I lost my lists of upgrades and possible improvements? (wish list)? for? "PSUD-3".....and that was years? ago.?
The colours were one item.
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Here is some additional ideas.?
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(A)? 3 phase rectification...with either 50 hz? or 60hz.? Typ, 6 x rectifier legs are used. The big advantage with 3 phase rectification is... the raw DC? is just 5.2% ripple....so most of the filtering is already done.? It makes the subsequent filtering an easier? task.? ?With a FWB / FWCT / FWD setup....on 60 hz, the raw DC has 67% ripple.? Ripple freq? is 2F? ?with single phase (100/120 hz)? ?vs? 6F? with 3 phase (300/360 hz).? With a FWB, on 50/60 hz single phase, caps get charged up...or....'topped up'? 100/120 times per second.? ?With 3 phase, and a FWB, caps get topped? 300/360 times per second.? ? The static and dynamic regulation is vastly improved with 3 phase power.
(B)? Resonant choke input.? This was used by a lot of RF amplifier manufacturers, and also commercial broadcast in the past.? From the output of the rectifier assy, B+ goes through the series choke, then the usual shunt filter cap.....the difference being..... there is an extra cap? ?wired in parallel? with the choke.? ?The choke is parallel resonated? at the ripple freq,? typ 100/120 hz....(when single phase 50/60 hz used).? ?Choke resonated at 300/360 hz? when 3 phase used.?
(C)? When a? C-L-C? filter is used...... it would be nice to have the option to parallel resonate the choke at the ripple freq...sorta like an elliptical filter.?
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###? ?The drawback to resonating the choke in (B) and also (C) is.... it only provides additional attenuation at the ripple freq...and not the harmonics of the ripple freq.? ?I saw this on small commercial? 5 kw FM broadcast PA's.... (single phase 60 hz).? A resonant choke was used to kill ripple at 120 hz.? However, the 5 kw PA? did not meet the FCC......'AM noise spec' used for FM broadcast.? The fix was a 2nd LC filter (this time the choke was not resonated).?
(D)? ?PSUD-2? only depicts P-P? ripple at the ripple freq. What's needed is? P-P ripple at all the harmonics of the ripple freq.? IE:? ripple freq is 120 hz.? ?What is the ripple at 240/360/480 / 600 hz? etc.?
(E). Using the? stepped load function of? PSUD-2 works, but doesn't represent what really happens with a dynamic load, like with an audio amplifier or? SSB.? ?I need to be able to differentiate between a static load....and a dynamic load.? ? With a dynamic load, the average? current is low, while the peak current is high.? ?Duty cycle on SSB ( with a lot of speech processing)? is 50% or slightly less on the B+ end of things.? ? The peaks as seen on an RF monitor scope are extremely narrow.? ? Meanwhile, when using the PSUD-2 stepped load option, the best I can do is to toggle between normal idle current..... and the max peak current.? IE: idle current of say 100 ma for XXX msecs, then slam on the full 800 ma load.? ?In reality, on SSB, the duration of the 800 ma peaks is mere msecs.? With enough C in the HV supply, the B+? won't sag as much.?
(F)? on these? HV? B+ supplies,? typ a HV fuse is wired in series with the B+..... followed by a 25-50 ohm 'glitch' resistor.? ?If any mishap occurs, like an anode to grid arc, or B+ to chassis arc, the 50 ohm resistor will limit the fault current to a safe value.? Meanwhile the resulting fault current will open off the hv fuse.....and fast like < 1-2 msecs.? ?IE:? 2.5 kv / 50 ohms? = 50 amps of fault current.? ?50 amps of fault current will open off a 800 ma rated fast HV fuse in 1 msec every time.? The HV fuse and? resistor will? save the HV supply....and also the tube.? ? I install a 2nd HV fuse, this time between one leg of the plate xfmr secondary (either leg, but one leg only) and the input to the rectifier assy.? ?Any B+ to chassis arc, inboard of the 1st HV fuse....and the 2nd fuse? will open off asap.? ? The 800 ma through the 50 ohm resistor will of course cause a 40 Volt,? V drop in the output.? PSUD-2 does not factor in the additional V drop....... but I just subtract it from the final results..... which works, but real difficult to do when a dynamic load is applied.?
I had a few additional ideas from years ago, for enhancements to PSUD, but have lost the paperwork....and can't remember what I had written down.? ??
