| Dead amp, need a tad bit of help fixing - Click HERE for Original Thread |
| ccdoggy |
So my Alpine E4300 died the other day. I open it up and see that all 6 of the power supply caps are burst. just out of the random too, I just got it all setup and how i liked it and it died.
So I am in the process of taking it apart and I cant for the life of me get the pressure clips off the fets. I got one off just by wedging a screwdriver into it and hitting the edge with a hammer and inching it out. but i cannot do that for all of them.
SO how do i get these off so i can remove the board so i can desolder the caps and replace them. hopefully fixing the problem, other problem? i cant find any other damaged or odd looking components.
Thanks for the help! |
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| jol50 |
| You are supposed to put a small screwdriver or whatever in the hole and pry then they pop loose. I like to take needle nose and grab the end at the top, I twist a little the right way and they pop off and don't fly anywhere, and I don't smack anything in the amp. That works great on the RF and some other amps but have not done an alpine like that. |
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| 1moreamp |
Perry here on the forum has a how to on his web site showing how he removes these.
I can tell you that you need to slow down, and take your time on removing these or they will be worthless when you get done. Replacement are tough to come by unless you have a amp graveyard.
Perry uses a driver that has been cut down to fit the slotted hole in the center of the clamp to do this job. The trick is to pull away from the sink at a horizontal direction. Perry does this, and so do I... Seems to work every time. The trick as I see it is to cause the clip to rise up and out of its lip seat in the sink as you pull away from the sink < without gouging up the seat area of the sink >
Check any of Perry's posts he has his link under his posts. Just click his link and scan his web site. I think you will find it very helpful, with answers to a lot of questions you will be having very shortly....:) |
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| jol50 |
| Yes he does show how to do it. I forget but I don't twist them out. I push in and lift the hook off the sink with a little twist of the wrist and they come right out if you do it right, I've never put a mark on one doing that. But like I said some amps might be different or something I don't know. Whatever the case, be very careful of them like 1moreamp says. I don't like them but I didn't build the amp. I have used a tool but they get too airborne for my liking in the area I work in, and it seemed to take a lot more effort/prying. |
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| ccdoggy |
I took a look at his site but couldent find it right away, ill take a more in depth look tomorrow.
Thanks for the suggestions, ill see what i can do tomorrow and i am sure ill be back with more questions.
ooh, because its a power supply cap i shouldn't be worried about the 30% tolerance that is on every cap that i look for right? |
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| Perry Babin |
Here's the thread where the tools were shown. This is a modified cotter pin remover. I also use a screwdriver that's bent and ground to fit the slot but they're dangerous to make (screwdrivers don't like being bent 90°) unless you have an acetylene torch.
http://www.diyaudio.com/forums/show...224#post1434224
You stick the tip of the tool in as far as it will go and pry back on the handle. Further down the page, it shows you what you need to reinstall them. |
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| ccdoggy |
Awesome, thanks for the help. Just got all the clips off and slid the board out.
I took a look at all the fets and it appreas (and smells) like the 2nd group of 3 mosfets are burned out. the other 3 may also be dead. everything else looks/smells fine.
I am new to all this, so can i just buy some IRFZ44N from digikey, along with 6 caps, replace them and have a go?
Or should i do some testing before hand? not that fluent but know power basics. |
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| 69CamaroSS396 |
| quote: | Originally posted by ccdoggy
Awesome, thanks for the help. Just got all the clips off and slid the board out.
I took a look at all the fets and it appreas (and smells) like the 2nd group of 3 mosfets are burned out. the other 3 may also be dead. everything else looks/smells fine.
I am new to all this, so can i just buy some IRFZ44N from digikey, along with 6 caps, replace them and have a go?
Or should i do some testing before hand? not that fluent but know power basics. |
Check out Perry's tutorial DVD. I purchased it recently and it paid for itself with one fix that I didn't have to farm out to someone else.
