Hang on - I have one more question about the wiring of the power supply! Here is a picture from the manual showing the wiring of the first part of the A3600 power supply:
Terminal 6 of the power transformer (PT6) in the bottom right is the output from the rectifier. Wire #1 goes from PT6 to terminal two (47uf) and one (47uf) of the first multi-section cap in the power supply - together, these two 47uf caps make up C1 (C301). Wire #2 goes from PT6 to the input terminal (1) of the C2006 choke. Wire #3 goes from the output terminal (3) of the C2006 choke to the first 47uf cap and wire#4 connects it with the first terminal of the second multi-section cap - together, these two caps (47uf+47uf) make up C2 (C302).
So here is my question: Is there an electrical difference and advantage in taking the end of wire #2 currently connected to PT6 and instead connecting it to terminal 1 of the first multi-section cap?
Terminal 6 of the power transformer (PT6) in the bottom right is the output from the rectifier. Wire #1 goes from PT6 to terminal two (47uf) and one (47uf) of the first multi-section cap in the power supply - together, these two 47uf caps make up C1 (C301). Wire #2 goes from PT6 to the input terminal (1) of the C2006 choke. Wire #3 goes from the output terminal (3) of the C2006 choke to the first 47uf cap and wire#4 connects it with the first terminal of the second multi-section cap - together, these two caps (47uf+47uf) make up C2 (C302).
So here is my question: Is there an electrical difference and advantage in taking the end of wire #2 currently connected to PT6 and instead connecting it to terminal 1 of the first multi-section cap?
Perhaps make a schematic sketch of that part of the circuit, and identify the change you propose.
Thanks, T - here you go! You can hopefully see the change I've made to wire#2 that creates a logical (to me!) path from the rectified supply (PT6) to C1 (terminal 2) and out of C1 (terminal 1) to the input terminal of the C2006 choke. Of course, electrically, there might be a good reason for the existing wiring or it might make no difference, electrically.
Perhaps make a 'circuit' schematic sketch of that part of the circuit, and identify the change you propose.
Sure! I've doctored the PSUD diagram to show you what it is supposed to be, electrically (top), and how it looks to me as it is wired (bottom):
How is PT6 also the rectifier point of connection?
Perhaps re-read post #29 about the influence of different wiring configurations. The reason for suggesting the choke is fed from the cap terminal is similar to that in post #24. A good reference with diagrams is Merlin's doc (https://www.valvewizard.co.uk/Grounding.pdf) which focusses on the benefit of staring from a cap negative terminal for grounds - but is similarly applicable for staring from a cap positive terminal for B+ distribution.
Perhaps re-read post #29 about the influence of different wiring configurations. The reason for suggesting the choke is fed from the cap terminal is similar to that in post #24. A good reference with diagrams is Merlin's doc (https://www.valvewizard.co.uk/Grounding.pdf) which focusses on the benefit of staring from a cap negative terminal for grounds - but is similarly applicable for staring from a cap positive terminal for B+ distribution.
Thanks, I re-read both posts and I've read the Valve Wizard and many other similar posts on grounding I could find.
I'm not sure what to make of your question about PT6 - except to check you are clear that the page from the manual in post #44 is about the B+ supply, not the ground wiring.
I'm not sure what to make of your question about PT6 - except to check you are clear that the page from the manual in post #44 is about the B+ supply, not the ground wiring.
Your schematic in post #46 shows PT6 is connected to the diode bridge, but you refer to PT6 as a terminal on the power transformer - I wasn't able to reconcile where the diode bridge was? Perhaps the bridge rectifier has a wire connecting to PT6 terminal, as a convenience ?
Ah, yes - I see I was too brief! There are four RA-3C silicon diodes connected to spare terminals on the power transformer on either side of PT3 and PT4 terminals, which are the 370V and 0V secondary winding terminals on the power transformer. PT1 is the ground terminal after rectification and PT6 the B+ terminal.
I've gone back again to Valve Wizard's grounding tutorial and this is the diagram that stands out for me:
I've looked again at the grounding scheme in my amplifier and I think this is what it looks like if I followed his advice (see diagram below). The only difference from the way the amp is currently wired is that the heater grounds for both the preamp and output tubes are connected to the left multi-cap negative terminal for the preamp and driver stages when Merlin reckons they'd best be connected near (to?) the negative terminal of the reservoir cap (as pictured below).
What isn't shown below but is shown in the grounding scheme picture from the manual is the ground bus connection to the Bias 3x100uf multi-cap on to the preamp PCB ground plane, which is connected to the chassis via a single mounting bolt. The common speaker terminals are connected (each separately) to the negative terminal of the Bias multi-cap (as per advice from @trobbins (thanks).
I've looked again at the grounding scheme in my amplifier and I think this is what it looks like if I followed his advice (see diagram below). The only difference from the way the amp is currently wired is that the heater grounds for both the preamp and output tubes are connected to the left multi-cap negative terminal for the preamp and driver stages when Merlin reckons they'd best be connected near (to?) the negative terminal of the reservoir cap (as pictured below).
What isn't shown below but is shown in the grounding scheme picture from the manual is the ground bus connection to the Bias 3x100uf multi-cap on to the preamp PCB ground plane, which is connected to the chassis via a single mounting bolt. The common speaker terminals are connected (each separately) to the negative terminal of the Bias multi-cap (as per advice from @trobbins (thanks).