Hi everyone... I've got a tricky problem that I'm hoping someone can help with my Pioneer A-A9-J 2 Ch amp. The amp sounds great except.... randomly the amp pops. It happens to both channels and through the preout too. The pops increase in volume as the volume is increased and the speaker cones visibly move in and out. It can go on for days without a hitch and then pop and fart driving me crazy. I have opened it up a few times, removed the various boards and inspected every component, track and solder connection with a magnifying glass. There are no obvious dry joints and anything that looks anything less than 110% I have resoldered. I have checked the capacitance and Esr of all the main caps which all check out good - the idle current & dc offsets are spot on. I have also replaced the standby power relay and associated cap. On the last boards-out foray it worked perfectly for 3 weeks but alas a couple of days ago it came back with a vengeance..... so I put the amp on my bench, pulled the lid off and waited for a couple of hours with the volume at 3/4 and no input. It popped and the speaker protection switched the unit off. I checked the schematic, grabbed my freezer spray and waited. It popped - I sprayed one of the RCH power transistors (Sanken C3519a) and the popping stopped. I let it warm up, the popping started again so I sprayed it and the popping stopped. I sprayed it intermittently to keep it cool and the popping didn't return. The trouble is I can't get the popping to come back even by blowing a hair dryer on it. Is this fault typical of a failing transistor
Lets clarify a couple of points...
1/ Firstly, freezing a good transistor should have no effect, and so if it seems to 'heal up' after freezing then that points to it being defective. That failure mode is common on many small devices and particularly T0220 style devices but it is not I have to say common on large output devices.
Is it possible the chilling effect could have transferred to one of the drivers as you blasted the output with freezer ?
2/ If the volume control reduces the amplitude of the popping then that needs confirming and investigating because that all points to a problem before the power amp stages.
1/ Firstly, freezing a good transistor should have no effect, and so if it seems to 'heal up' after freezing then that points to it being defective. That failure mode is common on many small devices and particularly T0220 style devices but it is not I have to say common on large output devices.
Is it possible the chilling effect could have transferred to one of the drivers as you blasted the output with freezer ?
2/ If the volume control reduces the amplitude of the popping then that needs confirming and investigating because that all points to a problem before the power amp stages.
^ This. Though you never know what a randomly-shorting transistor in the power amp might do to preamp supplies.
Thank you for your replies. I am convinced that the popping volume increases with volume and any less than 17db on the volume control and the speaker protection activates. The popping is intrusive at lower volumes but less aggressive - coincidence perhaps. The amp is of dual monoblock construction with separate toroidal power transformers & rectifiers etc.
Subjectively I would say that the popping is loudest in the right channel then the left followed by the preout. I have an active sub on the preout. I started on the right channel for this reason.
I used a narrow pipe to direct the freeze spray which was delivered in very short bursts. This would have affected the emitter resistor which is adjacent and the heat sink but the driver is probably 25mm away.
I'm thinking I do another round of resoldering and then maybe run the amp with the right channel disconnected?
Subjectively I would say that the popping is loudest in the right channel then the left followed by the preout. I have an active sub on the preout. I started on the right channel for this reason.
I used a narrow pipe to direct the freeze spray which was delivered in very short bursts. This would have affected the emitter resistor which is adjacent and the heat sink but the driver is probably 25mm away.
I'm thinking I do another round of resoldering and then maybe run the amp with the right channel disconnected?
Does it pop when no music is playing, but with the volume turned up ?
Its very difficult to say for sure what is going on here. You need to try and pin this down a bit further to come to any conclusion.
It would definitely be worth disconnecting the main speakers when it is doing the noise and then seeing if the pre-out feed is still affected. Not just one channel but both.
A transistor in the power amp section that was intermittent would tend to cause the same level of noise irrespective of the volume control, and it would also usually be a destructive fault with speakers connected due to the current that could flow (which this obviously isn't).
Also, just trying to cover all possible bases here... make sure there isn't a whisker of wire shorting between the speaker terminals at the speaker connections. Its also good practice to confirm that the DC offset of the amp is zero on both channels and remains like that when in use.
Its very difficult to say for sure what is going on here. You need to try and pin this down a bit further to come to any conclusion.
It would definitely be worth disconnecting the main speakers when it is doing the noise and then seeing if the pre-out feed is still affected. Not just one channel but both.
A transistor in the power amp section that was intermittent would tend to cause the same level of noise irrespective of the volume control, and it would also usually be a destructive fault with speakers connected due to the current that could flow (which this obviously isn't).
Also, just trying to cover all possible bases here... make sure there isn't a whisker of wire shorting between the speaker terminals at the speaker connections. Its also good practice to confirm that the DC offset of the amp is zero on both channels and remains like that when in use.
Ok first things first
Ripcurler :
In your first post 99% of your targeting is wrong no bias,offset ,main capacitors,stand by relay and capacitors is related to the specific problem .Doing those could be a nice precaution but nothing else .What you described is clearly a transistor or IC mechanical failure .
Mooly
My good friend you are so wrong in this one !!! freezing a transistor will alter beta , freezing an LTP transistor in a working amplifier will effect offset heating it will do the exact same thing ...( Gosh Mooly this is how a Vbe multiplier works !!! )
As about output failure in all my 35 year experience i have only found 1 (one) output transistor that behaved like that ...at normal room temp and normal operating conditions amplifier presented offset of 13V Freeze the output and amplifier worked like a charm( transistor was Fujitsu though ) . That was one and only but it counts .. I have found some TO220 and very plenty TO92 transistors .
Now ... for the specific amplifier at this point it is not clear to me where the failure comes from .... One should isolate the main amplifier L+ R respectively from the preamplifier to find out what is wrong ...Remains a problem that this one is a DC coupling amplifier so any behavior like that coming from the preamplifier or the power supply of it will be transferred to the main amplifier and of course will be "volume controlled ".
Volume controlled though could apply to amplifiers with classic and passive volume control In your case it doesn't seem to apply since the volume is digital and the pre out is coming from the digital IC R2S15205FP.
Troubleshooting ...
heat gun with narrow nose and freeze spray is your weapons First you need to isolate the problem to make sure where is this coming from My gut says that this should be the IC but as said reading your post didn't explain to me where the fault comes from .
Either this is a pre or a main issue the best thing to do will be to monitor voltage in the output of the main amplifier before the relay at a first stage and start trying to trace it down and after you are sure its not the main amps then you should monitor DC voltage in the input of the amplifier .
One thing about the freezing spray:
freezing spray is most of the times a pointer to a direction BUT when the problem is minor often there is chance that freezing the opposite transistor and alter the working conditions and the characteristics of the specific transistor might momentary solve the problem but this doesn't mean that you got it ....Momentary fix is because the frozen transistors effects the circuit in a way that helps it doesn't always mean that is broken . Heat Gun will behave alike you will be very surprised to see the variations of offset when you apply heat in the input transistors .
One thing you should look at also is grounds , make sure that all ground connectors are firm , clean and tight I have seen amps having stability problems because the screws of the RCA input bay was not tight and failing to provide proper ground to the circuits (manufacturer wrong chooses to provide ground to circuits this way , behind some RCA there was a metal string and the screw had to tight the external cover , the RCA bay and the ground string .... )
Kindest regards
Sakis
Ripcurler :
In your first post 99% of your targeting is wrong no bias,offset ,main capacitors,stand by relay and capacitors is related to the specific problem .Doing those could be a nice precaution but nothing else .What you described is clearly a transistor or IC mechanical failure .
Mooly
My good friend you are so wrong in this one !!! freezing a transistor will alter beta , freezing an LTP transistor in a working amplifier will effect offset heating it will do the exact same thing ...( Gosh Mooly this is how a Vbe multiplier works !!! )
As about output failure in all my 35 year experience i have only found 1 (one) output transistor that behaved like that ...at normal room temp and normal operating conditions amplifier presented offset of 13V Freeze the output and amplifier worked like a charm( transistor was Fujitsu though ) . That was one and only but it counts .. I have found some TO220 and very plenty TO92 transistors .
Now ... for the specific amplifier at this point it is not clear to me where the failure comes from .... One should isolate the main amplifier L+ R respectively from the preamplifier to find out what is wrong ...Remains a problem that this one is a DC coupling amplifier so any behavior like that coming from the preamplifier or the power supply of it will be transferred to the main amplifier and of course will be "volume controlled ".
Volume controlled though could apply to amplifiers with classic and passive volume control In your case it doesn't seem to apply since the volume is digital and the pre out is coming from the digital IC R2S15205FP.
Troubleshooting ...
heat gun with narrow nose and freeze spray is your weapons First you need to isolate the problem to make sure where is this coming from My gut says that this should be the IC but as said reading your post didn't explain to me where the fault comes from .
Either this is a pre or a main issue the best thing to do will be to monitor voltage in the output of the main amplifier before the relay at a first stage and start trying to trace it down and after you are sure its not the main amps then you should monitor DC voltage in the input of the amplifier .
One thing about the freezing spray:
freezing spray is most of the times a pointer to a direction BUT when the problem is minor often there is chance that freezing the opposite transistor and alter the working conditions and the characteristics of the specific transistor might momentary solve the problem but this doesn't mean that you got it ....Momentary fix is because the frozen transistors effects the circuit in a way that helps it doesn't always mean that is broken . Heat Gun will behave alike you will be very surprised to see the variations of offset when you apply heat in the input transistors .
One thing you should look at also is grounds , make sure that all ground connectors are firm , clean and tight I have seen amps having stability problems because the screws of the RCA input bay was not tight and failing to provide proper ground to the circuits (manufacturer wrong chooses to provide ground to circuits this way , behind some RCA there was a metal string and the screw had to tight the external cover , the RCA bay and the ground string .... )
Kindest regards
Sakis
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Yes amp pops with volume up with or without music playing and also with or without inputs connected. Amp also pops with only a single speaker connected on either side and through preout with no speakers connected. It seems more quiet through the sub but probably because I have turned it down to prevent damage.
The dc offset has been zero every time I have measured it but I have not measured it during a pop.
I took out all of the boards today and carefully resolder ing every joint. Just got the right channel power amp left to do - haven't found anything obvious so far
The dc offset has been zero every time I have measured it but I have not measured it during a pop.
I took out all of the boards today and carefully resolder ing every joint. Just got the right channel power amp left to do - haven't found anything obvious so far
as about "mechanical failure " of transistors ( stand alone or inside an IC ) you have to think about it as a metal plate with the die ark welded on it ....
When the transistor warms up from room temp to operating temp parts expand inside (and outside ) when the transistor powers down then it cools to room temp and sizes come back to the previous stage .
This type of daily torture of the die and the metal plate often causes a minor destruction of the welding ...So freezing it while warm makes actually the welding to work again since the all part will shrink ....or by heating it if in room temp will present you a bigger failure that will only show up if the transistor is warm to operating temp or far above that .
This is more or less heat or freeze help you out to trace the specific mechanical issue of the transistors ( Remember transistors have other types of failure also )
Kind regards
Sakis
When the transistor warms up from room temp to operating temp parts expand inside (and outside ) when the transistor powers down then it cools to room temp and sizes come back to the previous stage .
This type of daily torture of the die and the metal plate often causes a minor destruction of the welding ...So freezing it while warm makes actually the welding to work again since the all part will shrink ....or by heating it if in room temp will present you a bigger failure that will only show up if the transistor is warm to operating temp or far above that .
This is more or less heat or freeze help you out to trace the specific mechanical issue of the transistors ( Remember transistors have other types of failure also )
Kind regards
Sakis
"It happens to both channels and through the preout too. "
So, problem must be somewhere around Board-A Function Assy. or its power circuit. I do not think power amplier or any other circuit is faulty.
Intermittent problem is hard to solve.
