| nsxxtreme |
I didn't want to stomp on the other guys post so I created my own thread.
I'm working on a 500/1. Power supply kicks on for a brief second then shuts off. It keeps trying to start the supply then dies.
I dont have a schematic for this amp.
All power supply transistors have been replaced. All Audio transistors 540s have been replaced. Light turns green and stays green. Will even play audio for a brief second but then shuts down.
Any ideas? |
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| Perry Babin |
Will it shut down if you drive signal into it but don't have a speaker connected to it?
With a speaker connected but no signal, does it remain on?
Does it produce a pop through the speaker when it turns on?
Does the green light go off when it shuts down?
Will it come back on after it shuts down or do you have to disconnect and reconnect the remote turn-on? |
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| nsxxtreme |
Doesn't matter if a speaker is connected or not.
Power supply start up then immediately shuts down. Then starts back up again then shuts down. It just repeats this.
I have the remote tied to B+ so it just continues this cycle on its own. Audio will play for the brief second its turned on. Even without the speaker it does this.
I do have a scope so I can see whats going on. Just not sure what is shutting the supply off.
Both soft start and compensation are immediately pulled low on the PWM.
U601 gets warm to the touch and so does Q612 but without a schematic I dont know what these do. |
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| Perry Babin |
These amps are very sensitive to low voltage. Are you sure that the supply voltage isn't dropping as the amp powers up?
U601 is the 5v regulator for the logic IC (most are between the top and bottom boards).
Q612 drives the yellow transformer which generates the low voltage for the preamp level ICs. I think it may also be used to produce drive voltage for the high-side outputs.
Neither Q612 or U601 should get hot. |
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| nsxxtreme |
I have the amp current limited to 3 amps.
Amp turns on sinks 500mA. I imagine this is before it "actually" turns on. Few seconds later the amps tries to really turn on. It then sinks the entire 3 amps and immediately shuts down.
I dont have the amp in the heat sink which is why I current limit. But I have never ran across an amp that cant turn on without a load and 3 amps of current.
I'm thinking of pulling the soft start leg up just to see what happens. If it would stay on long enough for something to get "hot" this would be easier. |
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| Perry Babin |
The amp may not have a problem. These amps are the worst when it comes to sensitivity to voltage drop.
Let it try to power up for a minute or so. If none of the heatsink mounted devices get hot (out of the sink), I'd suggest mounting it back to the sink and removing the limiting. If you have a large supply (rated at more than 10 amps continuous), install a 10 amp fuse.
For non-class D amps, it's often OK to defeat the protection circuit but on class D amps, it can often lead to instantaneous destruction of the power semis. |
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| nsxxtreme |
| Cranked the current limit up to 25amps. There is definetly shutting this amp off. There must be a second PWM that goes to T601 because I see somewhat of a square wave on that. |
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| Perry Babin |
There is a small driver IC that drives Q612 which drives the yellow transformer. I don't know of anything on that circuit that can shut down the amp (but that doesn't mean it's possible).
Did any of the outputs or power supply transistors get hot when you powered it up out of the sink?
If you connect your meter to the the speaker terminals (black lead on negative, red lead on positive), is there any DC voltage?
How much current did it draw when you removed the limiter?
What rev. amp do you have?
If it continues to go into protection/shutdown, pull the outputs. That will allow you to check most of the rest of the amp for proper operation. |
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| nsxxtreme |
No DC output on the output. The output seems to be ok when it is on.
The supply transistors dont even get warm. I have a really nice Tek supply PS2520G for low current but anything higher then 3 amps I have to switch to a piece of **** 25 amp switching supply so I have no way of measuring current with it. So no clue on the amount of current its pulling. But I dont think it gets a chance to pull any significant current because it powers up and shuts off instantly. Basically the instant it turn on the instant it turns off.
Do you know what type of signals I should be seeing on T601? Each side of the transformer. I'm really tempted to bypass the protection and let her rip. What's the output out of the supply? |
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| Perry Babin |
This photo is the signal on the tab of Q612. The timebase is set to 5us. The vertical amp is set to 10v/div.
