Denon Poa 1500 Help.. Advice......

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migkiller1971

Member
Joined 2010
Hi Everyone,

last night while listen to Bill Evans, My Left Channel went out. I turn it off, Removed it from my rack, took the Covers off and just when I plug it in (Smoke) Which I didn't get to see since My kids came down stair wondering why the hell I turned off the music. Timing I tell you...I'm Pretty Positive it came from the Sp Unit:

http://i1223.photobucket.com/albums/dd513/Migkiller1971/DSC00769.jpg


I took the speaker binding off the the board and on a closer view, It's obvious that this board is cracked and the previous owner did what he could to fix it. Its cracked precisely where the Left Channel relay(?) is connected to the board:

http://i1223.photobucket.com/albums/dd513/Migkiller1971/DSC00783.jpg

http://i1223.photobucket.com/albums/dd513/Migkiller1971/DSC00790.jpg

http://i1223.photobucket.com/albums/dd513/Migkiller1971/DSC00780.jpg


Of course this unit is at least 20 years old, So parts are going to be hard to come by. I need a recommendation on substitute Relays? The resistors, Caps, Connectors and parts should be no problem.

http://i1223.photobucket.com/albums/dd513/Migkiller1971/DSC00798.jpg

The another thing is.... The PCB Board. Can I salvage it by Soldering the hell out of it even more or I've seen youtube Clips on how to make your own PCB Board. Its pretty straight forward but I don't have the Software. Is there anyone on here who can probably print it out for me? Thank you and Happy Holidays..
 
sakellogg

sakellogg

Member
Joined 2008
i would make a new board.
if you make a scematic.
take lots of pictures... and then remove the components, clean all the extra solder off the board and through holes, clean well in a solvent. ive had luck just putting boards on a scanner and coping them using a laserprinter. iron that on the new board and etch.
if you need to modifiy for diffrent parts a sharpie works good.
i would see first what went belly up in the channel first. chances are that somthing from the output went bad to cause this.

just as info some solder wick placed neatly works alot better than globs of solder to fix this kinda stuff. i know it wasnt you but.....if it ever comes to you doing this...mental note
 
M

migkiller1971

Member
Joined 2010
sakellogg said:
i would make a new board.
if you make a scematic.
take lots of pictures... and then remove the components, clean all the extra solder off the board and through holes, clean well in a solvent. ive had luck just putting boards on a scanner and coping them using a laserprinter. iron that on the new board and etch.
if you need to modifiy for diffrent parts a sharpie works good.
i would see first what went belly up in the channel first. chances are that somthing from the output went bad to cause this.

just as info some solder wick placed neatly works alot better than globs of solder to fix this kinda stuff. i know it wasnt you but.....if it ever comes to you doing this...mental note
Click to expand...


Yeah, I was kind of pissed when I saw that solder work. Never thought about scanning it. I have the Schematics. I have to go hunting and see what went wrong.

Thanks!
 
M

migkiller1971

Member
Joined 2010
Cracked 22uh inductor..:mad:

CrackedInductor.jpg
 
sakellogg

sakellogg

Member
Joined 2008
mig...
first off post #4: you will proably have to remove it to test it, but you will definatly have to to replace it.
post#5: 22nf film cap like newark part# 32R8853 from newark.com would work. might plan on changing the ones in the other channel also???? i dont know might change the sound considring its looks like its part of the LC on the output. someone else might be able to tell u more.
post#6: if it is a coil with shrink tube on it, and it got hot enough to shrink the tube more to split it. it might be ok.take it out,allong with one of the other ones of the same value and ohm it out.
i might have that scematic but just incase... can you post it?
off the top of my head i would say that some of the semiconductors in the output went bad and shorted. giving rail voltage where it shouldnt have been. i would plan on changing most if not all of the semi's in that channel. if you cant find replacements you can use alldatasheet.com to get the values and search from there. not the end of the world, plus you can tweek it also.
might be a good time to make both channels better.


so...where you a fighter pilot?
 
