Soundcraft Folio SX mixer problems - Replaced PSU as suggested... still there.

[moamps]

First you might want to check your connector (with a DVM). If the connector is indeed faulty, you should change both ends with 3-pin DIN connectors (locking type). That's what I did and it worked like a charm.
Also, I believe it may be feasible for you to source the power transformer 30VA-36V CT locally at an affordable price and then replace the combo you're using now. I may have the schematic of the power supply lying somewhere around here if you need it.

Regards,
Milan

 

[TheGuitarist]

I'd need a PCB Probably... unless its simple. I'm terrible with breadboards. Might head up to jaycar and see if they have anything i can use. I might take your advice on the DIN connectors though

 

[TheGuitarist]

OK!

So i got my transformer, an 18-0-18 160VA (i know MAD over kill VA wise, i only need 600mA, so hopefully this will still work, maybe i can use it to power multiple things...) But anyway, just a question on how to wire it. Has 6 wires, 2 orange then red pink white and black, its all labelled on what they are, the orange are the 240v ones and then there is 18 and 0 for each pair of colours. The existing cable i have from the psu (i might as well still use it) is Brown Black and White. Now Correct me if i'm wrong but white is hot, black is neutral and brown is ground.

So how would i wire it for 18-0-18?

And to ground it, do i just connect the brown wire to the ground pin of the mains cable?

EDIT:

Orange = 0, Orange = 240v
White = 0, Pink = 18v (4.44A)
Yellow = 0, Red = 18v (4.44A)

 

[moamps]

.. But anyway, just a question on how to wire it. Has 6 wires, 2 orange then red pink white and black, its all labelled on what they are, the orange are the 240v ones and then there is 18 and 0 for each pair of colours.

white - 18V
pink+yellow - 0
red - 18V

http://www.diyfactory.com/data/transformer_connections.gif

The existing cable i have from the psu (i might as well still use it) is Brown Black and White. Now Correct me if i'm wrong but white is hot, black is neutral and brown is ground.

??? Usually code is
brown - live
blue - neutral
green/yellow - ground.
www.hkeca.org/English/html/t.../Technical%20Papers%207E.pdf

Regards,
Milan

 

[TheGuitarist]

sorry, different colour codes in Australia i guess... or maybe i'm thinking of something else.... hmm.

Any way to test which cable is doing what?

And so what do i do with the grounding pin. Sorry about all the questions, i really did search and i couldnt find a schematic to tell me where everything is going.

 

[TheGuitarist]

bump for updates on first post.

 

[phatch]

Hi TheGuitarist
I guess you still are having problems.
Firstly as you probably know Jands are the agents for these and their tech dept is very competent hence why they charge a lot to keep those people there !
You may be confused with dual supply ...heaps on the net about this
think back to maths  a zero centre line and a positive to the right and negative to the left.
Its kinda like 2 supplies with two wires each but one wire from each is joined to make a common so we have *......*  and *......*  but we end up with *......*......*
18volts......0volts......18volts. So you could have bought two seperate 18volt transformers and joined them at one point to get the required supply and mounting the lot in a safe insulated plastic or jiffy box.
I guess you bought the Jaycar toroidal where it has 2 seperate secondaries.
The post by moamps includes a link showing typical wiring.
So you should end up with the 18.0.18 to connect to the connector .

I would suggest changing the connector to something stronger like a 5 pin XLR or similar chosing something that some idiot cannot plug into the wrong place !

The original setup you had should not cause hum and I gather after  all the other advice you still have the original problem.
They are not the most friendly mixer to pull apart but I suspect some of the internal components first up (R507) the 100 ohm resistor and cap (whose value I cannot read )that connect the electrical ground and the chassis ground together.
Next the regulators and associated filter caps.
Here's a schematic I've put some grafiti on although its for the smaller mixer the principle is the same (the circuit is probably too).

Whoops  just realized that you got it working (not good for a first post !)  :
I cannot see any problem in connecting the mains earth (green/yellow to the chassis earth) while leaving the 0 rail or electrical earth (ground) isolated via R507
to avoid ground loops with external gear.

 

[TheGuitarist]

Well its still got this really low... sort of a hum... farty sound? kinda sounds like aircon in the background... i mean it could be aircon or the fridge on  the same circuit which i can't do much about but hey. Also, if i max out the preamps, hiss city.

But i mean, this isn't a high end desk... maybe thats all that the issue is.