What revision is your amp? There were modifications to this drive circuit. |
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| nsxxtreme |
Ya mine looks like that. I have a rev3 board.
I was going to post the output of mine but photo bucket doesn't like the TIFF image my scope produces.
High of 28.8V
Freq 58.06 kHz
How about Q613 I am seeing this jump to 13V then drop to 0.
I also drove 30V onto the output capacitors. No current draw once the capacitors were charged. So the output is not shorted that I can find.
A schematic would make this soooo much easy. I appreciate your effort. Thank You!
Finally got it converted
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| Perry Babin |
It's probably not important but... the rev3 uses a UC3843 to drive the FET that drives the yellow transformer. The rev10 uses a different drive circuit.
These are the rest of the waveforms (from a rev10). Right-click to zoom in to read the timebase and vertical amp settings.
http://bcae1.com/temp/jl500slashonelowvtransformer.swf
As far as I know, the schematics were never released.
Make a quick check of the output inductors and the filter caps across the outputs to make sure none have broken leads. Also, resolder all of the connections on ALL of the long buss bars. Sometimes they cause problems.
Does it stay on long enough to check the rail voltage and the ± voltage on a few of the op-amps?
What scope are you using? |
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| nsxxtreme |
opamps are +13.0v and -15v and this voltage is always on no matter what.
No supply never stays on long enough to measure the output voltage of the supply.
My rev3 is using a UC3525ADW to drive the FETs
I checked the output caps for shorts seem to be ok. Ouput inductor doesn't appear to be shorted either.
I'm using a Tek3034B
Measured the transformer and I am only noted the differences I see with what you have in the images.
Pin 6 is the same as pin 8 -> Meaning waves look the same
pins 7 flick on then shuts off.
1-4 all look like image 2. None of them bias up.
pin5 looks like the output of Q612 |
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| Perry Babin |
The 3525 drives the main supply. The UC3843 drives the yellow transformer. The UC3843 is under the preamp board.
If you run out of ideas, pull the outputs. If nothing else, it will eliminate that as a problem (if the amp still shuts down).
The legs break on the inductors and the output caps. Either one will cause the amp to shut down. There's also a large resistor next to the output inductors. I've seen a few with bad connections and that caused the amp to shut down or pull excessive current.
To do troubleshooting under the preamp board, you'll have to make a set of jumper cables. The amp will not power up with the preamp board out of the circuit.
Tek3034B:bawling: I want one. |
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| nsxxtreme |
All output caps were replace. I learned long ago that when power supplies burn up your better off buying all the parts you might think you need. The audio ouput transistors, power supply transistors, and large caps on the audio stage were replaced. 10 ohm resistor measures 10ohms.
I am only resisting pulling those transistors because my desoldering iron sucks :D
See above post for additional measurement that I edited in.
Time for bed work on it some more tomorrow. I'll think about pulling those output transistors tomorrow.
Again thanks for all the help! |
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| Perry Babin |
You don't need a desoldering iron to remove the transistors. Apply extra solder to all 3 legs and lay your iron down so it heats all 3 pads. When all 3 heat up, the transistors will fall out (or pull out easily). Then all you need to do is remove solder bridges and power it up.
What's the voltage on pin 1 of U509? It's 5v on the one I have here. It's connected to the output of the comparator used for over-current protection. |
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| nsxxtreme |
Getting them out is the easy part getting them back in is a little bit harder without a good desolder iron.
The one I have pin1 of u509 is 5v. I pulled the output transistors.
One thing that has me wondering is the op-amp + rail its only 13.0v instead of +15V the negative rail is -15v. Could mean nothing but some of the op-amps get warm to the touch so maybe something is yanking this rail low and causeing the shutdown. Do any of yours get warm? U1,U2,U3 get warm to the touch not hot just warm.
I may need to make a cable to pull the upper board off. |
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| Perry Babin |
Does the amp still shut down without the outputs?
Did you check pin 1 with the outputs in the circuit?