M

migkiller1971

Member
Joined 2010
sakellogg said:
mig...
first off post #4: you will proably have to remove it to test it, but you will definatly have to to replace it.
post#5: 22nf film cap like newark part# 32R8853 from newark.com would work. might plan on changing the ones in the other channel also???? i dont know might change the sound considring its looks like its part of the LC on the output. someone else might be able to tell u more.
post#6: if it is a coil with shrink tube on it, and it got hot enough to shrink the tube more to split it. it might be ok.take it out,allong with one of the other ones of the same value and ohm it out.
i might have that scematic but just incase... can you post it?
off the top of my head i would say that some of the semiconductors in the output went bad and shorted. giving rail voltage where it shouldnt have been. i would plan on changing most if not all of the semi's in that channel. if you cant find replacements you can use alldatasheet.com to get the values and search from there. not the end of the world, plus you can tweek it also.
might be a good time to make both channels better.



so...where you a fighter pilot?
Click to expand...


Hi Scott,

Thanks for the help. Yes I have a schematic, I'll post it up or send it to you. I just finished modding up my phono preamp and bang. 2 hours of listening pleasure..What a sweet sounding amp.

I barely touch that transistor and it came apart. Both channel feed into that Sp unit with the 22nf caps. I'll test it. I might as well change that inductor. Looks weird. like a clown in there. I'm going to replace all the caps also. Thanks for that alldatasheet. That will come in handy!!

sakellogg said:
so...where you a fighter pilot?
Click to expand...

I was feared in the skies of Deutschland!!! I used to play tons of simulation flight games when I was younger. The name just stuck and my kid is the "migkiller" in xbox360 live..
 
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sakellogg

sakellogg

Member
Joined 2008
ok send or post..if you post more help might be avaliable. most guys around here have forgot more than i know.
never fails when its sounds the best it gose bad.
ive always liked denon. i still use them as my home theater pre/pro. and i recomend them to any one who is in the market .

and i get the migfighter now.

by the way i cant spell and the spell check dosent work on my phone
 
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M

migkiller1971

Member
Joined 2010
sakellogg said:
ok send or post..if you post more help might be avaliable. most guys around here have forgot more than i know.
never fails when its sounds the best it gose bad.
ive always liked denon. i still use them as my home theater pre/pro. and i recomend them to any one who is in the market .

and i get the migfighter now.

by the way i cant spell and the spell check dosent work on my phone
Click to expand...


Denon POA 1500:

denon_poa-1500_[ET].pdf

Right Now I'm using a backup sony tan330es until I get this denon up.

Thanks for all the help!!
 
M

migkiller1971

Member
Joined 2010
The more I dig into this amp, the more I get fustrated. Now I'm by far far no expert and haven't read a schematic in 20 years until acouple of weeks ago when I modded my phono preamp but this is what I just noticed: Call me crazy but this doesn't look right?

Led-LampBoard.jpg


goes to:

Led-LampBoard2.jpg



Now, these amps are notorious for the lamps to go out. It took me 2 minutes to find a denon service bulletin for this:

1. change TR 35 & TR 36 from 2SC1815 to 2SC2655
2. changed lamps from 28v / 40mA to 28v / 60mA
3. Change Resistors R101 & R102 from 15K to 4.7K

Wham. Done. Why would someone do this? Can this powersource going to the lamp board plus having the board plugged in to the control board cause problems? Even if you couldn't find these parts or lamps. Would soldering in a Resistor at the lamp board power up a LED? :mad: I need a smoke!!!
 
sakellogg

sakellogg

Member
Joined 2008
well i cant say why they did it .... i just glanced at the print. q26 looks like if it shorted it would put the output to ground.. i think. i just looked at it breifly. im going to have to print it out and tape it together to look at it right.
wait so someone added a secpnd power source to the lamp board by adding a resistor to b+ and ground?
and you have replaced theses per service bilitin?
have you removed these wires?
 
M

migkiller1971

Member
Joined 2010
sakellogg said:
well i cant say why they did it .... i just glanced at the print. q26 looks like if it shorted it would put the output to ground.. i think. i just looked at it breifly. im going to have to print it out and tape it together to look at it right.
wait so someone added a secpnd power source to the lamp board by adding a resistor to b+ and ground?
and you have replaced theses per service bilitin?
have you removed these wires?
Click to expand...


I haven't touched anything yet. I'm waiting for parts and caps to come in. I'M just digesting this in right now. I won't mess with anything until I get most of it in. That way I can keep track. I still have to order the semiconductors to went and anything I missed. Yes, there is a second power source coming straight in from b+ and ground "NO RESISTOR"..I have not done the bulletin upgrade. Maybe I'm wrong but that doesn't seem right to me.
 
