The whole world seems to buy matched pairs or quads.
There doesn't seem to be a need for this when buying ceramic triodes, although
some users at VHF and UHF still try to buy matched pairs.
I see that Richard Measures advocates the use of grid fuses to protect the
glass triodes, but I found that his theory does not work in practice for me. A
good control board will work, a resister of low wattage doesn't do the job.
73,
Mike
W2AJI
Sent from my iPhone
> On Aug 13, 2014, at 11:03 AM, "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de> wrote:
>
> That may be a little too optimistic, Mike.
> Purchasing matched pairs does not assure they are going to draw equal
> current throughout their life, but it does improve the chances.
>
> I have a hunch if you would pull several matched pairs after a couple
> hundred hours and check them again, some may not be matched anymore.
>
> On the other hand, there doesn't seem to be any other choice. Seems being
> able to monitor and adjust the bias individually just requires too much
> extra hardware.
>
> We don't really have that problem here in DL because we're only allowed
> 750w.
> The single 3-500z handles that just fine.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike
> Schatzberg
> Sent: Wednesday, August 13, 2014 3:01 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Hercules 444 amp
>
> The matching of the tubes when purchased assures they will draw
> approximately the same grid current in the amp.
>
> Proper biasing will help assure the cleanest signal for the selected class
> of service. The 3-500 is a zero bias triode, but needs to be properly biased
> for good linearity for the desired class of service. Greater bias voltage
> will increase the needed drive to reach full output.
>
> 73,
>
> Mike W2AJI
>
> Sent from my iPhone
>
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