Low Output of Right Channel DENON pma 520 Amp

[lifewater]

Dear Friends,

I have received an amplifier as mentioned above yesterday from one of our forum members. I find that the output of one channel is relatively lower than the other. I tried keeping the balance pot in the mid position and the right channel output was way below the left channel. However please note that there was no distortion from either of the channels. I even tried swapping speakers (Right to left and vice versa) and the input cable from the source. No joy --- same thing happens.

Can anyone please provide some inputs about what could be the problem ?? Has such a problem been faced by anyone and if yes how was it rectified. Thanks a ton in advance.

lifewater

 

[captrajesh]

Hi Pranjal
I had faced it once & I was told that it is due to non linear voltage control of the volume pot. As per the technicians advice, I turned the volume knob vigorously a few times with the amp playing but the speakers off & the problem was solved.

 

[lifewater]

Thanks Captain,

Will try it today and let you know.

lifewater

 

[lifewater]

Tried it,

No Joy, looks the problem lies elsewhere. Have got the service manual, will try to do something tomorrow

lifewater.

 

[sonic_nirvana]

I am having the same problem with NAD C340 which I picked up from For Sale section. It's known issue while it is on the sale though.

The problem might be in Preamp or Power Amp section. I will try to isolate the problem once my preamp and power amps arrives. They are on shipment.
If there is no clue there, then I need to get it serviced. Vector System, Hyd told me that they can get it serviced.

Are there any places in Hyd where it can be serviced?

Thanks
Satya

 

[lifewater]

UPDATE Low Output of Right Channel DENON pma 520 Amp

Hi all,

Amp repaired and running like new. In fact maybe better. The problem was with the biasing of the power transistors and not the volume pot. The biasing was totally wonky and after biasing the amp sounds as if I put a tiger inside pulling on its lease !!

If anyone is interested, I can post photos taken while the work was in progress.

Cheers

lifewater

 

[captrajesh]

Hi Pranjal,

That is great news. Enjoy the new toy.

Regards


Rajesh

 

[r0kka]

Hi Lifewater,

my Denon pma 520 is having these issues. Did a google search and stumbled on this ancient post of yours. You wouldn't happen to still have those pictures you mentioned? Would be a tremendous help! Also any guidance would be greatly appreciated.

Cheers,
r0kka

 

[lifewater]

Hi Lifewater,

my Denon pma 520 is having these issues. Did a google search and stumbled on this ancient post of yours. You wouldn't happen to still have those pictures you mentioned? Would be a tremendous help! Also any guidance would be greatly appreciated.

Cheers,
r0kka

Hi,

I have passed on the amp many moons ago. I do however have the circuit schematic and the biasing procedure. Do PM me your E-mail ID and I will mail a copy to you with the procedure.

Regards,

Lifewater

 

[Tientie]

Hi,

I have passed on the amp many moons ago. I do however have the circuit schematic and the biasing procedure. Do PM me your E-mail ID and I will mail a copy to you with the procedure.

Regards,

Lifewater

Hello Lifewater.

I have the same receiver as rokka has... and you had. I mean the Denon PMA-520A. Only mine has the same isseu with the left channel. So i was wondering if u could help me out by sending me the schematics and the biasing procedure(if u still have them), that would make me a very happy guy.
i know the posts are a bit old but i'm hoping you wil reply.

Regards,

Tientie

 

[lifewater]

Hi,
received your PM too.. trying to locate the schematic. will share as soon as I am able to find it.

Best wishes,

Lifewater

 

[lifewater]

Hello Lifewater.

I have the same receiver as rokka has... and you had. I mean the Denon PMA-520A. Only mine has the same isseu with the left channel. So i was wondering if u could help me out by sending me the schematics and the biasing procedure(if u still have them), that would make me a very happy guy.
i know the posts are a bit old but i'm hoping you wil reply.

Regards,

Tientie

Hi, please check your mail...:licklips:

 

[Tomy_xyz]

Hi Lifewater,

Could you please also send me pictures and shematics for biasing amp.

Regards

 

[Tomy_xyz]

Hi,

I already figured myself.... thanks anyway

 

[DiederikWiersma]

UPDATE Low Output of Right Channel DENON pma 520 Amp

Hi all,

Amp repaired and running like new. In fact maybe better. The problem was with the biasing of the power transistors and not the volume pot. The biasing was totally wonky and after biasing the amp sounds as if I put a tiger inside pulling on its lease !!

If anyone is interested, I can post photos taken while the work was in progress.

Cheers

lifewater

I know this post is old, but I have the same problem. Is there any way that you could send me the biasing procedure? Would be so much appreciated. Thanks!

Diederik

 

[lifewater]

I know this post is old, but I have the same problem. Is there any way that you could send me the biasing procedure? Would be so much appreciated. Thanks!

Diederik

This is the bias setting procedure on the PMA-520

Power- OFF
Volume- Minimum
Loudspeakers- Discconnected (A and B)
All other settings at midpoint (Bass, Treble Etc)

1.Turn Power ON. Measure at TP1/TP3 with voltmeter. Immediately after turning ON : .5mV +/-.2mV.
2. After 5 minutes: 3mV +/-.5mV.
3. After15 minutes: 5mV +/-.5mV. Adjust VR403 (L) and VR404 (R) for these values.
4. Inject a 1KHz/100mV signal into the tuner input and turn Volume to maximum.
5. Measure at TP2/TP4 with voltmeter. Adjust VR405(L) and VR406(R) to 20mV +/-3mV.

You are done. Schematic will be mailed if you share your mail ID