Pioneer AV Receiver VSX-324 Power button issue

[wilder1626]

Hi all.

I have a Pioneer VSX-324 AV receiver whose only problem is the power button.
Schematic of the receiver: https://www.manualslib.com/manual/1027739/Pioneer-Htp-072.html?page=1#manual)

The problem I'm having is that when I use the remote to turn on the receiver, I just hear a click, but it doesn't turn on.

The only way to turn it on is to hold down the button for 2-3 seconds and it turns on without any further problem.

Holding the buttons down, I hear the clicks every fraction of a second, about 3-5 clicks. Then it turns on.

This problem started one day when I wanted to activate the receiver and TV using the remote control.

As far as I know, I've never had a power cut or power surge, nor a cable change. I have no other problems, such as sound quality or anything else.

I'm thinking that the problem may come from the button connection himself or maybe in that part of the circuit.

Do you have any ideas on how I should start looking for this problem?
Any help would be greatly appreciated.

Thank you very much.

 

[wilder1626]

7.8V on the -30V line ??

Sorry, i meant -7.8V. This should be good since it should be lower than 1V.
This is what I get when it's plugged in, but not switched on. If I press the Power ON button, and after the 3 clicks, it goes to -30.76V.

 

[Tony Stewart]

next step?

 

[wilder1626]

next step?
View attachment 144283

Ok. I actually tested it this morning. I got 3.286V.

 

[wilder1626]

While i was there, I started testing for shorts on the transistor attached to the heatsink.
This also seems OK, no shorts.

 

[Tony Stewart]

poke around with fingers for loose connections to make work on CPU interface

 

[wilder1626]

Okay, I'll give it a try and let you know. Thanks again for your time and help.

 

[wilder1626]

Still no luck with loose connections. It's obviously an intermittent problem on a component somewhere.

One day, I suppose, it will just stop once and for all to power up, thus identifying the source of the problem more easily..

 

[wilder1626]

Well well well. What did I just find?
If I disconnect the CP2200 cable from the D-Main ASSY card, I can use my remote control normally without any problem.

The problem may therefore lie with this card. The cable looks OK after testing it.

Now I need to find the real problem. I think it might be one of the jacks, because I think that for one of them, I had a problem with the sounds while the picture was correct. But not sure yet if this would be the cause.

 

[wilder1626]

I don't get 12V on pins 1, 2 and 3. On the resistor, I get 12V with the tester. So now I'm wondering if it's the C292 capacitor that could be faulty in some way.

But i still also think that one of the HDMI jacks could be the cause also, and who knows if the IC chip EP9442 could also be impacted.

What do you think?

 

[wilder1626]

I've just removed the card, and under the microscope I can see corrosion on CP2200. I'm not sure at the moment whether this could be the cause of the problem. I'm going to clean it.

 

[wilder1626]

Testing the EP9442 integrated circuit for a potential short-circuit, I have this capacitors which have a resistance (0.4ohlm) on the multimeter in continuity mode, i.e. beeping.

Do you think it could be a problem like a short-circuit and that the IC could be damaged? Or another short circuit in the external circuit connecting the IC and capacitor to ground? Or perhaps the capacitor is defective (less likely)?

 

[rjenkinsgb]

Those look to be labelled "CBxxxx" rather than just C.

Possibly they are actually ferrite beads, which would read as a short circuit? Odd labelling, but it is different to the rest of the ceramic or electrolytic caps.

 

[wilder1626]

Those look to be labelled "CBxxxx" rather than just C.

Possibly they are actually ferrite beads, which would read as a short circuit? Odd labelling, but it is different to the rest of the ceramic or electrolytic caps.

Thanks.

So CB could be a prefix for "Component Bead". That's interesting. If that's what it is, and if it should never be shorted to ground, I can now figure out a few more things.

Please tell me if this makes sense in my statement.

According to the diagram, that CB is connected to the IC chip EP9442 pin 78 "PVSS" used for grounding or voltage reference. In the event of a short circuit on the CB, this could potentially damage the IC, especially if it's not protected against overvoltage or overcurrent.

*** Pin 78 is currently connected to ground after testing it with the multimeter.

I could then understand why even the 4 HDMI ports on my TV no longer work as well. A short circuit on the HDMI circuit could have lead to an overvoltage or overcurrent in the HDMI cable, which could have damaged the electronics of the TV connected to the other end of the cable. I also suspect that the TV's integrated circuit chip will have to be changed as well, since none of the ports are working.

Such a small component could have done all that damage in the end.

 

[rjenkinsgb]

CB2021 & 2022 are shown as inductors, so fit with being ferrite beads. 2022 is a direct link to VSS (0V), and 2021 is in VDD.

Those and the two caps are interference filters in the power connections, to reduce radiated noise, by the look of it.

 

[wilder1626]

CB2021 & 2022 are shown as inductors, so fit with being ferrite beads. 2022 is a direct link to VSS (0V), and 2021 is in VDD.

Those and the two caps are interference filters in the power connections, to reduce radiated noise, by the look of it.

If I'm not mistaken, this means I should start by removing the shorted beads, putting new ones in place and seeing if I'm still shorted afterwards. Then I may have to change the IC, so I need to be prepared for that.

Is this the case?

One thing's for sure, I'm learning a lot at the moment, so thanks to all those who are helping me.

 

[Nigel Goodwin]

If I'm not mistaken, this means I should start by removing the shorted beads, putting new ones in place and seeing if I'm still shorted afterwards. Then I may have to change the IC, so I need to be prepared for that.

Is this the case?

No - the beads are just a piece of wire (a short circuit) with a ferrite bead slid over it to give a tiny bit of inductance.

They don't go wrong, there's nothing to go wrong, and you've checked them as perfectly OK (0.4 ohms) - the short is supposed to be there, it's what they are.

Changing the IC would make no difference whatsoever, other than it may never work at all

 

[wilder1626]

No - the beads are just a piece of wire (a short circuit) with a ferrite bead slid over it to give a tiny bit of inductance.

They don't go wrong, there's nothing to go wrong, and you've checked them as perfectly OK (0.4 ohms) - the short is supposed to be there, it's what they are.

Changing the IC would make no difference whatsoever, other than it may never work at all

Thanks for your feedback, but now I'm more than confused.

 

[wilder1626]

I'm going to put the HDMI board back in place and see if I can find anything heating up that might indicate a problem. Will get back with the result.

 

[Nigel Goodwin]

I'm going to put the HDMI board back in place and see if I can find anything heating up that might indicate a problem. Will get back with the result.

I wouldn't have thought your problem is going to be caused by something overheating anyway, if it's thermal at all it's faulty when it's cold.

 

[wilder1626]

I wouldn't have thought your problem is going to be caused by something overheating anyway, if it's thermal at all it's faulty when it's cold.

So, if I understand correctly, I'll have to keep looking.
This would also mean that the card may not be the problem, although the problem disappears when I unplug the power supply from this board.