Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: turbofeedus on February 03, 2019, 12:17:09 pm
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Hey all, first post :headbang:
I went in search of a layout for the clubman, to no avail. This post has mostly dead links unfortunately. (https://el34world.com/Forum/index.php?topic=5730.0)
I've never made a layout before, but I figured I'd try and contribute. All criticisms and suggestions welcome.
Here is a link to the layout PDF. (https://drive.google.com/file/d/1oeADjmY29rDj6kkFgpG_2Rt_lzQJufWx/view?usp=sharing)
Here is a link to the bill of materials. (https://docs.google.com/spreadsheets/d/14nIBaNWnXO531wwtAq0mG2P83FqF1cu3lOKz4uuQ36A/edit?usp=sharing)
Here is the schematic off which I'm working. (https://drive.google.com/file/d/15WjR0o0htTBTLuSwIg5pvAvvLpoRISy3/view?usp=sharing)
A few notes:
1) I haven't determined the transformers yet, I'm talking to the company (Transformer Design & Supply) that made them originally for Matchless to see if they're still available.
EDIT: Just got off the phone with Bill at Transformer Design and Supply. They are in fact still making sets of Matchless transformers, the clubman set is going for $299+shipping. By phone is the best way to reach them it seems, (951) 654-9199.
2) The layout isn't perfect in terms of absolute OR relative sizing. If you reference the physical dimensions directly from this layout, you're gonna have a bad time. I do think that's sort of the point of a layout though, so once I'm sure of components, I'll update the layout to be more accurate.
Thanks in advance!
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The layout PDF is missing the .005uF cap on the brilliant control.
It looks like on the schematic on pin 6 of the 6sh7, you should only have the 1M to +DC and the 0.1uF to ground. In your layout you also have the .047uF tied into this junction with red dotted line. If they were supposed to be connected, the schematic would have a black dot where the lines cross, it doesn't.
I'm not familiar with 6hs7, and the reliability of online schematics isn't 100%, so double, triple check.
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The layout PDF is missing the .005uF cap on the brilliant control.
Thanks, yeah I forgot to add that, my intention was to have it off board, probably why. Fixed.
It looks like on the schematic on pin 6 of the 6sh7, you should only have the 1M to +DC and the 0.1uF to ground. In your layout you also have the .047uF tied into this junction with red dotted line. If they were supposed to be connected, the schematic would have a black dot where the lines cross, it doesn't.
Good catch, thanks. Fixed.
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Update, just got off the phone with Bill at Transformer Design and Supply. They are in fact still making sets of Matchless transformers, the clubman set is going for $299+shipping. By phone is the best way to reach them it seems, (951) 654-9199.
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Very nice sounding amp. Thanks for the goodies. Nice to get schematic,BOM and layout with Transformer contact.
A friend has one and it seem to be able to get good tone without blowing out the windows. Thx!
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Very nice sounding amp. Thanks for the goodies. Nice to get schematic,BOM and layout with Transformer contact.
A friend has one and it seem to be able to get good tone without blowing out the windows. Thx!
No worries, and like I said, still a work in progress. I'm hoping to build one soon.
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You measure 25 mA over 270 ohm that is 93 mA quiescent current. At this point say that there is about 15 mA from G2 so the anode gives 78 mA. This at 430 Volts at the anode gives us a disipation of 30 watts. In the datasheet of an EL34 you will see that this tube is build for 25 watts max. May be choose another tube or less quiescent current.
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You measure 25 mA over 270 ohm that is 93 mA
25mA should be 25vdc? just for the new math kids following along :laugh:
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Those voltages were already on the schematic. I don't think the OP has even built this amp yet.
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You measure 25 mA over 270 ohm that is 93 mA
25mA should be 25vdc? just for the new math kids following along :laugh:
You are right, I meant 25 Vdc, the mA was a typo error. :)
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You measure 25 mA over 270 ohm that is 93 mA quiescent current. At this point say that there is about 15 mA from G2 so the anode gives 78 mA. This at 430 Volts at the anode gives us a disipation of 30 watts. In the datasheet of an EL34 you will see that this tube is build for 25 watts max. May be choose another tube or less quiescent current.
I have a feeling those marked voltages from the PT are not accurate. I don't see any other matchless schematics listing 400V+ HT voltages, most are in the mid 300V.
Even still, using robrob's calculator (https://robrobinette.com/Tube_Bias_Calculator.htm), and a more modest guess of 350 plate to cathode voltage, still sitting at 122% plate dissipation.
Is the usual choice here to raise the cathode resistor? 330 ohms with the same setup above yields 100% plate dissipation, which is fine for cathode bias correct?
If I wanted to know voltages better before I build it/shell out the $300 for the transformers, is it reasonable to ask transformer design and supply what the high voltage on the secondary is?
Those voltages were already on the schematic. I don't think the OP has even built this amp yet.
Correct, have not built this amp. The schematic is not mine, just one google search away though.