Ok, the last amp I purchased to add to my collection of JL audio gear was a 300/2 which produced no output and had the protect light on. I pulled the amp apart and looked it over. nothing appears to be out of the ordinary except for the chokes connected to the center leg of the rectifying diodes.
-positive side had a cracked solder joint and the negative side had a broken lead at the first wrap
-all power supply fets, diodes, and output fets do not show any signs of failure. they check OK with a meter.
I removed a turn off of the choke with a broken lead. soldered both chokes back in place and attempted to power the amp.
-protect light is still on, no dc voltage at the speaker terminals, rail voltage is not as I would expect. +67 volts, -22volts (with all components installed in amp)
-lines labeled on amp as +-53 volts check ok, driver boards have all lights illuminated, and the +-15 volts checks in at +- 17.
-removed the chokes and check rectified voltage at the center legs of the diodes at +63 and -62 volts. I'm not sure what I should look for that is causing the protect light and the out of whack rail voltage with the chokes installed.
-positive side had a cracked solder joint and the negative side had a broken lead at the first wrap
-all power supply fets, diodes, and output fets do not show any signs of failure. they check OK with a meter.
I removed a turn off of the choke with a broken lead. soldered both chokes back in place and attempted to power the amp.
-protect light is still on, no dc voltage at the speaker terminals, rail voltage is not as I would expect. +67 volts, -22volts (with all components installed in amp)
-lines labeled on amp as +-53 volts check ok, driver boards have all lights illuminated, and the +-15 volts checks in at +- 17.
-removed the chokes and check rectified voltage at the center legs of the diodes at +63 and -62 volts. I'm not sure what I should look for that is causing the protect light and the out of whack rail voltage with the chokes installed.
Ok, oddly enough I powered it up to take some measurements and I no longer had the protect light this time.
-24.28 side of inductor connected to negative diode
-22.21 other end of inductor
first time I tried measuring the positive side I had 44.20 and could not get a dc reading on the other leg.
however after moving the amp around to get a better angle with my probe I had 61.42 on the side connected to the center leg of the positive diode and 61.40 on the other end of the positive inductor.
I'm thinking these inductors have issues. I did however at one point also get measurements on the negative side around -35 for both sides and the positive was near 36 on both sides.
currently the outputs are not installed in the amp, and also the protect light is no longer coming on when I power up. (correction after a few more power cycles on and off the protect light is back on) still seeing in the low 60's on the positive side and the mid -20's on the negative side (for both sides of the inductor)
-24.28 side of inductor connected to negative diode
-22.21 other end of inductor
first time I tried measuring the positive side I had 44.20 and could not get a dc reading on the other leg.
however after moving the amp around to get a better angle with my probe I had 61.42 on the side connected to the center leg of the positive diode and 61.40 on the other end of the positive inductor.
I'm thinking these inductors have issues. I did however at one point also get measurements on the negative side around -35 for both sides and the positive was near 36 on both sides.
currently the outputs are not installed in the amp, and also the protect light is no longer coming on when I power up. (correction after a few more power cycles on and off the protect light is back on) still seeing in the low 60's on the positive side and the mid -20's on the negative side (for both sides of the inductor)
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I've been playing with shifting the inductors around while powered up and I can get the protect light to go out and the negative side to climb up to -35 isn and the positive side will drop from the mid to low 60's down into the low 40's. What should my voltage be at the inductors? Where do you recommend sourcing wire from to rewind these?
There's a reason that budget meters are cheap. More expensive meters are more complex. Use what you have. I think that part of the problem is that you keep trying to measure things that aren't generally checked. I've repaired MANY JL 500/1 amps and have never measured the voltage on the pads of a missing D600. We spent what seemed like weeks on that for no reason. Keep the meter you have and recognize that it has limitations.
Install the outputs too see what changes.
Install the outputs too see what changes.
I've found that it might not be the inductors causing the protect light. When I lift the board slightly near the output side the protect light goes out. It seems almost like there is a solder joint somewhere that is bad and makes connection when the board gets slightly twisted. I'm going to start review the board for cracks and or bad solder joints. I would still like to rewind the inductors so they both have the same amount of winds and the wire is not worn through in places. Any recommendations on where to purchase the enamel wire to rewind them? I do have some calipers not to take an accurate measure of it.
Perry, after extensive checking I wasn't able to find any solder joints that appeared to be bad. I think I've spent what seems like hours reflowing solder on basically every joint in this amp and the protect light was still coming on when pressing on the board near the power supply side. I did however find a via that might have been causing the issue. On this particular board there is a via that is physically located near c506 and r507, do you know if a poor connection here would cause the negative rail to not fully come up to voltage and trigger the protect light. I've poked at this particular via and the protect light issue seems to be resolved. I was hoping you might know off the top of you head if that would potential effect the negative rail.
Would it be suitable to solder a jumper through this hole to know for sure that there is a solid connection there?
I'm installing the outputs now and will have some rail voltages once they are in. Wanted to solve the protect light issue first.
Would it be suitable to solder a jumper through this hole to know for sure that there is a solid connection there?
I'm installing the outputs now and will have some rail voltages once they are in. Wanted to solve the protect light issue first.
Any time you see a via that's questionable, you need to scrape the pads/traces on both sides and insert a wire, soldering it on both sides of the board. You may have to pull a strand out of a larger gauge wire to fit through the via.
I can't see that area on the photos I have so I don't know what it connects to.
I can't see that area on the photos I have so I don't know what it connects to.
Ok, finally tracked down another bad connection that was causing the protect light to trigger and now with the outputs in and clamped it's alive. Rails are +- 39ish. Still need to source some wire to rewind the inductors. Do you have any suggestions for epoxy to hold them to the board after rewinding?
You need to look at the vias with a high-power lighted magnifying glass if more than 1 failed. See section 6 on the Repairing Physically Damaged Traces page. It shows you what to look for.
The wire isn't critical beyond getting the right diameter. See Tech Tips 7, item #11 for links to wire distributors.
The wire isn't critical beyond getting the right diameter. See Tech Tips 7, item #11 for links to wire distributors.
Thanks for the recommendation. Looking at an inductor it doesn't look like it would be to hard or time consuming to rewind... I sure underestimated that! First one I ended up re doing a few times to perfect my winding technique... I can see why they invented fancy toroid winding machines now... My fingers might not ever be the same.
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