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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 15th Oct 2017, 6:54 pm   #1
filmprojectors
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Join Date: May 2016
Location: Exeter, Devon, UK.
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Default Help wanted with my French Hortson amp.

My spare cinema valve amp has developed a strange fault. If I touch the bass control there's a loud humming noise from the speaker and sometimes if the bass is turned up over half way there's a thumping sound from the speaker but not all the time. It was working fine the last time I used it 10 months ago. Am I right in thinking it's a capacitor leaking to earth somewhere?
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Old 15th Oct 2017, 7:12 pm   #2
Boater Sam
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Default Re: help wanted with my thumping spare amp

Guess. Motorboating? A rhythmic base oscillation. Is this it?

Failing decoupling or smoothing capacitors.

But without any circuit diagram or make and model my ouija board won't work.
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Old 15th Oct 2017, 9:28 pm   #3
filmprojectors
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Default Re: help wanted with my thumping spare amp

I don't have a circuit diagram it's a 1968 French Hortson amp
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