bench tested used JL 300/4, bad results.

[nathanh 10+ year member]

so i hooked up my amp to my xbox with my ipod and a car battery. second time i have bench tested it. first everything was cool, but noticed that the...

low ohm light

was on... but everything worked fine. so i decided to test the amp on a full load of a componant set. and still the same thing, works wonderfull but the low ohm light was on, so i picked it up to put it back and called it good... but i noticed something...

the f'er was Hot!

like not like hot hot like burn me, but that was heated up pretty well for just running 4 little speakers at low levels. like deffinalty past warm. so anyone know what this could be from?

i have another 300/4 that i bench tested the same way and it was fine, no light and cold when i was done. fyi.

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[n2audio 5,000+ posts]

it would be helpful to know what voltage that battery was at.

If the battery was 12v or less I'm guessing the RIPS system was drawing some serious current since it is a stiffly reg'd amp.

But just a guess.

 

[nathanh 10+ year member]

huh, well, as i suspected! one hundred and twenty dollars! or in numbers $120 f'ing dollars! to fix this abortion! lol apperently due to the use of the 300/4 among beginner installers, fuses are never added leading to total amplifier fryige! i payed 100 for this amp, what makes them think i want to spend another 120 on repairs?

 

[dave_damage 10+ year member]

right

 

[nathanh 10+ year member]

well looked at a couple sites, and ran into this... one man comments on it being a

"This can happen if the amp has an internal fault such as a shorted output transistor"

so i looked around and...

very interesting amp rebuild

so i looked into my amp... and for some odd reason, there are two output transistors that are tagged with red paint... humm... wonder why that is.

so i am going to try and locate parts to replace all the output transistors on my amp for safe measure and redo the glue as this guy had done and see where it gets me.

now all i need is a website that will carry output transistors.

 

[nathanh 10+ year member]

k so i have 16 of the output transistors, but only two of them have the mysterious red paint on them. so should i replace all the the 16 at 3 dollars a peice? or just the two with paint on them? the back of the board has bubbles around the two with red paint... like where the epoxy sealent has burned... thats kinda why i looked in the first place. but is there a way to test them? i'd like to order all at the same time, just so i only pay one shipping fee

 

[nathanh 10+ year member]

how to test transistors

problem solved! //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[NB50 10+ year member]

You may want to check out these for the parts.

http://digikey.com/

http://www.mouser.com/

http://www.alliedelec.com/

 

[valter 10+ year member]

I'll give you $100 for this amp, or I can fix it for you twice cheaper then you were quoted //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[nathanh 10+ year member]

you sound very positive that you know what's wrong... i would rather fix it myself so i can learn how, can you just give me a recommendation on how to test and fix?

 

[valter 10+ year member]

It's either one of the output FET's leaking/blown or one of 4 driver boards damaged. Do you have DC current in one of the channels?