Hi everyone!
i buoght a semi-new Audison LRx1.400 with broken power supply and output mosfets.
I substitute original 60N06 with new IRF3205 in the power supply (with 10ohm gate resistor) and the PS works fine.
The output stage is made by 8 IRF9640 + 6 IRF640N.
I have a problem that i cannot resolve:
At idle (1.4A current draw..correct) the amplifier works fine. Non heat, no ringing, everything's ok.
When i put a test signal (sinewave 50hz for example) 1Vrms and gain at minimum, with 4ohm resistive load (or speaker), the amplifier works fine for some seconds...than it goes on protection because there's an output N mosfet broken.
Only N mosfet (IRF640N) get broken..and it's random which mosfet fails.
I check all gate resistor (47ohm) and other resistors beside the output stage. All value are ok (all measure with desoldered component, obviously).
I replace output stage 10 times!!! Every time one, only one, N mosfet fail.
I try to reduce biasing..but same problem.
I try to increase biasing (3A idle) but same problem.
Always 3-4 seconds play......then, without blow, heat or fire.....random one fails!
At idle, gate N voltage is 4.5V. P gate voltage is -4V. All clear.
Rail voltage is +-52V regulated.
Emitter resistor are 0.15ohm. All desolder have similar 0.15ohm value. seems correct.
Driver stage is made by 2SD2400A and 2SB1569...could be them? They seems fine..
With o-scope, before the failure, everything seems ok. No distortion, no clipping..nothing. Only clear signal.
The failure happens with easy load (4ohm) and low power (20Wrms).
The amp should be capable of 900Wrms @1ohm!!!
With no-load, the output stage don't fail, even with clipping.
How could it be??
I'm going crazy!
I repaired lots of amplifier in my country, but i cannot fix it!
Please help.
thank you guys!
i buoght a semi-new Audison LRx1.400 with broken power supply and output mosfets.
I substitute original 60N06 with new IRF3205 in the power supply (with 10ohm gate resistor) and the PS works fine.
The output stage is made by 8 IRF9640 + 6 IRF640N.
I have a problem that i cannot resolve:
At idle (1.4A current draw..correct) the amplifier works fine. Non heat, no ringing, everything's ok.
When i put a test signal (sinewave 50hz for example) 1Vrms and gain at minimum, with 4ohm resistive load (or speaker), the amplifier works fine for some seconds...than it goes on protection because there's an output N mosfet broken.
Only N mosfet (IRF640N) get broken..and it's random which mosfet fails.
I check all gate resistor (47ohm) and other resistors beside the output stage. All value are ok (all measure with desoldered component, obviously).
I replace output stage 10 times!!!
Every time one, only one, N mosfet fail.I try to reduce biasing..but same problem.
I try to increase biasing (3A idle) but same problem.
Always 3-4 seconds play......then, without blow, heat or fire.....random one fails!
At idle, gate N voltage is 4.5V. P gate voltage is -4V. All clear.
Rail voltage is +-52V regulated.
Emitter resistor are 0.15ohm. All desolder have similar 0.15ohm value. seems correct.
Driver stage is made by 2SD2400A and 2SB1569...could be them? They seems fine..
With o-scope, before the failure, everything seems ok. No distortion, no clipping..nothing. Only clear signal.
The failure happens with easy load (4ohm) and low power (20Wrms).
The amp should be capable of 900Wrms @1ohm!!!
With no-load, the output stage don't fail, even with clipping.
How could it be??
I'm going crazy!
I repaired lots of amplifier in my country, but i cannot fix it!
Please help.
thank you guys!
"Driver stage is made by 2SD2400A and 2SB1569...could be them? They seems fine.."
Possibly it could have bad driver transistors.
I work on Audisons here in the US and I have repaired a few of these but nothing like what you described. Perhaps we are missing something like the drivers and integrator circuitry, I have seen bad ICs, and leaky drivers cause similar issues. After all this is class D either the fet is full on or full off. Have you checked dead time for cross conduction issues ? This might explain repeated blown single outputs device at any power level.
Audison is local to you, I am amazed they have not been of assistance to you already. Can they supply you a PDF of the output and driver stage of this amp ? I have never needed one so far. And my only reference is the LRx5.1k..But I will try to help if possible....Ciao
Possibly it could have bad driver transistors.
