Something worng with amplifier, please help

[grandam888 10+ year member]

Alright, my amp is a rockford t15002 2 channel amp. 1500 watts rms @ 2ohm bridged, and 1 ohm stable stereo per channel and 750 watts rms.

When i turn my car on, amp makes a high pitched whining noise(coming from inside amp, not from speaker.) and volts on volt meter drop from 14 volt to 10 volts. and i am not even playing music through it, head unit is set at 0 volume when this happens.

i almost think i have a short somewhere inside the amp, before this started, amp worked fine except when turned up it would draw every bit of power out of may car down to 10 volts, so i stopped turning it on @ all to avoid damaging the amp. rms is 1500 watts so its pulling in the ballpark of 100-120 amps when turned up, and thats just rms. Also i have a 117 amp alternator, so we know i am underpowered.

i am almost leaning towards amp always having an issue with some kind of short as i have asked others about how fast it pulls down my voltage, and they find it odd that it does not play for more then 5-10 seconds. also i havent upgraded my big three, and i am running 0 awg straight from battery.

just want some opinions before i crack this amp open and start trying to find the short.

all help is appreciated. thanks

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[plugitin 5,000+ posts]

my guess is you damaged it by showing it low voltage

 

[grandam888 10+ year member]

well last night before i turned in for the night, i went out to my car and played a little bass, turned way down, and it was working fine.

now i get up this morning and its doing this.

i have noticed that even when barely turned up, it pulls more amperage and voltage than i feel it should be.

i have a 900 watt planet audio monoblock also, and its a class d. i can turn it up all the way and it doesnt even show any voltage drop(unless i am idling). but when this thing rockford is barely turned up, and hitting no where near as hard as the planet audio amp, and pulls my voltage down. of course this was before this mornings incident.

i opened the amp, and all looks good as far as capacitors and i cant see any shorts. i did find a stray piece of wire floating around, but i have a suspicion this has nothing to do with it as it would have blown that little piece of wire like a fuse.

i guess it off to retesting amp, then testing all mosfets and transistors.

if anyone has any ideas, i wold appreciate it. thanks

 

[bubbagumper6 5,000+ posts]

my guess is you damaged it by showing it low voltage

agreed

 

[CL1CKCLACK 5,000+ posts]

Thats actually a good sized stock alt. once you figure out the issue do the big 3, and maybe add a second batt.

i would just send the amp into RF instead of trying to do it yourself, unless you know A LOT about electronics

 

[kr15 5,000+ posts]

10v is pretty bad drop, I would wager that most amps would get damaged at this point...and 117a is actually decent for stock. Do the big 3, get amp repaired and you should be fine

 

[grandam888 10+ year member]

i have repaired a few amps myself, if i can find out whats wrong, with only my multimeter, i can fix it pretty easily. but the wierd thing is i dont even get a protect light, or thermal etc.

usually in amp amp the most common part to go bad is a mosfet, then after that a capacitor, transistor so on. i live near an electronic components store, so buying components is pretty convenient.

thanks for the advice, its appreciated.

 

[Spooney 10+ year member]

It sounds like you have some FET's that are probably on their way out. A part doesn't have to look burnt to be defective. It can look perfectly new and still be internally shorted or leaking. If you have a multimeter you can start by setting that to continuity check or the lowest ohms range and checking between the legs of the heatsink mounted FET's and transistors. If you have any real low numbers here you definitely have some shorted/leaky FET's . If you get anything near zero between any two legs on a FET then it is most definitely shorted. I wouldn't really attempt to play anymore sound through it at all until you get something figured out. If you can, try powering the amp up through a 15 - 20 amp fuse with no signal driven into the amp. If the amp won't turn on and idle without blowing that size fuse then you definitely have a defective output or power supply FET. If this rockford amp uses the mehsa system for mounting the FET's you are going to have a hell of a time trying to repair it yourself. If it is mehsa the FET's themselves are soldered directly onto little boards that are then screwed/secured to the heatsink to aid in heat transfer. There is no way you are getting those FET's off of those strips with a regular soldering iron without Fxxxking up the mehsa strip so don't even try it. These rockford amps are a pain for even experienced techs. If you only kinda know what you are doing and honestly it sounds like you have maybe a very very basic knowledge of amplifier repair I wouldn't even mess with the amp. Either send it to a reputable repair shop or sell it as is.

 

[grandam888 10+ year member]

yeah i beleive what your saying is correct. i looked inside, and everything looks fine. and i know the output transistors can look fine and still be stuck open or closed, my guess is one is stuck closed.

the fets are soldered onto a board that is then screwed to the heatsink, with thermal grease applied. i am glad you mentioned this as i dont want to go and try to repair it myself and screw things up even worse. i will check the mosfets and output transistors but beyond that i will send am in for repair.

thanks for the advice.

 

[Spooney 10+ year member]

Yeah your amp has the mehsa system. Works great for heat transfer but a huge pain to work on. I know a few techniques for doing it but I myself shy away from these for that reason. There are ways around it but its just not worth the time or effort to me.