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In Reply to: RE: Slight change in power supply cap value - problem ?? posted by euro21 on June 16, 2015 at 08:37:17
Hello,
I understand your point about the 805 as a starting project, but circumstances sort of dropped me into it. An abandoned 805 project came available, consisting of all of the correct, NOS Tango iron for the project, which includes the extremely large power transformer and 2 huge output transformers (as called out in the schematic) - also the correct 2 interstage transformers and choke, plus a couple of large caps (shown above). The transformers are beautifully built and finished - my only remote fear is that the iron are Chinese fakes, but they seem correct and way too nice for that, and I am not sure they ever went for the custom Shishido / Tango transformers.
I actually have recently communicated with Ronald, the author of the first article you included. He was very helpful. I gather many of his issues were because he could not source the correct transformers. I will indeed read the second article you provided.
I was trained as an electrical engineer back in the day of discrete components, and spent a fair amount of time at a bench building and testing boards, but that was 20+ years ago and had nothing to do with tubes. I do tend to want to validate things that I come across that are not clear (like the capacitor structure), so hopefully that will help me avoid a lot of blunders. I understand that it is quite complicated and a real undertaking, but I feel pretty comfortable with it and am not in a rush (which helps a lot).
Regards -- Roger
Follow Ups:
"(like the capacitor structure)"
As you can see this is the classical voltage doubler.
C1 and C2 may be such 2x...uF/500V Cerafine you showed, but C3 and C4 are single capacitors. R1 and R2 are medium wattage (2-3W) balancing resistors for stacked capacitors.
In my practice, single diode in voltage doubler sometimes busted. Over the 300V I use two series 600-1200V (SiC) diodes.
IMHO in SE amplifier last capacitor is more important, so this position I would use Cerafines. Paralleling each 2x100uF, then stacking them.
Partsconnexion ( http://www.partsconnexion.com/capacitor_ele_jensen_radial_sgl.html) sell Jensen 500-550V radial single capacitors. These types good for first stacked capacitors.
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