None of the op-amps are getting hot. In some of the JL amps, some op-amps run hot but these are all running cool. U1, 2 and 3 seem to run slightly warmer than the others. They are also at a lower voltage.
The regulated voltage is approximately ±14.8v on most of the op-amps.
Most of the supply voltages pass through 10 ohm resistors at various points on the board. You can measure the voltage across the resistors to determine if there is excessive current flow.
Earlier, you stated that the voltage on your amp's low voltage transformer wasn't biased high. That's because there was no rail voltage.
I used to have a desoldering station and several desoldering irons. They were all a pain. I use an Edsyn DS017 and it works very well.
Check all of the op-amps to see if any have DC on their outputs.
If you need the connector and cable part numbers for the extension cables, let me know. |
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| nsxxtreme |
Amp still shuts down without the output transistors installed.
Pulled transistors before I checked pin 1, but the amp still shuts down without them so I dont think that is the problem.
So I think what ever is driving Q613 may be my problem. Do you know what the voltages on this trasistor are supposed to be.
The gate swings to about 13V then drops back to 0. The Drain and source both stay at about 0V. I'm thinking this transistor is driving the output of the supply to 0. |
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| Perry Babin |
There's no Q613 in the rev10 that I have here.
There should be a difference in the voltage from drain to source. Is the transistor shorted?
In most cases, the drain/source voltage will only be equal when the gate-source voltage is high (greater than ~4v). Maybe the source feeding the transistor is missing/open.
What are the other components that connect to this transistor? |
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| nsxxtreme |
I'm thinking this transistor is some kind of feedback to regulate the output supply. It has a 100 ohm 2 watt resistor from the output of the supply to drain of Q613. Source is tied to ground. The gate then goes somewhere but I dont know where.
I removed Q613 power supply stayed on a little longer but then fried. :( oops.
Once Q613 was removed U4 also got hot!! and r21 desolodered itself. Not sure how U4 comes into the equation, its a 555 timer to something.
Removed the supply transistor and R21 and amp turn back on and the gate of supply transistors stays switching.
So now I need to order more parts from digikey. I might have to give up on this amp before it sinks me in a hole.
have you had any luck with Vishay transistors?
I'm thinking of buying these because I would like to also replace the rectifier and digikey doesn't carry it. http://www.mouser.com/Search/Produc...pFoqVUQ5w%3d%3d |
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| Perry Babin |
R21 feeds the 555 timer which drives the small transformer near it. It drives it through C7.
It's possible that there was a problem with the 555 or the transformer and when the transistor was removed, the protection circuit could no longer shut down the amp.
If I'm not mistaken, this tiny supply powers the U1, 2 and 3. They are used for signal sensing to power up the amp. If any of these op-amps were shorted, it could have caused excessive current flow in this circuit. |
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| Perry Babin |
| I've never had any problems with any vishay device. |
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| nsxxtreme |
| I'm not sure what the 555 timer and transformer supply but its not u1,u2,u3. These still have +15, -15 with R21 removed. |
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| nsxxtreme |
| I'm ordering some parts from mouser now. Do you know what voltages need to be on each pin of the transformer next to the 555 timer? |
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| Perry Babin |
When the square yellow transformer is operating, U1-3 get power from it (via the diodes next to R25). When that supply switches off, the 555 switches on and those ICs get their power from the tiny transformer. The voltage is significantly lower than ±15v. There is a 15-20 second turn-off delay for the square transformer.
If I'm not mistaken, there was a diffference between rev3 and 10 with regards to the operation of the 555. In the later revision, the 555 didn't receive power unless signal sense was selected. In the rev3, the 555 oscillated no matter the setting of the signal sense switch.
I don't think you'll find any voltage on the tiny transformer with the 555 out of the circuit. |
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| nsxxtreme |
I was looking for the voltages to expect once I get my parts in from mouser should be here Tuesday.
Have you had any problem powering up JL amps without the heatsink and no load? |
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| Perry Babin |
I haven't had any trouble working on them without the sink.
