[Boatanchors] B&W 5100 xmtr

Mon, 04 Aug 2003 08:14:59 -0500

>From: Al Klase <[email protected]>
>To: David Wilke <[email protected]>
>CC: [email protected]
>Subject: Re: [Boatanchors] B&W 5100 xmtr
>Date: Sun, 03 Aug 2003 22:30:16 -0400
>
>David Wilke wrote:
>>Does anyone know the resting bias (both PA and Modulator)current in mils 
>>recommended for the B&W 5100 xmtr?I cannot find this info in the manual.   
>>[email protected]
>>
>
>The PA is class C, so resting bias really isn't an issue. You want to see 
>17 mils of grid drive and load the plate to a max of 220 mills, per the 
>manual.  I think that's all we need to know.

Is there a possibility, that the fixed bias could be excessive, biased so 
far beyond cut-off that the normal level of excitation from the previous 
stage is insufficient to drive the PA into conduction on the positive peaks 
of the excitation?  If so, then you may need to know what is the proper bias 
on the PA (Assuming there is a fixed bias for all I know the transmitter may 
use grid-block keying and is biased unkeyed way way beyond cut-off, but when 
key down, there too may be a fixed bias applied and it should be at the 
recommend level.

Jim, wd4air

>The modulator is another story.  Mine shows 100 mils resting, but the tube 
>data sheets I look at indicate it should be something like 32 mils. (Class 
>AB2 with 600 volts on the plates.) It's a shame B&W doesn't state the tube 
>element voltages. Have you located R44, the pot in the grid circuit?  I 
>haven't.  I'm inclined to crank the bias up and watch for distortion of a 
>test tone into a dummy load, but need to find the adjustment.  Set's been 
>working great, and haven't had it out of the cabinet.
>
>Al
>--
>Al Klase - N3FRQ
>[email protected]
>Flemington, NJ 08822
>Web Page:  http://www.webex.net/~skywaves/home.htm
>
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