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Re: [Amps] SB-220 diode failure

To: Gary Smith <wa6fgi@sbcglobal.net>
Subject: Re: [Amps] SB-220 diode failure
From: R.Measures <r@somis.org>
Date: Tue, 9 Aug 2005 13:57:31 -0700
List-post: <mailto:amps@contesting.com>
On Aug 9, 2005, at 1:27 PM, