Hi all,
First time poster here. I just recently bought a Denon PMA 1060 stereo amplifier which has an issue. The audio will cut out at about quarter volume. The actual volume varies slightly with different music (louder music will cut out at a lower volume, quieter music will cut out at slightly higher volume). I have to power cycle the amp to restore audio but if I go too loud again, it will cut out.
I'm guessing the protection circuit has kicked in but don't know why.
I've checked for stray strands of speaker wire, but I use banana plugs and don't see any stray wires.
I have tried left and right channels connected by themselves, with no change.
I have tried the second (B) set of speaker terminals, no difference.
The speakers connected are Aaron ATS4, rated at 160W at 6 ohm so should be able to handle the power. The amplifier I replaced but is still working doesn't cut out with these speakers at quite loud volume.
I do have a multimeter, but am not strong with amplifiers or analog electronics. I've measured the voltage across the speaker terminals and there does not appear to be a big DC offset voltage on the terminals. I've found a service manual online and there is a procedure to adjust the idle current, but I don't think that would cause this issue, would it? From what I've read, too high idle current makes the amp run hot, and too low affects sound quality. I don't think either of this is happening in this case.
I'm wondering if anyone knows what the issue might be? I can take it to a repair shop who seem confident on what the problem is, but wondering if it's a cheap and/or common fix, or more complex!
Thanks in advance.
First time poster here. I just recently bought a Denon PMA 1060 stereo amplifier which has an issue. The audio will cut out at about quarter volume. The actual volume varies slightly with different music (louder music will cut out at a lower volume, quieter music will cut out at slightly higher volume). I have to power cycle the amp to restore audio but if I go too loud again, it will cut out.
I'm guessing the protection circuit has kicked in but don't know why.
I've checked for stray strands of speaker wire, but I use banana plugs and don't see any stray wires.
I have tried left and right channels connected by themselves, with no change.
I have tried the second (B) set of speaker terminals, no difference.
The speakers connected are Aaron ATS4, rated at 160W at 6 ohm so should be able to handle the power. The amplifier I replaced but is still working doesn't cut out with these speakers at quite loud volume.
I do have a multimeter, but am not strong with amplifiers or analog electronics. I've measured the voltage across the speaker terminals and there does not appear to be a big DC offset voltage on the terminals. I've found a service manual online and there is a procedure to adjust the idle current, but I don't think that would cause this issue, would it? From what I've read, too high idle current makes the amp run hot, and too low affects sound quality. I don't think either of this is happening in this case.
I'm wondering if anyone knows what the issue might be? I can take it to a repair shop who seem confident on what the problem is, but wondering if it's a cheap and/or common fix, or more complex!
Thanks in advance.
How loud is loud ?
I'd be very very surprised if you were driving the amp hard enough for it to trip... however faults like this need quantifying with basic measurements. It is possible to provoke some protection circuits by driving an adverse or reactive load hard.
This thread allows you get a good idea of the voltage and power you are delivering to your speakers. It might be worth trying this... drive the amp to the point you find it trips and then leave the volume control where it is and try this. Instructions and files are in post #2
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
I'd be very very surprised if you were driving the amp hard enough for it to trip... however faults like this need quantifying with basic measurements. It is possible to provoke some protection circuits by driving an adverse or reactive load hard.
This thread allows you get a good idea of the voltage and power you are delivering to your speakers. It might be worth trying this... drive the amp to the point you find it trips and then leave the volume control where it is and try this. Instructions and files are in post #2
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
Something like this is often indicative of a resistor that's gone high somewhere near the output of the power amp (emitter resistors of outputs or drivers and other things in the vicinity). Fortunately a resistor in-circuit may read lower than what it is, but will newer read higher unless it really is out of spec. A good look at solder joints tends not to be a bad idea either.
Thanks for your responses guys.
@Mooly - Quite loud (yes I know, subjective). To be honest, I'd only want to drive the amp slightly more and even then I think the neighbours would have something to say if it was late at night. I might do as you suggest and see how much power is delivered at the point of shutting off, I'd be interested in how much power the amp is outputting at that volume level.
@sgrossklass - Thanks, I have a schematic which I'll look over. Given that this problem also occurs with independent channels (left connected only, right connected only, and both connected), is it likely to be the power amp output? The power amp would separated into left/right channel correct? So if the problem was a resistor, it would have to be the same resistor on both, or a component which is common to both.
Since I have the service manual, I am going to try and measure/adjust the idle current. But I don't think this will fix the problem unless it's high and running hot? (I haven't touched the heatsinks but with the casing on, the air being vented is warm, not hot.
