Rockford Fosgate BD15001

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#21
Perry Babin said:
Occasionally, if the pot is at the very center position, the FETs will switch on/off too quickly and the amp will go into protect but I've never seen them fail with the pot connected as shown. If you do the same thing with the op-amp removed (pot wiper connected to pad for pin 6), it's VERY easy to blow the outputs. That's why I recommend connecting it as you did.

While you have the outputs out, re-check the gate-source voltage to make sure it's still switching. If it's OK, you can remove the pot and re-connect the resistors. After tinning the backs of the transistors, check for leakage from the gates to the other legs (meter on ohms) to confirm that there is absolutely no leakage before soldering them to the MEHSA insulator.
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Ok that makes sense because the pot was at center position when the failure occurred. What am I looking for on my ohm meter to detect leakage? What will the readings be when they leak and what will they be when they dont leak. How can I test the remaining ones in the circuit for leakage so I dont have to replace any that dont need it? Do I desolder the gate leg and check the other legs? Can I do this while the other legs are still soldered in the circuit?
 
#22
One thing I thought I would add Perry when the output went upon removing the board from the sink the rail caps were completely discharged not even a trace of voltage. Why would this be I usually always have to discharge. Thought that was kind wierd....
 
#23
Just thought I would also add Q25, Q8, Q104, Q101 are the fets that blew. I havnt checked any others for leakage but the standard test I do with my meter checking from gate to source still in circuit tells me none else are shorted but not telling me if they are leaking. What do you think??
 
#24
Hey Perry another heads up this amp has that wierd mod I see alot on U14. There is a jumper wire from pin 5 to pin 8 and a 2.2uf 50v cap form pin 7 to 8. Think this may have had something to do with it not going into protect and saving the fets??
 
#25
Well down for now till I head to radio shack installed new fets fired up amp and blew a gate driver. I think they are 25 ohm ?? Not sure was hoping you could tell me. The BD1000 uses a different one I think 15 ohm so no donor parts. Hope to hear from you soon.......Thanks again
 
#26
Anything I should check before firing up the amp again? Dont want to blow anything again. Let me know what you think when you catch up on all of my posts. I am concerned about the mod that has been done, and wondering if thats why it didnt go into protect and if I should remove the mod? I just dont know what it does, the last 3 amps you helped me fix didnt have it but I have several amps that do so just wondering what the heck it does?
 
#35
Hey Perry those gate drives for the ouput fets we talked about?

1st band red = 2
2nd band yellow = 4
3rd band white = 9

4th band gold = 0.1 ( multiplyer)

5th band brown = 1% tolerance

So what I get is 24.9 ohm ?

I would assume these are 1/4 watt or are they 1/2 watt?

Having a hard time locating them. Any ideas??
 
#40
Perry Babin said:
If you have to replace ALL of the outputs, check the gate drive (view gate waveform on the scope) while you have them out of the circuit.
Click to expand...


Hey Perry I am going to remove all the output fets and start over. I think it would be wise after a major failure such as I have had. This will give me the ability to do the testing you requested with out failures. I am also going to replace all the gates as well. I have 100's of IRF 6215 and IRF 3415 output fets so parts are not an issue just dont want my eye put out by exploding fets. I saw a qoute that someone wrote in a forum one time. Their version of "FET" was "FIRE EMITTING TRANSISTOR" thought that was kinda funny.

TTYS on this one waiting on parts......Thanks again
 
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