Jl 500/1 irf540n?

[mbates14]

I assume you cannot use the IRF540Ns in a IRF540 JL audio 500/1 unit?

Reason I ask is becuase its doing something weird. it had failed outputs and a few bad SMPS transistors. replaced all those and resistors associated that were burned up. none burned up in the output circuit.

Amp will take a tiny bit to startup, and plays fine. but cuts out. plays, cuts out. plays, cuts out. itll stay cut out for about 1 or 2 seconds. play for about 5 to 10 seconds.

So i put the amp on a 40amp power supply. and it played and sounded fine for a little bit. then started cutting out and turning back on. it was pulling the 13.8v 40amp power supply down to about 10v at idle. so something wrong...

is it the 540N?

[Perry Babin]

I think I'd recommend replacing the N-version with either the IRF540A or the IRF540. There could be another problem but you need to eliminate the outputs as a possible problem before you spend too much time troubleshooting.

[mbates14]

Nothing in the amp is getting smoking hot or anything. its just drawing way too much current, then SMPS will shutdown/restart. I replaced all the SMPS FETs, but there are a few that are not in the same batch number. but they were all ordered at the same time to be replaced.

[Perry Babin]

At idle, does the heatsink behind the outputs heat up?

[mbates14]

nope. nothing gets hot unless i am blasting music through it. at idle, heatsink does not get hot.

[Perry Babin]

Change the outputs to a different, non-N IRF540. It may not solve the problem but it will eliminate it as a possible problem.

[mbates14]

Well i was reading posts around here that 540 and 540N cant be substituted in certain class-D amps, so thats kinda what has drawn me to that conclusion. I notice this amp uses a 4427, and N is logic level, so the use of the 4427 isnt necessary with the 540N?

[Perry Babin]

The IRF540N isn't a logic level FET. The IRL540 is a logic level FET. Logic level FETs have a lower threshold voltage and can be fully saturated by a 5v (logic level) drive signal.

[mbates14]

then i must have mis-understood posts in this forum from other threads. Anyway, whats the difference between the IRF540N and IRF540 then?

[Perry Babin]

There are minor differences. You could download the two datasheets to compare their specs. Generally, they seem like they should be a good substitute but it appears that they are not. I can't tell you why they don't work but I know, especially in punch class AB amps, they don't.