When troubleshooting, I don't generally have the amp 'on' for long periods of time. I'll turn it on long enough to check the voltage at key points, power it down, follow the circuit a bit farther, power it up and check the voltage at the next point.
If there is a problem that's taking a long time to troubleshoot and the amp has to be powered up during the entire process, I'll pull the outputs or watch their temperature very closely.
As long as you monitor the temperature of the power transistors that are normally on the sink, you shouldn't have any problems.
How many parts failed?
Have you determined the function of Q613? |
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| nsxxtreme |
All the supply transistors died. I'm still not sure what purpose that transistor has. Its an irf540 and has a 100 ohm 2 watt resistor going from the output of the supply directly to the drain of q613. The Source is tied directly to ground.
On start up there is 13V tied to the gate. So I haven't figured out what purpose it serves yet. My guess is its some kind start up circuit. Maybe ties one of the inductor coils low until a start up check is done then release it once start up check has passed. That's my only guess.
If its just a start up circuit I dont know why it would have caused the transistors to die. There would need to be a serious short somewhere to kill all 8 Transistors that way, as well as being current limited to 3amps. After they shorted they could sink the entire 3 amps without getting warm to the touch. So that made me think its some kind of feedback to limit the output voltage and maybe that went high enough to fry the transistors. But that doesn't make much sense either, and I dont see any other connection that could possibly be used as feedback unless its an internal layer. |
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| Perry Babin |
It sounds like it's part of a shunt regulator. It could be a drain for the rail caps (like MTX used in some of their amps) but removing it from the circuit shouldn't have caused the damage you found.
With the damage you described, I would have expected it to be a regulator for the 12v feeding the gate drivers in the PS and the 555 via R21 but a 100 ohm, 2w resistor can't drop 60+v.
It wouldn't have required any significant current to kill the PS FETs if the drive voltage went above 20v. Are the tabs of Q609 and Q610 tied directly to B+? |
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| nsxxtreme |
| The resistor is actually on the outside of the filter comming from the supply. It connects the + terminal of the rectifier to ground. I'll take a picture of it later tonight. |
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| nsxxtreme |
Posting pic of Q613 its the irf44z transistor sitting between the filter and the transformer. You can see the resistor sits between these as well. That resistor connects to the + terminal of the rectifier and the drain of the transistor. The source is tied to ground.
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| Perry Babin |
| Does the drain connect to anything other than the resistor? |
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| nsxxtreme |
| Not that I can find. I was thinking it was some kind of feedback circuit, if the drain is connected to anything else it's internal to the board. But without the second connection I can't figure out its purpose. |
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| Perry Babin |
Again, I think it's only purpose is to drain the rail caps. Under normal operating conditions, from a cold start there is no voltage (80v rail). When the amp starts, the control/servo circuits receive power THEN the main rail voltage is generated. It's possible that the amp makes a loud pop or has other difficulties if cycled on-off-on very quickly. Q613 could be used to make sure the rail caps are drained before the amp starts. Of course, this is only a guess.
It appeared that pulling Q613 caused the amp to fail. Is it possible that something else caused the failure?
Does the amp still shut off with no Z44s in it? |
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| nsxxtreme |
No the PWM stays on. Amp never really shut off before just the power supply would cycle on and off. The green light stayed lit the entire time. Something would pull the compensation and soft start pins low causing the supply to cycle.
I dont know what else would have caused the failure because nothing else was different. |
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| nsxxtreme |
| Got my parts in today and the power supply is still being shut down. |
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| nsxxtreme |
So when the power supply tries to kick on Vin on the UC3525 goes away. I haven't found what is supplying this yet. So far I have traced this to C617, and Q614.
No power for the chip makes sense why it would keep reseting. Just need to figure out the why now. |
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| nsxxtreme |
| So I traced it up to d400 and the transistor it connects to. This looks like what supplies the power to the PWM. When the amp tries to turn on the voltage dips and d400 does not recover immediately this drops to 0 and gets stuck there. It also looks like the transistors supplying the Z44s are shot. Does anyone know the part numbers for these? |
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| Perry Babin |
You're correct Q400 drives pin 8 of the 10 pin connector which goes to pin 13 of the PWM driver board. This transistor is controlled by pin 1 of U400. The amp is probably shutting down due to a fault and the protection circuit is sending a shutdown signal to U400.
