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
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
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
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
Also need for Scematics
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
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
Re: Thank's !!!
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
godzich said:
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
Re: Also need for Scematics
Hi
Did you get the schematics ?
Maybe I can help if you want .
Ricardo
erajoma said: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
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
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
Hi everybody !
Maybe it can help.
Denon POA-6600 schematics...
http://www.audio-circuit.dk/Schematics/Denon_POA-6600.pdf
and others...
http://www.audio-circuit.dk/Schematics.html
Cheers.
Bernard
Maybe it can help.
Denon POA-6600 schematics...
http://www.audio-circuit.dk/Schematics/Denon_POA-6600.pdf
and others...
http://www.audio-circuit.dk/Schematics.html
Cheers.
Bernard
Hi Bekimbekim said:
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
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
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
Ok,
I had similar problem with many equipment, including denon power amps. Seems that, you have many "bad solder" to remove and put new one across the whole pcb.
What you have to do is:
-remove all 2sa1492/2sc3856 from pcb,
-check resistor value in each transistor placement, i.e. in each npn transistor should be the same value, might be any connection broken....
-instead of posistor you put 100ohm (or 220ohm) resistor,
-make sure all transistors are ok, be sure to check each of them,
-replace trimmer pots, in both pcb, and approximately slide the new pots to the same value like old ones,
-existing zeners are 5.1volts/400mW, put new ones 5.1/500mW you can find philips bzx5c1,
-replace all biasing diodes, those standard ones 1s2076, with 1n4148 usualy are better than those on your amp,
-check for 8pin ic's, M5238 & NJM2068, might be trouble.. you can replace temprorary with ne5532 or equivalent,
.....
As I can see from problem you have with this amp, I think that, bad solder causes this blowing of all trannies.. It happen before to me as well. Is very important to have very good solder and clean iron in order to make good joint, is prefered to remove the older solder and put new one.
Ricardo, big power amps run pretty hot and, ,ost of the fault is done from bad soldering.
Make sure to check all parts, you might missed some bad part, or similar causing problem maker. Is very important if you change electrolytes on amplifier pcb, in case there are not many, there 10uF/50v replace with 10uF/63v and check bipolars as well, 1uf/100v.
check transistor value of TR601 RSN1205 might be problem..
R553 & R554 1kohm resistors might loose thier values, or might have bad solder.
When you are sure about all this and you want to check your amp, usualy don't connect all trannies on output, instead you can put just one pair - one 2sa1492 and one 2sc3856, and to check is it working or not. Or better, if you have any other cheaper pnp/npn pair put there instead of original ones, just for testing.
And, most important is to set biasing according to service manual.
If you don't have service manual I will send it to you.
Let me know do you have problem only with one or both amps..?
bekim
I had similar problem with many equipment, including denon power amps. Seems that, you have many "bad solder" to remove and put new one across the whole pcb.
What you have to do is:
-remove all 2sa1492/2sc3856 from pcb,
-check resistor value in each transistor placement, i.e. in each npn transistor should be the same value, might be any connection broken....
-instead of posistor you put 100ohm (or 220ohm) resistor,
-make sure all transistors are ok, be sure to check each of them,
-replace trimmer pots, in both pcb, and approximately slide the new pots to the same value like old ones,
-existing zeners are 5.1volts/400mW, put new ones 5.1/500mW you can find philips bzx5c1,
-replace all biasing diodes, those standard ones 1s2076, with 1n4148 usualy are better than those on your amp,
-check for 8pin ic's, M5238 & NJM2068, might be trouble.. you can replace temprorary with ne5532 or equivalent,
.....
As I can see from problem you have with this amp, I think that, bad solder causes this blowing of all trannies.. It happen before to me as well. Is very important to have very good solder and clean iron in order to make good joint, is prefered to remove the older solder and put new one.
Ricardo, big power amps run pretty hot and, ,ost of the fault is done from bad soldering.
Make sure to check all parts, you might missed some bad part, or similar causing problem maker. Is very important if you change electrolytes on amplifier pcb, in case there are not many, there 10uF/50v replace with 10uF/63v and check bipolars as well, 1uf/100v.
check transistor value of TR601 RSN1205 might be problem..
R553 & R554 1kohm resistors might loose thier values, or might have bad solder.
