[LAU] OT: Behringer PSU UB-SPSU2 for an Eurorack UB2442FX-PRO

[gene heskett]

On Tuesday, May 08, 2012 10:32:50 AM Ralf Mardorf did opine:

> Hi and sorry for the OT,
> 
> perhaps somebody is able to help me.
> 
> When I turned on my 7 year old Behringer mixer there was no power for
> the mixer and effect. When I also turned on the phantom power, there
> still was no power for the mixer and effect, but the phantom power LED
> started "pumping" (it's on, but slowly becomes lighten and less
> lighten).
> 
Using its age as a clue, I think I would be gong through it with a 
"Capacitor Wizard" checking the caps in the psu in particular.

I haven't a clue what it may be called on your side of the pond though, so 
I will describe what it does in hopes it might be recognizable as a euro 
made and named testing device.

It is a small, low power oscillator, generating about 85 millivolts of rf 
signal, at a nominal frequency of 100 kilohertz, the currant it can send 
through a capacitor is presented on a meter, usually calibrated with a knob 
so that it reads full scale when the probes are shorted together.

At 100 kilohertz most power supply and coupling capacitors should be quite 
close to a dead short, a full scale meter reading if they are good, but 
older caps tend to suffer from poor connections internally between the 
leads you solder into the circuit, and the actual aluminum foil of the 
capacitor's plates.  This test device measures this failure mode, usually 
displaying it as ohms.  Its called the capacitors ESR, Equivalent Series 
Resistance.

Any reading above 2 ohms is generally grounds to warm up the soldering 
tools and replace that capacitor.

This tool costs about $175 on this side of the pond, overpriced considering 
what is in it, but he also has a patent on it.  I did, when I googled for 
it, come across a DIY site that had built one, and has schematics, but no 
'kits' for sale.

This, quite frankly, is an empty spot in the techies tool arsenal that 
someone familiar with e.a.g.l.e. might well be able to fill as the US 
patent (I haven't checked) should be about to run out. The pcb would be 
close to the most expensive part in it, and while I could probably make it 
on my milling machine, that would be a one-off for my own use because the 
time involved to do so would, at a tenner an hour, be several hundred 
because of the time to make a palette to hold the board blank precisely 
enough to cut & drill double sided, plus the sensor tools to auto set the 
etching tools height dependably took no little thought and imagination.
The sensor stuff I wouldn't have to re-invent for the next project though.

If it worked, then I would send the eagle files to someplace in china for 
100 pieces.  But marketing costs, for the number sold would likely remove 
any profit at $100 USD/copy.  Far better to put a link to a blurb about it 
on my web page in the sig and maybe just sell it as a DIY $50 kit.

> The original fine fuse is ok. I unmounted the PSU. Everything looks ok,
> excepted of one resistor. When it was unsoldered I measured it. The
> resistor seems to be ok. It at least is ok, when not under load.
> 
> There's a brown stain at the resistor where one of the resistor's wires
> emerges. It looks like soldering flux and it's possible to scrape it
> off, so it simply might be soldering flux.
> 
> I first should have measured the PSU outputs, since it's possible, that
> it's not the PSU. Anyway, I still suspect it's the PSU, model UB-SPSU2.
> 
> Since I don't own an isolating transformer and it's very unhandy if the
> mixer is opened and everything is mounted, I won't do troubleshooting
> during operating at the moment.
> 
> I do a google.de search for UB-SPSU2 now.
 
Having a spare for that sort of thing is a good idea.  Asking if it will 
fail is like asking if freshly poured concrete will crack.  The "if" is 
wrong, the correct word is "when", because it will, always. :)

> I'm sure a friend is able to help me, but he isn't easy to reach and I
> will test my tuned Ubuntu Studio right now.
> 
> Any hints are welcome!
> 
> Regards,
> Ralf

Good luck Ralf.

Cheers, Gene
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