I have a couple of angry 500/1 mono amps. One I've had since new the recently zonked on me on startup. A short squeal and a mild thump and it was quiet.
I replaced it with a spare I had on the shelf in the basement that worked fine for a couple of weeks and then performed the same noise and silence program. I was pretty worried that something in my truck caused the two failures. I double checked the power supply, switching and signals and all looked as it should.
I pulled the first amp apart and found a smoked transistor and FET on the power output side. Thinking those shouldn't be too tough to swap out, I landed here looking for advice and parts.
Realizing I might have a donor amp, I pulled the second one apart and found all of the gate resisters smoked on the Power Supply side. Everything else looks in good condition relative to the other amp.
With the two completely different issues it looks like the truck isn't the problem, just two failures in two old amplifiers.
The parts for the repairs don't look too expensive. Cheapest would likely be to bring the amps to a proper repair shop, but then I wouldn't be any smarter. So I'm looking at buying a couple hundred in parts and tools to make the replacements in the two amps.
I'm not sure that's the smartest route to take, but I'll throw it out there for your input.
J
I replaced it with a spare I had on the shelf in the basement that worked fine for a couple of weeks and then performed the same noise and silence program. I was pretty worried that something in my truck caused the two failures. I double checked the power supply, switching and signals and all looked as it should.
I pulled the first amp apart and found a smoked transistor and FET on the power output side. Thinking those shouldn't be too tough to swap out, I landed here looking for advice and parts.
Realizing I might have a donor amp, I pulled the second one apart and found all of the gate resisters smoked on the Power Supply side. Everything else looks in good condition relative to the other amp.
With the two completely different issues it looks like the truck isn't the problem, just two failures in two old amplifiers.
The parts for the repairs don't look too expensive. Cheapest would likely be to bring the amps to a proper repair shop, but then I wouldn't be any smarter. So I'm looking at buying a couple hundred in parts and tools to make the replacements in the two amps.
I'm not sure that's the smartest route to take, but I'll throw it out there for your input.
J
Power supplies don't burn up by themselves. Their failure is generally a symptom of a problem inside the audio section of the amp also. So its not as cut and dried as it looks to be in 99% of the cases.
For the money your talking about JL used to be able to replace these, although due to their age I am not so sure this repair / replacement program still applies. It did in the 90's when these amps were new.
I can say that when the power supply mosfets burn out they tend to take out the gate resistors and the gate drivers 90% of the time, and once repaired the audio output section generally has fried outputs also along with the possibility of the driver section having sustained serious damage also. Most class D amps are total rebuilds anyway, and with the age of your amps you may also be in need of new caps inside the amp among a few other things that tend to go bad with age and use.
So unless your in love with these yesteryear amps you might want to look into newer ones since prices have dropped significantly for these devices since back in the 90's and suitable replacements are fairly cheap now and they come with some handsome warranty lifespans now also. As I recall these amps only had 90 day warranties anyway, maybe one year at most, even back then when they were newish and still the hot ticket to have.
With that all said, the parts to repair one of these will likely be less then $40.00 US retail in most cases. Its the time sink involved and the tools required and the other related possible causes that will price drive any repair attempt.
Also these amps are NOT the simplest to work on, and often require finding new replacement clamps that hold all those power devices clamped to the sink surface. I see folks looking for them all the time here on the DIY. I think Perry Babin has a second source for them listed in one the 2 dozen or so threads about these amps and their repairs that he has posted here.
Perhaps a use of the site search bar at the top of the page could bring all of those up for you to thumb thru to get a general idea of what your headed for repairing these Jl amps. Perry has done a lot of excellent work on them already posted here on the car audio forum of the DIY. More then enough to guide anyone thru one of these amps on a self tutoring adventure.
Please don't take my word for all of this, and please do by all means use the site search bar located near the top of the page to search JL amp repair. Use that info as your best guide to weather or not you have chosen the best pathway for your endevour. I know as I have read most of his threads concerning these exact same amps and I am sure you can and will find just about every question you might run into answered in his repair threads he has already posted. If anything you will at least be able to pickup on whats inside of these amps and how to go about completing common repairs they tend to need upon failure.
For the money your talking about JL used to be able to replace these, although due to their age I am not so sure this repair / replacement program still applies. It did in the 90's when these amps were new.
