[Amps] Help with HP 428B Clip On Ammeter

[Bob Sullivan]

David,

That would be V8, (head drive amp), which is a 12AU7 ("selected by HP").

73, Bob
WØYVA
Personal site: http://www.isquare.com/personal_pages/ras-hardware.htm


At 08:47 AM 5/3/2006, David C. Hallam wrote:
>I recently acquired a nonworking HP-428B.  The price was right, free.  I
>downloaded a 428B manual from BAMA but find that HP introduced modifications
>that are not covered in the earlier BAMA manual version.  Mine has a serial
>number prefix 0995A.  It has tubes and discrete transistors mounted on a
>printed circuit board, no point to point wiring.  One of the tubes is
>missing and there is no identification of the tubes on the PC board, no tube
>number or V-X reference to a BOM.  The socket is for a 9 pin miniature tube
>and is located immediately to the center left of the power transformer.
>It's not a rectifier as there is a SS diode FWB.
>
>Can some one identify the tube for me and/or suggest where I might be able
>to locate a manual that covers my version of the HP 428B?
>
>David
>KC2JD
>
>
>
>
>
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