Switch mode supply again

[Khron]

Corollary to 1b. Silicon will (most) often sacrifice itself in order to save the fuse.

 

[ccaudle]

Corollary to 1b. Silicon will (most) often sacrifice itself in order to save the fuse.

Yeah, seeing a blown fuse on a switching supply is a bad sign. That means that the protection circuitry didn't work to shut the supply down safely in some fault condition, and some device could not be shut off before the fuse opened, i.e. shorted silicon instead of opened.

 

[Chrisfromthepast]

The latest victim is a Focusrite scarlett 18i20 2nd generation. Date code 2009 on the PSU.
@Bo Deadly the official focusrite part is reasonably priced, and has the rails you would need for a preamp.
+ 5, + 15V, -15V, + 51V 10W total
Focusrite part number: PSUI001007.
I may try to fix this one, starting with the caps:
https://scotttroyer.com/2019/02/focusrite-liquid-saffire-56-power-supply-unit-fix/

 

[Bo Deadly]

The latest victim is a Focusrite scarlett 18i20 2nd generation. Date code 2009 on the PSU.
@Bo Deadly the official focusrite part is reasonably priced, and has the rails you would need for a preamp.
+ 5, + 15V, -15V, + 51V 10W total
Focusrite part number: PSUI001007.

This is a great looking supply!

This could save people a lot of hassle.

If I were building a small pre, I would definitely look into this.

It even has 5V for a little bit of digital and maybe even relays if it has enough umph.

Great find.

Bookmarked.

 

[ccaudle]

Just in case the original blog post goes away for some reason:
Replacement PS link at Full Compass

If someone has one in hand (@Chrisfromthepast ?) please check if there is a manufacturer logo or part number somewhere on the PCB, like Delta, LiteOn, MeanWell, etc. that might indicate whether the model is available under a generic part number in case the part number marketed specifically as a Focusrite replacement gets dropped out of inventory at some point.

 

[Chrisfromthepast]

I haven’t received the replacement part yet, but the Focusrite part is an improved replacement for what originally shipped.
Pictured is the original, which seems discontinued.

 

[Bo Deadly]

I haven’t received the replacement part yet, but the Focusrite part is an improved replacement for what originally shipped.

The new one does not look like it's improved really. Both boards are clearly minimal SMPS. But it should work as well as the old part.

For a DIY project, it might need a little help but I think it would probably work fine. It was designed for a pro-audio product so it can't be that bad.

 

[Chrisfromthepast]

1402vlz4 is on the bench this time, and I was hungry for some confirmation bias, but the supply is a classic liner with a sort of mu metal sleeve.
It was on a generator, idk this is a rare failure mode from my vantage point.
Replacement transformer is $37 IIRC

 

[Chrisfromthepast]

I've got another opportunity to save a switch mode power supply from the landfill.
This one is coming from a Midas DL32.
The replacement part is available here.
Llike the focusrite supply, the PSU supplies +/-15V, +48V and a low voltage for the digital side. (7.5V in this case).

Under load, the 15V rail measures 8.5V and the -15V rail measures -8.5V. 48V rail measures 70, and the 7.5 V rail measures 4.1V
i didn't measure unloaded because the thing was squealing audibly when unplugged from the main pcb and it was too scary.

The capacitors on the secondary side are bulging, and get to about 15 degrees F hotter than the rest of the circuit.
I checked those, and the values are WAY off, like hundreds of uF off in some cases.
After replacing these should I be good?
The semiconductors appear to be fine.