[Amps] What Do you think?

[Clark Turner]

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 at outlook.com>
> To: Amps group <amps at 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
>
>
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