When you are sure about all this and you want to check your amp, usualy don't connect all trannies on output, instead you can put just one pair - one 2sa1492 and one 2sc3856, and to check is it working or not. Or better, if you have any other cheaper pnp/npn pair put there instead of original ones, just for testing.
And, most important is to set biasing according to service manual.
If you don't have service manual I will send it to you.
Let me know do you have problem only with one or both amps..?
bekim
Can not find replacements in farnell can you help ?bekim said:
Should I replace all 1s2076 in the schematics or just the bias ones ? Can you please point them on the schematic ?bekim said:
Do you mean replacing IC601, IC602 and IC401 (NJM2068AD) all by the same type of opamp (ne5532) ?bekim said:
?
Also can not find TR601 on the pcb can you point it out for me ?bekim said:
I have two amps and one is working perfectly.
I just received the HZ5C1 from UK and have some output TR that I believe to be fake ones.... Can I use these for testing ?
As I can not find true 2SA1492 and 2SC3856 anywhere, can I use 2SA1294/2SC3263 instead ?
Thank you very much Bekin
Ricardo
Hi Ricardo,
regarding helping you to find original 2sa1492/2sc3856 I don't believe that I can help somehow. I live in Kosova and, all parts which I order are from asia - somewhere, don't know the origin precisely.
biasing diodes you have to replace only, not all. You point on those near zener diodes like, D511, D514, DS515, D516, D517, D518, D519, D520 these are 1S2076, and you can change them with 1n4148. Diodes D512 & D513 are zener HZ5C1 you can replace with BZX5V1 if you cannot find original ones.
OP's IC601 & IC602 you can change with NE5532, or NJM2068AD in both places, I did this on one broken amp like yours until I fix it then, I put new original ones. But, if you're sure that, those IC's are ok, don't change them. Eventhough, you can replace both IC's with M5238 when you finish fixing your amp.
TR601 is placed near R608 and C604 on your power amp board. Desolder it and check does it show short circuit, and if is ok put it back.
You can use 2SA1294/2SC3263 but, remember to not destroy all transistors on output, put just one pair on power amp board; example TR513 & TR514. You can always put any other cheaper trans there even fakes, just to see does it work. just make sure that bipolars you will use for testinga re not darlingtones.
replace all these electrolytes - is highly recommended:
C501, C507, C508, C523, C547, C601, C602 - 10uF/50V, you can replace with 10uf/63V;
C604 10uF/16V;
C516, C517 - bipolars 1uF/100V;
C524 22uF/100V;
C543 & C544 10uF/100V bipolars.
I don't know how old this amp is, therefore all these electrolytes are better to be replaced. condensers are pretty annoying and difficult to be sure that old ones are ok, regardless how much time you spent on measuring them.
bekim
regarding helping you to find original 2sa1492/2sc3856 I don't believe that I can help somehow. I live in Kosova and, all parts which I order are from asia - somewhere, don't know the origin precisely.
biasing diodes you have to replace only, not all. You point on those near zener diodes like, D511, D514, DS515, D516, D517, D518, D519, D520 these are 1S2076, and you can change them with 1n4148. Diodes D512 & D513 are zener HZ5C1 you can replace with BZX5V1 if you cannot find original ones.
OP's IC601 & IC602 you can change with NE5532, or NJM2068AD in both places, I did this on one broken amp like yours until I fix it then, I put new original ones. But, if you're sure that, those IC's are ok, don't change them. Eventhough, you can replace both IC's with M5238 when you finish fixing your amp.
TR601 is placed near R608 and C604 on your power amp board. Desolder it and check does it show short circuit, and if is ok put it back.
You can use 2SA1294/2SC3263 but, remember to not destroy all transistors on output, put just one pair on power amp board; example TR513 & TR514. You can always put any other cheaper trans there even fakes, just to see does it work. just make sure that bipolars you will use for testinga re not darlingtones.
replace all these electrolytes - is highly recommended:
C501, C507, C508, C523, C547, C601, C602 - 10uF/50V, you can replace with 10uf/63V;
C604 10uF/16V;
C516, C517 - bipolars 1uF/100V;
C524 22uF/100V;
C543 & C544 10uF/100V bipolars.
I don't know how old this amp is, therefore all these electrolytes are better to be replaced. condensers are pretty annoying and difficult to be sure that old ones are ok, regardless how much time you spent on measuring them.
bekim
Hi Bekin
I will do as you indicate during this weekend.
