Hi Skipp
Interesting comments. I saw the amps and agree they look pretty nice.
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.)
The standard also states 4.5mm through solid insulation for 3.3kV, but again
that assumes poor quality insulation (wood?!) and worst case conditions.
That is considerably more than the insulation on any electrolytic capacitor
I have ever seen, and in fact many seem to be marked as 'un-insulated' even
when they have heat shrink.
Not sure any of that proves anything, but FWIW.
73 Roger
VE3ZI
>From: nospam4me@juno.com
>To: amps@contesting.com
>Subject: [AMPS] re: Dayton and Emtron
To: <amps@contesting.com>
>Date: Wed, 23 May 2001 22:42:26 -0700
>
>
>[snip]
>: From: "vk4sx" <vk4sx@dingoblue.net.au>
>: any comments from the Dayton visitors in rgds the
>: new range of EMTRON amps? rgds Dennis
>-
>-
>Hi Dennis and the group,
>-
>I actually took a camera full of pictures of the different amplifier
>mfgr's products and display booths. I used the "analog method"
>so it will be a few days before the pics are available for amps
>member viewing.
>-
>Emtron was one of the mfgrs I spent a bit of time looking
>at. Significant items of interest were the models with the
>4CX1600 tube which the rep mentioned would be phased
>out as the tube is getting rather hard to obtain in long term
>stable amounts. Not the first or only person I've heard
>that from...
>-
>They also had other nice looking amplifier models with the ever
>present Eimac 3cx800a7 tube(s) on board. The current "major
>valve" of choice seems to be the Eimac 3cx800a7, used by most
>mfgrs as the most popular amplifier work horse tube. The
>3-500z is no longer in the "sweet spot" although Ten Tec and
>Ameritron had glass valve circuits on Display.
>-
>It might be more practical to just mention some of the things that
>I noticed right away about the Emtron.
>-
>Some of the power supplies of the models I could inspect
>(covers off) had series banks of 85c filter caps. But potential
>trouble might not be too far off.
>The radial lead capacitors are mounted horizontal and the
>"top" of the individual capacitors are very near the side bare
>chassis. I mean real close with no insulation other than the
>actual cap factory shrink skin.
>The cap to chassis distance appeared less than 1/2 inch...
>and at 3kv plus potentials, that would worry me a great deal.
>There was no obvious side mounted insulator between the
>capacitor bank (cap tops) and the bare chassis.
>-
>The capacitors were also mounted right next to each other.
>Cap cooling is something less than desired. In my opinion,
>an issue that should be looked at. Although I wasn't able
>to check the values, the capacitor bank looked "rather light
>duty" for the power supply level so these close spaced caps
>will get at least very warm with significant ripple current.
>-
>The plate blocking caps appeared to be low current "disc
>style" units. In my recent (less than a year ago) tests I've
>found these units don't handle high power (current) as well
>is I had hoped and quickly get hot and fail/change value
>in key down (continuos) conditions.
>For SSB and other low duty cycle operation, they
>will probably "hold up."
>-
>Most all the amplifier models I saw had healthy pi-tank
>circuits, caps and coils although everyone pretty much
>is still using air variables.
>-
>The rep spent a lot of time talking about the hefty power
>transformers. The physical layout was traditional and
>the cosmetics pretty good. Your results may vary...
>-
>cheers
>skipp
>-
>
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