Hi Friends,
I have a pair of mythos sts speakers, which are ok, but one of them doesn't turn on when I play some music. Those speakers have an amp in them for the bass speaker and it senses when signal is played trough my amp. I have connected the speakers trough the + / - speaker cables, since my amp doesn't have an LFE output.
If I connect the power cable of the speaker it starts, but if nothing plays for some time or it isn't very lout it powers off and doesn't turn on again. The red light on the back doesn't light up too. The other speaker is better, but also stubborn sometimes on power on and I have to plug out/in the power cable.
My knowledge is limited, but I would be happy if I manage to find the fault with your help.
I opened one of the amps and having read many stories with problems about them, I made some upgrades to the known capacitors which tend fail. That had no affect on the auto power on feature, but now when the amp starts, I don't get a loud popping sound . I changed the caps for bigger ones, following an advice from video on YouTube, about a repair of an def tech amp.
I have encircled with yellow the place on the board where the two wires giving the auto on signal connect, coming from the wire connectors of speaker cables. They are red and white and one of them goes to the big green resistor and I still haven't found where the other one goes.
Here is schematic of the auto on part.
Here, as well as in the manual it states something I fail to grasp : 40-60min delay - is that turn of delay?
What components on the board should I check so that I repair this issue. Or any hints would be appreciated
Here is a gallery with more photos of the board :
>>> google drive folder <<<
Any help would be helpfull.
Thanks in advance!
The whole pdf schematic is attached as an pdf. It is for the BP models, but from what I see, they are basically the same.
I have a pair of mythos sts speakers, which are ok, but one of them doesn't turn on when I play some music. Those speakers have an amp in them for the bass speaker and it senses when signal is played trough my amp. I have connected the speakers trough the + / - speaker cables, since my amp doesn't have an LFE output.
If I connect the power cable of the speaker it starts, but if nothing plays for some time or it isn't very lout it powers off and doesn't turn on again. The red light on the back doesn't light up too. The other speaker is better, but also stubborn sometimes on power on and I have to plug out/in the power cable.
My knowledge is limited, but I would be happy if I manage to find the fault with your help.
I opened one of the amps and having read many stories with problems about them, I made some upgrades to the known capacitors which tend fail. That had no affect on the auto power on feature, but now when the amp starts, I don't get a loud popping sound . I changed the caps for bigger ones, following an advice from video on YouTube, about a repair of an def tech amp.
I have encircled with yellow the place on the board where the two wires giving the auto on signal connect, coming from the wire connectors of speaker cables. They are red and white and one of them goes to the big green resistor and I still haven't found where the other one goes.
Here is schematic of the auto on part.
Here, as well as in the manual it states something I fail to grasp : 40-60min delay - is that turn of delay?
What components on the board should I check so that I repair this issue. Or any hints would be appreciated
Here is a gallery with more photos of the board :
>>> google drive folder <<<
Any help would be helpfull.
Thanks in advance!
The whole pdf schematic is attached as an pdf. It is for the BP models, but from what I see, they are basically the same.
Have tried the same on my BP 7004 amp. That seems to had serious failure, since one line was burnt of on the main board.suspect that smal coil might have shortened the mosfet legs. Since it's placed just over the legs.
Fixed it.
Changed all mentioned caps.
Changed 3 mosfets.. Amp turns on, Red led lights up. But no sound. Can measure sound signal on the input leg, small vertical amp board...
Still have a mythos amp, that I will do the same with. Hopefully it will start working again..
Fixed it.
Changed all mentioned caps.
Changed 3 mosfets.. Amp turns on, Red led lights up. But no sound. Can measure sound signal on the input leg, small vertical amp board...
Still have a mythos amp, that I will do the same with. Hopefully it will start working again..
Attachments
Hi, all the output transistors burned out, after replacing them, the amplifier worked, but there was a strong background and distortion, it turned out that the 3.3kOhm resistor on the small output amplifier board burned out.