I work on Audisons here in the US and I have repaired a few of these but nothing like what you described. Perhaps we are missing something like the drivers and integrator circuitry, I have seen bad ICs, and leaky drivers cause similar issues. After all this is class D either the fet is full on or full off. Have you checked dead time for cross conduction issues ? This might explain repeated blown single outputs device at any power level.
Audison is local to you, I am amazed they have not been of assistance to you already. Can they supply you a PDF of the output and driver stage of this amp ? I have never needed one so far. And my only reference is the LRx5.1k..But I will try to help if possible....Ciao
Hi,
thank you for reply.
This is NOT a class D
This is a class AB with drivers in full class A (heat a lot!).
I've repaired other Audison like VR/LR series and Thesis Series, but anyone had this type of schematic.
The schematic is simple, like all class A/B.
Differential amp, driver, output mosfet.
Differential amp is in SMD, but works because there's not distortion.
For that 3-4-5 seconds, the amps work.
I try connect a ReAudio subwoofer and play music for 2 minutes. Amplifier seems work but then......failure..same random N channel mosfet
I never see that problem before in class AB amplifier
I know that Audison/Elettromedia is in my country but they always answer "if you have a problem, send the amplifier to our tech assistance....." (i add....""and pay so much!!"")
I post some measure.
- Gate resistor are 47 ohm.
- There is a 22ohm SMD resistor with one leg on emitter, and other leg together with other 22ohm resistor from other output N mosfets.
If i measure every resistor desoldered, i measure 22ohm correct.
But, if i mount all of them, i measure 3.8ohm...
Maybe 22ohm paralleled for 6 times, makes 3ohm....mmmm..maybe to little.
This afternoon i try to re-check those resistor, but in the P-channel section, all 22ohm paralled for 8 times, makes 3ohm
- For emitter resistor measure i use a volt-ampetometric measure. I put 1V and measure the current. Then i calculated the resistance.
Not professional, but efficent. all value are 0.16, 0.17,... 0.15 +- 0.02. Seems ok for indicated 0.15 value.
Do you have and output mosfet (IRF640/IRF9640) or bjt??
If you have mosfet, could you measure the gate idle voltage??
Mine is 4.5V for n-channel and -4V for p-channel. Seems right
Thank you!
Ciao!
ps: driver pin voltage are:
- external (1 and 3) to rail voltage (both positive or both negative)
- central (pin2) has the gate idle voltage: 4.5V for gates N channel mosfet, -4V for gates P-channel mosfet
thank you for reply.
This is NOT a class D
This is a class AB with drivers in full class A (heat a lot!).
I've repaired other Audison like VR/LR series and Thesis Series, but anyone had this type of schematic.
The schematic is simple, like all class A/B.
Differential amp, driver, output mosfet.
Differential amp is in SMD, but works because there's not distortion.
For that 3-4-5 seconds, the amps work.
I try connect a ReAudio subwoofer and play music for 2 minutes. Amplifier seems work but then......failure..same random N channel mosfet
I never see that problem before in class AB amplifier
I know that Audison/Elettromedia is in my country but they always answer "if you have a problem, send the amplifier to our tech assistance....." (i add....""and pay so much!!"")
I post some measure.
- Gate resistor are 47 ohm.
- There is a 22ohm SMD resistor with one leg on emitter, and other leg together with other 22ohm resistor from other output N mosfets.
If i measure every resistor desoldered, i measure 22ohm correct.
But, if i mount all of them, i measure 3.8ohm...
Maybe 22ohm paralleled for 6 times, makes 3ohm....mmmm
..maybe to little.This afternoon i try to re-check those resistor, but in the P-channel section, all 22ohm paralled for 8 times, makes 3ohm
- For emitter resistor measure i use a volt-ampetometric measure. I put 1V and measure the current. Then i calculated the resistance.
Not professional, but efficent. all value are 0.16, 0.17,... 0.15 +- 0.02. Seems ok for indicated 0.15 value.
Do you have and output mosfet (IRF640/IRF9640) or bjt??
