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I was given a 1622fx mixer board which is dead. I swapped in a SMPS from a ub1240fx and it fired right up so the power supply was bad. I checked the obvious stuff and found that D8 was open so I replace both D8 and D6, tried it and I now get the flub flub of a SMPS trying to fire up but something else is dragging it down. I statically checked all the components in the +-15 volt section and they all seem to be good. Just for the heck of it I replaced the T1/2 transistor pair and the C12/C16 capacitors but no success. Rather than poke around more I thought I would put this up on this BBS and see if anyone has any thoughts on this. I have heard these SMPS's are notorious for failures and maybe someone else has run across this and can save me some time and effort. Some of the parts are SMD's and I really hate to fiddle with those things even with my glasses on unless I'm pretty sure the fault lies there.
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... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it! -
This was posted in a DDX3216 repair.
Read through it, maybe something will apply to your issue. -
Read through it and checked the referenced schematics however the fix with C52 is not even referenced on the schematic. I don't really know what this guy is talking about and the SMPS referenced is radically different from the Xenyx one. Anyway thanks for the post but I'm still looking for some experienced advise with these particular supplies. I read a letter from a Berhinger engineer which suggested a few things that were somewhat helpful but not the ultimate solution. I really hate SMPS's that almost work... flub flub :-(... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!Comment
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Well, here is the schematic if anyone cares to chime in.
There is not all that much, as far as protection/ shutdown is concerned..
I have seen a number of these where that part was way more complicated.
The feedback path is from the +15 volts.
That triggers IC4 optocoupler.
The opto can be checked with a meter.(diode check)
And IC3 should be checked. (3 leg zener package)
Also the TOP245 may not be able to drive the main transformer (although they usually do or do not work)Comment
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I agree, the UR feedback line was getting high frequency AC so there was reverse current flowing through the programmable Zener, IC3 for 1/2 the cycle. Check the opto-coupler and its associated circuit.
As switching supply go, this one is pretty simple and reliable. Sure of lot have failed but a million were made so a pretty small percentage have ended up in repair shops.Comment
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Thanks you Jazz P Bass and km6xz for the suggestions. I'm really sure there's nothing amiss on the back side now having completely tested every component there. This is where I found an actual failed HER303 diode (D8) which I thought at first was the real problem. These are amazingly simple supplies, I have worked on much more complex ones with greater success before. Well, it off to the front end now as you suggest. Sometimes it's the simple things that throw you a curve. I have already replaced the TOP245Y and that seems to be OK... had to replace it because that multi-legged thing had to be clipped out so as not to wreck the circuit traces, good thing it only costs about 3 bucks. I'll keep you posted.... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!Comment
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Invest $12 for a kit of Chip Quik so you can remove difficult to remove-easy to damage ICs, jacks and connectors without hurting traces or removed components. A 5 ft length of the low temperature solder will be good for several dozen surface mount devices which will be unhurt and can be reused if they are good. Video: Using ChipQuik to Desolder Surface Mount Components - YouTubeComment
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Great tip! Thanks, I'll order some today.Originally posted by km6xz View Post... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!Comment
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Check diodes with an analog multimeter. don't use DMM!! set to x10k range..Comment
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I've grabbed a good power supply from another broken Behringer mixer with other more extensive problems to put together a good working mixer that is needed immediately for a recording session. So for now the busted junk sits on the "to do" shelf for the time being. I have some more pressing issues to address with other jobs right now but I will get back to that thing as soon as I can.... That's $1.00 for the chalk mark and $49,999.00 for knowing where to put it!Comment
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Hey. it took 2 to make one.
I would consider the other one for parts (what is left).Comment
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Check those opto-isolators.Comment
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