would bet they are actually 2S types, but replacements are now at Onkyo's discretion. They will be more expensive - or even not available. I would try to determine what they really are so that I could substitute if I needed to at some point. As a technician  I resent that Onkyo has put this unnecessary obstacle to service in my way.

So far as I know " TTA0002(q) and TTC0002(q)" are not legitimate part numbers.

[jbkiansiang]

I measured the dc offset and i am getting -38.5V on all channels after switching on and drops off slowly after that. The VPRO voltage is also -38.5V. Not really sure how to interpret this result. Where should I check next?

[Chris56000]

Hi!

If your transistors are of the multi–pin type as seems to be suggested by the maker's circuit–diagrams, then the Sanken SAP15P/SAP15N are the most likely substitute for the house–coded devices!

These are 150W Complementary Darlington devices with current sense and thermal–compensation pins, and datasheets are readily available!

The transistors can still be got but watch for ultra–cheap fakes!

Have you looked at them carefully? – sometimes a fibreglass pen, etc., can be used to reveal the original correct type number underneath the OEM's one!

This example is a classic case of why it's so much easier to work from the Factory Published PDF rather than a scan or photocopy, and my thanks to the OP for the link to it!

Chris Williams

[mzacharias]

I measured the dc offset and i am getting -38.5V on all channels after switching on and drops off slowly after that. The VPRO voltage is also -38.5V. Not really sure how to interpret this result. Where should I check next?

Check every power supply source you can find. + and - 12 or 15 volts, 5V, -5V, anything. Pay particular attention to any 3 or 4 legged TO-220 packages.

[jbkiansiang]

I checked the rail voltages, there were some differences but not sure whether its okay or not. Specified voltage is in brackets.
JL8002B = 14.6V (12V)
JL901A   = 14.6V (12V)
JL9501B = 14.8V (9V)
JL9501B = 5.84V (5.9V)

It felt weird that the 9V was way off.  But when I checked output voltage regulators downstream for +5VDG, +3.3VDG, +1.8VDG, +5/3.3VMPU, +5/3.3VST, +5VST2, were all spot on.   So I guess regulators were still able to handle the higher voltage, or the 9V written on the schematic is wrong.
Also discovered 12/13V connector points turning into 15V on the other end, which is also clearly a mistake.

Discovered I was not getting 12V for the fan rail from D9410, which in turn is also not providing power for all relays on BAPS-0182. I thought it might be bridge rectifier fault, but in circuit tests ok.  But I did discover R9410 was 26ohms instead of 0.22, going to replace this but not sure if it will solve the 12V problem.  Since the number of parts around that area is limited, should be able to get it sorted out with time.

For dc offset voltage, I had another go after making sure everything was grounded properly in including the chassis, and it is 26mV,  and this is not causing the amp to shutoff anymore(yay!).

Also accidentally discovered the op amp board, some were very hot only after 2-3 seconds powered on.  My guess was shorted op amps and q1205, q1209 was shorted on pin2&6.  q1206 shorted on pin8&2. Going to remove q1205 and hope it really is a bunch of op amps gone wrong causing problems. 
 

[mzacharias]

Yeah - op-amps don't get got, especially not quickly. Sounds like you're on the right track.