Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: sgbrewing on December 30, 2024, 06:06:09 am
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Hello guys hope all is well and you've all had a good Christmas!
Just finished making a layout from a F DS Schematic I found online (a few minor changes to the pre amp & el34's instead), haven't included heater wiring to save extra mess.
I've gone through and checked my layout and can't find any potential errors, I would appreciate it if I could have this proof checked please before I start the build :laugh:
Thanks a lot,
Shawn.
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Power supply is wrong.
No 5 acv heater wires, only 1 choke wire, B+ 500mA fuse is wired wrong, no B+ CT.
That's as far as I got.
You should read this on grounding before you build the amp that way and re-do your filter cap layout and grounding.
https://www.valvewizard.co.uk/Grounding.html (https://www.valvewizard.co.uk/Grounding.html)
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Power supply is wrong.
No 5 acv heater wires, only 1 choke wire, B+ 500mA fuse is wired wrong, no B+ CT.
That's as far as I got.
You should read this on grounding before you build the amp that way and re-do your filter cap layout and grounding.
https://www.valvewizard.co.uk/Grounding.html (https://www.valvewizard.co.uk/Grounding.html)
Thanks for your reply, appreciate it!
I have omitted all the heater wiring due to saving mess on the layout, didn't bother with the B+ CT but i've added it now for clarity.
There's actually 2 choke wires but they are really close together I have separated them now to make it more clear.
With the B+ fuse, I'm not bothering with a standby switch as its not needed, I thought this is how it should be wired, how would you recommend it?
Regarding the grounding, all the power section is grounded on a tap by the power transformer and the preamp is all grounded at a lug near the inputs, is this not standard grounding?
Thanks for your help,
Shawn.
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Power supply is fine. Grounding is good, but the speaker jack sleeve must be connected to power ground since you have a NFB loop.
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Power supply is fine. Grounding is good, but the speaker jack sleeve must be connected to power ground since you have a NFB loop.
Thanks a lot for your time! Good catch, I've added and updated.
Cheers!
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Power supply is fine.
What are you talking about? Several mistakes in that layout of the power supply.
Grounding is good,
Ever read Merlin's grounding page? The grounding schem he is using could be changed to a wired local star grounding system. It will be quieter.
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I have omitted all the heater wiring due to saving mess on the layout, didn't bother with the B+ CT but i've added it now for clarity.
You can't ask for help confirming you layout is right and leave wires out. That's not clarity. :BangHead:
With the B+ fuse, I'm not bothering with a standby switch as its not needed, I thought this is how it should be wired, how would you recommend it?
A B+ stand by switch has nothing to do with a B+ fuse.
Your schematic shows the 500mA B+ fuse in the B+ CT to ground. Your layout shows that B+ fuse in the B+ coming off the tube rectifier. These contradict each other for location.
Regarding the grounding, all the power section is grounded on a tap by the power transformer and the preamp is all grounded at a lug near the inputs, is this not standard grounding?
Yes, I see what your drew, read the Merlin link on grounding before you build that amp.
Biggest problem is you have the B+ CT and 1st filter cap grounded wrong. B+ CT should go directly and only to the 1st filter caps ground lead, NOT to the chassis, then run a wire from that junction to chassis power ground. And run a wire over to the B+ screen filter cap, node B. It's drawn in Merlin's link.
And where your taking the heaters dc stand off voltage from and where you put the 2 x R's and the filter cap and where it's grounded, is not the best place for it to be in the layout. It should not be grounded with the B+ CT. I'd move the dc stand off to the very last B+ filter cap node and inject it into the heater string on the 1st preamp tube.
And I'd move each B+ filter cap to right where it feeds the circuit it powers and form a ground star there. Then daisy chain each ground star B+ node together.
Read the link.
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Merlin's grounding scheme is great, but it ain't the only game in town.
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Hey guys there is something that doesn't looks right in the schematic
V5 anode(plate) is connected to the screen resistor and B+1, shouldn't it go directly to the OT ?
see picture
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Merlin's grounding scheme is great, but it ain't the only game in town.
Yeah, yeah, yeah, but it's proven scheme before you build it with any amp.
We just went all through this and I know you read it. And your still being antagonistic towards me on this subject. What is your problem, it's just not necessary.
https://el34world.com/Forum/index.php?topic=32271.msg357452#msg357452 (https://el34world.com/Forum/index.php?topic=32271.msg357452#msg357452)
And it's the best game in town. And it's not just Merlin that uses it, Kevin O'Connor, Randell Aiken, R. G. Keen and others.
Look you can build your amp anyway you want, buy I stand by local ground star wired grounds.