• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

YAMAHA PC4002 bias current(voltage)?

O

ooops420

New Member
Hello

I am writing from Japan.
Please excuse my poor English.

I am doing maintenance on YAMAH PC4002. 　
Please let me know the bias current value of PC4002.
The outlet voltage in Japan is 100V.
When I measured it before adjustment, it was about 2.5mV.

Connect the tester to the test point,
Rch rotates VR202. (Upper VR)
Lch rotates VR201. (Upper VR)
How many volts should I adjust to? (DC voltage mode)

When adjusting the above
Is it okay to set VR201 for Rch and VR202 for Lch, which are lower VRs, to the maximum value?
You don't use the lower test point in normal vise adjustment, do you?

I would appreciate it if someone could help me.
Thank you
 
Register to hide this ad
I could not find the service manual, suggest wait for someone who has worked on the unit,
 
ooops420 said:
Hello

I am writing from Japan.
Please excuse my poor English.

I am doing maintenance on YAMAH PC4002. 　
Please let me know the bias current value of PC4002.
The outlet voltage in Japan is 100V.
When I measured it before adjustment, it was about 2.5mV.

Connect the tester to the test point,
Rch rotates VR202. (Upper VR)
Lch rotates VR201. (Upper VR)
How many volts should I adjust to? (DC voltage mode)

When adjusting the above
Is it okay to set VR201 for Rch and VR202 for Lch, which are lower VRs, to the maximum value?
You don't use the lower test point in normal vise adjustment, do you?

I would appreciate it if someone could help me.
Thank you
Click to expand...
Welcome to the forum.

Edited - The previous text was for PC2002 which did not correspond to PC4002, it was deleted to remove any confusion. Please see below for info on PC4002.

Added: Just downloaded the SM from the link provided, if you haven’t so far, please look at the following for PC4002M
88A38C5B-9AEC-4EE9-A745-9C37644A865C.jpeg
 
Last edited:
  • Like
Reactions: mbz
Thank you ETLS
I was able to get the schematic.
This is of great help to me.

Thanks you Sparkplug
Exactly the information I wanted.
This is the service manual for PC4002/4002M.
can i get all of the service manuals?
Thanks to everyone's help, we'll be able to hear the sound of PC4002 in the new year.
thank you everyone
 
accidentally shorted the + and - of the test point while adjusting the idling current.
There were sparks around the power supply on the back of the unit, but there was sound.
Is it possible it's broken somewhere?
 
Check the output transistors for a short between collector and emitter.
If you still get normal audio on both channels then all good, it's a high power amp so a few amps doesn't hurt it.
 
thank you mbz
I appreciate your advice.
After checking, connect to the speaker and check the sound.

Thank you
 
Last edited:
ooops420 said:
accidentally shorted the + and - of the test point while adjusting the idling current.
There were sparks around the power supply on the back of the unit, but there was sound.
Is it possible it's broken somewhere?
Click to expand...
LOL, that happened to me once and I almost had a heart attack. Had to check every voltage on the schematic to make sure all was okay. As it was pointed out, you can check the output Xistors but you’re most probably fine.

For the full manual, the link @ETLS kindly provided works if you perform a search for ‘PC4002’ (I always avoided Electrotanya because they made me jump through hoops but not this time). It’s a .rar file:
https://elektrotanya.com/yamaha_pc4002_pc4002m.rar/download.html

At the bottom of the page confirm that you’re not a robot (you’re not, right?;)) and click on ‘Go to download page’.
 
Last edited:
wow
Great, perfect!
Thank you
Did the same thing happen to you?
was your amp okay?
I feel the need to replace the testpoint connector.

I just hope the parts aren't broken.

Thank you Sparkplug
 
ooops420 said:
I feel the need to replace the testpoint connector.

I just hope the parts aren't broken.
Click to expand...

After adjustments, power up and play some music, if all sound okay, no need to change anything. Please do check all the solder joints, using magnifying glass if needed. They’re your worst enemy. Good luck.
 
Now I connected to Magnepan MMG and played music.
The music seems to play just fine.
I would like to see how this goes for a while.

I also want to respect the original, but I'm interested in replacing the NE5532P, which is right after the input, with a higher quality op amp. (For example, OPA2604, etc.)

What do you think?

Thank you
 
ooops420 said:
Now I connected to Magnepan MMG and played music.
The music seems to play just fine.
I would like to see how this goes for a while.

I also want to respect the original, but I'm interested in replacing the NE5532P, which is right after the input, with a higher quality op amp. (For example, OPA2604, etc.)

What do you think?

Thank you
Click to expand...

If you really want to see how the sound changes you can give it a try. First though, make sure supply voltages are compatible (I think they are) from the schematic or direct measurement (+Vcc and -Vcc). Gains are also about the same so there should not be a problem. Be very careful.
 

Attachments

ooops420 said:
Okay, I think I'll give it a try.
Thank you for giving me various advices.

Tanks Sparkplug
Click to expand...
No problem.

According to the schematic, supply voltages are ±15V, so you’re okay, :thumbsup:.
87CDB99F-5EE2-4238-A59A-275498E12DD4.png

I would also try Muses8820 or Muses02, they are sort of expensive but the sound is extraordinary, different level altogether. The only thing is they have somewhat higher gain (110dB as opposed to 100dB for NE5532P) which may or may not cause instability … but definitely worth a try.
 
Last edited:
I've been listening to music by connecting the DENON PLA-2000Z to the PC4002.
After that, PC4002 is playing music smoothly.
Thanks to everyone for their advice.

I would like to try a high quality op amp.
If I don't like it, I can easily change it back.

I had a lot of fun with it.

Thank you
 
Yeah
These are essential.
The min-grabbers in the image look easy to use and I like them.

I was born and raised near our headquarters in Vessel.
I also love Vessel.

Thank you for your advice rottalpha
 
You must log in or register to reply here.
Back
Top Bottom