posted
This is a RF 401sp 2 channel amp. Supposedly 200w rms x 2 @ 2ohms.... The right channel is dead. As you view it in the pic below it is on the left side...
this is a close up of the resistors you see on the left side of the amp in the pics above - notice the burn marks on them:
here is how they are wired in directly to the mostfets...
Now those resistors have infinite resistance...where as the good ones on the other side are reading 0.5ohm...
Is this the main culprit of why the amps right channel doesnt work?
What do these resistors do?
Where might I find some just like these?
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posted
fry's has a decent collection. look up the color code online to find their value or unsolder one and take it in & buy some new ones. It's cheap and easy.
Probably a couple bucks and maybe a half hour of your time...worth it to test.
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quote:it would all be for nothing without my favorite cawk-smoker NAvi
damn, it's hard to tell what color it is...don't think it's red though. I'd just unsolder it, measure the resistance with a dmm, take it in and find a match.
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quote:it would all be for nothing without my favorite cawk-smoker NAvi
posted
My guess would be brown-black-gold, or .1ohm I think. But a DMM isn't going to measure a .1ohm resistor very acurrately. since those are connected to the Source or Drain of the FETs you can't get any current on that channel if you have opens instead of a low resistance. What I would be worried about isn't just changing the resistors, an exercise that will just cost you some time and 10 bucks, but what cuased the resistors to go bad. There might be an underlying problem that just swapping the resistors won't fix.
Posts: 2575 | From: GA | Registered: May 1999
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quote:Originally posted by jc2: What I would be worried about isn't just changing the resistors, an exercise that will just cost you some time and 10 bucks, but what cuased the resistors to go bad. There might be an underlying problem that just swapping the resistors won't fix.
good point.
Don't know if the time and money is worth it to you to tinker. How much would to have a shop fix it Yota?
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quote:it would all be for nothing without my favorite cawk-smoker NAvi
quote:Originally posted by jc2: My guess would be brown-black-gold, or .1ohm I think. But a DMM isn't going to measure a .1ohm resistor very acurrately. since those are connected to the Source or Drain of the FETs you can't get any current on that channel if you have opens instead of a low resistance. What I would be worried about isn't just changing the resistors, an exercise that will just cost you some time and 10 bucks, but what cuased the resistors to go bad. There might be an underlying problem that just swapping the resistors won't fix.
yeah,I agree.Your mosfet's could be bad also,in Rockfords,on the output side,you have N-channel,and P-channel mosfet's. I suggest you have a repair shop fix it. ;)IRF540=N-channel,and IRF9540=P-channel.
-------------------- MR.SEARS(LOUD) LIL WHITE CAVY TEAM SUPREME AUDIO TEAM DB TEAM PSYCHO(RIP) PRO TRUNK 1x NSPL 2005 TRUNK STOCK WORLD CHAMPION 1x NSPL 2005 TRUNK STOCK WORLD RECORD HOLDER Posts: 154 | From: Elizabeth City | Registered: May 2005
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posted
those are like 2 watt resistors... I'd replace them with 5 watt... and do the same on the other side...
they won't fit the same way however, but thats alright.
the mofsets being open circuit wouldn't kill the resistors, if the mosfets had died, and gone a dead short, they would have blown the fuse in the amp...
the resistors are used to match the outputs from the mosfets, anything 0.1 - 0.5ohms / 5watts should be fine, but replace both sides with the same.
its quite possible the old resistors just got hot, from a fairly low load on each channel, just one channel suffered, and the other didn't. but having said that, I've seen resistors turn brown from heat, but still work fine...
posted
check the power supply fets as well...also check the drivers which drive the PS fets in the t0-220 casings that lead off of the pwm chip, need to check the power supply first to make sure its healthy.
www.bcae.com to learn how to properly check semiconductors.
go to diyaudio.com and we'll have you up and running.
-------------------- Proceed with caution when you feel me hittin at the stoplight... Posts: 50 | From: earth | Registered: Oct 2007
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quote:Originally posted by Death By Bass: those are like 2 watt resistors... I'd replace them with 5 watt... and do the same on the other side...
they won't fit the same way however, but thats alright.
the mofsets being open circuit wouldn't kill the resistors, if the mosfets had died, and gone a dead short, they would have blown the fuse in the amp...
the resistors are used to match the outputs from the mosfets, anything 0.1 - 0.5ohms / 5watts should be fine, but replace both sides with the same.
its quite possible the old resistors just got hot, from a fairly low load on each channel, just one channel suffered, and the other didn't. but having said that, I've seen resistors turn brown from heat, but still work fine...
so... goodluck
Yea, ive just been wondering that...how many people mod their amps with higher wattage resistors?...been wondering what kind of positives that would bring or if it'd be unnoticeable..?...
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First and only dual-alternator Saturn on the planet Sub and sub amp: 18" Fi BTL fully loaded, fed by a SoundStream XXX10000 Handmade custom bracket replacing AC with 250 amp alt Soon - 225 amp alternator in stock location Batteries: Trunk-(2) XS Power D3100's 4 power+4 ground 0-gauge runs to rear Posts: 576 | From: OH | Registered: Apr 2007
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posted
Why don't you check the mosfets of this channel?
Measure them as they are connected on the board and if you have a short circuit reading then start cutting their terminals one by one checking step by step which one of the mosfets is the damaged.
They maybe connected in parallel so if only one will be blown you will get the short circuit reading for all of them.
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