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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 22nd November 2017, 02:42 PM   #11
Junm is offline Junm  Philippines
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Quote:
Originally Posted by Ketje View Post
Here is something wrong
Mona
Yes those are the original values and reading are not in conformance against original voltages. Even in the cathode of the triode. So i wander why?
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Old 22nd November 2017, 02:50 PM   #12
Kay Pirinha is offline Kay Pirinha  Germany
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Your readings aren't even in conformance with each other. So, just to repeat artosalo's question: Which meter did you use? What is it's input resistance?


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Old 22nd November 2017, 02:58 PM   #13
Junm is offline Junm  Philippines
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Yes not really in conformance. I use fluke and sanwa dmm. I tried measuring those voltages several times and this is the actual voltages im getting. When i remo remove the tube and measure plate volage after plte resistor its good as the source of 167v. On saturday i will be using another set of dmm to monitor every nodes,
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Old 22nd November 2017, 03:01 PM   #14
Junm is offline Junm  Philippines
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I will check the input resistance of those dmm once home. Im on travel now.
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Old 22nd November 2017, 03:10 PM   #15
Ketje is offline Ketje  Belgium
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Quote:
Originally Posted by Junm View Post
Yes those are the original values and reading are not in conformance against original voltages. Even in the cathode of the triode. So i wander why?
Your voltages (in red) are right if you supose the anode resistor of the concertina is 182k.The voltages on the input pentode are to low all together, but that is another question. Mona
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Old 22nd November 2017, 03:24 PM   #16
Kay Pirinha is offline Kay Pirinha  Germany
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Maybe the - possibly carbon comp - triode's plate resistor has heavily increased it's value, and maybe the pentode's 33 cathode eletrolytic has dried out and shorted?


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Old 22nd November 2017, 03:25 PM   #17
Junm is offline Junm  Philippines
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I had tried to put another 100k in parallel with 150k. The pentode plate reads close to 70v and catho is around 1.5 v but vg2 pegs at 22v. Triode is at the same mode. I trird to inject music it sounds but weak. Before the sound is nothing but hum.

Thanks for the tip i try to
Look on that, i didnt touch on triode yet since my time was wasted in the pentode. I check on the cathode cap and seems not shorted since the resistor value is read. I will try to disconnect it fot testing.
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Old 22nd November 2017, 03:50 PM   #18
artosalo is offline artosalo  Finland
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Is there possibly DC at g1 of the pentode (pin8) and does it vary if you adjust volume pot. ?
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Old 22nd November 2017, 04:04 PM   #19
Junm is offline Junm  Philippines
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Yes theres a 1.3v posite on g1. When i put 500k on g1 to gnd it does not dissapear. I did not yet tried to varythe pot.
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Old 22nd November 2017, 04:13 PM   #20
artosalo is offline artosalo  Finland
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Put the grid directly to gnd (with less than 1k resistor, preferably with a jumper wire).
How are the voltages now ?
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