It might have 7KV on the plate. I have seen amps where the builder used
HALF scale on the HV meter as he did not have a meter scaled properly OR
did not want the FCC to know. My last amp was that way. I thought I was
running 6V when it was really 12KV. I spent a month trying to get the RF
deck not to arc in various areas before measuring the HV. Anytime I
would get over an indicated 5KV, (10KV in reality) it would start to let
out random arcs. LOL
Buy an HV probe for your DVM and use it. That is the only way to really
know.
C
On 9/11/2016 6:38 AM, Jim Thomson wrote:
Date: Thu, 8 Sep 2016 21:44:18 +0000
From: Bill Turner <dezrat@outlook.com>
To: Amps group <amps@contesting.com>
Subject: Re: [Amps] What Do you think?
Something is wrong with the numbers. 3500 V at 500 mA is 1750 watts DC
input. If you were measuring 1500 watts RF output, that would be an
efficiency of about 86%, which is impossible with a class AB linear
and highly unlikely even if operated class C.
I would recheck the meter calibration before buying.
73, Bill W6WRT
## I agree, something is amiss...and it might be the B+ meter...and /or the
plate current meter. You could temp place a fluke DVM in series
with the existing analog 0-1 A meter to get an accurate p;ate current reading.
## Most of those 0-1 A dc ammeters are fairly accurate. The B+ meter
could easily be out to lunch... typ caused by using carbon comp resistors
in the series string for the B+ multiplier..for the B+ meter. They will typ
drift
30% on the high side. That means your B+ meter will be reading way down
on the low side of the actual B+ voltage.
## The other concern is the tubes, and availability. Half decent 4-1000s are
rare.
3-1000 Zs are very rare. If 4-1000s used, typ no load B+ is 4800-5500 vdc.
They require a lot more drive than a 3-1000Z. 3-1000Z sucks a lot more idle
current,
and requires more bias vdc.
## If it has 2 half decent tubes in it, plus some spares, you are probably
ok. Any Single
3-1000 Z or 4-1000 will do an easy 1800-2000 w pep out. Any 2 x holer, with
200 w
of drive should be aprx 4-5 kw out... provided the xfmr is big enough.
## the B+ meter would be easy to fix, if outa whack, just use the correct
resistors for the string.
Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|