Fw: Re: [AMPS] re: Dayton and Emtron

nospam4me@juno.com nospam4me@juno.com
Thu, 24 May 2001 08:48:26 -0700

: From: "Roger Parsons" <ve3zi@hotmail.com>
: Hi Skipp
: Interesting comments. I saw the amps and agree they look 
: pretty nice.
Hi Roger,
My wife was lucky I only carried one suitcase on the plane 
and it was already loaded with Motorola Spectra-Tac voter 
shelves.   Else I might have been tempted to buy amplifiers 
and parts.  I agree that most all the amplifiers I saw on 
display looked pretty nice.   Notice I said most....
: I would also allow a much greater clearance for high voltages, 
: but in fact it is probably OK. IEC standard 60079-11 related to 
: Intrinsically Safe equipment allows a 10mm clearance in air 
: for 1kV. That standard is _extremely_ conservative as the 
: clearance is supposed to be that at which arcing/conduction _
: cannot_ occur even in the worst case damp conditions and 
: then with at least a 50% safety factor. (The table does not go 
: as high as 3.3kV.) 
I was trying to stay very conservative with my estimation of the 
distance from the cap bank "tops" to the bare metal chassis. 
They honestly looked very close and IMO, the 10mm value 
might not be too far off.  It was something that "jumped right 
out" at my first cover-off inspection. 
I've had doubts about trusting the capacitor shrink skins to 
provide the insulator function when close mounted/spaced. 
The 7kv power supply capacitor bank (in the 386 computer 
case) I described a short time back on amps failed in it's first 
Erbtec life because of said shrink skin fail and follow up 
flash over/arc... well within the rated cap values.  It was just 
mounted close spaced to the chassis.   Chassis spacers 
made of poly plastic place the repaired cap bank 2 inches 
above the chassis in the 386 power supply and it's been 
"cooking along" at  7kv ever since.  The original Erbtec 
supply voltage was only about 6kv. I'm using the Erbtec 
surplus cap bank board with a different xmfr. 
Should an Emtron Amplifier ever appear in my shack, some 
sort of HV insulator sheet glued/placed/mounted onto the 
chassis (near the cap bank "top") would be completed before 
the power cord was unwrapped.   
skipp   wv6f 
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