A quick Google search shows several opportunities to purchase a HP 428B. A
call or email might turn up the information you need. The first URL lists
both HP 428A and HP 428B service manuals.
http://www.w7fg.com/search.php?find=HP%20428
http://www.used-line.com/cgi-bin/a_search/b_searchresult.cfm?criteria_1=428B&time_frame=1&type=inv&p_n=1
http://cgi.ebay.com/HP-428B-CLIP-ON-MILLIAMMETER_W0QQitemZ7598283353QQcategoryZ4678QQcmdZViewItem
73 de Bob - K0RC
----- Original Message -----
From: "David C. Hallam" <dhallam@rapidsys.com>
To: "Amps" <amps@contesting.com>
Sent: Wednesday, May 03, 2006 7:47 AM
Subject: [Amps] Help with HP 428B Clip On Ammeter
>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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