Presonus 16.0.2

[dmeek]

If anyone by chance has a Presonus mixer open, I need to know the value of R8 in the power supply, It's completely charred and open. Thanks.



Edit: Just as I clicked the post button I thought of googleing for a photo of the board. There are many. Looks like 2.7 Ohms 2 or 3 Watts.

[Jon Snell]

Looks to me like 2.7R 2W MO. R16 doesn't look good either.

[dmeek]

R8 is a 1% resistor. I always get confused reading them. The online colour code calculator says 2.7. Good catch on R16 I didn't notice that. It's just slightly brown in the middle

https://www.allaboutcircuits.com/too...de-calculator/

[Jon Snell]

I edited my typo, didn't notice, sorry.
The usual cause for R8 to fail catastrophically is short circuit D1.

[dmeek]

D1 looks OK but I'll replace it anyway.

It's all back together and working now. Here is the list of burnt parts:

C14 470/16v bulged top
C19 220/35v bulged top
D16 1.5ke6.8a TVS cracked open
D2 MBR2045CTG melted
R8 2.7R burnt open
R16 1K overheated but still 1K

I beleive R16 was not involved in the melt-down. It seems to feed D8 zener diode.

I fixed a 24 channel version of this board just last week. It had 2 bulged caps and the same cracked TVS diode.
In my opinion these mixers need better ventilation, the power supply gets very warm and the vent holes are too small.
If anyone has the schematics, please post if you can.