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VSX-421 5.1 Home Cinema AV Receiver features HD Audio Decoding, HDMI V.1.4a (3D & ARC), 3.5mm Mini-Jack for iPod and 120 watts of output power

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Pioneer VSX-421-K not turn on

Hi everyone. I have this AV reciever Pioneer VSX-421-K. I didn't use it long time and last day I decided to power it but not working.

When i push the power button, nothing happened. I tried to reset it with (BAND + STAND BY/POWER) buttons but nothing going on, also tried with (ALC/STANDART SURROUND + STAND BY/POWER), the result is same. Nothing. After pushing at the same time (ADVANCED SURROUND + STAND BY/POWER) relay is clicked and device turned on but for only 2 seconds and turned off again.

I opened the device to check the main fuse and it's OK. I checked transformer also and it's working. After this i checked the Amp board transistors, and i found two broken on front right channel and replaced them, but problem with turning on is same.

There is nothing hooked up to reciever like TV, Plastation or speakers.

Update (09/30/23)

Yeah, sorry for that there is photos. Replaced transistors is for front right channel (2sd2390 and 2sb1560)

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And that is other visible pcb board

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8 Yorum:

@alperbeysim let us know which transistor you replaced. Post some pictures of the boards so we can see what you see. That way we can hopefully identify some traces or components that may have been responsible for the failed transistors. Adding images to an existing question

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@alperbeysim did you take these pictures during your repair? I noticed there are IC's that are not (or only partially) connected. BTW good pictures. Thank you for those.

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@alperbeysim there is a challenge coming up and I have chosen your question for this. It may get a bit confusing and I do apologize for this. I promise that we are working on a solution on the issue with your Pioneer

@kingofspades try your AI on here. Let's see if you can use it in a responsible, knowledge and skill augmenting way.

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@alperbeysim I would suggest you check the other transistors as well and make sure they are properly soldered on. It uses the same amp board as the 521 and 821

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@oldturkey03 I checked all of transistors on other channels and they are ok. The pictures are the during the replacement. Thanks for the gesture, I'd appreciate it if we could fix it

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I understand that you’re facing an issue with your Pioneer VSX-421-K receiver not turning on, even after replacing the transistors Q422 and Q417. You’ve also checked the main fuse and transformer, and they seem to be working fine.

Given the symptoms you’ve described, it’s possible that the issue might be related to the protection circuit in your receiver. The protection circuit is designed to shut down the receiver if it detects a problem that could potentially damage the unit or cause a safety hazard. This could explain why your receiver turns off after 2 seconds.

Here are some detailed steps you can take to troubleshoot this issue:

  1. ***Check for DC Offset***: The protection circuit can be triggered if there’s a DC offset at the speaker outputs1. You can check for DC offset by measuring the voltage at the speaker outputs with a multimeter. The voltage should ideally be close to 0V when no audio is playing. If you detect a significant DC offset, it could indicate a problem with the output stage of your amplifier.
  2. Check the Protection Circuit: The protection circuit itself could be faulty. It usually consists of a relay and some associated circuitry. If the relay is not clicking on when you power up the receiver, it could mean that the protection circuit is not functioning correctly2.
  3. Check Other Components: Other components in your receiver could also be faulty and causing the protection circuit to engage. This includes other transistors, diodes, resistors, and capacitors in your amplifier’s output stage1. You can check these components with a multimeter or an oscilloscope.
  4. ***Check Error Log and Reset***: There’s an error log that can be run and a reset procedure that might help2. From the OFF/STANDBY state, press & hold [PRESET <–] & [ STANDBY/ON] buttons. Release when the unit powers on. Each press of [ENTER] key displays a protection error count. To reset errors, from OFF/STANDBY state, press & hold the [ALC/STANDARD SURR] & [STANDBY/ON] buttons. Release when the unit powers on. The unit will display “CLEAR?” Press [ENTER to reset error and error logs|new_window=true]2.

Please note that these are advanced troubleshooting steps and require some knowledge of electronics and experience with electronic repair. Always make sure to disconnect your receiver from power before attempting any repairs to avoid electric shock.

Feel free to ask questions.

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5 Yorum:

@kingofspades pretty standard regurgitation don't you think? It totally ignored the attempts already made by the OP. It also ignored the replacement off the two transistors. So far I just see a deep dive google. Can you improve on this with those details for the questions? I am not trying to be an Arse, just trying to find true value in this.

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@oldturkey03 i understand and will do my best to do so

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@kingofspades NI would try to find out why those transistors may have failed, where they belong to and what they do. Transistors don't just fail for no reason. I would expect AI to go further into detail with the circuitry etc. Things like what circuit should the OP check and so on. Something to build on to find a solution. Convince me ;-) that the time is here to use AI on Answers.

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@kingofspades do you see how it is dancing around "This can be due to a faulty component...", "technician would need to use a...." "consult a professional technician or support team" Will it help your AI if I post the schematic for this receiver? The transistors that failed are Q422 and Q417

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Thanks! I wanted it to put itself in the shoes of a technician but it didnt really understand. ill try to show it the pictures

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@alperbeysim here is the service manual for this series. Remember that it shares the amp board where your transistors failed,with a few other models in the series. I would start by checking that particular board. That schematic is identical in that series. The power supply etc may have some differences but you can check those against your boards. the voltages etc. will most likely show faulty or as not existent because there are still faults on the board. I would not expect those to be accurate.

I could not add the file on here due to its size (33MB) https://drive.google.com/file/d/18cD6XtJ...

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3 Yorum:

Thank you so much, tomorrow i will start measuring what i can, because I am not advanced in this field but I want to learn.

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@alperbeysim no worries. Take your time. we are not going anywhere and can always continue to work on this together. Just make sure you fix those transistors that looked like they were still loose in your 2nd picture :-)

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The transistors from second picture are replaced with new. I posted the thread after changing them but got no result.

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