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My MDX4400 blew the tranny. Replacing it and the 7915 did not bring it back to live so I would need a schematic to TS the issue (which I beleive is still around the power section)
Thnx
bluesfreak
Thnx
bluesfreak
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I can fix everything, where is the duct tape? -
Originally posted by bluesfreak View Post
I don't have that one. MDX1400 and 2600 but no 4400 Sorry. -
Can u send the 2600? MAybe the PS Section is the same...
ThnxI can fix everything, where is the duct tape?Comment
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Hello, I have the same unit and my transformer also blew. I have replaced the transformer and now the unit stays on for about 30 seconds before shutting down. I'm wondering if there is a thermal cutout in there or something. Bluesfreak, did you sort yours out? If you did I would love to know what the problem was.
Thanks in anticipation,
Ian.Comment
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Soon, Behringer will take the #1 spot of the most-searched term on this forum, only bested by Google's 466,000 entries when searching "Behringer problems".
Brad1Comment
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If you had to replace a power transformer, there was a reason the first one blew. Now with a new one in place, you are facing that problem.
Google for today.
Behringer problems, 405,000
Fender problems 2,620,000
Marshall problems 45,500,000
Peavey problems 233,000
Crate problems 2,020,000
Ampeg problems 857,000
All in all, if you are going by problems on google, Behringer comes off looking better than everyone but Peavey.
As a rule in service, the more popular something is, the more of them you will see in service.Education is what you're left with after you have forgotten what you have learned.Comment
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Given Behringer's huge popularity and relatively low Google count, it would seem that they are doing pretty well in the QC area nowadays (which they are, I can assure you).Originally posted by Enzo View PostComment
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Hi Ian,
I found the 7915 being blown in addition to the tranny. Be careful when replacing the voltage regulators, if you have some with the Voltage present on the cooling/mounting flange you need to isolate them from the chassis (or use fully isolated one's like the installed units). Unfortunately there was more killed on mine and the front PCB is dead silent (no LED illuminated, nothing), I suspect a bunch of the OpAmps being blown even when measuring resistance between 15Vdc and GNd gives me ~380 Ohms which would indicate approx 40mA of current... think mine is one for the junkjard...
cu
StefanI can fix everything, where is the duct tape?Comment
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There is a very good chance that you have at least one .1uF decoupling cap shorted on the opamp rails near the IC's.
However, given the price point and the level of repair difficulty on the MDX4400 Multicom Pro, I concur that it is probably time to toss it.Comment
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Are you referring to C19, 20...etc decoupling -17V rail from GND? I will check, I have the bitch still disassembled anyway but I doubt that its an easy fix.. too much SMD in the box... Thanks anyway
PS: Just a quick feedback: Checked 100nF on the front pcb C65, C69, C66, C70, C67, C71, C68 and C73 are shorting ...??? Think I'll gonna throw these buggers out.I can fix everything, where is the duct tape?Comment
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If you read a short across all of those caps, you probably just have one shorting. The Behringer trick is to "smoke 'em out" by passing unregulated rail voltage to the opamps via shorting the input and output of each regulator. The same trick is used on Behringer mixers. We have power supplies modded with "burn" switches, just like they did in Germany.
It's tough to find that one cap otherwise, but you can also find them using a milliohmmeter. You use a fixed ground point, zero-out, and then read each cap to ground, finding the path of least resistance. It might only be a few tenths of an ohm difference from the others, but that will be your smoking gun.Comment
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At least I now know that the problem is on the front PCB as there is no issue when disconneting the 2 ribbon cables from the back panel so I can exclude the caps there. I have inspected the front PCB optically and found C 70 discolored... this will be the first to inspect closer...
Update: Threw out C70 and wohoo, life's back in the Unit! Measured resistance +/-15Vdc to GND (TT3/GND 475 Ohms, TT4/GND 615 Ohms, TT3/TT4 770 Ohms). The last one makes me some headache, seems like more Cs are damaged as normally there should be ~ Ohms... or am I wrong?Last edited by bluesfreak; 06-02-2010, 10:22 AM.I can fix everything, where is the duct tape?Comment
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Thanks for the replies, I didn't have my settings set to receive notifications so I didn't know until tonight there had neen any.
I guess I will strip mine down a bit further and see what I can find. You've pointed me in the right direction so hopefully that will save me some hassle. If I don't find anything I'll bin it and keep the new transformer as a spare (if it still works). I think the transformer had been replaced before as the screw head was a bit mangled, probably why the unit was sold on (I bought secondhand).
Thanks again,
Ian.Comment
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Stefan/ Bluesfreak, can I just ask what is the voltage of your transformer. Mine is an 18volt unit but I am not sure it is the original. I have no reason to suspect it is the wrong voltage but I just wondered. A visual inspection of my caps has revealed nothing so I guess I will have to delve a little deeper once the voltage regulators have been replaced (they look okay but I'll do them anyway).
Behringer seem to always attract a fair bit of stick regarding reliability issues. Having looked inside this unit I have to say that it seems a little unfair that we expect them to work at all considering their price. In the past I have built kits that cost more than these things and I doubt that the parts would cost less than the whole unit does anyway.
Cheers,
Ian.Comment
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