Behringer Xenyx 1202 Power Supply

[GRAHAM99]

I have been given one of these to test out but it does not have a power adaptor.
I think it requires a centre tap power supply with 17v,0v,17v.
I can’t find one anywhere.
Maybe I could buy a suitable transformer to make a power supply?

[N i g e l]

is this the one ?
https://www.andertons.co.uk/behringer-p ... gIThvD_BwE

once you know the part number you can shop around, or look at images showing the label and work out the voltages. Probably a lot easier to just buy the PSU [with UK mains pins of course, if appropriate]

[ef37a]

Yes, 17.5V 0 17.5V AC Behringer part # MXUK5.

I have had two 1202s and they are very good for the money, bit daft operationally but quiet and flexible. Both my supply connectors were unreliable but others have had no trouble with theirs.

Dave.

[GRAHAM99]

Many thanks for this I will get on to it!

[N i g e l]

Yes, 17.5V 0 17.5V AC Behringer part # MXUK5.

I have had two 1202s and they are very good for the money, bit daft operationally but quiet and flexible . Both my supply connectors were unreliable but others have had no trouble with theirs.

Dave.

I have a 1204, its very usefull as a sub mixer & for recording.

There is no block diagram so I had to guess what it could do but as its small that was reasonably straight forward.
The mute does the thing of assigning the channel to aux out 3/4. hmmm ive seen that somewhere else.

It can record accoustic while monitoring on headphones

[GRAHAM99]

I think these adaptors are difficult to get hold of now.
Apparently the EEC outlawed ac to ac adaptors?
Maybe I will have to get a transformer?

[Wonks]

Apparently the EEC outlawed ac to ac adaptors?

I can't find anything to back that statement up. They are after all just transformers in a plastic box, and you can't just ban transformers!

But since 2020 the no-load current to full-load current value of an adapter has been increased, as has the overall minimum energy efficiency value (compared to the required values in force from 2009).

https://eur-lex.europa.eu/legal-content ... 82&from=EN

So it may well be that previous AC/AC adapters that came with products couldn't meet those efficiency values and can no longer be sold in the EU/UK. Either the manufacturers have now come up with more efficient AC/AC adapters for current products, or they dropped those products from their ranges and don't/can't supply replacement power supplies for their older units.

[Hugh Robjohns]

Not outlawed, but there are tighter regulations on efficiency and no-load power consumption. These are very similar to US regulations, I believe.

Replacement PSUs as service spares for legacy products are not affected by the 2019 regulations.

[ef37a]

Apparently the EEC outlawed ac to ac adaptors?

I can't find anything to back that statement up. They are after all just transformers in a plastic box, and you can't just ban transformers!

But since 2020 the no-load current to full-load current value of an adapter has been increased, as has the overall minimum energy efficiency value (compared to the required values in force from 2009).

https://eur-lex.europa.eu/legal-content ... 82&from=EN

So it may well be that previous AC/AC adapters that came with products couldn't meet those efficiency values and can no longer be sold in the EU/UK. Either the manufacturers have now come up with more efficient AC/AC adapters for current products, or they dropped those products from their ranges and don't/can't supply replacement power supplies for their older units.

Wonks, I was told several years ago that AC'AC power supplies (below about 50VA I think?) were "effectively" banned. The problem is I think is that these small transformers draw nearly as much power off load as on and such supplies tend to get left connected to the mains supply.

I was involved in the HT pedal series that originally used a 16V* 800mA AC supply. A 22V DC SMPS was substituted but this needed some creative mods to obtain the correct op amp supplies. The only other option would have been a major redesign of the PSU PCB, not an enviable task as the board also contained the DC-DC converter that produced 300V for the valve.

You cannot run the older pedals on the 22V DC unit but I believe the AC supplies can still be obtained? If anyone is stuck I have ONE NOS they can have.

*This produced around 22V off load, an indication of the inefficiency. (I have had one for years powering my door bell!)

Dave.

[Wonks]

Both up to 49W and above, the off-load power consumption has to be less than 0.21W. Which means the smaller the wattage of the PSU, the harder it is to meet the requirements.

The on-load efficiency requirement is some complicated formula (see the relevant appendix in that document I linked to).

