Creek CAS 4140 (not S2) schematic

Synthpeter

Member
2016-03-05 11:23 pm
Hi everybody,

I've been looking for the schematics to the Creek CAS 4140 but have been unable to find them. It's not an S2, but a regular 4140.
I've read other threads here stating that the 4140 is "the same" as the 4040 but my starting point for the repair is the PSU.
As seen on the photo below, it contains 8 diodes, as if there's one power supply per channel or something.
oi5nmnT.jpg

All the photos and schematics I've found only have one rectifier bridge so I am assuming none of them are correct for the model I have.

If anybody's curious, the customer reported loud mains hum suddenly appearing on the outputs. I didn't start it myself but saw the PSU filter caps (4700uF) were bulging slightly so I desoldered them and tried measuring them with an ESR meter, but it didn't register anything, as if they're open circuit, both of them, which I find weird. So I'm assuming the caps have failed, but since BOTH have failed at seemingly the exact same time I'm wondering if something else has overheated, cooking the caps dry (the area above the caps halfway to the heatsink looks slightly scorched). That's why I'd like the schematic.

Does anybody have the 4140 schematics, with two diode bridges in the PSU please? :)
 

Synthpeter

Member
2016-03-05 11:23 pm
I've emailed Creek but have gotten no response yet (it was only yesterday).

I'd like an opinion from you. Though I've already got my own, I'd like to see if this is something anyone has reflected over before.

If the 4140 is very similar to the 4040, some of the areas in the 4040 schematics (seen here http://www.diyaudio.com/forums/solid-state/66036-creek-cas-4040-amp-schematic-2.html#post2786045) apply to the 4140 as well.
For now I'll assume the PSU (minus transformer) is "identical" but having one diode bridge+filter cap per channel instead of one shared.

Note the mains transformer and the 44VAC written. Following that is the usual full-wave rectifier bridge and main filter cap, a 4700uF/63V.
Then above the fuse, the voltage coming from the filter caps is noted as 62V.
Follow that trace to the top right to the FS2 fuse. Directly after it is another smaller filter cap 47uF/63V.

The 4040 schematic DOES say 4700uf 63V/80V, but the ones in the 4140 I have are 63V and, like I said in my post above, don't even register on my ESR meter, and the 47uF a bit further down the line is also 63V.

Does anybody but me think it's a bit bold to expect 62V DC straight from the transformer and rectifier, and then put filter caps rated at 63V DC in there (and put some nice heating power transistors next to them and seal them in a closed chassis?)