[TenTec] Hercules 444 amp

[Mike Schatzberg]

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 at 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 at 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
>