That sounds bad! I haven't heard of a runaway supply for these... Testing of the power supply is in order. The LED's are all driven from the +15 volt supply which is secondary regulated by a three terminal regulator... probably a 7815. I have seen failures of this chip in another Behringer product so it may be a bad batch. The question now is if this has fried the main switching power supply.
Thanks for pointer. I got my meter on the psu and found no DC readings on outputs or any on the ICs or transistors. There are only AC readings of around 2 to 4 volts. I could not find a 7815, but there are a 7885 (a 8.5v regulator) as well as a complementary pair of TIP31/32C's. I also found a BD239C on other side of pcb. All the readings at the terminals were around 2 to 4 volts AC. The same readings were found at the rectifiying diodes by the transformer. Also I found a 4N35 (optocoupler IC) which is a 6-pin thing. The readings on this were (approx) Pin 1; 4v - P2; <4v - P4; 0.3v - P5; 35v and P6; 0.3v all on the AC setting on meter....no DC readings at all.
All in all I assume this has indeed fried the main power supply. I have not as yet got the soldering iron on the job. Any further clues?
Yep! The 4n35 is the feedback for voltage regulation of the switching power supply. The TIP transistors are post regulators and unlikely to have failed... one regulates the Phantom 48 volts... Likely failure is the TOP245Y switching regulator chip. The schematic will be just an expansion of the Xenyx 1222 which you can download from here: http://elektrotanya.com/behringer_xenyx-... Scroll down to "get manual" and click to download. Ignore other links. Open the last file of the compressed... SPUS2 which is the power supply schematic.
Thanks. I ordered a new TOP245Y and it came yesterday. I had a go at fitting it, but the same readings appear.....still no DC. Well it serves me right if I wasted my money. Question is did I fry the new one myself while soldering it in place?....
I guess I'll have a good look at the rest of the circuit first before trying to fit another chip.
Do you have any pointers as to what sort of readings I should be getting in the early part of the circuit....maybe the capacitors or bridge rectifier or the transformer gone??
If it all looks normal then I'll get another new TOP245Y. I think a good place to start might be to get myself a magnifying glass and check my soldering!!
Or maybe one of the components around the TOP245Y could be at fault? I do realise that the TOP245 has a static sensitive cmos type of thing in it, so maybe I wasn't careful enough........anyway back to the drawing board!!
You are att the point of requiring moore test equipmment... To work on this supply for personal safety you should be using an isolation transformer since this supply runs off the line. If you were careful the TOP you installed should be OK. With power applied, check voltage across C7. It should be around 160 volts or so. Check voltage from pin 2 of the TOP to pin 5. This is kind of a startup voltage monitor that is both under aand overvoltage detection. The high value 680K resistors should be checked as if they open up due to mechanical breakage the supply will not start. C13 if shorted would cause a problem. If the supply is dead, you should see aboout 160 volts from pin 7 of the TOP to pin 4. If the top had shorted, possibly the 10 ohm surge limiter before the input rectifier opened up. We are nearing the point of needing an oscilloscope to do much more troubleshooting. Since this supply ties to the utility power, one needs to be super careful if not using an isolation transformer. In regards to static... I haven't lost a chip yet and I do not use wrist straps although I use a grounded soldering iron. Get me some voltage readings or maybe a couple check ones I gave you will show the way.
Hi. Thanks for your help, you've been really good.
I took on board what you said last time and realised that if I was to do any more testing, I'd need a decent work bench set up with isolation transformer and oscilloscope and clamps and more gear than I have got. I was working on the kitchen table. It just would not be safe.
Bearing this in mind, I ordered a complete replacement psu from the Behringer service centre. It came today and I fitted it no prob and everything works fine now. Job done, though a bit more expensive than I hoped. I just thought I'd say you've been a great help and I appreciate your efforts....thanks. Al
Save the old board for spare parts. You are lucky to get quick service of the part as often Behringer is taking months to get the part.
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Problem. no voltage output on any rail.
Replaced the TOP245Y, TL431AC and the P6KE200 diode. 15 + and - rails came back, no 5v. replaced the 7805 regulator......all good.
Now all I have to find is the original short which caused this. I am still testing with a 60w bulb in series with the hot line..........with only the main board supplied there is still a small glow in the bulb. With everything connected the bulb ramps up very bright then drops off, this keeps repeating till switch off.
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