QSC PLX3402 repair, this is a very hard repair, not for beginners.

[@gmespia]

Kudos. Great detective work.

[@danielolund7063]

you did not set bias on vr166 and vr43 ??

[@erwinvalisno6031]

good morning sir thanks to share vedio nice your explanation, ihave questions to my power amplifier qsc plx3002 done replace regulator and rgvt transistor and ir 0121, sg3525an and i check the power supply section is no shorted and the output transistor ic all okey no shorted the primary power supply turn on good supply but not secondary not comes supply sir , how to determine problem thanks

[@kansasnutt]

Ok here’s the deal …I think…, The switch mode is on full all the time, operating like a traditional power supply, it has 5 V across it error amp at all times… The energy is stored in the caps like a traditional amp, for fast transient response, I thought pulse width modulation is how it would control current to the speakers but evidently it is not fast enough?but it is also could be why it blows the crap out of everything when it fails If I ever get this thing working I will test the over current shut down .

[@RGD-Audio-Repairs]

the small bias transformer.. Located at T1.. What are the input and output voltages meant to be, please? Im struggling to trace a fault with my PLX 1202...

[@jimmykhan2398]

My qsc cx404 not audio input and not showing signal lights

[@edwarddilleyjr.1270]

anyone else have this problem everything else checks fine!

[@edwarddilleyjr.1270]

I just replaced all the same parts on a plx 3602 it ran fine on my Variac but when I plugged it into straight power q96/97 exploded an r358/359 an d78/79 opened?? I'm a tech of 38 years experience

[@clintronicsrva]

check this out. electronicshelponline.blogspot.com/2016/06/plx-series-qsc-plx-1202-plx-1602-plx.html#google_vignette

[@edwarddilleyjr.1270]

Would like to thank clintronic for your help I fixed 2 other amps for the same custr just typical shorted drivers! Strange the problem amp ran for several hours on my Variac at 110 volts ac! An 0 DC offset an great audio wish I could find a good used board LoL I'm thinking of getting the house keeping kit.thanks again

[@edwarddilleyjr.1270]

These amps are junk!!! I've been a technician for over 40 years an a professional touring drummer!! We have 4 of these boat anchors!! I've had to repair 3 out of the 4 this last one I fixed the shorted channel ran great on a Variac at 110 volts ac!! But when I plugged in to main power it blew q96/97d78/79 an the 2 ten ohm surface mount resistors!! This is after i installed the power supply restoration kit!! The schematic I have has no voltages except for the 16 an 5 volt checks what's the best way to check this pile of crack to make sure it's safe to power up ??? I've got crown amps I've had for 20 years 0 trouble!! A pro amps should be able to handle the rigurs of touring etc!! I don't trust these!! Everything checks help!!!!

[@roymoxley2587]

I see your in Va so I will have my friend contact you and bring you the amp

[@kansasnutt]

Clint, Looking at the schematic, The - input of the sg3525 regulator ic is tied to the PRI_LO , is this a mistake or what? How can this work? I see nothing that comes from the secondary as feedback

[@clintronicsrva]

Think of the Pri-lo as a floating ground. The Vref should read 5.1VDC

[@kansasnutt]

@@clintronicsrva Yes but what pin is changing The 5.1 is referenced to this it will stay 5.1 V difference no matter what

[@kansasnutt]

@@clintronicsrva Besides aren’t you supposed to sample the output where is the feedback?I mean how can you have a nice regulated secondaries without getting feedback from the secondaries

[@susie8222]

Kl fet swicing dikasih IRF PE 50 BISA

[@tibipoka6467]

Hi, one of my step driver mosfet is hotter then the other 3 ? after start .1 min this is 40C while the other 3 are 20C , should i be concerned ?

[@clintronicsrva]

yes, you still have one more problem to figure out. For some reason that part is working harder than it should be.

[@roymoxley2587]

I have a 3602 amp when the power is turned on all it does is the blue power light blinks You have a idea what is wrong

[@kensimon4478]

did you ever find out what was wrong with yours? i have the same issue. my speaker wires touched during a gig.. i don't know for how long. i just used my tops. i saw my 1/4 cable was damaged and touched. amp powers on and just clicks..