@Mooly - Quite loud (yes I know, subjective). To be honest, I'd only want to drive the amp slightly more and even then I think the neighbours would have something to say if it was late at night. I might do as you suggest and see how much power is delivered at the point of shutting off, I'd be interested in how much power the amp is outputting at that volume level.
@sgrossklass - Thanks, I have a schematic which I'll look over. Given that this problem also occurs with independent channels (left connected only, right connected only, and both connected), is it likely to be the power amp output? The power amp would separated into left/right channel correct? So if the problem was a resistor, it would have to be the same resistor on both, or a component which is common to both.
Since I have the service manual, I am going to try and measure/adjust the idle current. But I don't think this will fix the problem unless it's high and running hot? (I haven't touched the heatsinks but with the casing on, the air being vented is warm, not hot.
Hi lordsnipe,
You might want to check the capacitors in the protection circuit. For this kind of fault it is the most likely. They are probably not dead, esr measurements might not tell you much. For this you want the effective capacitance and dissipation reading as a measure of quality. If you don't have a capacitance checker (LCR meter), then just replace those capacitors in that section.
I don't have the manual for this model or I could have given you the part location codes. Another thing to check will be the speaker protection relay. It may need replacing due to burned contacts by now.
-Chris
You might want to check the capacitors in the protection circuit. For this kind of fault it is the most likely. They are probably not dead, esr measurements might not tell you much. For this you want the effective capacitance and dissipation reading as a measure of quality. If you don't have a capacitance checker (LCR meter), then just replace those capacitors in that section.
I don't have the manual for this model or I could have given you the part location codes. Another thing to check will be the speaker protection relay. It may need replacing due to burned contacts by now.
-Chris
Thanks anatech, I would attach the PDF service manual I found online but it's over 3Mb.
Found a link to the schematic, not the same PDF that I found which had the service manual and parts list, but can still be useful:
http://support.karat-service.net/Un...s-2/schematics-29/info-293/Denon PMA-1060.pdf
Found a link to the schematic, not the same PDF that I found which had the service manual and parts list, but can still be useful:
http://support.karat-service.net/Un...s-2/schematics-29/info-293/Denon PMA-1060.pdf
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Hi lordsnipe,
That link is incomplete for the protection circuit. Check capacitors C603, C604 and C605, and there are probably others off the page.
-Chris
That link is incomplete for the protection circuit. Check capacitors C603, C604 and C605, and there are probably others off the page.
-Chris
So I pulled off the cover this evening to take a look at the protection circuit, I was going to replace the caps because I don't have an ESR meter (and to use an ESR meter, the cap has to be removed anyway).
I've disassembled my fair share of PCs, game consoles and even CRT arcade monitors/CRT TVs, and never have I seen the board interconnections like this before.
It looks like wire wrapped around a long header pin? Surely this wasn't the pinnacle of Japanese electronic engineering in the early 90s? The amp has quite a few of these connections, so I don't think it was a home job...?
It looks to be a pain to remove this speaker terminal/protection circuit board. It has a number of these connections, the screw holding it to the back panel has a cap soldered to the end of it .. this is all odd looking to me!
I've disassembled my fair share of PCs, game consoles and even CRT arcade monitors/CRT TVs, and never have I seen the board interconnections like this before.
It looks like wire wrapped around a long header pin? Surely this wasn't the pinnacle of Japanese electronic engineering in the early 90s? The amp has quite a few of these connections, so I don't think it was a home job...?
It looks to be a pain to remove this speaker terminal/protection circuit board. It has a number of these connections, the screw holding it to the back panel has a cap soldered to the end of it .. this is all odd looking to me!
Attachments
Wirewraps were really common in 70's and 80's gear. Done correctly they offer a better connection than solder (really) because the wire cuts into the post.
From what you describe about volume levels and so on, I'm beginning to think you just might need a more suitable amp for those speakers.
From what you describe about volume levels and so on, I'm beginning to think you just might need a more suitable amp for those speakers.
Mooly, thanks for info. After some googling and youtube, I notice that a tool is required to properly do it.
I'm not big on hifi audio, so I'm not sure what you mean about my amp/speaker combo. I understand the speaker impedance is 6ohm, rated at 160 watts RMS, and the Denon amp puts out 105W RMS at 8 ohm and 180W RMS into 4 ohm. So, the amp should supply around 140W RMS at 6 ohm?
I would've thought the amp would've been ideal for the speakers, and that more than quarter volume would be possible.
I'm not big on hifi audio, so I'm not sure what you mean about my amp/speaker combo. I understand the speaker impedance is 6ohm, rated at 160 watts RMS, and the Denon amp puts out 105W RMS at 8 ohm and 180W RMS into 4 ohm. So, the amp should supply around 140W RMS at 6 ohm?
