[TenTec] Hercules 444 amp

[Mike Schatzberg]

There are control boards available to trip out at adjustable levels of grid current. If you want to monitor each tube individually, you could switch which triode you are monitoring, or install a second board. 

I rely on the control board to do the work as I can't watch all the meters all the time. 

73,

Mike
W2AJI 

Sent from my iPhone

> On Aug 12, 2014, at 7:56 PM, "Bob McGraw - K4TAX" <RMcGraw at Blomand.net> wrote:
> 
> The issue I've observed with amps using 2 tubes in parallel, there is typically no way to determine what each tube is doing.  One needs to be able to determine, at least,  the individual grid currents.  In doing so, one can see that the tubes are operating within their design range.  The same applies for 3 tube and 4 tube amps.
> 
> As I pointed out earlier, if the recommended total grid current is 260 ma maximum, thus individually 130 ma per tube.   If one tube be drawing 60 ma then the other tube is drawing 200 ma., which is well above its maximum rating.  Premature failure of this tube can be expected due to excessive grid dissipation.
> 
> I did modify a SB-200 by adding a toggle switch allowing the grid current for each tube to be displayed.  This took some circuit changes but being an amp that was converted for 6 meters, this pushes the limit of the 572B's and we prefer to keep them in their sockets.  Otherwise, the previous owner had experienced a good amount of FLASH, BANG, POP,  followed by oh crap the smoke comes out of the box.
> 
> 73
> Bob, K4TAX
> 
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> 
> ----- Original Message ----- From: "Carter" <k8vt at ameritech.net>
> To: <tentec at contesting.com>
> Sent: Sunday, August 10, 2014 8:32 PM
> Subject: Re: [TenTec] Hercules 444 amp
> 
> 
>>> On 8/10/2014 2:08 PM, Duane Calvin wrote:
>>> This was certainly true of the  EIMAC tubes, as long as you cared well
>> > for them.  I've not had as good a luck with the current
>> > Chinese-sourced tubes (specifically, the 3-500ZG's from RF Parts,
>> > which the Centurion uses.)
>> 
>> My Centurion (which I obtained used 20 years ago) finally had one of its tubes [rather spectacularly] go to the great beyond.
>> 
>> Unless I get really lucky and find a NOS pair at the e-place, it seems like my only other option is a matched pair from RF Parts.
>> 
>> Could you please elaborate a bit on your statement above that says "I've not had as good a luck with the current
>> Chinese-sourced tubes (specifically, the 3-500ZG's from RF Parts)".
>> 
>> 73,
>> Carter K8VT
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> 
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