Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Papa Jim on November 03, 2018, 06:03:18 am
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I bought London Power Master Volume Kit that is nothing but a dual gang 1Meg pot and a couple 10K resistors. The 1Meg pot replaces the two 1Meg resistors in the LTP with their wipers each going to the grids of the PI tubes thru the 10K resistors supplied in the kit. That is all it is. I lost the schematic and can't seem to find anything online either. I know the two pots replace the 2 fixed 1M resistors in the LTP. Only question is the whether to wire it in so that this dual gang pot's pin 1's connect together or if one of the dual gang pot's pin 1 connects to the other gangs pin 3. Each pots wiper connects thru the 10K fixed resistors to it's PI tube grid. I hope this explanation is clear enough. If not I could possibly try to figure out how to make a drawing and add it here. Thanks in advance.
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My schematic shows x and o so not sure about the numbering but yes o-pins are connected together so i think in your case pin1 connects to other pin1.
If you pm me your email i can send you the schematic i have that was on the power scale kit instructions
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No need to email it. I have the Power Scale instructions. I didn't realize that the MV-1 Diagram was shown on them. Thanks.
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Thanks sluckey. I am trying to post the schematic but after I choose the file I get this message below and nothing to let me post the file I have chosen.
"Please copy all your text first:"
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Your file posted just fine. I see it.
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ok, great. Do you think those two fixed resistors connections are removed or cut, or that they are still connected and it is just a bad drawing. Which it is. Lol Mostl London Powers drawings are done by hand.
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KOC's TUT4 says you can either remove the existing grid leak resistors or leave them in the circuit, your choice. In either case it is beneficial to add identical grid stopper resistors to each grid. 10K is a good starting point.
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Thanks again. Glad you had Kevins book. I've heard they are an excellent source of info.
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...after I choose the file I get this message ... "Please copy all your text first:"
That bright red warning is because sometimes the file attachment process gets stuck, and you may lose all your typing.
Under that is a Browse button. This should pop-up your computer's file browser. You may have to click around to find the folder your file is in.