If you have mosfet, could you measure the gate idle voltage??
Mine is 4.5V for n-channel and -4V for p-channel. Seems right
Thank you!
Ciao!
ps: driver pin voltage are:
- external (1 and 3) to rail voltage (both positive or both negative)
- central (pin2) has the gate idle voltage: 4.5V for gates N channel mosfet, -4V for gates P-channel mosfet
Last edited:
Original original i don't know because it arrived with only 2 P-channel and no N-channel.
Original P's are IRF9640 from IR.
Then, i buy fist IRF640N from Ebay (not fake), than IRF640NPbF from RSComponent.
Same problem.
Yesterday i replace all output, both P's & N's with all Pb Free parts, IRF9640PbF and IRF640NPbF.....but same problem.
Random N-channel mosfet fail without blown or something.
Failure consiste in both Gate-Drain and Drain-Emitter 0 ohm reading.
Original P's are IRF9640 from IR.
Then, i buy fist IRF640N from Ebay (not fake), than IRF640NPbF from RSComponent.
Same problem.
Yesterday i replace all output, both P's & N's with all Pb Free parts, IRF9640PbF and IRF640NPbF.....but same problem.
Random N-channel mosfet fail without blown or something.
Failure consiste in both Gate-Drain and Drain-Emitter 0 ohm reading.
OK so we are dealing with a linear amp stage not a digital one, opps my bad .
I see so many of the D class amps. I have not seen a linear mosfet output stage Audison product. All the LRx 400's I have seen here were D class not linear AB.
I currently have 8 LRx5.1k's and four LRx500.2 and three LRx400.2's here for repair. None of which have a linear mosfet output stage in any of them.
The random fet failure is puzzling, I have seen insulator failure in these amps. With holes being blown into the sink through the insulator that has failed, and of course output failures. Audison loves to run high voltage rails inside their amp products, everything I have here has +&- 80 volt rails inside of them.
Are you just replacing the single bad fet upon failure ?
I don't have a sample amp to check the 4 and 4.5 volt gate drive voltage reference your mentioning but something has to be causing these fets to be pushed into failure like they are. And if its not bad outputs then it has to be the driver circuitry breaking down somewhere and possibly causing the outputs to be pushed into failure mode. The speed at which it is happening is just crazy fast.
I have seen similar issues in Phoenix Gold mosfet amps and it was always a problem with the diff amp and driver stage and the bias circuitry running outside of spec. How is this 4 and 4.5 volt signal derived in the circuitry, and what is it using for a temp sensor for thermal tracking ? Please can you post a close up picture of the amp driver section and output stage for me, or PM me with them.
I need to be on the same page with you, so I do not speak redundantly about this amps troubles.
Ciao
. I see so many of the D class amps. I have not seen a linear mosfet output stage Audison product. All the LRx 400's I have seen here were D class not linear AB.
I currently have 8 LRx5.1k's and four LRx500.2 and three LRx400.2's here for repair. None of which have a linear mosfet output stage in any of them.
The random fet failure is puzzling, I have seen insulator failure in these amps. With holes being blown into the sink through the insulator that has failed, and of course output failures. Audison loves to run high voltage rails inside their amp products, everything I have here has +&- 80 volt rails inside of them.
Are you just replacing the single bad fet upon failure ?
I don't have a sample amp to check the 4 and 4.5 volt gate drive voltage reference your mentioning but something has to be causing these fets to be pushed into failure like they are. And if its not bad outputs then it has to be the driver circuitry breaking down somewhere and possibly causing the outputs to be pushed into failure mode. The speed at which it is happening is just crazy fast.
I have seen similar issues in Phoenix Gold mosfet amps and it was always a problem with the diff amp and driver stage and the bias circuitry running outside of spec. How is this 4 and 4.5 volt signal derived in the circuitry, and what is it using for a temp sensor for thermal tracking ? Please can you post a close up picture of the amp driver section and output stage for me, or PM me with them.
I need to be on the same page with you, so I do not speak redundantly about this amps troubles.
Ciao
Last edited:
Now i go lunch
Then i'll try to replace mica insulator, and i'll post some pics
thank you!
