Behringer Xenyx 1202 Power Supply

[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.

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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?

[Sam Spoons]

The fixing bolt passes through the centre of the toroid and needs to be insulated from forming a complete loop with the chassis, i.e. a secondary winding with one turn. If it does a very large current would flow through the bolt and the chassis. Have a look at those instructibles on making a spot welder with the transformer out of a broken microwave, the secondary is 3 turns and the current it can produce welds metal.

[Folderol]

Indeed! In fact it's quite common practice these days to secure torroids with plastic cable ties to eliminate this problem.

[Drew Stephenson]

Ah, got you. Thanks.

[N i g e l]

The mounting bolt that goes through the middle of the torrid is subjected to the magnetic field and acts like a 1 turn seconday coil, with a potential at either end.

The bolt should only connect to a metal chassis at one end and be an "open circuit".
If both the top and bottom connect to the chassis, a circuit is formed and current will flow [possibly quite a lot ].

A torrodial transformer probably comes with a mounting kit, like this one [transformer shown mounted on top here rather than on a base]

[Steve Jupe]

I have one of these excellent mixers (Xenyx 1202 with Klack Teknik FX) but my power supply (MXUK5) has a broken DC connector plug. Any idea where I might be able to get a replacement plug that I could solder on? It looks like a quirky behringer design, with three metal pins and a black rectangular (plastic?) pin.

[ef37a]

I have one of these excellent mixers (Xenyx 1202 with Klack Teknik FX) but my power supply (MXUK5) has a broken DC connector plug. Any idea where I might be able to get a replacement plug that I could solder on? It looks like a quirky behringer design, with three metal pins and a black rectangular (plastic?) pin.

No Sir! Not a "DC" 3 pin supply but 17.5-0-17.5 volts AC. The connector is total crap. I bought two of those mixers and on both the power connector (loosely based on the old PS2 'puter conn') was prone to cause serious hum as it moved about.

I modded both mixers by going inside and removing the offending socket and fitting a short piece of balanced mic cable. The first mixer was fitted with a mini XLR 3 inline plug and socket (but mixer side cable tied to chassis). Very neat but those connectors are **AST***D fiddly to solder and assemble, at least for me, so the next one had a chunky standard XLR on it. The neat one went off to France to my son.

I am fairly sure those *&&^%$! plugs are moulded on so I doubt you will find a 'solderable' one. Best bet is the correct supply from Behringer or Ebay. You might even be lucky enough to find someone with a burned out traff who will sell you the cable? Bit o solder, bit o heat shrink..Bob's yer whatsit.

Steve! I rarely throw anything 'lectrical away and so I have found one o f the 3 pin plugs with about 50mm of cable attached. There is red, green and black so you would have to work out what goes where but, being AC you just need to establish common which is chassis and the other two don't matter.

PM me with an address (UK ish I assume?) and I will post it off PDQ.

Dave.

[ajay_m]

A truly Frankenstein setup could also be cobbled together from two 18vac adapters (about £12 each on amazon). Plug them both in to a two socket adapter block and glue them in so one can't come out. Then just connect the two outputs in the right phase to make 18-0-18. This is electrically perfectly safe just rather Heath Robinson. I would wire a pair of 1.5A fuses on the outer power rails perhaps just to assuage my conscience here.

[Wonks]

A truly Frankenstein setup could also be cobbled together from two 18vac adapters (about £12 each on amazon). Plug them both in to a two socket adapter block and glue them in so one can't come out. Then just connect the two outputs in the right phase to make 18-0-18. This is electrically perfectly safe just rather Heath Robinson. I would wire a pair of 1.5A fuses on the outer power rails perhaps just to assuage my conscience here.

It's just the connector that's broken here, not the PSU, which is still providing power.

[ef37a]

There could be a problem with using a nominally 18-18 volt transformer? That would put an extra half volt across each regulator, not a lot I grant you but Behringer are not known for rugged 'worse case' engineering!

Also. a transformer with a higher VA rating will deliver even more than nominal 18V. In the general case of an 'alien' transformer it is wise to fit a resistor in each 'leg'. Start at say 4R7 and see how the voltages come out.

Dave.

[Hugh Robjohns]

He doesn't need a transformer... he needs the plug!!!!!