Crunch GP3000D-PRO FET Repair Questions

[Undisputed King 10+ year member]

Alright so I have 3 burned FET's on my amp. When it happened the amplifier was still playing, but I disconnected because of the smoke and havent plugged it in anymore. The circuit is complete, theres continuity between the positive and negative lead.

I am not a beginner when it comes to electronics repair, its just I haven't repaired an amplifier. I have good soldering skills and component testing.

I know that these amps have the IRFP360lc for the output transistors, and IRFP064N for the power supply transistors. My power supply FET's are the ones that are out. I should just be able to replace my power supply FET's and not have to touch the output FET's right? Anyone know how many power supply FET's there are? FET's are FET's right? Or are there better quality ones than others? The ones I am planning to get are from a China Ebay seller.

What other components should I check? the resistors look a little blackened, I should just check their value and make sure they are within spec right?

Ok well I want to know what tools and supplies I will need. I have a DMM, 40W soldering iron(but I need a finer tip), and dikes, then I need .04" solder 60/40 rosin core, 20 IRFP064N transistors(29.99), desolder braid, heatsink compound. Can anyone tell me any more specifics to any tools or supplies I will need?

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[gunz4me2 10+ year member]

You will need to troubleshoot and try to figure out what caused the FETs to blow. Failure to do so could result in the replacement fets going up in smoke as soon as you power up the amp.

 

[mclerico83 5,000+ posts]

10 fets total, but something caused them to fry in the power supply, or the electrical of your car. a lot of times theirs somethign else that went bad, need to go threw and check the whole board.

 

[Undisputed King 10+ year member]

Yeah i'm going to admit that it was probably the electrical of my truck as I have a pretty much stock electrical. If I get it working again I will be running it at 2 ohms on 4-10's probably REX10's, so I won't abuse it so much with voltage drops.

Could it be strictly voltage drops that caused the FET's to burn up? Did the voltage drops also tear up the other components as well? I'm just asking just in case everything else checks out ok, so I don't think I overlooked something. Thanks for the help so far guys!

 

[Haunz 10+ year member]

Could it be strictly voltage drops that caused the FET's to burn up?

Absolutly not. This is a common misconception.

The psu fets could have gone on thier own, but there could easilly be problem with the output fets. Also keep in mind the amp may not have liked the load and the psu fets just went first. Your safest bet is to replace all the fets on the board. If you do only start with the psu fets make sure to use a power supply with a limited amount of current capacity to test the amp. (250watt computer supplies work great- and you should do this when first powering up the amp anyway). upon powering the amp up you will know very quickly if their is still a problem because the fets will get hot! If you are so inclined and have access to an O-scope you could remove and test the output fets. Definitely remove and check out any other suspect components like resistors and the retifying diodes as well.

I'd be wary of buying components from an ebay seller from china due to the large number of counterfit semiconductors on the market... check out digikey or mouser instead... I prefer a solder sucker and use a 140watt gun... you might also want to check out the amp repair primer over on bcae1.com before you get started...

 

[gunz4me2 10+ year member]

BUT, voltage drop CAN cause the power supply transistors to fail. Remember the first Gen Orion HCCA amplifiers and the 280 GX? When exposed to low voltage, one generally had the pleasure of changing EVERY FET in the power supply section. If you were really unlucky, you also had the pleasure of changing every FET in the audio output section too.

EDIT: Argh, I just noticed that the Crunch amp uses the same transistor clamps as the Hifonics amps. They are relatively easy to pull but extremely annoying to put back.

 

[Louisiana_CRX 5,000+ posts]

BUT, voltage drop CAN cause the power supply transistors to fail. Remember the first Gen Orion HCCA amplifiers and the 280 GX? When exposed to low voltage, one generally had the pleasure of changing EVERY FET in the power supply section. If you were really unlucky, you also had the pleasure of changing every FET in the audio output section too.
EDIT: Argh, I just noticed that the Crunch amp uses the same transistor clamps as the Hifonics amps. They are relatively easy to pull but extremely annoying to put back.

i hate those clamps //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[Haunz 10+ year member]

BUT, voltage drop CAN cause the power supply transistors to fail.

Tell that to dbr... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[bubbagumper6 5,000+ posts]

That and to get the board out you have to slide it to one end which will cause the fets to catch the insulators that sit between them and the heatsink. Then there's also several ground wires that go from the board to the chassis (between the board & chassis) that are fun to try and take off/put back, then there's also the small circuit board under the Crunch logo with a piece of plastic that seems to always catch on the board supports. I have plenty of experience working on this amp and it's a PITA.

 

[gunz4me2 10+ year member]

Tell that to dbr... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

I'll send you one of my Orion 280 GX amplifiers to low volt if you promise to completely repair it before you send it back to me!