I had my DVD in hand in 4 days after ordering, and had my amp repaired the next day. |
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| jol50 |
Yes maybe. You should check the resistors on the gates of the fets. Also should put say a 10a fuse before amp and it is nice to run a large 2 ohm resistor in the power wire, those will keep it from toasting or blowing as bad should something still be wrong with it. You might fire it up and be fine, or it might go poof again on full power...and you would be :bawling: ...:(
Oh yes, Perry's DVD is priceless for doing this stuff. I have it. |
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| Perry Babin |
You should replace all 6 power supply FET.
When ordering the capacitors, you'll need to select replacements with the same capacitance, voltage rating, diameter, height and lead spacing. If the caps are rated at 105C (temperature rating), the replacements need to be rated at 105C also.
You need to check the output transistors also. If you read anything near 0 ohms between the legs of any individual transistor, the transistor (or one in parallel with it) is shorted. You would need to pull all that appear shorted and re-check them out of the circuit. The output transistors are the ones near the large white resistors.
In the photos there is a clip that's not on the transistors. Did you do that or was it like that already? |
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| ccdoggy |
Yes, that was the one i experiments getting off. i slid it off with a bit of force.
All the output fets look good. The surface mount resistors on the dead fets look as if the solder popped off. 2 of the resistors still have the correct value (confirmed by checking against the other resistor on the other 3. but the middle one is about double the value at 80ohms. I believe the number on it is 470. What should i do about this part? The other 2 i think i can just clean them up and solder them back on with out much problem.
Thanks so much for the help. I would be totally lost without it.
Off to find some fets and caps. |
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| Perry Babin |
You should replace all 6 of the gate resistors if some of them failed. They are 47 ohms. Most of the JL amps I've worked on used 1206 size resistors. You can measure yours to determine the size.
1206 means it's 0.120" x 0.060". If they're smaller, they're likely 0805s.
After you replace the resistors but before you reinstall the FETs, measure the DC voltage on the FET gate pads. They should all read ~1/2 of the B+ voltage across the amps B+ and ground terminals. The amp will have to be powered up normally (B+, ground and remote). Place the black meter lead on the ground terminal of the amp. If the voltage is not the same (they're generally within ~1%) at all gate pads, there may be problems with the gate drive components.
As was mentioned before, either use an inline current limiting resistor or a small fuse (~10 amps) in series with the B+ line when you power up the amp initially. Also have the transistors clamped to the sink. This will help prevent damage to the amp if there are other problems. |
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| wakibaki |
You have to wonder why it blew.
Check the speakers or cables aren't shorted.
It's nice to power up with a lab power supply, you can wind the voltage up slowly and watch the current doesn't run away, all the time checking with your fingers (carefully!) that nothing's getting hot. You can use a couple of low wattage 8ohm resistors as dummy loads although these can easily burn you if you've got a fault, so the bigger the better in some ways, you shouldn't see more'n a few tens of millivolts worst case differential across the outputs undriven. I've no idea what the quiescent current should be for this device, but somebody does.
w |
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| wazzy |
| i would also replace all six of those fets if i were you, they may seem fine and work okay for a while... and then you break them all again trust me take the time to test everything, irfz44's are rated over 40 amps if they blew there is something pretty big wrong. fix it all now and you may never open that amp again except to improve it? |
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| ccdoggy |
the surface mount resistors are of the 1206 size. There are 3 pages to choose from on digikey. any suggestion on which one i should go with? given i only need 6 tops, seems like min on some is 10 which is fine with me. but which ones?
I found some caps that are not exactly the same size but the same voltage, farads, and pole spacing. should i be good and go with these? they are taller and a little skinnier, but should still clear in the case.
Thanks for the suggestion on checking the wires, that was the first thing i did when i took the whole thing apart. no problems there.
Yea, i will be replacing all 6, might as well its not that much more money especially when not paying shipping on them. |
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| Perry Babin |
http://search.digikey.com/scripts/D...311-47.0FRCT-ND
As long as the ratings/specs are the same and they will fit in the alloted space, they will work. If you're looking at the caps at digikey, check the FC series by panasonic to see if they will fit. You can select the series in the filter dialog window if you use the search function to find the caps that match yours. |
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| Perry Babin |
Those FETs will work.
If the caps will fit, they will work. |
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