But I have no idea what sort of efficiencies are possible here. Presumably they can be achieved with the right type of transformer.

[ef37a]

Both up to 49W and above, the off-load power consumption has to be less than 0.21W. Which means the smaller the wattage of the PSU, the harder it is to meet the requirements.

The on-load efficiency requirement is some complicated formula (see the relevant appendix in that document I linked to).

But I have no idea what sort of efficiencies are possible here. Presumably they can be achieved with the right type of transformer.

I believe the 'ban' can be sidestepped as it were by fitting a switch in the mains feed. This is of course problematic for very small supplies and safety consideration hard to meet. Modern SMPSUs are now so reliable and cheap that it is probably easier to redesign the gear?

I have in fact fitted an inline SP switch in my 1202 supply.

Dave.

[GRAHAM99]

Still can’t find a power supply!
Maybe I could buy a suitable transformer but it would need to be safely housed etc

[ef37a]

Still can’t find a power supply!
Maybe I could buy a suitable transformer but it would need to be safely housed etc

https://uk.farnell.com/block/rkd-40-2x1 ... dp/2362151

That would serve but as you say, it would need housing and making safe. The other drawback is the 18V secondary (you are unlikely to find 17.5V as a stock transformer) this will cause the internal regulators to dissipate a little more heat but would probably be acceptable. You could insert resistors in each winding to drop the voltage half a volt. One Ohm would be a good first guess.

Dave.

[Wonks]

The output voltage will depend on the input voltage anyway. I doubt the Behringer PSU for the EU had a different transformer in to the UK version, just a different mains plug, so the AC output was likely to be higher than 17.5v (it’s not 17v) when used in the UK depending on the local mains voltage.

I doubt whether 18v as opposed to 17.5v would bother it, especially when allowable mains tolerances are added on.

Assuming that it's selected for 17.5V at a nominal 230v, then you would get 18.2V AC at 240V. from the Behringer PSU.

[ef37a]

The output voltage will depend on the input voltage anyway. I doubt the Behringer PSU for the EU had a different transformer in to the UK version, just a different mains plug, so the AC output was likely to be higher than 17.5v (it’s not 17v) when used in the UK depending on the local mains voltage.

I doubt whether 18v as opposed to 17.5v would bother it, especially when allowable mains tolerances are added on.

Assuming that it's selected for 17.5V at a nominal 230v, then you would get 18.2V AC at 240V. from the Behringer PSU.

Well, one has to start with design centre values! The transformer I showed would in any case have better regulation than Behringers, might get away with 16V?
Equipment should be designed to work to specification within the 10% mains tolerance but I wonder how many do, especially at this end of the market? I mention the extra regulator heat because Behringer do not have a good record for power supplies in the past!

Dave.

[Wonks]

Without an actual PSU to test, we're just guessing here. I did have a UB1202 for a short while which I gave to a friend, and that uses the same PSU as the Xenyx. That's been working quite happily for ages. Unfortunately it's residing about 80 miles away from me now, so a 160 mile round trip just to measure some voltages is not on the cards.

[Drew Stephenson]

I have one in the garage that I could test if someone gave me suitable instruction?

[Wonks]

I have one in the garage that I could test if someone gave me suitable instruction?

What's black and attached to a multimeter?

[ajay_m]

36V CT or 18-0-18 will give you 25.5V unloaded instead of 24.75V for 17.5V in using a standard bridge rectifier. Now I know behringer cut corners but I'd assume using 25V caps would have been cutting it too fine so they will probably be 50V caps. So you should be fine.

[ef37a]

36V CT or 18-0-18 will give you 25.5V unloaded instead of 24.75V for 17.5V in using a standard bridge rectifier. Now I know behringer cut corners but I'd assume using 25V caps would have been cutting it too fine so they will probably be 50V caps. So you should be fine.

Even if the supply caps are only 25V I would not sweat it. The only result of the very slight over voltage would be a tiny increase in leakage current. The enemy of electrolytics is heat, not so much a volt or two over rating. In any case, the caps would soon reform to the voltage.

