Amp wont power up after FUSE blow?? Visonik4000D

[ultimate157 5,000+ posts]

wat ? the behavior you describe is quite contrary to Ohm's law..
That amp has an unregulated power supply and the rail voltage and power output is going to be proportional to input voltage.... The amp is not going to pull more current as voltage drops, it's going to pull less...

Even if it was a tightly regulated amp, it would be designed to work reliably with the PSU switching at 100%...

Not sure how the circuitry is setup, but...

If an amp is trying to output the same power as voltage drops, then current will have to increase to keep output the same.

 

[Haunz 10+ year member]

^ that only happens with a tightly regulated power supply.... and even then it is more correct to think of the amp pulling less current with more voltage, rather then more current with less voltage...

 

[lilmaniac2 5,000+ posts]

wat ? the behavior you describe is quite contrary to Ohm's law..
That amp has an unregulated power supply and the rail voltage and power output is going to be proportional to input voltage.... The amp is not going to pull more current as voltage drops, it's going to pull less...

Even if it was a tightly regulated amp, it would be designed to work reliably with the PSU switching at 100%...

I have no other reason, other than personal experience to base this on, but on every class D amp I have ran, the lower the voltage dropped the less efficient it became,and the more current it drew.

Also I have tested 20+ amps and even tho voltage drops significantly power doesn't drop proportionally, so even without a regulated power supply in my personal experiences amps pull more current at lower voltages.

 

[AdrianD 10+ year member]

FET's heat up more when trying to pass the same amount of power thru them at lower voltages. More heat = physical damage to the semiconducting material inside of the MosFet's.

To put it short...the FET's cannot close fast enough with low voltage and as soon as the voltage drops below a level there's a risk of running the amp with both fet's open (both sides) which causes them to blow //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Quickest thing you can do to check if your amp (power supply side) is blown is to measure the resistance over the power terminals.

 

[Livin' Loud]

Has nothing to do with cheaping out, I had a holder, it broke, replacment holder and 2 300amp fuses are coming from ebay, the only local audio store we have is future shop. And when I just went to go buy there last 150amp fuse, it was gone......
So now I have to go out of town, just to buy an overpriced fuse, just to test to see if my amp is pooched, I just checked the firewall gronmet (pretty much the only tight spot the power wire might have frayed) and it was perfect.

But I'll get that fuse and report back, and probably unmount the amp and take it apart and post up the pics later tonight

rofl yes it does *** haha j/k ur fuse showing how it is is the dumbest shit i have seen today

 

[WOT]

Alrighty seems to have rolled off topic, but heres where I stand.

Pulled the power wire from the amp, disconnect batteries, install new fuse, connect batteries, left for 5 min, fuse was fine.

Disconnect batteries, connect power wire to amp, connect batteryw ire grounds. Fuse obviously still fine.

Turn the stereo on, instantly heard a pop under the hood. Fuse blew as soon as I turned the cd player on.

So, I took the amp off the amp rack and took the back plate off, board LOOKED perfect, mind you I dont know what Im looking for, but one guy mentionned checking the opposite side of the amp form the power wire connection really well. I fintoothed the comb pretty well and didnt see a single burn spot or melted reisitor or anything. A few shitty lookin solders......

So Im assuming its my amp, I just dont see anything. I'll post pics of the board tonight if anyone can review it for me....

WHat can I do from here? Fix anything myself or send it out for repair?

 

[Haunz 10+ year member]

is the amp going into protect ? I think you said it's doing nothing but blowing the inline fuse ?

you can test for shorted out fets with a DMM.. if that shows nothing obvious I'd put it on a bench and power it up with a 10 amp supply... it will either power up, or you'll know which fets are bad cause they will get hot real quick..

sounds like it may be toast... you should sell it to me so I can fix it... //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[WOT]

umm to be honest I dont know if it went into protect, those LEDS are on the other side of the amp and I wasnt over there when the fuse blew, so i dont know what it did other than not power up and blow that fuse....

When you say toast, can I atleast get it repaired?

 

[WOT]

Id love to know how to check anything I can before bringing it to a shop, I'll post pics of the board later tonight but it looks just fine to me.

Dont know how the thing worked for such a short period of time then just kapooted

 

[wolfman1966 10+ year member]

Dont know how the thing worked for such a short period of time then just kapooted

lol, new word for me to use

btw Is that a technical term?

 

[WOT]

Yes, its the installers term for paperweight.

bump for some help here

 

[audioarsonal 10+ year member]

You probably low volted it.What kind of batteries are they.You did say you had 2 of them correct?

 

[Haunz 10+ year member]

You probably low volted it.

so, the fets couldn't close fast enough and were running open.. //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

O.P. I'd put the amp on a small 12v supply... it will isolate any possible wiring problems and if the amp is OK it should power up fine.... if something is wrong with the amp itself the supply will not be able to deliver enough current to cause anything to granade/burn up or cause any traces in the board to fry....

a small 10amp battery charger should work... just hook it up briefly and see if it turns on, goes into protect, or does nothing at all...

 

[WOT]

I dont know about low volting it, it was only playing for maybe 1 min when it blew and Ive had it paying for longer the same day. They are just simple optima blue top batteries with good wiring.

I dont have a battery charger, but I'll try and find one around maybe.

 

[AdrianD 10+ year member]

Quickest thing you can do to check if your amp (power supply side) is blown is to measure the resistance over the power terminals.

Guess I'll try again...//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif