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Philips MFB speakers
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Fatmangolf View Drop Down
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Points: 9695 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2022 at 6:19pm
I'm back in front of my hifi after a pleasant week in south Suffolk. It is surprising how much difference changing the feedback capacitors made.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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allant 0 0

HomeBoard indexTechniekMFB boxenSearch
544 crackling, popping and banging


Hello, can anyone help please? 
I have owned my 544s for over 20 years, but in the last couple of days they are popping and crackling when activated, it's happening about every 30 seconds, in only one speaker, I am guessing it is going to be a failing component, possibly a capacitor, but I am not an electronic specialist.
Does anyone know if it is an easy fix, I can solder and was an electrician by trade. Things are made harder now by living on a Greek Island for having a repair done, hence wondering if I would be able to repair it myself. Thank you for reading.
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Fatmangolf View Drop Down
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Points: 9695 		Post Options Post Options   Thanks (1) Thanks(1)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 29 Dec 2025 at 5:33pm
Welcome Allan. I have a pair of 544 speakers as discussed above. They didn't have that fault so may I ask you some questions?

Do you hear crackling on other household audio and are the noises present on other sources feeding your MFBspeakers? Does the noise occur when no music is playing?
How are the speakers connected? Is it DIN cables, and are they wired one after another? If so try unplugging and reconnecting the cables and swapping them over.

This will help to determine where the fault is. Most likely it is inside and on one of the circuit boards. On the faulty speaker I suggest resoldering some or all of the PCB connections. The service manuals may help. Given the age of the speakers I suggest replacing the electrolytic caps.

Please let us know how this goes.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Points: 9 		Post Options Post Options   Thanks (0) Thanks(0)   Quote AllanT Quote  Post ReplyReply Direct Link To This Post Posted: 30 Dec 2025 at 8:39pm
Thank you for the quick reply, the one speaker is the only unit in the house that has the problem, as soon as it's triggered, it crackles, then stops, but repeats about every 30 seconds, music or not until I turn the music off and it powers off. It is connected with the original Din cables and has been working perfectly for 3 years we have been over here. I do have the service manual, but was hoping someone would know what most likely would be the faulty component /s.
I will pull it apart and check for dry joints as the first solution. 
Cheers, Allan. 
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Fatmangolf View Drop Down
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Points: 9695 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 31 Dec 2025 at 7:46pm
Thank you for the answers. If the crackle comes from all three drivers that suggests both amps are fine, please confirm this assumption. Also do you use the automatic on/off feature? If so please turn it off then turn the speaker back on. It will probably show the same fault but eliminates a possibility.

Unless the bass come is pulsing, the MFB sensor and feedback circuit are probably okay. So I would start with the power supply capacitors and other large electrolytics as they can dry out after 50 years and can leak.

A fault on the input stage and active crossover could cause the pop and crackle. Maybe a poor solder joint or failing component as you suggested 

Disconnect the power and open up the up the amp after some time has passed, the door hinges out to allow the circuit board to be visually inspected as you probably know already. Look closely for charred circuit board, leaking electrolytic caps, and furry transistor leads. If not of these try resoldering the various connections on the other side of the board.

I hope this helps.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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I will hopefully get a chance to look into the issue next week, also noticed that the Led is not lit any more despite the speaker having power and triggering on. 
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Ah. I think that is helpful for diagnostics. On my 544's the LED is Q480 and it runs off the main 57 volt power supply rail and loses power when the standby relay (on main PCB near transformer) goes off. Does the auto on/off switch make any difference?
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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