For you folks that come across? ?lytics, like the? 450 vdc variety, that have a threaded stud? (typ? 12mm threads, that stick out the dead center of the bottom of the can by? typ? 1/2")? look out, the threaded stud? will read? zero ohms, between the stud and the NEGATIVE? terminal? ?at the top end of the can !??
Strung in series, the lytics have to be insulated? from each other..and? chassis / ground.? ? Usually? when they have been used,? folks will? drill? an undersized hole, then? tap with a 12mm? tap.... and? typ into? 3/4" wood.?
I can see that being a potential? source of either leakage / fire hazard etc.? ?With say? ?300-400? vdc? across? each lytic, the V potential? between? ?studs is also 300-400 vdc.? ?3/4" wood, and loads of spacing between? studs is probably not that big a deal,? except in the case where? 9-25 caps? are used.? ?Typ with 9 caps, they are arranged in a 3x3 matrix, and wired like a snake..in series.? Ditto? with? ?16 x caps in a 4 x4 matrix,? I have seen? 24 caps in a 4 x 6 matrix.? Mine is? 25 caps in a 5x5 matrix.??
The caps? towards the hot end have one helluva lot of? B+ on em... and you don't want studs close to angle aluminum, which is typ what's used to support the 3/4"? wood etc.? You also can have a huge potential? ?if the? 1st and last cap are close to? each other, like adjacent, as is sometimes done on the last row,? done so the? B+ and B-? leads? are also close.... which is? really not a smart idea.? ?Even wired in the normal? snake routine,? Cap? #1 is at hot end.... and? cap? # 10? are adjacent...with a? 2772 V potential? between. their adjacent studs..and as much as? 7700 vdc between cap #1..and any? supporting angle Aluminum on the underside of the UHMW / wood etc.??
Mine are going into? 1" thick? UHMW sheeting, also drilled and tapped for the 12mm stud threads.? ?To support the weight of the? 25 caps ( at 3.3 lbs each =? ?82.5 lbs),? 2" x 2"? angle aluminum? is run down each side of rack, front to back.? ? ?Flat side up.? ?UHMW? sits on top? of the angle Aluminum.? ?Problem is, the rack is? 24" wide and not? 19"? wide.? ?1" UHMW is not as? strong as you think, I tested it with weight, it will flex.?
The fix for that is some more? 2x2? angle aluminum running transverse, across the? 24"? width of the UHMW, but underneath the UHMW,? to support it.? ?Those transverse pieces? ?bolt to the underside of the Al pieces that
run front to back, down each side of the rack.? But that also leaves a gap? ( = the thickness of the al used? that runs front to back, down each side).? IE:? ?UHMW? won't sit flush to the transverse supporting AL, but? 3/16" to 1/4"? above it.? ?The fix for that is yet another sheet of UHMW,? like? 3/16 -? 1/4"? thick, to fill in the gap, but? 4" narrower, so it sits flush to the edges of the front to back al.? ? It's that OR cut the transverse supporting pieces shorter, so they sit flush? to the edges of the front to back al, then there is no gap.? ?But then the transverse supporting pieces? ?are not supporting the last 2 " of the 1" thick? UHMW? down each side.?
82.5 lbs? (? + misc stuff like? eq resistors +? 50 x 10-32 screws etc, etc ), even though evenly distributed? in a 24 x 24 rack , is a lot of weight to support.? ?Worse is me trying to slide a completed, populated? sheet towards the? top of the? 6' tall rack.? ?Since the front / rear /and both sides are all quick release type,? it's almost? easier to mount the? pre-drilled sheet in the rack 1st, bolt it down, then? start screwing in? ?studs, one at a time, down the middle? row, (#3) ,? then? installing eq resistors etc, then adding the row on either side of center,? ( rows #2 +? #4)... then rows # 1 +? #5? dead last.? ?Then repeat for 2nd bank of? another 25 caps, lower down in the rack.? Then the misc HV fuses, and the? 127 lb dahl choke go in the bottom..or close to the bottom.?
From a safety view,? each bank of caps will get it's own dedicated? ?B+ meter.? ? Other cabinet with the 50 ohm glitch assy, B+ fuse, 2 x parallel diode boards, + plate xfmr etc, will? also get a dedicated B+ meter.? ? Each RF deck gets? 1 x B+ meter....so 5 all together.? ?IF the? choke went open, and NC vac relay engaged, so choke is in the circuit,? each bank of caps would be independent, with an open between em..and both? charged up to max B+.? ?IF the B+? fuse just inboard of glitch Resistor opened up, the? B+ meter in the RF deck will read zero... meanwhile both banks of caps have full B+ ..which of course is lethal..since they are still being fed from the plate xmfr and diode boards.? ?Any box I have that has B+? in it, gets a B+ meter.? ?Normally that's one in HV supply..and a 2nd HV meter in the? ?RF deck.? But in this one off case, the filter caps and choke are in a separate rack from the? xfmr + diode boards.. so 3 x racks in all for? the entire mess... for just 1 RF deck.? ?2nd RF deck goes into yet another rack (rack #4).?
After this gong show is done, that's it,? no more RF decks and B+ supplies for a while.? ? ?It's? over the top as is.?However, the ends justify the means, lol.? ?
