Behringer UB2442FX Mixer Schematic/voltages Needed

[Jake Joseph]

I have a Behringer UB2442FX Eurorack mixer. Before the flames start,
I liked it, when it was working. It did exactly what I needed.

It died, out of warranty, and the switching power supply looks to be
toasty. Behringer US doesn't have PS modules yet, so it looks like
board level repair is where it's at.

It uses very close to a demo circuit from Power Integrations from
their TOP245Y chip. However, I don't know what the final voltages are
other than there should be a +5V (Based on the 7805 regulator) and
there should be a 48V. There are 5 voltages available, guessing from
the connector.

ANyone help out with at least the voltages coming out of this
doohickey would be appreciated. Any other help would also be
appreciated.

Thanks

Jake Joseph

 

[Scott Dorsey]

I have a Behringer UB2442FX Eurorack mixer. Before the flames start,
I liked it, when it was working. It did exactly what I needed.

It died, out of warranty, and the switching power supply looks to be
toasty. Behringer US doesn't have PS modules yet, so it looks like
board level repair is where it's at.

It uses very close to a demo circuit from Power Integrations from
their TOP245Y chip. However, I don't know what the final voltages are
other than there should be a +5V (Based on the 7805 regulator) and
there should be a 48V. There are 5 voltages available, guessing from
the connector.

I'd guess a +15V and a -15V. Maybe a little higher, but probably not
much higher than that.

If it's a switching supply, my guess is that the regulation is probably
done using the 5V line as a reference. If it were done properly, they'd
be using the difference between the +15V and -15V rails as as reference,
though.
--scott

 

[Lord Valve]

Almost always +/-15VDC. What are the rated voltages on the caps?
Most of that Chinese stuff uses 16V caps on the rails.

LV

 

[Jake Joseph]

I'd guess a +15V and a -15V. Maybe a little higher, but probably not
much higher than that.

If it's a switching supply, my guess is that the regulation is probably
done using the 5V line as a reference. If it were done properly, they'd
be using the difference between the +15V and -15V rails as as reference,
though.
--scott

Well, you are right about the 5V - it gets its reference off of the 5V
- shoots this through a TL431 regulator.

I'm guessing that either the switcher has gone bad or the optoisolator
xsistor has gone bad...any good way to diagnose?

Jake

 

[Pooh Bear]

I have a Behringer UB2442FX Eurorack mixer. Before the flames start,
I liked it, when it was working. It did exactly what I needed.

It died, out of warranty, and the switching power supply looks to be
toasty. Behringer US doesn't have PS modules yet, so it looks like
board level repair is where it's at.

It uses very close to a demo circuit from Power Integrations from
their TOP245Y chip. However, I don't know what the final voltages are
other than there should be a +5V (Based on the 7805 regulator) and
there should be a 48V. There are 5 voltages available, guessing from
the connector.

ANyone help out with at least the voltages coming out of this
doohickey would be appreciated. Any other help would also be
appreciated.

Interesting. I'm designing around the TOP245Y myself right now.

I've had a look at that PSU - at least I reckon it's the same one. Might
even have a record of the voltages.

Remove the PSU from the mixer. First suggestion - look for a short circuit
output recifier. Just plug it in and see if it attempts a 'hiccup start'.
That means a short on the secondary side normally.

If it doesn't even try starting - suggests the TOP has died. In which case
check the zener clamp and RC snubber. Even seen a similar Panasonic part
stop working with a failed diode round the RC snubber - that's all it took
to fix it.

Just a couple of ideas.


Graham

 

[Robert M. Braught]

I have a Behringer UB2442FX Eurorack mixer. Before the flames start,
I liked it, when it was working. It did exactly what I needed.

It died, out of warranty, and the switching power supply looks to be
toasty. Behringer US doesn't have PS modules yet, so it looks like
board level repair is where it's at.

It uses very close to a demo circuit from Power Integrations from
their TOP245Y chip. However, I don't know what the final voltages are
other than there should be a +5V (Based on the 7805 regulator) and
there should be a 48V. There are 5 voltages available, guessing from
the connector.

ANyone help out with at least the voltages coming out of this
doohickey would be appreciated. Any other help would also be
appreciated.

Thanks

Jake Joseph

Simple, quick, common fix; one of the secondary rectifiers is shorted
(usually Ref #D6), be sure to replace with a 'fast' rectifier (we use
# HER508).

