Hello all, this is my first post and my first amp repair. Bare with me here, I'm not an electrical genius, and most of what I think I know is self-taught, so I may use incorrect verbage or component names, but I'm a quick study. My background comes from outside these cases we call High Current Amplifiers and more into the install world, but with my background in USAci, db-drag and several local to me leagues, it's a logical movement for me to look to diy repairs, and something that has always interested me. Now I'm willing to put in the time.
This is my amp, I've had it for several years now, one day last summer it let the smoke out, and the amp has sat since then. Last week I opened it up to find about 4 out of 16 irf3205 power transistors fried and completely broken, and all 4 fmu32u diodes with the legs broken from the board.
I was able to easily source and purchase the irf3205 transistors, so I replaced all 160f them. I was not able to find the fmu32u diodes anywhere besides japan, and they theoretically test fine with the meter so I simply soldered the legs back into the board after desoldering and removing the short broken off pieces.
Now the amp doesn't immediately blow the main power fuse when connected to a battery. success! no, when I apply remote power to switch the amp on, the protect LED will light for about 500mS then quickly turn off, and about 3 seconds later the internal relay clicks on, but the amp has no signs of life other than that.
At this point I have no clue where to go from here, or what else could be causing a problem, unless it's those diodes. it seems like I have no power on the output side of the board as all I show on the Volt meter anywhere is either 0.000 v or - 0.011v (negative voltage?)
Can someone help point me in a new direction so maybe I can successfully repair this amp?. Perhaps point me at a good replacement for the fmu32u's (can I use 2 similar diodes in each ones place?)
I'm willing to do whatever I need to do to get my amp back up and running again if possible ( I know it's possible )
This is my amp, I've had it for several years now, one day last summer it let the smoke out, and the amp has sat since then. Last week I opened it up to find about 4 out of 16 irf3205 power transistors fried and completely broken, and all 4 fmu32u diodes with the legs broken from the board.
I was able to easily source and purchase the irf3205 transistors, so I replaced all 160f them. I was not able to find the fmu32u diodes anywhere besides japan, and they theoretically test fine with the meter so I simply soldered the legs back into the board after desoldering and removing the short broken off pieces.
Now the amp doesn't immediately blow the main power fuse when connected to a battery. success! no, when I apply remote power to switch the amp on, the protect LED will light for about 500mS then quickly turn off, and about 3 seconds later the internal relay clicks on, but the amp has no signs of life other than that.
At this point I have no clue where to go from here, or what else could be causing a problem, unless it's those diodes. it seems like I have no power on the output side of the board as all I show on the Volt meter anywhere is either 0.000 v or - 0.011v (negative voltage?)
Can someone help point me in a new direction so maybe I can successfully repair this amp?. Perhaps point me at a good replacement for the fmu32u's (can I use 2 similar diodes in each ones place?)
I'm willing to do whatever I need to do to get my amp back up and running again if possible ( I know it's possible )
I believe it to be the driver board at this point. After searching and reading several posts about the driver board in the DD amps failing. I used a dmm set to Hz and did not find the 22.5kHz that someone had mentioned I would need to see for an operational amp. also I am not seeing and rail voltage or anything above that of the battery voltage.
any help would be great as I now feel like I am in over my head, yet still wanting and willing to press on and get this bad boy repaired and working again
any help would be great as I now feel like I am in over my head, yet still wanting and willing to press on and get this bad boy repaired and working again
oops... last post happened before I wanted it to.
q11 12.67v
q10 12.65v
q9 12.67v
q9a 12.65v
q12a 12.63v
q14 12.67v
q13 12.62v
q12 12.64v
q20 12.67v
q19 12.66v
q18 12.66v
q18a 12.66v
q15a 12.67v
q17 12.63v
q16 12.66v
q15 12.66v
both with the amp powered via remote wire and not powered... also seeing identical voltages on second pins of 3205's and nothing on the third pins
q11 12.67v
q10 12.65v
q9 12.67v
q9a 12.65v
q12a 12.63v
q14 12.67v
q13 12.62v
q12 12.64v
q20 12.67v
q19 12.66v
q18 12.66v
q18a 12.66v
q15a 12.67v
q17 12.63v
q16 12.66v
q15 12.66v
both with the amp powered via remote wire and not powered... also seeing identical voltages on second pins of 3205's and nothing on the third pins
I think I verified that all of my power FETs are blown again after having been replaced.
Are there some other voltages that I should check? or should i just begin removing all of the FET's again and ordering parts?
Read the basic repair page (link in sig line below), paying special attention to the information in the yellow box. It will help prevent blowing new parts.
I don't have any information on this amp so I can't offer any specifics but the driver circuit may have been damaged. You need to test the driver circuit and its components before ordering or installing any new parts. Post a good quality photo of the board so we can see what you have.
I don't have any information on this amp so I can't offer any specifics but the driver circuit may have been damaged. You need to test the driver circuit and its components before ordering or installing any new parts. Post a good quality photo of the board so we can see what you have.
this will answer all those... my answers to the bullet points
- not under warranty
- I want to learn
- using a 10 amp fast acting breaker
- didnt have to do this after replacing the FETs, powered up first few times with a 1 amp kenwood current limited power supply at work, never showed any trip faults or excessive current draw
- never would I power it without doing such a thing first, I actually work on a lot of electronics at work, but none of them are as cool as a big power amplifier.
not a ppi amp - check
- check, all seems good
I used every tip I could for getting those pics with an iphone 3g (the only camera I have) I will attempt to borrow one from someone, but I know very few people, and nobody close to home. may take me a day or two to procure.
Maybe they all blew the first time I connected it to the battery thru the 10 amp breaker... I really don't know.
sorry about the pics being small. heres the larger ones
I have a single trace scope, albeit not a very good one but I do have one... a Midtronics EXP-1000...
Maybe I can get a better pic with my camera, now that it's daylight outside. I didn't have a great light source last night no matter what I tried, and those pics look very distorted after posting them here
Maybe they all blew the first time I connected it to the battery thru the 10 amp breaker... I really don't know.
sorry about the pics being small. heres the larger ones
An externally hosted image should be here but it was not working when we last tested it.
I have a single trace scope, albeit not a very good one but I do have one... a Midtronics EXP-1000...
Maybe I can get a better pic with my camera, now that it's daylight outside. I didn't have a great light source last night no matter what I tried, and those pics look very distorted after posting them here
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Those photos will be good enough for now.
The driver transistors are Q7, 8, 7A and 8A. The ones with an A prefix (A1275 possibly) are the ones that most commonly fail. After checking the drivers and replacing any that have failed, you'll need to remove the shorted FETs and look at the drive signal on the gate pads for the power supply FETs. Post a photo of the drive signal on the gate pad for the two FETs farthest away from each other on each side (4 photos).
The driver transistors are Q7, 8, 7A and 8A. The ones with an A prefix (A1275 possibly) are the ones that most commonly fail. After checking the drivers and replacing any that have failed, you'll need to remove the shorted FETs and look at the drive signal on the gate pads for the power supply FETs. Post a photo of the drive signal on the gate pad for the two FETs farthest away from each other on each side (4 photos).
I don't have a diagram for this amp. It's has a lot in common with other amps. The power supply layout is a lot like the hifonics amps (and others). Email me and I'll send you a copy of a schematic diagram for an amp that uses a similar power supply circuit.
babin_perry@yahoo.com
babin_perry@yahoo.com
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