Pioneer VSX-520-K Protection problem

[DjKrish]

I'm sure many had this issues with other models but now im having it sadly. The problem im having is DC 001. I suspected the amp block, i unplugged the amp block from the main board and speaker board. Turned it on on safe mode, still shows the same DC 001. So i suspected other boards, i removed the HDMI board, optical board, AV board, video board. Turned it on, still same DC 001. Tried resetting it, clear it, turned it on, shows same DC 001 and turns off after few seconds. Then i have to reset it again to be able to turn it on again. I suspect the main board. Checked all transistors, reading all good. Could it be the transformer? Could be somewhere else on the main board? Need some help here from Gurus. Anywhere shall i seek to troubleshoot or to measure voltages? Please check attachment pictures.

[Longbow]

Re: Pioneer VSX-520-K Protection problem

Unplugging various modules is not a valid test for anything except maybe a dead short that is blowing fuses. Snap it back together again and take some readings on your power output stages.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Unplugged the amp circuit, tested all the output transistors on the rail, all measured good with no fault, no resistors open either. No DC spotted on the speaker outputs either, probably cause the relay haven't click yet for the speakers to activate. This amp actually was left on standby when i went outstation. When i got back, i noticed it cant be turned on anymore. Nothing burned, all fuses are perfect, all caps seems to be in good condition. Im sorry im not a pro or a technical engineer. Just a normal DIY person with some basics. Hope you can guide me further on where to check and how. Deeply appreciate it. How do i measure the dc output from the transformer to know its fine? Pls see the picture. As per the video below, you can see this guy unplugged the amp cable from the main board and turned it in, it was perfectly fine and no DC error msg, so that confirms the amp block was faulty which is in case i tried the same, i still get the dc error msg. So in here i confirm, my amp block is perfectly fine. See the video from 5:40minutes.

https://www.youtube.com/watch?v=5H5gCZ_2VFA

[budm]

Re: Pioneer VSX-520-K Protection problem

Since the Relay is in the shutdown mode which may be due to the DC offset of the power amplifier, you need to check the DC on the relay pole that is connected to the output of the amplifier not at the output pole that is connected to the speaker terminal.

[budm]

Re: Pioneer VSX-520-K Protection problem

Service manual:

[rievax_60]

Re: Pioneer VSX-520-K Protection problem

I don't get to work on many amplifiers. I have noticed a trend in recent models where they go into a lock down state after certain faults such as DC protect have occurred a number of times. A key combination press needs to be done to make it turn on again.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

I don't get to work on many amplifiers. I have noticed a trend in recent models where they go into a lock down state after certain faults such as DC protect have occurred a number of times. A key combination press needs to be done to make it turn on again.

Already tried that, reset, cleared codes, still switches off.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Since the Relay is in the shutdown mode which may be due to the DC offset of the power amplifier, you need to check the DC on the relay pole that is connected to the output of the amplifier not at the output pole that is connected to the speaker terminal.

12v to the relay legs of speakers from the main board are perfect. However, i noticed there's at least about 60vdc on the second leg of the speaker relays I believe thats the ground. 60vdc on the ground? Now thats weird.

[stj]

Re: Pioneer VSX-520-K Protection problem

60v sounds more like a primary rail, are you sure your not mixing up the pins?

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

This is what i meant, its actually a speaker assy. Those 2 resistors i measure using a MM and showed near 60vdc before the power relay cuts off. See picture

[budm]

Re: Pioneer VSX-520-K Protection problem

You have 12Vdc for the relay coil, the relay contacts (poles) should not have any DC on them at all (the most will be in mV range), the DC PROTECTION trip point is usually around 1~2VDC range, it does not take much to damage speaker, when the circuit detects that Voltage on the output of the power amp, it will not allow the speaker relay to come on. See the service manual. Did you download the service manual so you can see where to test the Voltages?
So you do have problem with the power amp section.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

You have 12Vdc for the relay coil, the relay contacts (poles) should not have any DC on them at all (the most will be in mV range), the DC PROTECTION trip point is usually around 1~2VDC range, it does not take much to damage speaker, when the circuit detects that Voltage on the output of the power amp, it will not allow the speaker relay to come on. See the service manual. Did you download the service manual so you can see where to test the Voltages?
So you do have problem with the power amp section.

Ok will use the test points to troubleshoot the power problem first as stated in SM. Just a quick question. If its a power amp section failure, if i unplug the power amp connectors to the main board and speaker assy and turn it on under safe mode, it should boot OK right assuming power amp section failure? But still it shows DC error msg.

[budm]

Re: Pioneer VSX-520-K Protection problem

I did not look at the diagram in details on how the error signal from the power amp section is routed to the main board, so I cannot tell you what will happen if you remove the power amp sections.
When I work on the amplifier and see that I have large DC offset, then I will work in that section to find out why since you already know that there are DC offset at the output.

[stj]

Re: Pioneer VSX-520-K Protection problem

if it's a shorted output stage, you may need to remove power to that section.
doing that may create a different fault code.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

I did not look at the diagram in details on how the error signal from the power amp section is routed to the main board, so I cannot tell you what will happen if you remove the power amp sections.
When I work on the amplifier and see that I have large DC offset, then I will work in that section to find out why since you already know that there are DC offset at the output.

Here is the SM for your viewing pleasure

[budm]

Re: Pioneer VSX-520-K Protection problem

I gave you that link already in my post 5.

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Ok I will post more updates after i check the test points and go more in depth on the output block on the amp section

[DjKrish]

Re: Pioneer VSX-520-K Protection problem

Update : Fully checked the amp block, in and out. All 100% green light. Perfectly fine. No shorts. The short was from the main board. Below the board on the tracks, there was 2 tracks that's filled with corrosion. Manage to clean it out all fully, and installed everything, walla no more dc at output and 12v present for the speaker relay. Its clean

Now, IC101 pin 20 on the main board must have at least 3.3v at standby and 0.5v upon turning on as its the protection circuit. But my MM detects 2.5v at standby. I suspected something at the PT assy. I pulled out the PT assy and checked again pin 20, now its reading 3.3v accurately at standby mode. I will be checking all the transistors on PT assy.

Anywhere else should i be looking at? Now its fully pointing at main pcb as the last resort as everything else seems to be clean and in good order. I suspect this protection circuit happened due to the corrosion below the main board. Luckily the protection circuit saved everything.

[budm]

Re: Pioneer VSX-520-K Protection problem

Also make sure all the board mounting screws are tightened because that is how the boards are grounded to the chassis ground and for grounding connection between boards.

[tibimakai]

Re: Pioneer VSX-520-K Protection problem

Maybe a reset at this point, it wouldn't hurt either.