Behringer 1400W Class D for B1800D Repair help!!

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saj888

Member
Joined 2007
Hi,
I have a another Behringer contraption in the shop. behringer eurolive b1800d-pro active 18 subwoofer.
The audio cycles on and off. Comes on for a millisecond then instantly cuts off for approx 10 seconds. It's passing approximately 1volt dc. When the voltage drops to under .5 volts the audio comes on again for less than .5 secs. then instantly goes off. The cycle goes on. I have replaced the output transistors, 2 20957 ics,LM393, ic4, ic6, Checked most components. The audio is clean up to pin 2 on ic4. Does anyone have any suggestions.
Thanks.
 
G

guitardude57

Member
Joined 2016
saj888 said:
Hi,
I have a another Behringer contraption in the shop. behringer eurolive b1800d-pro active 18 subwoofer.
The audio cycles on and off. Comes on for a millisecond then instantly cuts off for approx 10 seconds. It's passing approximately 1volt dc. When the voltage drops to under .5 volts the audio comes on again for less than .5 secs. then instantly goes off. The cycle goes on. I have replaced the output transistors, 2 20957 ics,LM393, ic4, ic6, Checked most components. The audio is clean up to pin 2 on ic4. Does anyone have any suggestions.
Thanks.
Click to expand...

Did you figure out what was up with this?

I have one of these myself...on the bench. Found MOV R34 had a leg melted off of it, and replaced it with a similar device. Got it to power up. Was DOA.
I'm thinking the speaker likely took a bit of a hit, as it was driven hard several times a week in a PA install.

When it died there must have been a power (incoming) surge, to take out the MOV. It is functioning now, but not smoothly. No protect is kicking in, and no clip sensing from a cd player inputting signal. Going to try to drive an EV 12L, and see if the 18 in the cab is screwed up or not. Getting a good reading on the DMM.

This unit was replaced with a new one with the 3000 watt amp, and the Turbosound speaker. That one sounds great, and doesn't have the cab rattle this piece of stuff has...lol
 
F

flipse

Member
Joined 2017
saj888 said:
Hi,
I have a another Behringer contraption in the shop. behringer eurolive b1800d-pro active 18 subwoofer.
The audio cycles on and off. Comes on for a millisecond then instantly cuts off for approx 10 seconds. It's passing approximately 1volt dc. When the voltage drops to under .5 volts the audio comes on again for less than .5 secs. then instantly goes off. The cycle goes on. I have replaced the output transistors, 2 20957 ics,LM393, ic4, ic6, Checked most components. The audio is clean up to pin 2 on ic4. Does anyone have any suggestions.
Thanks.
Click to expand...

I think i'm having the same problem with my b1800d.
Do you have a schematic plan of the platine?
the signal LED ist on and switches to the input sound, but sometimes the sub is working for a while (especially under pressure) and sometimes it get's off (leds are still working).
but i have no electric plan of the amp, to solve the problem.

it seems that the OP1 gots melted, but i don't know, if replacing solves the problem and what kind of op it is.

Here some pictures
http://www.flipsoft24.de/temp/DSC07407.JPG
http://www.flipsoft24.de/temp/DSC07408.JPG
http://www.flipsoft24.de/temp/DSC07405.JPG
http://www.flipsoft24.de/temp/DSC07403.JPG

does someone have the electric plan and can send it to me?
or can someone see the problem on the platine?

thank you very much
 
P

PeppeH

Member
Joined 2018
I'm still struggling with my amplifier and now I am out of ideas! :(

I did find a few broken components (IC3, T1, T4, D2 and D7) in the initial fault finding process. I replaced them and powered up the amp only to hear the MOSFET (T1 and T4) pop again! :mad:


After replacing the IC3 again (just to be sure its not broken) and not installing the MOSFETs (T1 and T4) I apply a 100Hz 200mV sinus to the input and can follow the signal all the way to IC3 input (at this stage the signal is a square wave 180 degrees phase to input on IC11).