Its 4:30 AM here I will nap a bit as i had a late poker game last night and have not rested yet...More later....
mica replaced...
10 seconds plays at 20Wrms @4ohm.....then failure
good, the problem isn't mica.
Monday i'll buy new N parts.
I have IRF9640PbF from Vishay. Can i buy IRF640PbF (not NPbF) from Vishay???
IR doesn't product IRF640 without N. In the website they redirect to Vishay that product IRF640 and IRF640PbF.
IRF640 by IR are on ebay but i've to wait 20 days for shipping (from China or USA)
10 seconds plays at 20Wrms @4ohm.....then failure
good, the problem isn't mica.
Monday i'll buy new N parts.
I have IRF9640PbF from Vishay. Can i buy IRF640PbF (not NPbF) from Vishay???
IR doesn't product IRF640 without N. In the website they redirect to Vishay that product IRF640 and IRF640PbF.
IRF640 by IR are on ebay but i've to wait 20 days for shipping (from China or USA
)I don't know if the 640N is the problem but I do know that the 540N causes problems.
When using the 540Ns in Rockford amps, there are all sorts of problems. At their worst, they wouldn't even allow the amp to power up. It would instantly go into over-current protection. It did it so quickly that the amp meter on the power supply barely moved. Other times, they would fail as they're doing in your amp. Sometimes they would play but distorted intermittently. The problems are not consistent other than consistently causing problems. In all of the Rockford amps that I tried the 540Ns in, they caused problems. They were replaced with 540s or 540As and the amps worked perfectly with no other changes. You can't always rely on the specs in the datasheets to determine what will work and what will cause problems. I know people get tired of me telling them to use the exact original parts but I've seen too many amps that were sensitive to minor changes. Sometimes, minor changes in the original parts will make a part incompatible even though the manufacturer has the same part number on it.
Again, I don't know if this will solve your problem but if you've eliminated everything else, you should try using something other than the 640Ns.
When using the 540Ns in Rockford amps, there are all sorts of problems. At their worst, they wouldn't even allow the amp to power up. It would instantly go into over-current protection. It did it so quickly that the amp meter on the power supply barely moved. Other times, they would fail as they're doing in your amp. Sometimes they would play but distorted intermittently. The problems are not consistent other than consistently causing problems. In all of the Rockford amps that I tried the 540Ns in, they caused problems. They were replaced with 540s or 540As and the amps worked perfectly with no other changes. You can't always rely on the specs in the datasheets to determine what will work and what will cause problems. I know people get tired of me telling them to use the exact original parts but I've seen too many amps that were sensitive to minor changes. Sometimes, minor changes in the original parts will make a part incompatible even though the manufacturer has the same part number on it.
Again, I don't know if this will solve your problem but if you've eliminated everything else, you should try using something other than the 640Ns.
thank you Perry,
for me there's no problem try the normal IRF640. Cost is similar in my country. The only difference is that N version can be ordered single, and non-N version only in stock (50 pieces).
No problem because i can always use them for several works
Next week i'll buy them and try.
for me there's no problem try the normal IRF640. Cost is similar in my country. The only difference is that N version can be ordered single, and non-N version only in stock (50 pieces).
No problem because i can always use them for several works
Next week i'll buy them and try.
Hi,
thank you for reply.
This is NOT a class D
This is a class AB with drivers in full class A (heat a lot!).
I've repaired other Audison like VR/LR series and Thesis Series, but anyone had this type of schematic.
The schematic is simple, like all class A/B.
Differential amp, driver, output mosfet.
Differential amp is in SMD, but works because there's not distortion.
For that 3-4-5 seconds, the amps work.
hi,
can you please email me a copy of the schematic?
djquan128 'at' hotmail 'dot' com
I have one here that runs normally but goes into protect in random but when it doesn't, it plays fine.
thanks.
I have SOME documents but not this one, Sorry... I got a real nagging issue to ask about openly.
The number of output devices does not make sense to me. Please bear with this its a bit long.
You said "The output stage is made by 8 IRF9640 + 6 IRF640N."
In Class D amps you always see a 2 to 1 ratio of P to N outputs. Say four 9640 to every two 640. This is due to the fact that the P device is only rated at half the current of the N device. And in a few you see banks of three of each device to mimic a larger device but in balanced number like three P and then three N and so on.