I would've thought the amp would've been ideal for the speakers, and that more than quarter volume would be possible.
If you need to undo a wire wrap as a one off then its OK to remake the joint with solder, its not worth investing in the correct tools for such occasional use, and to do a wire wrap as good as the original isn't easy.
The speaker has a nominal impedance of 6 ohms but it could actually dip well below that figure at certain frequencies. At AC, things get complicated even more by loads being 'reactive' which means that the current and voltage flowing in the load can appear out of phase which all stresses the amp even more.
The only sure way to know whether there is a problem or not is to do measurements. Ideally if you have a suitable high wattage resistor to use as a load, then the amp could be tested to see if it meets its specification. You could also use an oscilloscope to check the actual peak voltage swing that your speakers are seeing when the amp trips.
The speaker has a nominal impedance of 6 ohms but it could actually dip well below that figure at certain frequencies. At AC, things get complicated even more by loads being 'reactive' which means that the current and voltage flowing in the load can appear out of phase which all stresses the amp even more.
The only sure way to know whether there is a problem or not is to do measurements. Ideally if you have a suitable high wattage resistor to use as a load, then the amp could be tested to see if it meets its specification. You could also use an oscilloscope to check the actual peak voltage swing that your speakers are seeing when the amp trips.
Hi Folks, I know this thread is 5 years old and newly to the forum, but I have found myself with this exact same problem, and running Bose 601 series 2. Though a speaker might be driving the protection on but a second set of modern speakers is the same result. First was out with a good dust down and nothing obvious os cap replacement I suspect is first port of call. Thanks for the suggestions as will look there first and see how I go.
Unsolder only one end of the R607 / R608 2k resistor and see if the problem still exists, but don't overdo it with the power supplied to the speakers.
Before that, turn the potentiometer for the volume completely counterclockwise, disconnect the speakers and check the output DC offset with a multimeter on speakers terminal.
Before that, turn the potentiometer for the volume completely counterclockwise, disconnect the speakers and check the output DC offset with a multimeter on speakers terminal.
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Thankyou for this and shall do. I did remove the three caps and the 22uf is only just 19uf so will refresh these and then move in to this. Just need a day to get the parts. Just takes time but will be disappointed if cannot achieve the fix, more to follow next update.
Okay so replaced C603, 604 & 5 and the two small ceramics from speaker to ground.
DC offset well warm (more than 5min) both channels settle around 3-5ma with the left being slightly higher. When cold and first startup (volume full) with no speakers and no input, the DC starts high as initial I thought was 150ma on left channel then, 90ma in seconds. After on minute settling on 35ma and from there dropping to warm settings over time. The right channel on startup about 50ma and quickly dropping.
One speaker on right channel only and no problem with audio up to 3/4 volume and presto I though I got luckily. Then Left channel to confirm and protection set in at over 1/3 volume, back to right channel and same condition. Unsoldered R607 and no difference as same symptoms. I did leave the test meters in place with speakers connected and could not detect a rise in dc offset.
Would there be any other suspect areas as a go to first before I start checking all the components and joints. Obviously caps first I think.
DC offset well warm (more than 5min) both channels settle around 3-5ma with the left being slightly higher. When cold and first startup (volume full) with no speakers and no input, the DC starts high as initial I thought was 150ma on left channel then, 90ma in seconds. After on minute settling on 35ma and from there dropping to warm settings over time. The right channel on startup about 50ma and quickly dropping.
One speaker on right channel only and no problem with audio up to 3/4 volume and presto I though I got luckily. Then Left channel to confirm and protection set in at over 1/3 volume, back to right channel and same condition. Unsoldered R607 and no difference as same symptoms. I did leave the test meters in place with speakers connected and could not detect a rise in dc offset.
Would there be any other suspect areas as a go to first before I start checking all the components and joints. Obviously caps first I think.
Folks, I mean to say, millivolts and not milliamperes. I do have a basic scope as well and had these speakers and amp pumping out solid sound over the years. Will check the relays and resistor values to see if open or high circuit. So dirty relay contacts would drive the resistance higher here as I too seem to have something common to both channels.
Why not work back from the relay and see what conditions are occurring for it to trip out. If the trip is 'permanent' and you have to power it off and back on to get it to reset then you should look first at the thyristor SC601 and whether anything is tripping it.
You can remove the thyristor as a test, however you then loose that area of protection should there be a real fault.
You can remove the thyristor as a test, however you then loose that area of protection should there be a real fault.