JL AUDIO 250/1

S Merlington · 2012-09-24 2:42 am

Anyone know the values of the power supply gate resistors ??

The gate resistors in this amp are all burnt to badly to read the numbers..

Its a REV 1 board

S Merlington · 2012-09-24 5:43 pm

Anyone know?

Perry Babin · 2012-09-24 6:06 pm

47 ohm

S Merlington · 2012-09-27 4:14 am

Replaced the Gate resistors , The drivers for the power supply fets and replaced the Power supply fets..

With just power and ground hooked up the amp will draw excessive current..

Any ideas on what to check?

Perry Babin · 2012-09-27 8:22 am

Do the power supply FETs heat up?

S Merlington · 2012-09-27 2:07 pm

Power supply fets are getting hot..

If the outputs are out of the amp the amp powers up and idle's perfectly..

If i put the outputs in the amp and only hook power and ground up NO REMOTE the amp will draw excessive current and the power supply fets and the outputs will get hot

Perry Babin · 2012-09-27 7:55 pm

Do you see any oscillation on the output pins of the SG3525 when the output FETs get hot?

S Merlington · 2012-09-27 9:09 pm

On Pin 14 i get a square wave but it is bouncing around the display on my scope.. Its a square wave but its not clean and not steady..

Pin 11 i get nothing that looks like a square wave at all It just line going everywhere

Perry Babin · 2012-09-27 9:15 pm

Is the signal sensing set to 'on'? If so, switch it off. Does that make a difference?

S Merlington · 2012-09-27 9:30 pm

Switching it to the off posistion makes no difference

I replaced the power supply driverboard with 1 from a working amp

Still have the same thing

S Merlington · 2012-09-27 10:38 pm

Setting the signal sensing switch to off doesnt make a difference..

If i remove 2 outputs -- Q404 and Q407 the amp will not draw excessive current..

With the 2 outputs still in the amp If i hook just power and gound up the amp will still draw about 1 amp of current..

Perry Babin · 2012-09-28 12:20 am

When you make/break the remote connection, does the power supply produce pulses and then stop producing pulses?

Do you get rail voltage when the amp is drawing 1 amp?

S Merlington · 2012-09-28 1:46 am

When you make/break the remote connection, does the power supply produce pulses and then stop producing pulses?

Yes

Do you get rail voltage when the amp is drawing 1 amp?

Yes i get 60 amps of rail voltage on the outputs with just power and ground hooked up

Perry Babin · 2012-09-28 2:14 am

Confirm that all gate drive signals are identical then post a scope cap of the drive signal at the gate leg of one power supply FET.

S Merlington · 2012-09-28 3:00 am

Still waiting for my phone to upload the pic to my email ..

The gate signal dont look good

S Merlington · 2012-09-28 3:11 am

Heres the pic of the gate signal hope the pic is big enough

Scope set to 2 us .5 volts/div

Perry Babin · 2012-09-28 3:18 am

Without the scope settings, it's difficult to tell. Please read the 'Best Initial Settings:' sections on the oscilloscope page of the site.

Try this, set the DC supply voltage lower. You want the drive to go to the full duty cycle. Does the current draw increase?

S Merlington · 2012-09-28 4:48 am

Is there anything i can stick in the B+ wire to drop the voltage since I cannot adjuust the voltage on the power supply?

Perry Babin · 2012-09-28 5:32 am

A resistor but it's not a good choice because the voltage drop will depend on the current draw.

What are you using for a power supply?

S Merlington · 2012-09-28 4:58 pm

I lowerd the voltage going to the amp and it doesnt draw excessive current..

With the voltage lowerd here what i get on all of the gate legs for the power supply fets..

Scope setting are 2volts div 10 us

JL AUDIO 250/1

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