As a precaution I now feed the amplifier +/-40V with an external power supply (with current limitation) while I still use the original power supply for both +/-15V and +A15V/+5VA thru connector X9/X11.

Do you see any major problem doing so? All voltages seems ok and the original power supply happily delivers all voltages (+/-75V, +/-15V and +A15V/+5VA) but the amplifier simply won't start, nothing happens on the output pins and also the current drawn from my external power supply is 0 amps (?)

Greatful for any tips on how to proceed...
 
F

Fleck

Member
Joined 2017
Thank you shepo1, have the same problem, cycling/limit led blinking. Desoldered bootstrap caps, the one that is close to output inductor has even changed color from blue to dark blue, and ESR for that one is 140 Ohms... it's BAD! :D Gonna solder new ones and test tomorrow, just wanted to say thanks for your efforts and reporting solution! I also changed caps C53 & C45, both got bumps.
 
F

Fleck

Member
Joined 2017
YESS, it's FIXED! Thank you shepo1 a lot! You made this fix super easy for me! :) So for those who read between lines:
Sub powers ON but gives you knocking sound in few second intervals for a really short time, limit LED blinks when this happens, fixed this by replacing caps:
C105 - bootstrap cap for IC11 10uF 25V
C36 - bootstrap cap for IC3 10uF 25V
The one that is close to output coil was toasted in my case, even color changed! 2nd is probably OK but, I changed both, just in case.
I also changed caps C61 and C1 cause one of them where close to coil also!
And finally, I changed C53 and C45 on the PSU board, those where with round tops.
 
M

mircam

Member
Joined 2016
shepo1 said:
HI.. Guess what .. ITS FIXED.. finally.. my god.. that was a tough one.
after many 20957 ic's and MOSFET's destroyed.. i finally got it.. Thanks all for your input and advice.
For anyone who cares.. this thing had multiple issues. Not sure what i caused or if one thing caused the next to be damaged.. But
initially, H04 ic ( the one that inverts the input to the 20957 ic for full bridge operation) was bad and just outputting DC. ( I think this was damaged when one of the 20957 ics fried) but not sure. FETS were shorted on one side. also 20955 ic was toast on same side. I replaced all those parts and then amp would just OC cycle. Found one side was not starting up.. the other was.. Just FYI The strange wave forms i was getting on the bad side VS and I posted earlier were due to the good side inducing voltage thru the common core inductor to the bad side. After many diffrent tests and trying diffrent things, I Finally figured out the HO signal was not turning on the High side FET on the bad side. Thought fet was bad but tested by manually turning on.. It worked ok so back to the IC being bad.. Replaced IC again.. still same.. WTF.. seemed like there wasn't enough current to turn fet on.. 12V supply was good SO i swapped Boot strap caps from bad side to good.. and now Bad side is ok!!! and Good side bad.. SO.. Boot strap CAP was no good.. It didn't really test bad though.. so. Tested like normal cap using ohm meter.. It was just kind of the last thing i could think of to try. Anyway.. replaced boot strap Cap and now both sides start up and everything is working.. Finally.. Well I learned a lot.. and hope my experiences are helpful to some one else here. Thanks again for all your input and ideas.. they were quite helpful..
Click to expand...
Hi, anybody know how to find boot strap Cap on this board? Thanks
 
B

BassAudioGuy

Member
Joined 2018
Jonaduma said:
Sorry to revive an old thread i have the same amp with the same problems, it keeps burning my IRS20957S drivers i changed all parts noted here (fets, drivers, h04 triple inverter IC) but all it does is turn on and show it receives signal but there is no sound coming out. I noted also the bootstrap caps were changed but i could not find what those were. Also my amp both drivers are IRS20975S, and does not have 20955 IC, should the drivers on both sides be different??
Click to expand...
IRS20955 is obsolete. Both IC to be IRS20957
 
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