I can say that when the power supply mosfets burn out they tend to take out the gate resistors and the gate drivers 90% of the time, and once repaired the audio output section generally has fried outputs also along with the possibility of the driver section having sustained serious damage also. Most class D amps are total rebuilds anyway, and with the age of your amps you may also be in need of new caps inside the amp among a few other things that tend to go bad with age and use.
So unless your in love with these yesteryear amps you might want to look into newer ones since prices have dropped significantly for these devices since back in the 90's and suitable replacements are fairly cheap now and they come with some handsome warranty lifespans now also. As I recall these amps only had 90 day warranties anyway, maybe one year at most, even back then when they were newish and still the hot ticket to have.
With that all said, the parts to repair one of these will likely be less then $40.00 US retail in most cases. Its the time sink involved and the tools required and the other related possible causes that will price drive any repair attempt.
Also these amps are NOT the simplest to work on, and often require finding new replacement clamps that hold all those power devices clamped to the sink surface. I see folks looking for them all the time here on the DIY. I think Perry Babin has a second source for them listed in one the 2 dozen or so threads about these amps and their repairs that he has posted here.
Perhaps a use of the site search bar at the top of the page could bring all of those up for you to thumb thru to get a general idea of what your headed for repairing these Jl amps. Perry has done a lot of excellent work on them already posted here on the car audio forum of the DIY. More then enough to guide anyone thru one of these amps on a self tutoring adventure.
Please don't take my word for all of this, and please do by all means use the site search bar located near the top of the page to search JL amp repair. Use that info as your best guide to weather or not you have chosen the best pathway for your endevour. I know as I have read most of his threads concerning these exact same amps and I am sure you can and will find just about every question you might run into answered in his repair threads he has already posted. If anything you will at least be able to pickup on whats inside of these amps and how to go about completing common repairs they tend to need upon failure.
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Thanks for the input. That's precisely what I was looking for. Spent the best part of Sunday on the amp tutorial and reading the various threads. There's lots to read and I can see there can be lots to replace when it goes wrong. The volume doesn't frighten me but I don't have the experience to know where to start and stop.
One has a damaged power supply but the other is just damaged output gear. The clips I have lots of. Is it worth stealing parts from one to fix the other? Perhaps as a learning exercise. Huh?
I'm not in love with these amps, but I'm not sure what direction to go either. I bought the old one in 2003. I know I can pick up new slash amps for cheap. Maybe another brand?
I have a spare 300/4 that I could use short term. I guess I'd rather fix than replace because I'm cheap. I like the idea of learning something too.
J
One has a damaged power supply but the other is just damaged output gear. The clips I have lots of. Is it worth stealing parts from one to fix the other? Perhaps as a learning exercise. Huh?
I'm not in love with these amps, but I'm not sure what direction to go either. I bought the old one in 2003. I know I can pick up new slash amps for cheap. Maybe another brand?
I have a spare 300/4 that I could use short term. I guess I'd rather fix than replace because I'm cheap. I like the idea of learning something too.
J
For the power supply, I've been using the IRF3205s. For the output transistors, I've been using the IRF3710Zs.
The cost of the parts is insignificant (compared to replacing the amps). If you have no soldering iron, desoldering pump, solder, desoldering braid..., it could get expensive to repair them but less than it would cost to have JL repair them.
The cost of the parts is insignificant (compared to replacing the amps). If you have no soldering iron, desoldering pump, solder, desoldering braid..., it could get expensive to repair them but less than it would cost to have JL repair them.
I got as far as finding the parts you suggested. Even put together the order on digikey. If the outputs and gate transistors are repair parts, I'm thinking I can make it all work. If the trail of disaster heads back up the board, I'm worried my brain and patience will suffer.
For the time and shipping, I think I'll place the order and see where I get to. I was thinking of using my automotive soldering iron, but I now think that's asking for trouble.
I think I'm going to look just a little deeper on the transistor side and get all 3 of the parts, just replace them all.
The one issue I'm still floating around is the resisters on the power supply side. Digikey part I've got in the cart is S47CACT-ND.
Sound right? J
For the time and shipping, I think I'll place the order and see where I get to. I was thinking of using my automotive soldering iron, but I now think that's asking for trouble.
I think I'm going to look just a little deeper on the transistor side and get all 3 of the parts, just replace them all.