I recommend to first check the soldering and serviceability of all passive elements, the printed circuit board, then check all supply voltages, the presence of +- 66V, +-15V, relative to the ground with a multimeter, an oscilloscope is needed for more complex repairs, check for a supply voltage of +-15V on all operational amplifiers of the preamp board
I recommend to first check the soldering and serviceability of all passive elements, the printed circuit board, then check all supply voltages, the presence of +- 66V, +-15V, relative to the ground with a multimeter, an oscilloscope is needed for more complex repairs, check for a supply voltage of +-15V on all operational amplifiers of the preamp board
Attachments
![20231214_192155[1].jpg](/community/data/attachments/1172/1172390-7869abde26c3727dccc37c6da944192b.jpg)
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the tracks on the board burned out, they are under the output amplifier board
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Tnx
I'll check those resistors. It's a few of that 3,3K resistor.
Some pics of my broken amp.
And a amplifier board from a audio vector subwoofer, seems to be the same...
I'll managed to get a working amp from UK, changed all caps. But would be great to actually manage to repair this problem.
Also have similar amp from BP7004. It turns on, but no sound, no trace of burnt parts. Changed those caps, but still silent
I'll check those resistors. It's a few of that 3,3K resistor.
Some pics of my broken amp.
And a amplifier board from a audio vector subwoofer, seems to be the same...
I'll managed to get a working amp from UK, changed all caps. But would be great to actually manage to repair this problem.
Also have similar amp from BP7004. It turns on, but no sound, no trace of burnt parts. Changed those caps, but still silent
Attachments
Hello, yes, this is the same amplifier, and my track also burned out, by the way, it’s better not to leave the +66V wire like that, the amplifier is very sensitive and this wire should not intersect with “out” and “mute”. Is there voltage + - 66V at the indicated terminals?
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I don’t see any point in changing the capacitors, I think they are reliable, by the way, the LM 324 operational amplifiers are also durable, the amplifier does not seem to work without a small output amplifier board, if it does not turn on, then you need to look at everything that is connected to the “U2” chip, capacitor C6 in conjunction with resistor R18 is responsible for turning off the amplifier in idle mode for 40-60 minutes
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I just got a pair of these as well.
When I play music the subwoofer does not turn on automatically (red LED not lit). If I unplug and plug the power cable from the socket the red LED then turns on and the subwoofer starts working. When playing the subwoofer continues to work and red LED stays on.
Any idea?
When I play music the subwoofer does not turn on automatically (red LED not lit). If I unplug and plug the power cable from the socket the red LED then turns on and the subwoofer starts working. When playing the subwoofer continues to work and red LED stays on.
Any idea?
Hello, I would start with the power source, check the presence of all voltages + -15V, + -66V, if everything is ok, look at the diagram at the beginning of the page posted by the respected windv. I would check the capacitor C6, C12, and transistor Q3, then check the soldering under a microscope and ring all the resistors in this circuit, practice has shown that in these amplifiers they are of poor quality, if everything is fine, we proceed to check the operational amplifiers, but here we need oscilloscope, although operational amplifiers are quite reliable and the problem is often in passive elements. Also check diode D2 with a multimeter
Hey guys. Thanks for the so much info.and help.
I also got around to fixing mine. It was a bad cap. Attached a photo.
@bchow
Mine was like that too, until I needed to crank my main amp so much that it switched off . Than the amp in the speaker stoped switching on completely after a while.
I also got around to fixing mine. It was a bad cap. Attached a photo.
@bchow
Mine was like that too, until I needed to crank my main amp so much that it switched off . Than the amp in the speaker stoped switching on completely after a while.
Attachments
What replacement transistor did you use. I am thinking of preventively changing mine.
I haven't made any serious observations yet, but the one speaker where I changed the caps with more expensive ones feel like it pumps out more bass! I will make a more careful test and write back.
I was thinking of changing all the other small caps, like the one that was giving me trouble, just in case.