Penta unusual loud noises. Like loud Scratching

[nigel_surtees]

Hi All
I am new to this forum. I have a beocenter 9500 with Penta mk3 active speakers. I have had the system for about 5 years with no problems. About 6 months ago one speaker starting making very loud noises. they are hard to describe so I made a recording and attached it to this thread. Its like static scratching and very loud.

I have replaced all the electrolytic capacitors using a kit bought online. Its made no difference. During the overhaul I replaced the trimmers and set the dc offset which is now practically 0v.
Could it be the big power capacitors?  I didn’t replace these as they were not in the kit.

Any ideas very welcome.

Thanks

[Epic B and O]

Hey mate,

I have the same problem. It’s  corrosion on the input level switch.

I had a complete overhaul of my Penta’s, but unfortunately they missed the switch. So at the moment I’m living with it by switching the problem speaker to another input level.

I have the Beocenter 9500 also since the 90s. Absolutely love it.

I’ve attached photos of the problem switch.

if you find a fix please let me know.

hope this helps.

 

[nigel_surtees]

Ah really! Thanks for that, I would never have thought of looking at that switch. I’ll have a play and see what I can do with it and let you know if I get anywhere.

Thanks again

[Homersaurus]

Would contact switch cleaner sprayed into the switches (when the control board is out of the Penta) be sufficient without resorting to physically dismantling the switches ?  I’d be interested to know the level of corrosion in the dismantled switches.

[Homersaurus]

An interesting cause of the fault though, which is very useful to know.  Switch cleaner/lubricant use as preventative maintenance might well be worth doing on the (pair of) Penta control board(s).

[Author]

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