[Amps] Bizarre SB-230 meter failure

[John Pelham]

I'm here to do my part to liven up this reflector.  Here's how my SB-230
meter saga worked out.  Recall that I took my Heathkit SB-230 out of 15-year
storage, and discovered that the powdered-iron permanent magnet in its meter
had disintegrated.  I checked with the usual sources of Heath parts and came
up empty.  I found a junker SB-230 (with an apparently good meter) at a
hamfest but was unable to bargain its owner down to what I considered a
reasonable price.

I eventually found that the company, Jewell Instruments, that made the
original meter for Heath is still in business and they can still supply the
very same meter.  So I bought one and installed it.  (I had to swap meter
faces as the original custom one for the SB-230 is no longer available.)
The amp is now installed in my station and working fine.  The only problem,
which I had to overcome, was the price of the new meter: $100.

73 es DX, W1JA

http://www.radiophile.com

----- Original Message ----- 
From: "John Pelham" <john at radiophile.com>
To: <amps at contesting.com>
Sent: Tuesday, August 29, 2006 6:37 PM
Subject: Re: [Amps] Bizarre SB-230 meter failure


> Thanks Martin, Tom, Ken and Clive (off reflector) for your responses.
>
> Clive said "what you have is what is left of a sintered neobium magnet
> that has simply disintegrated over time.  They simply had a limited life
> in their infancy and now following a lot more research and design and
> attention to the manufacture of the materials, their life is virtually
> unlimited."
>
<snip>
>
>>> John Pelham wrote:
>>> I have a Heathkit SB-230 amp (it's the fanless one that uses an
>>> 8873).
>>> It has been in storage for 15 years (inside the house living space,
>>> heated and air conditioned).  I just got it out, and found that the
>>> meter pointer was stuck at zero.  I disassembled the meter and found
>>> something very strange.  The moving coil is there, and in the center
>>> is
>>> what I assume is (was) a permanent magnet of some type.  This magnet
>>> has, while in storage, decided to partially or completely
>>> disintegrate
>>> into tiny shards of magnetic material.  It has grown outward to
>>> partially surround the coil and, I assume, the pivot, which may be
>>> why
>>> the coil and pointer won't move.