[Amps] AL-1200 Low High Voltage (HV)

[Will Matney]

John,

Check to see if an attenuator network has been added to the input or the 
tubes have been biased to cut them down. That sounds more like what
would be done to increase the drive.

Yea guys, I caught the 1000kw thing.

Best,

Will

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On 8/20/06 at 7:06 AM John wrote:

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>Greetings to the list,
>
>I could use some SME input on the above topic. First some history; I
>purchased the amp from someone who was driving it with up to 200watts
>input. I was told the amp was modified to allow for this so that it
>would not be over driven. That someone is long gone and I have no idea
>what modifications were done.
>
>Current: I measured input across both line fuses and its a healthy
>250vac. Measuring each input winding pair on the primary side of the
>transformer
>	Pair 1 Terminal 1 (Yellow [Black/Wht lead]) and Terminal 3(Clear [Black
>Lead]) is 124.6vac
>	Pair 2 Terminal 4 (Red [Brown/Wht lead] and F1 [Brown lead]I get 124.7vac.
>
>With the above configuration I show 3000v on HV
>
>
>All wiring on Relays 2 & 3 are in accordance to the Tech Manual
>
>I also reconfigured using the Green lead:
>	Pair 1 Terminal 1 (Yellow [Black/Wht lead]) and Terminal 3(Clear [Black
>Lead]) is 136vac
>	Pair 2 Terminal 4 (Red [Green lead] and F1 [Brown lead]I get 113.2vac.
>
>With the this configuration I show 3300v on HV.
>
>I have replaced all the filter caps (with 470uF 450V 105 degree Nippon
>Chemi-con) and checked all the bleeder resistors (all about 49k ohms).
>The rectifier board looks clean and no visual damage. Driving the amp
>with 100watts I get a clean 1000kw output (using the 3300v
>configuration) in which I validated the front panel meter with an
>external VSWR meter. Sideband peaks around 1100~1200kw out.
>
>The amp loads up and runs great. I have had good sig reports as is.
>
>So the question now is what else can affect the HV? Something around the
>plate end of the tube? or RF Choke?
>
>Thank you in advance, JohnF
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