[TzeYang]

So someone sent me the above combination for some fixing and I have limited time and tools figuring out in detail what went wrong with Sigma11 given the below scenarios.

Sigma11:
Unloaded voltage= 24V
Loaded with M3= ~24V (to show that under load that it's still within spec)

Basically it seems fine.

M3:
Everything seems to be working fine. Tested it with a 24VDC wallwart.


Here's the catch, when I connect the s11 to the m3, the TLE2426 blows off. I observed that the V- shorts to the GND and instantly overheats.

It does not happen to regular 24VDC wallwarts. All connections are using insulated jacks. The m3 only has 2000uF of main rail capacitance. Every component uses standard values. There is also a reverse voltage protection diode installed.


The only theory I have left is that the s11 does not react to a certain load in a stable fashion and it's oscillating. I don't have a scope to test it with various loads but I'm really relying on your experiences at this point before I get my scope (which is quite some time away)

Any suggestions for a fix? I'm really throwing treatments here until something works.

 

[amb]

It's unlikely that the σ11 is oscillating. These PSUs have been tested with a wide range of different loads and have been proven to be stable, not to mention that σ11 is the default PSU for the M³ and there are plenty of such combinations out there.

I assume that the PSU is in a separate case than the amp. You said that there is a short from V- to GND, I deduce that means virtual ground. If that's the case, then for sure that would kill the TLE2426 instantly. Since it doesn't happen to a wallwart, then it is likely that the short is somewhere in the σ11. A wiring mistake? It should be easy enough to check. V- should not be tied to the PSU or amp casing.

 

[TzeYang]

Oh wait, my bad.

I meant that the V+ is shorted to the GND since measuring V- and GND shows 24VDC.


The dc jacks are also insulated so I don't think it's a wiring mistake O_O.

 

[amb]

Remove the TLE2426 and check if V+is still shorted to virtual ground (with the power off, use your DMM in resistance mode). If it is, then that would blow the TLE2426 too, and you need to track down where that short is.