Thread: Motorboating
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Old 22nd Jan 2006, 10:56 am   #7
Heatercathodeshort
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Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: Motorboating

Hello Neil,
Interesting that you have motorboating with your ECL80 circuit. The ECL80 with its common cathode tends to be a bit unstable unless everything is in place. I spent a long while recently with the same problem but it was a Ferguson 988T television that was the problem. The chassis was out of the cabinet and I was using the bench speaker and output transformer as a monitor. After many frustrating attempts to stabilize the output stage I discovered it was the output transformers incorrect matching that was the cause of the problem.....Substituting the original cured the problem. Your circuit should work well and the previous suggestions regarding a common earth point and layout should cure your problem. The little ECL80 can pack a punch for one so small. If its any consolation I remember building a TRF set when I was about 10. I put the anode coil UNDER the chassis and the grid coil ON TOP of it and then puzzled for hours as to why the signals were SO weak..! The cog then fell in and I realized you had to wind the two coils on the SAME former....It comes with practise! Regards. JOHN.

Last edited by Heatercathodeshort; 22nd Jan 2006 at 11:02 am.
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