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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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30th Mar 2023, 5:10 pm | #41 |
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Re: Help with a HHSCOTT LK-72
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30th Mar 2023, 5:17 pm | #42 | |
Pentode
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Re: Help with a HHSCOTT LK-72
Quote:
From the schematic and grahams input I need 43-45vdc. |
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30th Mar 2023, 5:24 pm | #43 | |
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Re: Help with a HHSCOTT LK-72
Quote:
I can't think why you'd want to measure the resistance of the heaters.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
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30th Mar 2023, 5:27 pm | #44 | ||
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Re: Help with a HHSCOTT LK-72
Quote:
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30th Mar 2023, 5:42 pm | #45 |
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Re: Help with a HHSCOTT LK-72
I'm thinking as the tubes warm up they draw less current, that means the voltage will increase.
I'll leave them on to warm up and measure again. |
30th Mar 2023, 9:32 pm | #46 |
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Re: Help with a HHSCOTT LK-72
The tubes used for this amp are different brands but labelled v1 to v4, im wondering if the resistor choice was chosen based on the mismatched tubes, hence measuring the heaters going on what Lawrence said. Just thinking out loud, it may just be bull crap, im learning as i go along.
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30th Mar 2023, 9:41 pm | #47 |
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Re: Help with a HHSCOTT LK-72
You're overthinking this. Matching has nothing to do with heaters, heater currents or volts across the heaters.
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31st Mar 2023, 7:02 pm | #48 |
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Re: Help with a HHSCOTT LK-72
Agreed Graham I've ordered some different value 5W resistors to up the voltage.
I've also ordered some 7591A tubes to replace these unknown 6L6 tubes as I don't think they can handle the voltages. I've also got some other issues, with the rectifying tube in I'm getting 450V on pin ones of the 12AX7's when it should be 105V. |
31st Mar 2023, 7:37 pm | #49 | |
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Re: Help with a HHSCOTT LK-72
Quote:
Is that valves in or valves out? If it's valves out I'm not surprised as there'll be no volt drop across the chain of voltage dropping resistors leading from the cathode of V11 the rectifier. R202, R203, R204, R205 and R206.
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