D400 is a reverse protection clamp to protect Q400. The voltage on the collector of Q400 isn't switching back on because it's not being driven on by pin 1 of U400. It's probably a delay built into the protection circuit.
The following are the voltages I read on U400 in a working amp. Pins 1-14 top to bottom. Hopefully, only one pin has an error and you can track it from there.
0.972
5.73
1.388
13.47
5.80
5.05
12.20
12.29
5.63
9.79
0.000
1.406
5.24
0.969
The attached photo are the original part numbers. I've been using 2SB1260s for the PNPs because the originals are difficult to find. I've never seen one of the NPN drivers fail. |
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| nsxxtreme |
| quote: | Originally posted by Perry Babin
You're correct Q400 drives pin 8 of the 10 pin connector which goes to pin 13 of the PWM driver board. This transistor is controlled by pin 1 of U400. The amp is probably shutting down due to a fault and the protection circuit is sending a shutdown signal to U400. |
What I am seeing is the U400 side dip a little. When the voltage dips d400 shuts off completely. Waits half a second then turn back on. U400 never shuts off voltage just dips slightly. I am assumming D401 is the same style diode. This diode does not behave that way.
Thanks for the part numbers and measurements. |
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| Perry Babin |
The voltage on pin 1 of U400 should swing from ~1v (when Q400 is on) to nearly 12v (when Q400 is off).
Q401 is used to switch power to a different circuit so it won't react the same way as Q400. I think this controls the power supply to the low voltage transformer drive circuit.
With the scope probe grounded directly to the ground terminal of the amp and the probe on the B+ terminal of the amp, 'precisely' how low is the voltage dropping across the B+ and ground terminals as the amp tries to power up? |
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| EnvisionAudio |
There you guys are...I was snooping and found this thread. It will be interesting to see what happens. Though if you get stuck, send it my way. ;)
Aaron |
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| nsxxtreme |
Perry,
It'll be a couple days before I can get the power supply drive transistors off. I don't have a good enough solder iron station at home for that. Since these are toast and prevent the pwm from driving the transistors. I want to make sure I am just not overpowering the drive circuit of the pwm before I debug the pwm supply circuit any further.
Your a valuable resource on this forum thanks again! |
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| wickedgtr |
I am working on the same amp, and I forgot to mark the order of the transistors (only the heat sink mounted ones) so if some can post the order that would really help me out. I de-soldered them, and now I am pretty stuck...
Thanks in advance,
Alan |
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| Perry Babin |
Looking at the face of the transistors...
The 4 on the left are IRF540s.
In the group on the right, the left-most one is the rectifier, the rest are IRFZ44s. |
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| wickedgtr |
I have the 4 540's then I have the sensor, then the diode.
so the next 8 spots are for Z44n's? i have an extra 540 then, or I messed up bad... |
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| Perry Babin |
| Yes. The last 8 components on the right are IRFZ44s. |
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| wickedgtr |
First off, thanks for your help so far!
Does anyone know where to locate the data sheet for the diode? I've checked ICMaster.com and of course google. I cant seem to find what kinds of specs it needs to find a replacement.
T432
SFI606G
-|>|.|<|- <--- thats the symbol on it, two diodes pointing at
eachother.
^^^ Thats what I see, for sure one side of the diode is bad
If anyone know the specs, or an known working replacement, then I should have this amp up and running today.
Thanks in advance,
Alan |
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| Perry Babin |
These are good subs:
FEP16DT (mouser pt# 512-FEP16DT)
MUR1620CTG (mouser pt# 863-MUR1620CTG) |
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| Perry Babin |
| NTE rectifiers 'may' work properly. With NTE transistors, you never know exactly what you're getting. I'd recommend that you never use them. |
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