I will report after that.
Please inform if I can use 2SA1294/2SC3263 to replace original ones as I need to order them now.
I already have some 2sa1492/2sc3856 but I believe they are fake ones because I bought them very cheap and they look like some fakes I have seen in the internet.
Thank You for your help.
Ricardo
I will do as you indicate during this weekend.
I will report after that.
Please inform if I can use 2SA1294/2SC3263 to replace original ones as I need to order them now.
I already have some 2sa1492/2sc3856 but I believe they are fake ones because I bought them very cheap and they look like some fakes I have seen in the internet.
Thank You for your help.
Ricardo
Hi Bekin
Last night, after replacing the bias diodes with the correct ones, I installed two output TR and fired the amp.
It seems to be ok because it did not get hot and nothing burned.
Nevertheless I am still measuring differences in the base voltages of TR509 (1.55v) and TR510 (-1.69v).
Can I load the output of the amp and input some signal ?
Also I am reading the following voltages in TR551:
Base -1.16v (should be -1.1v)
Colector 1.74v (should be 1.75v)
Emitter -1.88v ( should be -1.7V)
This last reading is very troubling because the emitter should have lower voltage than the colector and I believe this is the source of the differences I am reading in th driver stage.
Can you please suggest a corrective action ?
Best Regards
Ricardo
Last night, after replacing the bias diodes with the correct ones, I installed two output TR and fired the amp.
It seems to be ok because it did not get hot and nothing burned.
Nevertheless I am still measuring differences in the base voltages of TR509 (1.55v) and TR510 (-1.69v).
Can I load the output of the amp and input some signal ?
Also I am reading the following voltages in TR551:
Base -1.16v (should be -1.1v)
Colector 1.74v (should be 1.75v)
Emitter -1.88v ( should be -1.7V)
This last reading is very troubling because the emitter should have lower voltage than the colector and I believe this is the source of the differences I am reading in th driver stage.
Can you please suggest a corrective action ?
Best Regards
Ricardo
that's good.
Ok, if isn't blowing anything, check sorrunding electrolytes of TR551 and other parts, because should be very near to data given on service manual.
Regarding TR509 & 510, that's normal, isn't very high difference.
Try to align bias according service manual and when you're sure about it, but REALY sure, then connect 8ohm speaker and turn speakers on, and without signal chack after 20minutes does the output trannies are getting little hot, as well check for voltage in base of output trannies. If doesn't blow, connect signal, but don't play it loud and see how it performs.... after that you can put additional two more trannies, and do the bias aligning and so on....
BUT, prior to this, did you check for "bad" soldering?
did you measure electrolytes or change them...?
did you check biasing diodes and zeners...?
try to check these parts, and be sure are ok.
bekim
Ok, if isn't blowing anything, check sorrunding electrolytes of TR551 and other parts, because should be very near to data given on service manual.
Regarding TR509 & 510, that's normal, isn't very high difference.
Try to align bias according service manual and when you're sure about it, but REALY sure, then connect 8ohm speaker and turn speakers on, and without signal chack after 20minutes does the output trannies are getting little hot, as well check for voltage in base of output trannies. If doesn't blow, connect signal, but don't play it loud and see how it performs.... after that you can put additional two more trannies, and do the bias aligning and so on....
BUT, prior to this, did you check for "bad" soldering?
did you measure electrolytes or change them...?
did you check biasing diodes and zeners...?
try to check these parts, and be sure are ok.
bekim
Hi Bekin
I did check for bad solder and fixed most of the visible points.
I am having trouble checking transistor value of TR601 RSN1205 ... can you explain how can I check it ?
I can not find this transistor in Portugal.... can you suggest a internet seller for me ?
I already ordered the el capacitors (10uF 63V) and (22uF 100V).
I will replace them this weekend.
Unfortunatelly I can not find any bipolars in Europe providers.... can you help ?
Best Regards
Ricardo
I did check for bad solder and fixed most of the visible points.
I am having trouble checking transistor value of TR601 RSN1205 ... can you explain how can I check it ?
I can not find this transistor in Portugal.... can you suggest a internet seller for me ?
I already ordered the el capacitors (10uF 63V) and (22uF 100V).
I will replace them this weekend.
Unfortunatelly I can not find any bipolars in Europe providers.... can you help ?
Best Regards
Ricardo
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