Hello everyone First post
Is there a bad cheap mosfets ? I'm trying to repair 2 Earthquake amplifiers 200 DHC, and not having any luck,
The first one was burn all 8 mosfets, the amplifier didn't turn on at all there was nothing showing on my power supply needles, I replace all the RFP50N06
and now there is a short, I check all the connections remove them one by one and the short still there, when I remove the last mosfet no more short
So after 2 hours I move to the next amplifier, this one turns on the load was high almost 20 amps, I open the amplifier and the transistors for the channels are burn only 4 I remove them and the amplifier turn on there is no more load
and notice that 3 RFP50N06 in the power supply are burn crack, so I replace 3 new RFP50N06 and now I have a short, and the amplifier is not turning on anymore, I remove them one by one, until the last one is out and the amplifier turn on.
Do I have bad RFP50N06 ? they are from ebay RFP50N06
the new ones have the F logo on the mosfets FAIRCHILD
the originals are Harris
Thank you for any input you can give me
Is there a bad cheap mosfets ? I'm trying to repair 2 Earthquake amplifiers 200 DHC, and not having any luck,
The first one was burn all 8 mosfets, the amplifier didn't turn on at all there was nothing showing on my power supply needles, I replace all the RFP50N06
and now there is a short, I check all the connections remove them one by one and the short still there, when I remove the last mosfet no more short
So after 2 hours I move to the next amplifier, this one turns on the load was high almost 20 amps, I open the amplifier and the transistors for the channels are burn only 4 I remove them and the amplifier turn on there is no more load
and notice that 3 RFP50N06 in the power supply are burn crack, so I replace 3 new RFP50N06 and now I have a short, and the amplifier is not turning on anymore, I remove them one by one, until the last one is out and the amplifier turn on.
Do I have bad RFP50N06 ? they are from ebay RFP50N06
the new ones have the F logo on the mosfets FAIRCHILD
the originals are Harris
Thank you for any input you can give me
RFP50N06
Rather than buying them from a questionable source, buy them from DIGIKEY. Only a little more money and they are real parts. 1.51 each vs .79 each. Was it worth it to save money if the parts are questionable?
Rather than buying them from a questionable source, buy them from DIGIKEY. Only a little more money and they are real parts. 1.51 each vs .79 each. Was it worth it to save money if the parts are questionable?
RFP50N06 is an old RCA part number, so those must be ancient amps. RCA has not made semiconductors for many years, so the fets you got from Ebay are either old, old parts or fakes (most likely). There are better parts these days that could be substituted to get the job done, obtainable from reputable sources.
Huh - I just looked on the web, and Fairchild is making a part now with the same part numbering scheme. It may be worthwhile buying some of the Fairchild parts from Digi-Key or Mouser and trying again, in case the Ebay parts were fakes. If the legit Fairchiild parts blow, then we can talk about better substitute parts. Before you go that far, though, also check the gate drive connections of all the fets. If they have gate resistors to prevent oscillation (they should), and one of them has been fried to a higher value, it may cause that particular fet to turn off late and grab all the load current to itself - bang!
Huh - I just looked on the web, and Fairchild is making a part now with the same part numbering scheme. It may be worthwhile buying some of the Fairchild parts from Digi-Key or Mouser and trying again, in case the Ebay parts were fakes. If the legit Fairchiild parts blow, then we can talk about better substitute parts. Before you go that far, though, also check the gate drive connections of all the fets. If they have gate resistors to prevent oscillation (they should), and one of them has been fried to a higher value, it may cause that particular fet to turn off late and grab all the load current to itself - bang!
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One more thought - there may not actually be anything wrong with the fets you got except that they are much newer devices, meaning faster and lower gate charge.
This means that they could quite possibly oscillate violently and blow up if they are used to replace an older, slower device. FETs operated in parallel should have gate resistors to prevent oscillation. If there is no provision for gate resistors on the amplifier that you are repairing, slip a ferrite bead on the lead of each mosfet before you insert it into the board. This should quell any tendencies to oscillate. Paralleled fets are particularly oscillation-prone without protective measures.
This means that they could quite possibly oscillate violently and blow up if they are used to replace an older, slower device. FETs operated in parallel should have gate resistors to prevent oscillation. If there is no provision for gate resistors on the amplifier that you are repairing, slip a ferrite bead on the lead of each mosfet before you insert it into the board. This should quell any tendencies to oscillate. Paralleled fets are particularly oscillation-prone without protective measures.
Thank you , I did order better parts from Digikey , I don't know why i waste my time with the ebay parts
Yes there are resistors, but they are all good, also this happens when i put power to the amplifier without the remote turn on , thank you
So, what you are saying is the parts pop as soon as voltage is applied, even though they're not switching? Sounds like fakes to me. What sort of voltage is applied to the parts at turn-on?
Correct I solder all 8 transistors clean everything, this time I use a 12 volt 10 amps power supply connected to the power terminal of the amp, ( no remote wire), I flip the switch and there is a big short, and transistor start to get warm. If I use my 55amps power supply I will fry them all
in this picture aim removing everything again, you can see the resistors near the small 8 pins ic chip
in this picture aim removing everything again, you can see the resistors near the small 8 pins ic chip
An externally hosted image should be here but it was not working when we last tested it.
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