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Old 27th November 2006, 12:31 AM   #1
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Default PSU for an 813 SE

Here is my preliminary design...the operation is striving for simplicity...There will be a simple HV rotary switch to run the differing contacts...the time pause from "Standby" to "Start" to "Run" should be perhaps 400 milliseconds...enough time to bring up the heaters to full power before B+ is applied.
I'm kind of confused as to the sequencing of heaters to full B+...my take on this has been...you can run heaters at 63% all day with no load and no harm will be done, this wastes power though. The thought is that one will switch this unit to "Standby" initially & a "Start" to "Run" would occur later, I am concerned of the time lag as one drives the switch thru the different contacts
The time lag with the resistors should start-up the HV caps without drawing too much current. The 450VDC cap rating is rather close to the 390 VDC.
Any thoughts would be appreciated........
___________________________________Rick........... ..
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Old 28th November 2006, 10:45 AM   #2
glennb is offline glennb  Australia
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I can see problems with the arrangement of zeners around the "F" and "G" switches. In the short time to switch over from the 6.3V to the 12V zener the output of the regulator will jump up to the rectifier voltage (15 - 20 V?). A good way to blow the filaments / heaters! It would be better to permanently wire in the 12V zener, and then switch in the 6V zener across it for the "standby" mode.

The rotary switch needs to be rated for > 1KV insulation and the contacts rated to switch (say) 10 amps. The peak currents at switching would be very high if there were filter caps after the "C" & "D" switches, or if the 3000uF and 3300uF high voltage caps weren't fully charged through the "A" & "B" stand-by resistors.
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Old 29th November 2006, 02:32 AM   #3
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The large rotary switch is rated at 2KV @20A & the switch is called "Make before break" which I'll assume at this point means the two contacts are bridged before contacting one or the other.
There will be no caps after the HV supply...Take a look-see at the switch, it is the smallest of the series.
PS...The monster cap for 900VDC is rated at 1.5KV not 3KV as written & measures 13.5""W, 7"" D,16""H. Flopped on its' side should be able to make room on the chassis...just need to write them now to see if it can function correctly laying down.
___________________________________Rick........... .
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Old 29th November 2006, 06:54 AM   #4
glennb is offline glennb  Australia
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Nice switch! The make-before-break vindicates all of my concerns. Good luck with the project, its a monster!
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