Back in the bad old days of 'domestic' valve gear caps were often just rated for the 'working voltage' and not the peak that a fast heating rectifier slammed on them (got even worse with Selenium rects!) Nonetheless, capacitors lasted decades in most bits of kit, the exception being TVs when Silicon diodes arrived and caps blew about every 3 or 4 years.

Dave.

[Folderol]

Back in the bad old days of 'domestic' valve gear caps were often just rated for the 'working voltage' and not the peak that a fast heating rectifier slammed on them (got even worse with Selenium rects!) Nonetheless, capacitors lasted decades in most bits of kit, the exception being TVs when Silicon diodes arrived and caps blew about every 3 or 4 years.

Dave.

I have grim memories of the weird multi cap assemblies - often festooned with an unholy array of add-on ones, with some of the original terminals cut off (S/C cap) while others were just hanging across dried out ones. Then there were the copper oxide, or selenium rectifiers bodged with a silicon one bypassing them (so just one tag retained as a support, sometimes with a 10W resistor in series in an attempt to limit the surge.

[GRAHAM99]

I have one in the garage that I could test if someone gave me suitable instruction?

Can you test it with a multi meter?

[N i g e l]

Yes, open circuit and under load preferably.

-------

My Behringer MXUK5 specs:

230V~ 50Hz 105mA 31W

2x 17.5V ~, 2x 650mA

measured 18.25v a.c. open circuit

note that there seem to be 2 types of MX5UK,
230V 31W &
240V 20W

maybe its only the label thats changed.

I got mine from either Thomann, CPC or Rapid, none of which sell them anymore. In fact no one seems to stock them.

[Drew Stephenson]

I have one in the garage that I could test if someone gave me suitable instruction?

What's black and attached to a multimeter?

Shocking!

[ef37a]

Back in the bad old days of 'domestic' valve gear caps were often just rated for the 'working voltage' and not the peak that a fast heating rectifier slammed on them (got even worse with Selenium rects!) Nonetheless, capacitors lasted decades in most bits of kit, the exception being TVs when Silicon diodes arrived and caps blew about every 3 or 4 years.

Dave.

I have grim memories of the weird multi cap assemblies - often festooned with an unholy array of add-on ones, with some of the original terminals cut off (S/C cap) while others were just hanging across dried out ones. Then there were the copper oxide, or selenium rectifiers bodged with a silicon one bypassing them (so just one tag retained as a support, sometimes with a 10W resistor in series in an attempt to limit the surge.

Yes, there were a lot of 'cowboys' about then Will. The old B&W TVs were a special case. The main caps were rated at 275V when peak mains is nearer 340V, the cheap buggers discovered that if you stress an electrolytic several tens of volts over its rating it draws a much greater leakage current and acts as a 'free' surge limiter. The caps did not take kindly to this and failed after just a few years. Then you could get an O/C heater chain so the set never drew any HT current...BIG bang and a big mess.

Dave.

[ajay_m]

This should do the trick https://www.mouser.co.uk/ProductDetail/ ... %2FA%3D%3D
only £17 quid ex vat.
Only 1 in stock though, better hurry

[ef37a]

This should do the trick https://www.mouser.co.uk/ProductDetail/ ... %2FA%3D%3D
only £17 quid ex vat.
Only 1 in stock though, better hurry

Well that transformer will 'do' but surely, if you have to buy a new one buy better specc? The mouser traff has a slightly lower VA rating than mine and nominally a volt more output and mine runs quite warm. A toroid will be more efficient, especially since it will be run constantly at close to VA limit. You are not subject to the cost restraints of production.

Dave.

[N i g e l]

https://www.rapidonline.com/Transformers

CPC & Rapid have a reasonable selection of 18-0-18V transformers.
The Rapid site is a bit more searchable/filterable. They also do enclosures [some plug top style].

Extra care is required mounting torroidals to make sure the bolt through the middle doesnt become a 1 turn coil !

[Folderol]

Torroidal transformers also have the advantage of a much weaker radiated field.

[Drew Stephenson]

Extra care is required mounting torroidals to make sure the bolt through the middle doesnt become a 1 turn coil !

Sorry, Nigel, for the ignorant amongst us, i.e. me, can you elaborate on that please?