Soundcraft Power Station

[boatman]

We have a ten year old Soundcraft 12 channel (8 mic + 2 stereo) Power Station which has a fault on one of the mic channels. Using a dynamic mic, the gain pot functions normally if phantom power is switched off. However, it becomes very scratchy on the lower half and stops working altogether on the upper half, if phantom power is switched on. I opened up the case (no mean feat I might add) and discovered that some recreational beverages had found their way inside at some time, leaving a nasty brown mess. Undaunted, I have cleaned up the board and changed the gain pot, but the fault is still there. I have also contacted the Soundcraft service desk who have never heard of a fault like this.

 

I suspect it might be one or both of the input capacitors, but they are nowhere near the area of the spillage. Anyone else seen or heard of a fault like this before?

[KevinE]

I was going to suggest the same thing before I scrolled down and you'd already written it!

Change them anyway, a scratchy pot is a sure sign it's getting DC from somewhere it shouldn't and the phantomk power is a good source of high voltage.

 

Hope u know which coloured knobs go back on which shafts!

[boatman]

It's fixed. It was a leaky electrolytic adjacent to the XLR socket. That pin on the mic amp had 1.2VDC on it instead of 0.18V which was on the other leg. No wonder it went into saturation. I changed both electrolytics on that channel just in case.

 

Incidentally, you can have a PDF copy of the service manual emailed to you for just £11.75 from the nice people at Soundcraft spares department, however if you want a spare pot there's a minimum order charge of £50.

[KevinE]

there's a minimum order charge of £50.

 

I think that should be £15

[boatman]

there's a minimum order charge of £50.

 

I think that should be £15

 

Ah, it sounded like £50 on the phone, but then I've only just got my new hearing aids, so I probably misheard. Luckily I already had the gain pot from previous repair.

[KevinE]

it sounded like £50 on the phone, but then I've only just got my new hearing aids

 

Mm..(saves that one for future use to my advantage)

[boatman]

The best part of having two hearing aids is you can take them out and not hear the phone ringing! It's especially advantageous when working on a sticky problem like this mixer fault. Concentrates the mind.