JL 1000/1v2 rebuild

[miniman82]

Rebuilding another JL, this one blew only half the power supply FETs and a rectifier. It got so hot one of the bussbars fell off the board. Reinstalled that and cleaned everything up, but what are these 4 diodes doing in the circuit? One exploded, and I removed the other to get the part number off it. Do they need to be ultra fast, or are normal diodes good enough?

 

[Perry Babin]

Normal diodes will likely overheat and fail.

 

[miniman82]

I have 4 ultra fast to put in.

Did they H-bridge the power supply on this? Seems different than their other offerings.

 

[Perry Babin]

Yes.

 

[miniman82]

Interesting.

Does the output section work more or less the same as the 500 watt ones? In other words, can I boot up the standby supply and verify gate drives on the outputs in the same way as a 500/1?

 

[Perry Babin]

On at least some of the 1000s, you are limited to about 4 seconds of drive unless you bridge pins 6 and 7 on U517.

 

[miniman82]

I have good gate drive to all output devices and the power supply as well. Put a pair of FETs into each side of the power supply and connected the remote wire, it tries to come online but then I hear a high pitched squeal and the low volt lamp flashes. I always use a current limited power supply for troubleshooting though, so it’s possible the 5 amps I’m working with isn’t enough to get this thing through the powerup inrush surge. I’m going to try something with a bit more a$$ to it when I get home, hopefully that does the trick and I’ll be able to pass some audio through it later today.

 

[Perry Babin]

Most of the JL amps of this series have problems with the limiter. The 1000 is the amp I had to buy a battery for to run hard. I have enough power supply for most amps but the JL 1000 was so sensitive to dips in voltage that it wouldn't run at high power without a car battery.

 

[miniman82]

Makes me wonder how these things blow up at all, I mean they seem designed pretty well and there's protection built into them. I don't think this one was abused at all, just looks like a random rectifier failure took it out.

RE: power supplies

If you need a good stiff power source for load testing, I figured out how to hack the converter from a Civic hybrid which gives you around 100 amps at 13VDC for power runs on large amplifiers. If I need to test something this size I'll use that and an 800 amp truck battery connected together, works pretty well and is cheaper than trying to buy a commercial supply that size.

 

[miniman82]

Got it to come on line with an 8 amp power supply, idle is just shy of 3 amps and it looks OK to solder in all the power supply FETs. Are IRF3709Z’s a suitable replacement for the original NLA ones?

 

[Perry Babin]

That's the transistor used in the newer versions.

 

[miniman82]

Excellent, soldering shall commence this evening.

 

[miniman82]

Power supply works but now I have the low ohm light, somehow I smoked an output FET. The originals are NLA but Mouser stocks STP40NF20 which looks like a viable candidate, see anything wrong with it? Original was 45n20.

 

[Perry Babin]

The newer models use FDP52N20 FETs with 22.1 ohm gate resistors. I don't know if the others will work.

 

[miniman82]

Bonus, the 52n20’s are cheaper. Ordering now.

 

[Perry Babin]

Order the resistors if yours has something other than the 22.1.

 

[miniman82]

I’ll have to see what it has currently

 

[miniman82]

Gates currently have 4.7Ω on them, I’ll get some 22’s.

 

[miniman82]

Almost forgot to ask, what’s the name for this soft material attached to the transistor clamps? Some of it got burned up when the power supply let go, so I need to source some to replace it.

 

[Perry Babin]

1466N12
McMaster-Carr