The one issue I'm still floating around is the resisters on the power supply side. Digikey part I've got in the cart is S47CACT-ND.
Sound right? J
The link didn't work. You need 47 ohm, 1206 size SMD resistor if it uses SMD gate resistors.
Also order 2SB1260 and 2SD1898 transistors. They will replace the driver transistors which sometimes fail.
Also order 2SB1260 and 2SD1898 transistors. They will replace the driver transistors which sometimes fail.
I'm going to be smarter after this for sure.
I've got two boards. Maybe I need two threads. Let me know.
My rev 11 board has the power supply issue. I've planned to order the fets and resistors (through hole R600-607) for the supply. I hadn't planned on picking up transistors (Q608-611).
My rev 3 board has the driver issue. I put fets and transistors in the cart on digikey for the driver side. I got the part reference from another of your threads on this amp. I added the 2sb1260 and 2sd1898 on top of the KSA1220a and ksc2690a I read on another thread.
I did double up on the quantities in case there's a do-over or they're needed on both boards.
J
I've got two boards. Maybe I need two threads. Let me know.
My rev 11 board has the power supply issue. I've planned to order the fets and resistors (through hole R600-607) for the supply. I hadn't planned on picking up transistors (Q608-611).
My rev 3 board has the driver issue. I put fets and transistors in the cart on digikey for the driver side. I got the part reference from another of your threads on this amp. I added the 2sb1260 and 2sd1898 on top of the KSA1220a and ksc2690a I read on another thread.
I did double up on the quantities in case there's a do-over or they're needed on both boards.
J
When you replace the 47 ohm through-hole resistors, leave about 1/8" between the body of the resistor and the board. If they burn again, they won't damage the board as much. Don't install them so high that they interfere with the clamp.
In another thread there were comments regarding the resistance between the RCA neutral and the head unit and amp grounds.
On my operational JL 300/4, there's a high resistance between the outer RCA conductor and the chassis of the amp. (2.2 MOhms)
On my head unit, the outer conductor is connected to the chassis ground of the truck.
I've got a slight snap from time to time when the amp powers down. I haven't narrowed it down, but I'm thinking that I'd be cautious and build some redundant grounding at the back of the headunit, and between the RCAs, chassis, battery, capacitor and Amplifiers.
Don't know if that will cure the noise, but I'll have something to do while I'm waiting for amp parts.
On my operational JL 300/4, there's a high resistance between the outer RCA conductor and the chassis of the amp. (2.2 MOhms)
On my head unit, the outer conductor is connected to the chassis ground of the truck.
I've got a slight snap from time to time when the amp powers down. I haven't narrowed it down, but I'm thinking that I'd be cautious and build some redundant grounding at the back of the headunit, and between the RCAs, chassis, battery, capacitor and Amplifiers.
Don't know if that will cure the noise, but I'll have something to do while I'm waiting for amp parts.
Back to the fun at hand:
I pulled out the supply and output FETs today. Of the 12, 2 tested good according to the test sequence. So gladly I have enough to replace them all.
I replaced all of the gate resistors and though they all looked burnt, they tested within 10% of each other. No shorts or opens.
I tested as many of the other resistors that I could find. I didn't find any that looked burnt or read outside of what I can interpret from their markings.
You had me pick up some driver transistors. Should I replace those just while I'm in there, or is there a test sequence I should proceed with before removing them?
Thanks for your help. J
I pulled out the supply and output FETs today. Of the 12, 2 tested good according to the test sequence. So gladly I have enough to replace them all.
I replaced all of the gate resistors and though they all looked burnt, they tested within 10% of each other. No shorts or opens.
I tested as many of the other resistors that I could find. I didn't find any that looked burnt or read outside of what I can interpret from their markings.
You had me pick up some driver transistors. Should I replace those just while I'm in there, or is there a test sequence I should proceed with before removing them?
Thanks for your help. J
With the power supply FETs out of the board, power up the amp and confirm that you read about 5v DC with the red probe on leg 1 and the black probe on leg 3. Do this for all 8 FETs.
You would only replace the drivers if necessary.
You would only replace the drivers if necessary.
I'll go light it up tonight.
While I was watching the ceiling fan this morning at 4:38, I realized that I measured continuity between the second and third positions on the board with the FETs removed. I'm not sure it's a dead short but there's some continuity. Those being the supply and drain, I don't see how there can be a connection.
The output FETs are out of the board as well. Could the output transistors be fried?
It would light up before I opened it up, so looking for the 5v is the next step, I'm just not sure why I've got continuity with the rail on both sides.
J
While I was watching the ceiling fan this morning at 4:38, I realized that I measured continuity between the second and third positions on the board with the FETs removed. I'm not sure it's a dead short but there's some continuity. Those being the supply and drain, I don't see how there can be a connection.
The output FETs are out of the board as well. Could the output transistors be fried?
It would light up before I opened it up, so looking for the 5v is the next step, I'm just not sure why I've got continuity with the rail on both sides.
J
'Continuity' isn't very specific. It could be 1 ohm or 1M ohms.
Second and third positions? Do you mean terminals or locations on the board? Either way, you need to give the circuit board designation for the FET and the probe placement.
Second and third positions? Do you mean terminals or locations on the board? Either way, you need to give the circuit board designation for the FET and the probe placement.
I made a bit of a mess pulling the supply FETs. Pulled a couple of gromets out of the board. I'll put them back and make sure I've got good connection, but that's where I was messing around. The measurement is 4-5 MOhms. That's the supply and drain lets of the FETs in Q600-607.
I'll plug in the board and look for 5 volts. Sorry to make this in to more words than it needed to be.
J
I'll plug in the board and look for 5 volts. Sorry to make this in to more words than it needed to be.
J
When removing the FETs in these amps, you need to first cut the burrs off of the tips of the legs (they almost always have burrs that damage the vias when pulled through). When desoldering, apply enough new solder so that you can lay the tip of the iron across all three legs and heat all three connections at once. When you do this, the FETs will literally fall out of the board. There will be no damage to the vias.
I'll try that on the next one. I had some success with a desolder pump on the output transistors. I'll try the three leg technique on the next one.
I put the amp on my test "board" across the engine compartment of my truck and tested the supply. 5V at all of the gate legs of the supply FETs.
Pretty happy. Small victories.
I did pull the output FETs so we should be able to move on to installing the supply side FETs and checking rail voltage before installing the output side.
Am I reading ahead? Thanks again.
J
I put the amp on my test "board" across the engine compartment of my truck and tested the supply. 5V at all of the gate legs of the supply FETs.
Pretty happy. Small victories.
I did pull the output FETs so we should be able to move on to installing the supply side FETs and checking rail voltage before installing the output side.
Am I reading ahead? Thanks again.
J
Quenching Diodes. That's exactly what I was dealing with. the "snap" in the system was coming from the remote lead from the head unit. I put a relay inline and it's gone. Of course I chased the power supply and signal for a few hours first. Now on to replacing components in the damaged amp. Back in a few hours...
So I'm not confident I measured the right things.
On COP3 I got 91v to ground
COP2 was the same
COP1 was 80v to ground.
When looking for "rail voltage" where am I to measure. I didn't find 40v anywhere.
And I broke a clip clamping the FETs to the heatsink. So another question: Where can I find spare clips. I know they're a challenge.
On COP3 I got 91v to ground
COP2 was the same
COP1 was 80v to ground.
When looking for "rail voltage" where am I to measure. I didn't find 40v anywhere.
And I broke a clip clamping the FETs to the heatsink. So another question: Where can I find spare clips. I know they're a challenge.
The rail caps or the output transistors are the most reliable places to find the rail voltage.
Did someone ask you to find 40v?
Did someone ask you to find 40v?
I can't say exactly where I read that. I've read a lot and I know that it's starting to blur.
The issue is I don't know where to put the probes. I've got the supply fets installed, the output fets installed and the heatsink attached to the works.
I measured the voltage at the 3 rails on the output side of amp as previous. I'm not sure if I was measuring the output of the power supply or something else. I'll go look at it again and see if I can make sense of your comment. My inexperience has surfaced and I haven't read enough to know where to head next.
J
The issue is I don't know where to put the probes. I've got the supply fets installed, the output fets installed and the heatsink attached to the works.
I measured the voltage at the 3 rails on the output side of amp as previous. I'm not sure if I was measuring the output of the power supply or something else. I'll go look at it again and see if I can make sense of your comment. My inexperience has surfaced and I haven't read enough to know where to head next.
J
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