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nigelwright7557

nigelwright7557

Member
Joined 2008
murtonpikesystems.co.uk
migkiller1971 said:
Hi Everyone,

The another thing is.... The PCB Board. Can I salvage it by Soldering the hell out of it even more or I've seen youtube Clips on how to make your own PCB Board. Its pretty straight forward but I don't have the Software. Is there anyone on here who can probably print it out for me? Thank you and Happy Holidays..
Click to expand...

If I have a cracked pcb I solder a single core solid wire to the tracks.
This gives it more strength than just solder.
 
sakellogg

sakellogg

Member
Joined 2008
ok the trouble makes sence now i looked a bit more(still havent printed) but if you look at your scematic q26 if it shorts to ground your output relay will not pick and all the current will try to go through most of the resitors you have posted as burnt. i cant find 66 but i might be blind. that would make that little transistor turning to dust a good clue.
are you unsure of the bulitin or why he added the second b+/Grnd? i dont know why the added b+ either
their bullitin sounds like they beefed it up a bit. higher current in that part of the cir.
if that is the case.
it might be easer to fix.
i would start one by one checking the simi's that are attached to the base/15k res off of tr36 and tr37. 36 and 37, those look like they light the bulbs behind the meters right?
you know i bet whoever did this "repair" lost the cir path to ground to light the bulbs....and didnt know why other than it didnt have B+/G at the bulbs so to fix it they found another power source. the transistors might have been shot when you got it and it shorted later. or
they burnt up bufor you got it and the "repair" made it light up and work untill a new problem arived.
what would you think about pulling the relays and isolating the protect cir and see if the output of the amp is ok? if that sound like somthing you want to try maybe we can both look at this a section at a time. thoughts?
 
M

migkiller1971

Member
Joined 2010
sakellogg said:
post #4 second pick.... where do the red and white wire go?
also please note how far the red wire is stripped and how close it is to other traces might be bad.
did the protect lights come on or just no sound and later smoke fizzle?
Click to expand...


I was just looking at that. I have no idea where that red/white goes. I don't remember pullingit off. I looked at the Connection schematic and could not find it. Another attempt to bypass or fix something?

REd.jpg
 
M

migkiller1971

Member
Joined 2010
sakellogg said:
ok the trouble makes sence now i looked a bit more(still havent printed) but if you look at your scematic q26 if it shorts to ground your output relay will not pick and all the current will try to go through most of the resitors you have posted as burnt. i cant find 66 but i might be blind. that would make that little transistor turning to dust a good clue.
are you unsure of the bulitin or why he added the second b+/Grnd? i dont know why the added b+ either
their bullitin sounds like they beefed it up a bit. higher current in that part of the cir.
if that is the case.
it might be easer to fix.
i would start one by one checking the simi's that are attached to the base/15k res off of tr36 and tr37. 36 and 37, those look like they light the bulbs behind the meters right?
you know i bet whoever did this "repair" lost the cir path to ground to light the bulbs....and didnt know why other than it didnt have B+/G at the bulbs so to fix it they found another power source. the transistors might have been shot when you got it and it shorted later. or
they burnt up bufor you got it and the "repair" made it light up and work untill a new problem arived.
what would you think about pulling the relays and isolating the protect cir and see if the output of the amp is ok? if that sound like somthing you want to try maybe we can both look at this a section at a time. thoughts?
Click to expand...


R66 is the last resistor before TP2 output (to speaker?) I think. its on page 9.. I don't know if the Bulletin was done. The reason I bought that up was because I found LED lights in the lamps and than that wire to B+ supply. The other possibility is that someone did do the bulletin and someone else bypass it.

sakellogg said:
what would you think about pulling the relays and isolating the protect cir and see if the output of the amp is ok? if that sound like somthing you want to try maybe we can both look at this a section at a time. thoughts?
Click to expand...

Cool. I can keep up but I need a little instruction.

Its been a really bad week. I just received a bad pressing on vinyl of John Coltrane Giant steps. Man I thought it was supposed to be Christmas!!!

http://www.youtube.com/watch?v=pgq-lpJcOzw
 
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