Sundown scv-6000d need help.

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Ok so this amp came in with a blown up power supply and one bank of output fets along with the driver ic on that bank.

I repaired power supply first and all seems well so I put new driver ic's in the output module card and tested the low voltage supplys and all were present so I went on to check the gate resistors and pull down resistors on the output they were fine as well then checked the lower value resistors in front of the output module they are fine and the little green inductors read 5 ohms.

I checked the lowside gates and had good drive so I put one 24n40f in each high and lowside of the four banks powered the amp up waveforms looked like most other Korean amps of this size so I put the rest of the output fets in then put it in the heat sink tested for audio and it worked great however the next day I went to take a video of the amp functioning for the client and was doing some endurance testing and after maybe 6-7 power on & off cycles on my last power up as soon as the rail voltage built up BOOM she let out a crack so I powered it down immediately and checked for damage and it blew 1 of 4 banks of output fets so back to square one :-(

So I replaced the driver IC on the bank that blew up before fitting the output fets in that bank I put the scope on the Gate of the high and low side and the drain of the high and low side and switch the amp off and on to see if anything looked out of place nothing looked out of place and all low voltage supplies were still reading fine so I thought I might have damaged the driver Ic when installed the first time so I placed new fets in the amp powered on wave forms look good so I hooked it up to an audio source it played fine sounded great I turn the amp off waited a few seconds not long switched it back on and the same Bank of outputs blew up again!.

So now I have all of the output fets out of the amp and I'm probing the output pads looking for DC but not really finding too much the driver IC that was attached to the bank that failed seems to still be working but I'm looking for some advice on what I should look for or go from here should I hook Perrys low voltage Supply up to the amp and see if they fail on low voltage and if there's any DC spikes if anyone's experienced this issue any help would be greatly appreciated pics of the boards below


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Ok perry the low voltage supply is working good from what I can't tell I get +/-15vdc but when I connect it to the rail caps I'm getting +/-44vdc on the rails and output vias should it be that high?

On the last amp I did with the low voltage I thought i had excactly +/-16vdc on rails and output vias so im a little confused about that maybe I was wrong on the other amp.

Anyways I noticed with the LV supply attached to the amp after the rail caps drain off completely on power up the bulb lights for a few seconds and goes out but if you turn it off and right back on it does not light up the bulb unless the rail caps have been drained and powered back on I do not have the output fets in the board at this moment I was looking for any DC on the output Vias and twisting and pulling on the output board and inductors to see if I had any DC spikes so far nothing should I place the output fets or bring that voltage down from +/-44vdc. 88vdc p/p
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If I discharged the caps and power the amp up the light comes on and the meter jumps to OL then when the light goes out it's at 37vdc and climbs up to 44vdc black probe was on main amp ground and +/- rail read the same on power up light comes on meter jumps to OL and when it gets to +/-37vdc the light goes out and it climbs to +/-44vdc.

Also on discharging the Caps if I let the Caps discharge down to 12vdc and under the light will light up on power up . But if the rail caps are at 13vdc or higher when I power amp on the light doesn't come on and a meter doesn't read OL the voltage climbs up as normal.
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The caps do discharge slowly down to 0v I'm just saying that when the caps are at 0vdc-12vdc the light will light up on power up butwhen rails caps are at 13vdc and up the light don't come on when powdered back on and the meter dosent jump to OL.

The secondaries seem to be in series so I grounded to were I think is the center tap there's pic below and pic of the way the low voltage supply is hooked up just in case I miss understood a step.


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None appear to have there two middle legs together each transformer has one secondary to the input of a rectifier and the remaining three are jumped to each other and it appears that one secondary of each transformer are all tide together in a group of 4. Then the remaining secondaries are in a series to each other I drew a diagram in a pic #1 below to show you how they are connected it's kinda hard to explain in words but I can show better in my pic.

So I believe I do have the secondary of the low voltage Supply soldered to the correct secondary ground I also soldered it to each other secondaries and tested each output voltage of the low voltage supply and they can be seen in pic #2 but with five turns of 22 gauge wire i feel the +/-15vdc is the correct voltage and the other voltages don't seem right to me.


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Not sure that's what I'm trying to figure out I know on the low voltage supply I got +/-15vdc on the outputs the when soldered to the rail caps I get +/-44vdc so ima disconnect the low voltage Supply and poke around with the scope alil bit and see if anything pops up that might give me more clues and report back asap.
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Ok Perry I took the low voltage supply off the board and the output fets and rectifiers are still out of the board.

I found 11.04vdc on all lowside gate pads and traced it back to the output module and it appears on pin 6 LO of the 21844 is 11.04 as well. But if the low voltage supply is attached to the rail caps or the rectifiers are in the amp I get oscillation on the correct pads for the high side and low side however I feel something is not happy on the lowside gates because when I check the lowside gates with scope I cannot get the scope to trigger in on the drive on the gates it will slow down at best but can't get it to lock on the signal but the rest of the waveforms look as they should. I replaced the driver ic's and it's still the acting the same on the lowside gate.

Why would there be 11.04vdc on the low side Gates with no rail voltage to the output side of the amp but when there is rail voltage supplied to the amp I don't get 11.04 vdc on the low side Gates I get a drive signal but the scope doesn't want to trigger and lock on the signal like its too fast.
can I disable the driver ics and see if the 11.04vdc volts goes away and try to figure out were on the output board is the issue if it's not the Ic's themselves
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No I'm not for sure why I had 44 volts after looking around with the scope and grounded to the main ground of the amp if I would touch the spot I had the low voltage Supply ground soldered to I was getting a square wave of +/-40vdc and the same for another but one out of the 3 read nothing so I think I was grounded to the wrong secondary.

When I tested the output waveforms the rectifiers were put back in and the low voltage Supply was taken off I only had one 24n40f in each high and lowside of the four banks. And had oscillation and the amp would play audio but on the low side Gates the scope doesn't want to trigger and lock on the signal I can get it to slow down almost to where it stopped but it's still moving somewhat.

Before I put the rectifiers and output fets in the board I was looking around with the scope and noticed I had 11.04vdc on the lowside gates and it appear to trace to the output board and the Lo pin 6 was sitting at 11.04vdc with no rail voltage.

The scope im using is Mains powered but I do have a battery powered scope if needed.
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Yea i try to adjust the time scale and volts divison and play with the trigger moving it back and forth slowly and can get it to stop but it really touchy if i move the trigger at all when locked on it with go back to a blur if I move the trigger all the way to the left or right it will slow the drive wave down but still moves.

I've never had an issue with the scope triggering in on a lowside gate drive I tested it on another amp and it triggers dead on but isn't wanting to on this amp
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