DENON POA-6600A schematic wanted !!

[godzich]

Hi !

I have this tricky POA-6600A Denon amp that I am not able to fix without a schematic. Please - help anyone !

This is my second request. The member Hardi kindly promised to send me the schematic but I am not able to contact him and have not heard from him since.

I am new to this forum and do not know if it is prudent to start this new thread about the same subject - but please understand - I'm desperate

Any help is more than appreciated !

Sincerely,

Christian

PS: My email is:

christian.godzinsky@sci.fi

[godzich]

Thank's to Lyra that helped me with the schematic. I now have the amp up and running again!!!

Great forum, great members !!!

[bekim]

Hi godzich,

My friend receive two poa-6600a few days ago from germany and both have some problems. I'm trying to fix them and I need schema for it. If is not problem to share schema for this amps, I will appreciate it.

thank you
bekimh@gmail.com

[erajoma]

HI
I also would be very happy if Lyra could send me a copy of the 6600A schematics, since Im trying to help my friend to solve his smoking power amp.

My email is:

erajoma@yahoo.se

[RCruz]

Originally posted by godzich
Thank's to Lyra that helped me with the schematic. I now have the amp up and running again!!!

Great forum, great members !!!

Hi

I am having trouble with a DENON POA 6600A.

I am getting some trouble getting the the bias simetrical in the pre drivers bases.

This is a push pull amp that relies on a optical ship to set bias.

On the top pre driver I get 1.67v and the lower predriver base I get -1.79v.

On the drivers bases I get 1.04v (top) and -1.19v (bottom driver).

The final stage is composed of four 2SC3856 and four A1492.

I should be able to get +-0.5v on the output transistors bases but I can only get 0.48v on the 2SC3856 bases and -0.62v on the bases of the A1492.

I have not soldered the output transistors yet so the readings are made in the drivers and pre drivers only (without output stage).

I did not solder the output transistors because I am afraid these voltage differences might provoque an oscilation and burn the outputs.

I really need some help and advise.

Best Regards

Ricardo

[RCruz]

Originally posted by erajoma
HI
I also would be very happy if Lyra could send me a copy of the 6600A schematics, since Im trying to help my friend to solve his smoking power amp.

My email is:

erajoma@yahoo.se

Hi

Did you get the schematics ?

Maybe I can help if you want .

Ricardo

[bekim]

Hi Ricardo,

Please, tell what kind of trouble you have with POA 6600... Does the protection acts normaly: Do you hear any sound from it..?

I will suggest to not touch the bias voltage before you are able to find out is there any damage done on the amp, i.e. any burns, any dead component, etc. I have fixed many 6600 amps, and I think I can help you with these one.
I have sm for this amp.

bekim

[Glyptoron]

Hi everybody !

Maybe it can help.
Denon POA-6600 schematics...
http://www.audio-circuit.dk/Schemati...n_POA-6600.pdf
and others...
http://www.audio-circuit.dk/Schematics.html

Cheers.
Bernard

[RCruz]

Originally posted by bekim
Hi Ricardo,

Please, tell what kind of trouble you have with POA 6600... Does the protection acts normaly: Do you hear any sound from it..?

I will suggest to not touch the bias voltage before you are able to find out is there any damage done on the amp, i.e. any burns, any dead component, etc. I have fixed many 6600 amps, and I think I can help you with these one.
I have sm for this amp.

Hi Bekim

The trouble is that wenever the amp is rebuilt with new drivers and output transistors, It starts ok.. keeps the bias seady for some seconds and then it starts to rise and the outputs burn.

Now the pcb is partially rebuilt (everything is in place but the output transistors and the posistor)

In place of the posistor I placed a 220ohm resistor (just for testing).

When I fire it up, the amp goes out of protection and the bias current appears on the drivers.

The problem is that the voltages are lower in the top driver.

TR511 B = 0.92v E = 0.4v

TR512 B = -1.07v E = -0.5v

I do not know if this happens because I have not installed any outputs .... and I am afraid to burn everything again.

I really need help. !

Regards

Ricardo

[RCruz]

Hi

Here you have actual measurements:

The problem is that the voltages are lower in the top driver.

TR511 B = 0.92v E = 0.4v

TR512 B = -1.07v E = -0.5v

I can lower these values all at the same time by rotating VR501 but when I turn VR502 nothing seems to happen (the only variation I can measure appears on pin 4 of chip IC501).

On this chip I read:
1 = 79.1
2 = 78.1
3 = -1.8
4 = -0.85 ~ -0.9 (when turning VR502)

Also I read on the TR551 (mounted under the pcb)
B = 1.1v
E = -1.82v
C = 1.67v

On C531 I read -1.8v
TR510 base = -1.69

On C530 I get 1.67v
TR509 base = 1.55v

D512 Katode = 3.12v
D513 Anode = -3.30v (On the working amp (I have two amps) I get +-1.5v on this zeners.

This zeners are not stock. (I can not find HZ5C1 anywere).

Can I mount the output TR and hope this voltage variations go away ?

Best Regards

Ricardo