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Neil Purling · 21st Jan 2006, 10:31 pm

I am part-way through the process of building my TRF radio and as I said I have completed the AF side first.
I switch on and after the HT has come up the thing is motorboating.
I think that is the right term. Even with no input it sounds like a boat on a lake.
The amplifier is a ECL80. I applied a signal from my record turn table to the grid of the triode section, via its coupling capacitor (0.01uf) and the volume would rightly be described as loud. However the motorboating doesn't go away when I apply the input signal and it distorts the audio of course so Status Quo sounds like a Dalek convention.

This is my first valve powered project. I have probably done something really silly but tell my why the amplifier would do this thing and i'll go look for the likely culprit.

21st Jan 2006, 10:31 pm	#1
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Motorboating I am part-way through the process of building my TRF radio and as I said I have completed the AF side first. I switch on and after the HT has come up the thing is motorboating. I think that is the right term. Even with no input it sounds like a boat on a lake. The amplifier is a ECL80. I applied a signal from my record turn table to the grid of the triode section, via its coupling capacitor (0.01uf) and the volume would rightly be described as loud. However the motorboating doesn't go away when I apply the input signal and it distorts the audio of course so Status Quo sounds like a Dalek convention. This is my first valve powered project. I have probably done something really silly but tell my why the amplifier would do this thing and i'll go look for the likely culprit.