[Amps] my little amp project of many hours..maybe 50% done

HAROLD B MANDEL ka1xo at juno.com
Fri Jan 6 09:36:06 EST 2006


Dear Chuck,

If you remember, a year ago one of my 100K-ohm, 50 watt bleeder
resistors failed, went to 29 ohms, somehow and the next 100K-ohm
50 watter opened up, and I ended up lifted right off the carpet and
across the room on my butt when only 750 volts out of the 4.4KV
supply touched my elbow.

My suggestion is to use a couple of 200 watt Ohmite 100K-ohm
resistors in series.

Hal Mandel
W4HBM
On Fri, 6 Jan 2006 09:20:13 -0500 "Partain, Chuck"
<Chuck_Partain at maxtor.com> writes:
> 
> looking back, I seem to remember 4kv being the good fit on this 
> tube.
> Looking now that folks have more info, perhaps its a bit too high. 
> Looking
> thru sites that list specs on it, I see 2.2-4.25kv listed as a 
> suitable
> plate voltage.
> 
> With my PS sitting at 3900v no load(250k bleeder) what can I expect 
> to see
> loaded? i'm sure I'll see drop. also I'm a bit concerned now with 
> some internal arcing
> if it way too high?
> Not as concerned with whats going on inside the case, i'm 
> designing/thinking of
> heavier components on that side(tank/blocking/plate choke) anyway
> 
> Any more thoughts?
> 
> thanks.
> 
> 
> 
> 
> >>Hi Chuck,
> 
> >>I think your anode voltage will be a bit high.
> >>The GU84B is a medium voltage, high current tube
> >>and normally sees 2,2KV.
> >>With the high impedance at 4KV you will run into
> >>trouble on 10m as the bandswitch is a bit far away
> >>and the minimum capacity of that tuning capacitor
> >>will be not low enough for reasonable Q on that band.
> >>If the ht-transformer has a center-tap I would go for
> >>half the anode voltage
> 
> >>73
> >>Peter
> 
> 
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> 


Harold Mandel
Superintendent of Construction
Baran Telecom Inc.
606 - 205 - 0172
hmandel at barantelecom.com


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