Behringer 1222FX power supply UB-SPSU2 - giving me double voltages ?

[Steve Conner]

Check the auxiliary power supply for the Topswitch. All SMPS controllers, integrated or not, need an aux supply of 12V at a few tens of milliamps. This often comes from a tertiary winding on the transformer, used in flyback mode with a single diode rectifier.

If the aux power supply is absent, the thing will hiccup on and off, powered by the kickstart circuit (usually a large resistor bleeding current from the DC bus)

If the aux power supply is out of spec (it is regulated by the main feedback loop, so if you messed with that, it may be) then the Topswitch may go into undervoltage or overvoltage lockout. Both of these lead to hiccupping.

Edit: I see that in the TOP245 they combined the aux power with the feedback signal. My head asplode.

[chazpope]

I gave up - who wants to have a go ?

I guess the word 'cheap' is relative.
$2.00 plus freight.
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Aha but in the UK it translates to $5.50 + freight = $10 in the end, and when I am not sure what the problem is it does not look appealing. I already wasted money changing caps and got nowhere. It could be that or something else - so I got sick of wondering and bought a new one. I hope when I put it in I won't find that there was some intermittent short in the mixer itself

Thanks everyone for your detailed help! I guess I gained some new experience - though reading the 50 pages TOP245Y pdf was as exiting as chewing on a piece of rubber.

Now if anyone here wants to have a go at this for discussion'a sake I am happy to send it UK wide !

failing that I might try to buy another bad one and start fixing that instead

[guitardad]

Check with fullcompass.com

They used to sell those smps boards for around 50-60 bucks.