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6AN8 Pre & concertina, what seems to be the problem?
6AN8 Pre & concertina, what seems to be the problem?
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Old 9th December 2017, 10:59 AM   #91
Junm is offline Junm  Philippines
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Have done some testing again today. Placing a new set of 6an8 tubes and restore the resistor values. Voltage measurement has come very close to what is expected. Done some sound testing and now better needs only little adjustment and refinement.

Thanks gentlemen for your help it”s really the weak tubes that cause the problems and voltage at input.which will im going to find .

I wanted a little more gain. Can i adjust the feedback resistor to a higher value?
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Old 16th December 2017, 11:29 AM   #92
Junm is offline Junm  Philippines
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Another problem folks. In the preamp output has 25 vdc reading. Cap coupled on the filter section has voltage readings?

Everything in the amp section had close voltage reading with the schema. When i fed my cd out direct to the amp input the power is still weaker than specified 50w. In my opinion its only around 12w not 50w. Way far with b+ of 410 v loaded. Coming from preamp its a little bit powerful. Pream is isolted with cap so that 25v will be blocked.
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Old 16th December 2017, 11:40 AM   #93
TonyTecson is offline TonyTecson  Philippines
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6AN8 Pre & concertina, what seems to be the problem?
replace it with anew one....is it hanging when you took the reading?
a resistor of say 220k to ground will keep the cold side to ground voltage and no dc...
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