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]

I can confirm for now that when the board is connected, as well as the power ON, the IC goes up to 98F and the bead to +/- 88F, whereas everywhere else, it's less than 75F.

seems to be ok based on the IC datasheet:

 

[wilder1626]

OK, then. I continue my investigation. I may have put my finger on a potential problem. Please let me know what you think.

When I disconnected the cable between CN112 and CP2200, by pressing the Power button, it turned on without any problem. So I suspected the problem before CN112 . So, without removing the MAIN ASSY board from the chasis, I used my multimeter to see if I was getting the 12v on pins 1, 2, 3 of CN112, and that's not the case. So I think the problem is prior.

This brings me to this part of the diagram:

I now suspect that numbers 2, 3 and 4 in the picture above could be the source of the problem.

I would then have the remove the board to test it as i cannot do it from above.

 

[Nigel Goodwin]

I don't see how just randomly guessing at components is going to help?. But of those three numbers, 2 & 3 certainly wouldn't ever go faulty, nor would they cause any problems if they did. Number 4 'could' potentially fail, electrolytic capacitors are prime failures - easily checked as long as you can get to the top of connector CN112, just push the wires of a suitable through-hole electrolytic into the connections on the top, see if that cures the problem. Doesn't need to be 10,000uF, anything in the range 1000uF to 10,000uF should be fine.

 

[wilder1626]

I've already tried several times, and I confirmed that the CN112 wires are correctly inserted.

May I ask why you're talking about "randomly guessing at components"?

I'm just trying to follow what I think is a logical path to try to find the origin of the problem, because it's not obvious.

I notice that I'm not getting any voltage from my CP113 from the transformer when it's on standby (not powered up). This doesn't seem normal to me. Should I normally be getting some voltages? Normally +12v.

 

[Nigel Goodwin]

I've already tried several times, and I confirmed that the CN112 wires are correctly inserted.

???? - I mentioned no such thing, read my post again.

May I ask why you're talking about "randomly guessing at components"?

R285, C293 - random components - neither of which would ever fail, nor cause your problem if they did.

I'm just trying to follow what I think is a logical path to try to find the origin of the problem, because it's not obvious.

I notice that I'm not getting any voltage from my CP113 from the transformer when it's on standby (not powered up). This doesn't seem normal to me. Should I normally be getting some voltages? Normally +12v.

My first thought would be no, if it's in standby then the mains supply voltages will be turned OFF, probably by a relay. You usually have two transformers, a small standby one, and a large one for actual power.

 

[wilder1626]

???? - I mentioned no such thing, read my post again.

First of all, my sincere apologies. I did misread what you said.

I will start by checking the no 4 (electrolytic capacitor).

 

[Nigel Goodwin]

First of all, my sincere apologies. I did misread what you said.

I will start by checking the no 4 (electrolytic capacitor).

I described the easiest way

 

[rjenkinsgb]

I can confirm for now that when the board is connected, as well as the power ON, the IC goes up to 98F and the bead to +/- 88F, whereas everywhere else, it's less than 75F.

If those ferrite beads near the HDMI port are heating up at all, it sounds like a short (or partial short) in the HDMI connector or the C2261 / C2263 caps at the connector side of the beads?

 

[wilder1626]

If those ferrite beads near the HDMI port are heating up at all, it sounds like a short (or partial short) in the HDMI connector or the C2261 / C2263 caps at the connector side of the beads?

Thanks for your advice. I'll check it out closely next weekend.

 

[wilder1626]

Sorry for the huge delay, I felt like I was going in circles. I've decided to take another, perhaps better, approach, by looking directly at the HDMY board.

rjenkinsgb > those ferrite beads near the HDMI port are mot heating up.

Right next to my EP9442 IC, I have 2 capacitors and 4 resistors. I used a temperature gauge and found that it goes up to 131 F, whereas elsewhere it's around 110 F or lower. From what I can see, it's also directly linked to the IC2012 EP9442. To me, i don't think is good. Could this be a potential problem? IC or capacitors?

What are your thoughts?

 

[wilder1626]

It's difficult without a thermal camera, but right beside it, the Voltage Regulators (IC400) NJM2387ADL3 rises to 138 F. Really hot. But the data sheet says the maximum can go up to 185 degrees Fahrenheit.

It's a real challenge when the temperature all around goes from 95 F to 110 F. Is that an issue or not!

 

[wilder1626]

So it seems that my pin 1 (IN) is at 9v5 when it should be at 5v. My pin 3 (OUT) has a voltage of 3v1, which seems correct. So I think it's the voltage regulator that's at fault. This is probably why the temperature is rising to 136F.

 

[rjenkinsgb]

If a "5V" rail is at 9V, whatever is producing that supply is at fault! The 5V to 3V reg is just hot due to the excess voltage drop, 6V rather than 2V.

 

[wilder1626]

OK, so I'll follow up on that 5v rail which seems to come from the IC BD9328 pin 3. I'll come back with what I found on that trail to start with.

I'm also going to make sure that the 12V is arriving on VIN pin 2. If I've got my 12V coming in, but I've got 9.5V coming out of pin 3, my IC would be the prime suspect.

Thanks again for your help rjenkinsgb
.

 

[wilder1626]

wow, my VIN pin 2 gives 9v7 while my PIN 3 gives 9v5. So I find myself at CP2200 where PIN 1, 2, 3 should have 12V, but I have 9v7. Same thing at CP2200 on PIN 1, 2, 3 at 9v7.

I'll continue to follow the rail from CP2200.

 

[wilder1626]

Since I'm not getting the required 12v at CN112, logic would suggest that the problem lies between CN112 and CP113 4v8 AC from the Trans.

So between the two areas, 2 resistors R284 and R286 where I get 4.7v, I see an untested 50v 8.0A bridge rectifier D72 (D121), then 2 other capacitors C292 and C293 and a resistor R285.

So I think the problem lies between the rectifier bridge / C292 / C293 / R285. Does this make sense?

To test it, I'd have to disassemble a part of the amp, that's for sure. At first glance, I can't see any visual damage.

 

[wilder1626]

I decided to confirm the 4.7v coming from the Trans, is it good or not.
If I look at the schematic correctly, I should have 12v, not 4.7.
So, is it the Trans that's the problem? I'm now questioning it.

 

[wilder1626]

On the STBY ASSY besides the relay, there's a Zener diode Zj7.5B. I decided to test it on the circuit, although it's better to test it outside it, but with a multimeter in Diode mode, reversed or not on the anode and catode, I get the same value 46.7 olms. This doesn't look good. But it does not look burned also. Might as well test it outside the circuit to be sure.

It's really not easy when there's no visible damage on the circuit to find the problem. But I like it and it makes me learn.

 

[wilder1626]

The diode zener is at 0.791v on the multimeter in Diode mode. If i reverse the probes, i get "OL".
Am I reading this correctly if I say that if I get 0.791v, I should have been between 7.07 and 7.45 outside the circuit?

 

[rjenkinsgb]

If the voltage on a "5V" feed is way too high - eg. the 9V you said earlier on - it's likely to be drawing far too much current and pulling down the source supply!
It's amazing the whole thing is not cooked by overvoltage!

The first and most critical thing is to get the 5V supply correct.


The zener sounds OK, you would need a higher voltage supply plus a current limiting resistor to be able to read the zener voltage.

Around 0.7V and open circuit is correct with a multimeter, that uses low voltage.