I forgot to mention that the 811A and 572B quit being zero bias above 1250V
for the 811A and around 1500V for the 572B. In the SB-200 the operating grid
voltage is around -3V, when that bias is removed the tubes have a tendency
to take off rather dramatically.
If you use a zener for bias then you must provide some means of supplying
full cutoff voltage when in standby.
Carl
KM1H
----- Original Message -----
From: "John Lyles" <jtml@losalamos.com>
To: <amps@contesting.com>
Sent: Sunday, February 24, 2008 8:08 PM
Subject: [Amps] Warrior power amplifier
> In addition to Carl, KM1H's, suggestions:
>
> You shouldn't need step start with this, unless the power transformer
> became much stiffer, heavier. The choke will resist a major current surge.
> Also, if you do get rid of the choke and only have C, it will need to be a
> lot more Capacitance, and will probably need step start to protect the
> diodes during chargeup.
>
> I wouldn't recommend mucking with the parasitic suppressors unless they
> failed. 811 and 572B aren't as hot in the VHF gain department as some
> other glass triodes.
>
> The zener bias is a good idea. As for grounding the grids, short
> connections to chassis are usually a good thing, unless Heath did
> something wierd. If the thing has neutralization, you may have to re-set
> that as it would probably change with different inductance from grid to
> ground.
>
> Someday I am going to get my Heathkit Chippewa KL1 working, I finally got
> the original KS1 power supply for it. The amp was hacked up by someone and
> I just need to trace the wiring and understand the mods (fixed screen
> power supply instead of string of VR tubes and dropping R). Now that was a
> stout Heathkit power amplifier!
>
> 73
> John
> K5PRO
>
>> ----- Original Message -----
>> From: "Allen Jones" <w9dz@yahoo.com>
>> To: <amps@contesting.com>
>> Sent: Saturday, February 23, 2008 9:47 PM
>> Subject: [Amps] Heathkit HA-10 Warrior
>>
>>
>> >I am in the process of refurbing a Heathkit HA-10
>> > Warrior amp. I have looked at some of the old threads
>> > dealing with this amp and have a couple of questions.
>> >
>> > The 866's will go in favor of plug-in solid state
>> > replacements. Am I going to end up with a lot of
>> > extra B plus? The power supply is choke input to a 8
>> > Mfd capacitor. Would a step-start circuit be of any
>> > value or will the choke be enough to limit the surge?
>> >
>> > Are the original parasitic chokes sufficient or should
>> > I replace them with something different?
>> >
>> > This amp has had two plate transformers fail for the
>> > previous owner. He used the amp on RTTY. I got a new
>> > transformer from Heyboer and asked them to build it
>> > for CCS. The vast majority of my operation will be
>> > SSB. I plan to scrap the fixed bias supply and go with
>> > a zener in the center tap of the filament xfmr in
>> > series with a high value resistor which will be
>> > shorted with a relay in transmit. I will ground the
>> > grids of the 811's directly to the chassis with heavy
>> > braid or copper strap.
>> >
>> > Any other suggestions?
>
>
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>
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