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Denon POA 2200 bias adjust

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Daniel Stan

New Member
Hi guys!
I have a Denon POA 2200 that I have recaped and I am now waiting for the power transistors to arive (one chanel has some equivalents in stead of the original thing).
So, I was looking at the bias adjustment procedure and I saw it should be 8 mV (+/-1) acording to service manual. So, I took a look at the newer brothers (2400 and 2800) and they have way higher values for bias curent (50 mV +/-5 mV for POA 2400 and 40 mV +/-5 mV for POA 2800).
I know they have similar specs and all I wonder why is that so different?! I dont think that's right; it's like they forgot some steps...
I have made some printscreens of the bias adjustment procedure in all 3 service manual of the amp and it does seem they did forget some steps in the POA 2200 service manual...
What do you guys think? How did you adjust yours?
Thanks!
 

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I am replying to everyone who is reading this (as I cant delete this thread):
POA 2200 - 8 mV +/-1 mV
POA 2400 - 5 mV +/-1 mV
POA 2800 - 5 mV +/-1 mV.

The other values have been obtained because in the POA 2200 service manual there is a specific Neutral Point Voltage Adjustment, and in the case of POA 2400 and 2800 this was conidered Adjustment and they were all listed under the bias adjustment and I got a little confused, then I saw that there were different adjustment point stated for the rest of the adjustments.

Sorry for wasting your time guys!
Admin, you can delete this thread (or leave it in case someoane else has issues.
 
Well, since I did start this thread, I might as well ask for advices since I have one and I should replace the output transistors...
So, I had the originals in the right side and some replacements on the left side. There was a difference between the 2 chanels. That is why I will replace both left and right side...
Any advice on the thermal paste? I want to point out this is the first time I am doing this. (I did change a STK one time in a Onkyo A-3100 and it worked well after that so I am not that unexperienced.) I was thinking of using mica insulating sheets and thermal paste on both sides of the sheets? (Or only on the transistor side/only on the radiator side?)
Also I did find a high end mod for this amp. Basically, that means changing the op amps in the unit (Mitsubishi M5218P) with something better (BurrBrown OPA 2134). Do you guys think that would be ok? Will it work? Will it sound better?!
Thank you!
I already changed all the electrolitics in the amplifier. I used Nichicon FW, FG and Muse for BP caps.
 
I bought thermal pads when I did mine bt as long as they are insulated from the heatsinks and transferring the heat you should be good.
If you use mica sheets then you need thermal paste also.

The thermal pads need no paste if you buy those.

I would be very interested in any opamp mods too if they are easy to make, but not sure if it would improve anything sound wisei hear changing opamp can be troublesome.
This denon is a pretty complex amp I have read.

Probably one of the best iv ever heard though.
 
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Thank you @PTL-Pioneer! Yes, the amp does sound very nice the way it was built (did not listen to it after recap since I wanted to replace the output transistors). I was hoping to get some advices in op amp changes before I get the parts to finish the job (if there is someone here that did it it and it sounded better, I still have time to make some changes but after instaling the output transistors I'm surelly not going to get them out again so I can acces the boards).
 
Hi!
Well, wish I was happier and had better news but, my Denon POA 2200 is not that ok...
So, I got the amp totally recaped. I did start the unit, it's not going in protection or anything but I cant seem to adjust bias on the left side...
When I got the amp, I took it home and listened to it for 1 hour and then the left channel just stoped working (no bang, no smoke, no nothing, just no more sound...)
I thought then that after the recap was done (and new output transistors), it will all be ok (hopped for a bad solder joint or a faulty cap).
Did not conect any speakers to it yet but I'm pretty sure there will be no sound (just like the first time).
So, any sugestions anyone?! Any advice is aprecieted.
Thank you!
 
Hello!
I did saw some topics on op-amps so I am curious what are your thoughts in using a OPA2134PA instead of a M-5218P in a Denon POA 2200?
Or some other better op-amp than the one I sugested? (For e.g. LME49990?)
Thank you!
 
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