recently deceased RF P200-2 :(

[kmarei]

i was running this amp to power 8" subs @ 2ohm each
and it used to get hot, but not crazy hot

now it won't power on
and there is a smell of something burnt
i opened it up and i can see one area that's all covered in black soot
i assume something in that region is busted
any tips?
i assume i'd need to change the 2 FETs below the heatsink on the right (near the blackended are)
i assume those are for the power supply area, as the one on the top left and the one on the left look similar so i think those are for the 2 channels
would also explain why the amp doesn't power up


[IMGDEAD]http://kmarei.homeip.net:8000/files/P200-2.JPG[/IMGDEAD]

 

[kmarei]

i removed the heatsink on the right
and both FETs have the leg towards the bottom of the picture burnt
they are labeled IRFP064N P709XD

 

[Perry Babin]

IRFP064N is the part number you'll need to order.

It likely also burned the gate resistors and possibly the driver transistors. The gate resistors would be near the first leg of the FETs. The driver transistors would likely be on the driver board near an IC marked TL494 or TL594.

You need to check the output transistors to see if they're shorted. If they are, they're the reason the power supply failed and you'll have to replace those also.

 

[kmarei]

ok i found the IC (tl494c), the resistors near it look fine, will measure them.
which ones are the output transistors?
the 4 on the middle to top right? (Q1003, Q1002, D1000, D1001
or the 2 on the left side of the amp and the 2 on the top left side of the amp (Q2011, Q2010, Q3091, Q3005

the gate resistors looks toast, will order those.

thanks a lot
you already rescued me on my Soundstream reference 405 that had one bad channel, i fixed that based on your advice, and it's working great and sounding better

 

[Perry Babin]

The output transistors are the 4 large transistors on the top and left of the heatsink.

When you order parts, also order MMBTA06s and MMBTA56s. Those will replace the drivers if they're defective.

Remove the power supply FETs and power up the amp. You should read approximately 5v DC on the gate resistors for the power supply FETs. If they're defective, you'll only read 5v on the end of the resistor connected to the driver circuit.

 

[kmarei]

ok i tested the amp with a power supply that puts out 11.5v
i measured the 3 holes for the power supply FETS (after removing them)
0v on S leg
11.5v on D leg
and 4.27v on the G leg
both gate resistors measured 4.27v on both sides of the resistor

does that mean i just need 2 power supply FETs?
i found 2 versions of the IRFP064N
55v 110A 200w
and 60v 70A 300w

which one should i get?

also how do i check the output transistors?
i measured them and the one on the left of each pair measured the same
and the ones on the right measured the same.

 

[Perry Babin]

I think one of those sets of specs are incorrect. The first one is what I see on the datasheet directly from IR.

http://datasheet.octopart.com/IRFP064NPBF-International-Rectifier-datasheet-27882.pdf

4.27 is probably about right with only 11.5v.

If no lead placement on any individual transistor read near 0 ohms, they're likely OK.

You should measure the resistance across the gate resistors for the power supply to confirm that they're within tolerance.

 

[kmarei]

i just searched on ebay for IRFP064N and got this
irfp064n items - Get great deals on Business Industrial, Electronics items on eBay.com!=
so based on the spec sheet you attached its the 55v 100A version

measured resistance of the 2 gate resistors
R1004 read 116ohms
R10 read 62 ohms
not sure what they are supposed to be
when the FETs blew that whole area is blackened so i can't read any numbers on them

do i measure the output FETs when the amp is powered ?
do i have to remove them from the circuit?

 

[Perry Babin]

I'd suggest that you don't buy semiconductors from ebay. There may be legit sellers but there are also sellers peddling counterfeit parts.

Try THIS.

I don't know if they have a minimum but you were going to pay $10 for 2 so I'd suggest that you order 10.

What are the numbers on the resistors? Clean the soot off with cotton swabs and either alcohol or acetone.

There's no need to measure anything more on the outputs if none had any 0 ohm readings.

 

[mike49504]

Do not apply power to the amp for testing the output transistors.

Set your multimeter to ohms place black probe on leg 1 and red probe on leg 2 (middle leg) then place black probe on leg 1 and red probe on leg3. The place black probe on middle leg and red probe on leg 3.

Post your results as followed

1-2:
1-3:
2:3

You can leave the outputs inside the amp.

 

[kmarei]

I'd suggest that you don't buy semiconductors from ebay. There may be legit sellers but there are also sellers peddling counterfeit parts.

Try THIS.

I don't know if they have a minimum but you were going to pay $10 for 2 so I'd suggest that you order 10.

What are the numbers on the resistors? Clean the soot off with cotton swabs and either alcohol or acetone.

There's no need to measure anything more on the outputs if none had any 0 ohm readings.

i just tried ebay cuz i could not find it on Mouser
but i'll get those, thanks

i tried cleaning the resistors, still can't read anything
they are labeled R10 and R1004 on the board

 

[kmarei]

Do not apply power to the amp for testing the output transistors.

Set your multimeter to ohms place black probe on leg 1 and red probe on leg 2 (middle leg) then place black probe on leg 1 and red probe on leg3. The place black probe on middle leg and red probe on leg 3.

Post your results as followed

1-2:
1-3:
2:3

You can leave the outputs inside the amp.

tried that
this is moving clockwise from the bottom left output FET to the last of the 4

1st one
1-2 no reading
1-3 0.284
2-3 0.581

2nd one
1-2 0.886
1-3 0.284
2-3 no reading

3rd one (top of the heatsink moving from left to right)
1-2 no reading
1-3 0.284
2-3 0.585

4th one
1-2 0.886
1-3 0.284
2-3 no reading

so i assume 1-3 and a set and 2-4 are another set since they read the same

 

[mike49504]

R10 And R1004 are the same value resistors. They are 60.4 ohm resistors.

 

[Perry Babin]

The gate resistor that reads 100+ ohms needs to be replaced.

 

[kmarei]

The gate resistor that reads 100+ ohms needs to be replaced.

I was hoping no one would say that
I hate soldering SMT stuff
Always use too much heat and burn the parts
Should I change both resistors while I'm at it?
Do why have to be a matched pair?

So basically the 2x IRFP064Ns and the resistor(s) need to be changed?

 

[Perry Babin]

To desolder, apply additional solder to both ends of the resistor. Lay your iron's tip across both solder joints to heat both at the same time. When the solder is molten, wipe the resistor off of the pads. It will take less than 5 seconds.

Desolder with desoldering braid to clean the pads. Apply solder to one end. Heat the solder and slide the resistor into the molten solder. Hold it there and remove the heat. Solder the other end.

Nothing has to be perfectly matched here because there are no parallel parts but the resistors have to be within tolerance.

As of now, it appears that you only need to replace the FETs and the resistors.

 

[kmarei]

any idea how many watts the resistor should be?
i found 1/16w, 1/32w etc

Search result for: 60.4 resistor - Future Electronics

i think the size is 2mm x 1.3mm

 

[Perry Babin]

Look at the dimensions. 0805 is 0.080"x0.050". That's what Rockford typically uses in their amps for gate resistors.

 

[kmarei]

what kind of current do the gate resistors carry?
when i was de-soldering one of them (R1004) i scraped off the soldering points, the other side is ok
so i scraped a little bit off the resin over the line that leads to that soldering point
can i just solder a wire from one end of the resistor to that part i scraped off?

 

[Perry Babin]

The current flowing through the resistors is insignificant.

You can repair it as you described.