So, problem must be somewhere around Board-A Function Assy. or its power circuit. I do not think power amplier or any other circuit is faulty.
Intermittent problem is hard to solve.
Focus please ...the info you give is useless :Yes amp pops with volume up with or without music playing and also with or without inputs connected
Amp also pops with only a single speaker connected on either side
and through preout with no speakers connected.
Now the last one is absolutely pointless one thing can and will not effect the other
One that have the skills to do clean soldering on these boards should be also able to understand the information i gave
Measuring in the pre out during the problem is all it takes and as it goes it points to the IC can you resolder that also ?
Firstly thank you for your help I really do appreciate it. I put the amp back together again and checked it was working fine. Music clean and no popping. I removed the input and used a heat gun onto the ic - it started popping immediately and a lot more frequently. I chilled it with the freezer spray and it stopped. The component density around the ic is fairly dense and it took a fair bit of heat to get it going but it seems the ic is the culprit and so too Sakis's original gut instinct. I will source a replacement and report back. The ic is restrained with a hard glue material - what do I replace this with?
I think you have misunderstood the context 🙂
If freezing a transistor suddenly corrects a fault such as random popping noise, then it (or surrounding parts affected by the cold) has to be suspect.
Obtaining an audio control IC (R2S15205FP) is not straight forward. Pioneer put me onto their parts supplier who want £100 to special order the item. There are however plenty listed on aliexpress for a fraction of that price.
I'm tempted to go to aliexpress - are counterfeit ICs likely?
I'm tempted to go to aliexpress - are counterfeit ICs likely?
I wouldn't like to say over the counterfeit question. £100 sounds like a made up price tbh, I would have expected something more in the £20-30 from a manufacturer.
Have you ever replaced anything like this before ? an 80 pin SMD device isn't something to experiment on.
Have you ever replaced anything like this before ? an 80 pin SMD device isn't something to experiment on.
Yes I have a background in electronics & done SMD repairs before. I have access to a SMD rework station although planning to use chip quik for the extraction.
I was surprised that the IC is on special order and not available from the usual suppliers either, Renesas the OEM have it listed as EOL. I have ordered from Aliexpress.
I was surprised that the IC is on special order and not available from the usual suppliers either, Renesas the OEM have it listed as EOL. I have ordered from Aliexpress.
I've watched a number of people try the DIY approach to sourcing and fitting microcontrollers. It really is a headache as well as a difficult and protracted exercise when any necessary firmware becomes an issue too. The costs keep mounting if practical help is finally needed to complete that, as I have more than once.
I wonder about this comment: "The ic is restrained with a hard glue material.." I would have thought 80 solder joints would hold anything with an iron grip, so where is the glue actually applied? If it's applied over the joins, then is this an anti-tampering measure or is it another IC format, where the chip itself is bonded directly to the board and covered with a blob of black epoxy?
It's not a particularly old amplifier and apparently has very good sound quality for the price, 'Not a cheap repair, but assuming you are successful at removing and replacing the chip without damage, should be worthwhile. The alternatives of selling it off as a dodgy amp. on Ebay or leaving it to gather dust in the attic, surely can't be attractive anyway.
I wonder about this comment: "The ic is restrained with a hard glue material.." I would have thought 80 solder joints would hold anything with an iron grip, so where is the glue actually applied? If it's applied over the joins, then is this an anti-tampering measure or is it another IC format, where the chip itself is bonded directly to the board and covered with a blob of black epoxy?
It's not a particularly old amplifier and apparently has very good sound quality for the price, 'Not a cheap repair, but assuming you are successful at removing and replacing the chip without damage, should be worthwhile. The alternatives of selling it off as a dodgy amp. on Ebay or leaving it to gather dust in the attic, surely can't be attractive anyway.
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excellent. Bonding of SMD chips to the PCB is standard practice. When you are sure all the legs are free, a little light 'lifting' pressure under a corner will usually crack it off cleanly. If its a 'toughie' then chunky pliers to grip and twist the package will crack it of in an instant. And if all the legs weren't free... that is the time you find out.
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