GRAHAM99 wrote: ↑Thu Feb 02, 2023 8:59 am
Still can’t find a power supply!
Maybe I could buy a suitable transformer but it would need to be safely housed etc
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.
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.
Wonks wrote: ↑Thu Feb 02, 2023 9:47 am
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!
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.
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.
ajay_m wrote: ↑Thu Feb 02, 2023 3:26 pm
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.
ef37a wrote: ↑Thu Feb 02, 2023 3:41 pm
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.