Now in all linear AB type amps using this device you always see equal number P devices to N devices. Say Five P to five N devices like Rf and many others Linear AB amps. Never any odd numbers.
In this amp you say you have Eight P devices and Six N devices and that it is a Class AB amp. This number puzzles me as that it is nothing like any other amp I have ever seen.
You also mention that the amp came to you missing most of its output devices, like someone else had removed them before you got the amp.
I am wondering if this amp uses Six P devices and Six N devices and there are two missing driver devices in there somewhere ??? This number makes sense to me as it is balanced and logical by all other designs I have seen.
Now I am very much need to see detailed picture of output stage and driver circuitry cause none of what I have ever seen matches what you say you have in this amp...I am very puzzled by this odd number thing.... Please advise me when you can, and if possible a picture please, as best as you can do.... I need to see why this amp is unlike any other I have ever seen....
djQUAN could you please verify for me that the output stage is a mismatched number of devices like pergo describes? I am very puzzled why this is. In my mind I can see no reason why the 8 P devices to 6 N devices ratio. This does not look right to me and my memory of all other amps I have worked on... Many thanks......Ciao
The number of output devices does not make sense to me. Please bear with this its a bit long.
You said "The output stage is made by 8 IRF9640 + 6 IRF640N."
In Class D amps you always see a 2 to 1 ratio of P to N outputs. Say four 9640 to every two 640. This is due to the fact that the P device is only rated at half the current of the N device. And in a few you see banks of three of each device to mimic a larger device but in balanced number like three P and then three N and so on.
Now in all linear AB type amps using this device you always see equal number P devices to N devices. Say Five P to five N devices like Rf and many others Linear AB amps. Never any odd numbers.
In this amp you say you have Eight P devices and Six N devices and that it is a Class AB amp. This number puzzles me as that it is nothing like any other amp I have ever seen.
You also mention that the amp came to you missing most of its output devices, like someone else had removed them before you got the amp.
I am wondering if this amp uses Six P devices and Six N devices and there are two missing driver devices in there somewhere ??? This number makes sense to me as it is balanced and logical by all other designs I have seen.
Now I am very much need to see detailed picture of output stage and driver circuitry cause none of what I have ever seen matches what you say you have in this amp...I am very puzzled by this odd number thing.... Please advise me when you can, and if possible a picture please, as best as you can do.... I need to see why this amp is unlike any other I have ever seen....
djQUAN could you please verify for me that the output stage is a mismatched number of devices like pergo describes? I am very puzzled why this is. In my mind I can see no reason why the 8 P devices to 6 N devices ratio. This does not look right to me and my memory of all other amps I have worked on... Many thanks......Ciao
Last edited:
Audison LRx 1.400 - Amp Guts
this is the amp.
real photos soon
It's true, it arrived without output stage but a friend (that use LRx1.400 power supply for 2 Ucd400) said that IRF9640 and IRF640 are correct model.
Luckly i'm not a noob and i agree with you...it's strange having 8 P-channel and 6 N-channel in linear amp.
But solder side said same thing: 8+6 output mosfet
They are really output mosfet: same gate resistor, same emitter resistor, same idle gate voltage (for each type), same supply, same signal (when i apply signal without load).
If it's a driver problem, i think that output stage should fail even without load.
But it fails only with load...an easy one (4ohm pure resistive)
Now i'm tired between this Audison and another repairs
Tomorrow some real pics
this is the amp.
real photos soon
It's true, it arrived without output stage but a friend (that use LRx1.400 power supply for 2 Ucd400
) said that IRF9640 and IRF640 are correct model.Luckly i'm not a noob
and i agree with you...it's strange having 8 P-channel and 6 N-channel in linear amp.But solder side said same thing: 8+6 output mosfet
They are really output mosfet: same gate resistor, same emitter resistor, same idle gate voltage (for each type), same supply, same signal (when i apply signal without load).
If it's a driver problem, i think that output stage should fail even without load.
But it fails only with load...an easy one (4ohm pure resistive)
Now i'm tired between this Audison and another repairs
Tomorrow some real pics
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.