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Beomaster 4000 good for repair practice?

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Chickene
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Chickene posted on Thu, Apr 15 2021 9:36 AM

Dropped by a fleamarket yesterday and picked up a BM4000 for 100kr- I felt it was too good a deal to pass up.

It turns on sometimes, but usually takes a good bit of fiddling with the switch. Both channels work ok, but the noise floor is really high. And even after a lot of contact cleaner, the potentiometers are noisy, but not as noisy as they were when I got it. When I move the balance knob I get a sound like bubbles popping.

Thing is, my repair skills are very much limited to potentiometer cleaning and alcohol wiping. I've never even considered things like recaps before, cause I suck at soldering, but I figured this could be a good starting point because of my low investment. What do you guys think of this unit as a starter? Could my balance knob woes be more than just a crap potentiometer? And does anyone have experience with cleaning out the switches? because they seem to be pretty deep in the machine, and I don't quite trust myself to be able to take this whole thing apart and put it back together again. When it comes to recapping, I wouldn't even know how to identify what to replace or where to buy the replacement...

Oh, and if anyone knows the trick to holding wires in place as you solder them, or how to get rid of old solder when desoldering, please feel free to demystify :)

Sorry for the messy post- I'm pretty clueless about this whole thing... Any help is appreciated.

-Joshua

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Saint Beogrowler
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Saint Paul
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Hello, the BM4000 is an enjoyable quality receiver. In my opinion, you will regret using it as a starter learning project. Your BM 4000 is currently in a place that can be repaired with moderate knowledge and skill or with simple mistakes, it can very quickly be in a condition that is repairable only by a skilled and experienced technician.

Soldering practice is best on a throwaway board where you practice removing and reinstalling components. Solder is removed with a solder sucker or copper wick. A cheap desoldering iron is helpful when you are just starting. Holding wires with a “third hand” makes it easier, a cheap readily available tool with alligator clams.

Problem is probably more than the adjustment pots. Recapping will probably help but if you’re not careful can cause more problems. When you’re ready to try recapping, ordering a kit from Beoparts makes it much easier. Match capacitor uF and volts, mind polarity.

Those lower switches are difficult to repair. Breakable plastic, springs, lots and lots of patience with pictures. The only way to do it right involves a lot of careful disassembly. I’ve done several and I dread it every time.

If I were in your shoes, I’d put it away, practice recapping something easier, maybe look for a second BM4000, having 2 units to compare functions and locations helps a lot when you’re starting and don’t know how they work or read schematics. Once you are ready for this project, you will be glad you didn’t make your job harder.

If you are computer savvy, maybe watch a few YouTube videos. Lots of free info available these days.

Chickene:

Dropped by a fleamarket yesterday and picked up a BM4000 for 100kr- I felt it was too good a deal to pass up.

It turns on sometimes , but usually takes a good bit of fiddling with the switch. Both channels work ok , but the noise floor is really high. And even after a lot of contact cleaner, the potentiometers are noisy, but not as noisy as they were when I got it. When I move the balance knob I get a sound like bubbles popping.

Thing is, my repair skills are very much limited to potentiometer cleaning and alcohol wiping. I've never even considered things like recaps before, cause I suck at soldering, but I figured this could be a good starting point because of my low investment. What do you guys think of this unit as a starter? Could my balance knob woes be more than just a crap potentiometer? And does anyone have experience with cleaning out the switches? because they seem to be pretty deep in the machine, and I don't quite trust myself to be able to take this whole thing apart and put it back together again. When it comes to recapping, I wouldn't even know how to identify what to replace or where to buy the replacement...

Oh, and if anyone knows the trick to holding wires in place as you solder them, or how to get rid of old solder when desoldering, please feel free to demystify :)

Sorry for the messy post- I'm pretty clueless about this whole thing... Any help is appreciated.

-Joshua

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