Cheers,
-Robert
QTS
http://www.Braught.com
(Authorized BEHRINGER Service)
Real Email Addy : [email protected] (Remove NoSpam to Reply :
Duh!)

 

[Scott Dorsey]

Well, you are right about the 5V - it gets its reference off of the 5V
- shoots this through a TL431 regulator.

I'm guessing that either the switcher has gone bad or the optoisolator
xsistor has gone bad...any good way to diagnose?

Diode tester function on a multimeter will help you check the switching
transistor in-circuit. You can do the same with the optoisolator. You
can't find all possible failures in-circuit but you can find some of them.
Worst case you pull it out, test the switching transtor with the Hfe function
on your multimeter and swap out the optoisolator (being sure to put a socket
on the optoisolator because this will happen again someday).

Switching supplies are no fun to fix, because you can't get them running
to do diagnosis. A storage scope can help a lot.

Don't forget the kickstart circuit either, which is a source of failure in
a lot of switching supplies.
--scott

 

[Pooh Bear]

Diode tester function on a multimeter will help you check the switching
transistor in-circuit.

Not much actually - it's an integrated mosfet and controller in a TO-220 style
package.

You can do the same with the optoisolator. You
can't find all possible failures in-circuit but you can find some of them.
Worst case you pull it out, test the switching transtor with the Hfe function
on your multimeter and swap out the optoisolator (being sure to put a socket
on the optoisolator because this will happen again someday).

Very unlikley the opto has gone - they only run at a few mA.

Switching supplies are no fun to fix, because you can't get them running
to do diagnosis. A storage scope can help a lot.

The OP hasn't yet indicated if the supply goes into 'hiccup start' mode - audibly
detected by 'tick - tick - tick - tick'.

That's a 99% certain output rectifier short.

Don't forget the kickstart circuit either, which is a source of failure in
a lot of switching supplies.

The bias winding on these only supplies a few mA. Worth replacing the 1N4148 just
in case I suppose.


Graham

 

[Jake Joseph]

Simple, quick, common fix; one of the secondary rectifiers is shorted
(usually Ref #D6), be sure to replace with a 'fast' rectifier (we use
# HER508).

Cheers,
-Robert
QTS
http://www.Braught.com
(Authorized BEHRINGER Service)
Real Email Addy : [email protected] (Remove NoSpam to Reply :
Duh!)

Thanks to all that helped! I think the secondary diode is bad. Scott
is right, these sure are not fun to diagnose - I'm used to tube amp
PS's which are a whole lot easier....

The fast diode is to cope with the frequency of the switcher - right?

 

[Pooh Bear]

Thanks to all that helped! I think the secondary diode is bad. Scott
is right, these sure are not fun to diagnose - I'm used to tube amp
PS's which are a whole lot easier....

The fast diode is to cope with the frequency of the switcher - right?

Yes, 'normal diodes' - 1N4004 etc don't switch fast enough to be of any use, so there are high speed equivalents for
example like UF4004. Also many others. Schottkies are fine but have a limited reverse voltage making then useful only for
5 and 12 V supplies typically.

Graham

 

[Mrhotmark]

Behringer UB2442FX-PRO Connectors

For those interested...

Behringer UB2442FX-PRO Power Supply Connectors

Looking at the rear of the power supply there are 3 connectors, a 2-pin, a 6-pin, and another 2-pin. All connectors have a red wire on the rightmost pin.

The leftmost connector attaches to the 48V phantom power switch. On/Off.

The center connector from left to right is:
1. Ground
2. +5VDC
3. +48VDC
4. Ground
5. -15VDC
6. +15VDC (red wire)

The rightmost connector is:
1. Ground
2. +12VDC (red) for the BNC lamp connector.

All replacement parts are available from Mouser.com (TOP245, TIP31C, TIP32C, etc)

If replacing any diodes, make sure they are high speed diodes.

When all connections are made, all the grounds will tie together including earth ground.

My experience with these mixers are that some of the high speed diodes tend to short
along with the small transistors driving the larger ones. (The larger ones being TIP31C for the positive voltages, TIP32C for the negative). A 2N3904 or 2N3906 SOT-23 transistor will work for a replacement.

In my opinion this mixer is probably the quietest most bang for the buck mixer, but really needs a better power supply design.

Hope this helps!

Mark