Quick & Easy request for help - Denon POA-2400

bluesmoke · 28th October 2007, 05:33 AM

Hi,

Missed my ol' Yammy full of Sankens, picked up a Denon for fun. Just noticed a slight temp difference between channels, thought it worth touching up.

Just wanted to know is someone has info on adjusting the bias (possibly ~K-amps?) Don't need the whole manual, just the bit about values, and what points to test. It's a bit of an odd layout on the boards (also multiple pots). There are a variety of test pins, so might be very easy if I knew they could be used.

It just uses a pair of A1492/C3856 per channel...

Lots of thanks ahead of time!

Bigred · 28th October 2007, 06:36 AM

Unfortunately I don't have the service info for this model. What I can tell you is that the 2200 & 2400 units had adjustments for the bias and distortion factor. The DC offset you just measure at the speaker terminals with no signal. It should be within +/-100mv. There should be 2 pots along with a set of test points on each board (Left & Right); one pot is for the bias adj. and the other will be for the distortion factor. To check the bias, hook your DMM on the test points (I use aligator clips and slide the rubber boots over the pins to prevent any "accidents") and measure the DC. Your looking for 8mV +/-1mV. You need to have the amp warmed up for this test. If you let me know the pot numbers on each board (will be VRxxx) it might jog my memory on what pot adjust what and possibly take some pictures of the boards. Its either that or purchase the manual if noone else can help.

bluesmoke · 28th October 2007, 06:53 AM

I'll pull it out right now and take notes and a picture. Back in a flash.

Can't see much of a difference from the 2200, other than the level controls are on the back. Heard that the direct input has a high pass filter... true?

bluesmoke · 28th October 2007, 07:11 AM

Left Channel...

bluesmoke · 28th October 2007, 07:12 AM

Right Channel

bluesmoke · 28th October 2007, 07:18 AM

DC offset is already pretty good...
Left: 13.2mv
Right: 7.0mv

Bigred · 28th October 2007, 07:25 AM

ok now measure between the test points TP2&3 (dc mV) and TP11&12 and see what you measure.

bluesmoke · 28th October 2007, 07:38 AM

testing... (about 5min per channel)

bluesmoke · 28th October 2007, 07:46 AM

Explains a lot...

Left Bias: 15mv
Right Bias: 0mv (can't get a reading for some reason...., but doesn't float)

Have an idea which pot is Bias? ... I have no clue which is DF, nor what it even does...

Bigred · 28th October 2007, 07:58 AM

This is a 2400 and not a 2400A(optical class A) version correct? Also, can u see any numbers on the actual pots? or just measure their resistance. IIRC from changing these out the bias pot is 10k. Memory is failing me at the moment sorry.

28th October 2007, 05:33 AM	#1
bluesmoke diyAudio Member Join Date: Mar 2006 Location: Great White North	Quick & Easy request for help - Denon POA-2400 Hi, Missed my ol' Yammy full of Sankens, picked up a Denon for fun. Just noticed a slight temp difference between channels, thought it worth touching up. Just wanted to know is someone has info on adjusting the bias (possibly ~K-amps?) Don't need the whole manual, just the bit about values, and what points to test. It's a bit of an odd layout on the boards (also multiple pots). There are a variety of test pins, so might be very easy if I knew they could be used. It just uses a pair of A1492/C3856 per channel... Lots of thanks ahead of time!

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28th October 2007, 06:36 AM	#2
Bigred diyAudio Member Join Date: Jul 2007	Unfortunately I don't have the service info for this model. What I can tell you is that the 2200 & 2400 units had adjustments for the bias and distortion factor. The DC offset you just measure at the speaker terminals with no signal. It should be within +/-100mv. There should be 2 pots along with a set of test points on each board (Left & Right); one pot is for the bias adj. and the other will be for the distortion factor. To check the bias, hook your DMM on the test points (I use aligator clips and slide the rubber boots over the pins to prevent any "accidents") and measure the DC. Your looking for 8mV +/-1mV. You need to have the amp warmed up for this test. If you let me know the pot numbers on each board (will be VRxxx) it might jog my memory on what pot adjust what and possibly take some pictures of the boards. Its either that or purchase the manual if noone else can help.

28th October 2007, 06:53 AM	#3
bluesmoke diyAudio Member Join Date: Mar 2006 Location: Great White North	I'll pull it out right now and take notes and a picture. Back in a flash. Can't see much of a difference from the 2200, other than the level controls are on the back. Heard that the direct input has a high pass filter... true?

28th October 2007, 07:18 AM	#6
bluesmoke diyAudio Member Join Date: Mar 2006 Location: Great White North	DC offset is already pretty good... Left: 13.2mv Right: 7.0mv

28th October 2007, 07:25 AM	#7
Bigred diyAudio Member Join Date: Jul 2007	ok now measure between the test points TP2&3 (dc mV) and TP11&12 and see what you measure.

28th October 2007, 07:38 AM	#8
bluesmoke diyAudio Member Join Date: Mar 2006 Location: Great White North	testing... (about 5min per channel)

28th October 2007, 07:46 AM	#9
bluesmoke diyAudio Member Join Date: Mar 2006 Location: Great White North	Explains a lot... Left Bias: 15mv Right Bias: 0mv (can't get a reading for some reason...., but doesn't float) Have an idea which pot is Bias? ... I have no clue which is DF, nor what it even does...

28th October 2007, 07:58 AM	#10
Bigred diyAudio Member Join Date: Jul 2007	This is a 2400 and not a 2400A(optical class A) version correct? Also, can u see any numbers on the actual pots? or just measure their resistance. IIRC from changing these out the bias pot is 10k. Memory is failing me at the moment sorry.

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