So you had to change just that one cap and now the sensitivity is back to how it was? That's excellent info, I will do this when the problem worsens.
Can you share the exact capacitor info so I can order them ahead of time?
A normal longer Philips screwdriver and allen key for the stand.
Remove the stand, than the bottom where the power cord is plugged in. The transformer is attached to it. Disconnect it from the board. Than the 4 screws which hold the lower passive radiator and remove it. Than you have acces to the amp. It's held in place by another 4 screws and you will need to disconnect all the wire connectors that go in it and be careful with them, because they are glued. You may use a small flat screwdriver to help you. Than you can take it out.
I believe there is a yt video showing how to change an amp so there you can see it too.
Remove the stand, than the bottom where the power cord is plugged in. The transformer is attached to it. Disconnect it from the board. Than the 4 screws which hold the lower passive radiator and remove it. Than you have acces to the amp. It's held in place by another 4 screws and you will need to disconnect all the wire connectors that go in it and be careful with them, because they are glued. You may use a small flat screwdriver to help you. Than you can take it out.
I believe there is a yt video showing how to change an amp so there you can see it too.
Hello, I installed all the transistors the same as they were, I repeat, carefully check all the passive elements on the boards and check the soldering (resistors, capacitors, check their values), the quality of the SMD resistors is very poor. I don’t see the point in changing everything indiscriminately; many people change capacitors based on power supply, but in my opinion this is a useless exercise. And an instruction for all owners of Mythos ST
acoustics - do not leave them constantly connected to the power supply, since the entire circuit is in operation all the time and there is no switch there, only the signal of the audio path is muffled.
acoustics - do not leave them constantly connected to the power supply, since the entire circuit is in operation all the time and there is no switch there, only the signal of the audio path is muffled.
I see many of the same capacitors (VT 10 16V) on the board. If the ones controlling the audio sensing circuit have gone bad (and these are probably the only ones that really result in an obvious issue), wouldn't it be a good idea to replace at least all of the same capacitors? Maybe even other capacitors on the board with some higher quality ones?
I'm going to open mine up and want to know what caps to buy before I do. Are these correct replacements? https://www.aliexpress.us/item/2251832629693676.html?gatewayAdapt=glo2usa4itemAdapt
I'm going to open mine up and want to know what caps to buy before I do. Are these correct replacements? https://www.aliexpress.us/item/2251832629693676.html?gatewayAdapt=glo2usa4itemAdapt
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I changed some with better ones with the same parameters but they are physically much bigger.
Also very important is that removing the old ones is tricky, because the board is **** and for every changed one you risk damaging the circuits in layed on the boardm be carefully.
Also very important is that removing the old ones is tricky, because the board is **** and for every changed one you risk damaging the circuits in layed on the boardm be carefully.
Well I should've followed your advice.
I am not good at soldering so I had someone fix my amps for me. I decided to also replace all the caps (mostly with Nichicons).
One of the amp works fine now, it turns on as soon as there is an audio signal.
The other amp, which before the "repairs" already seemed to have an issue wit the amp cutting in and out (the woofer moves...then stops...then moves etc), is now dead. It is either silent, or produces a constant soft static sound.
Here is what was done (names based on "Bp7006, 7004, 7002.pdf"):
Step 1:
Replaced capacitors (C5, C9, C6, C3, C15, C31, C30, C36, C35, C44, C48, C47, C43, C46, C45)
Step 2:
Swapped U2 between good & bad
Step 3:
Measured voltages at C6, C12, Q3, Input Voltage (M3) for Bad and Good PCB. Measurement values moslty are same.
Step 4:
Resoldered the capacitors.
Step 4
Measured resistances at R12, R99, R28, R29, R13, FB3, FB2, R27, R36, R11, R10, R9, R8, R7, R22, R21, R20, R19, R18, R17, R16, R5. Measurement values moslty are same.
The Vout at JP1 is 0.00V for good PCB, 0.10V for bad PCB. This seems to be the main difference between the two amps.
Can anyone advice what might be the issue?
I just fixed the exact same problem on a Definitive ProSub 800, which appears to use the same amplifier. Yep, bad SMD electro caps, 10uF and 4.7uF variety. One had 50 ohms ESR but read OK on capacity. I replaced all of them on suspicion.
I got the sub for $15, and wanted to do a zero-budget repair on it, so bodged in some regular radial capacitors I had on hand, and gooped them up with silicone so they won't vibrate. Worked great! Great sounding little sub, I'm impressed.
Bchow, I observed, as did previous posters... that the traces on this board are really fragile and easy to damage. I'd be looking for missing connections on the new components. They may have been damaged by vibration.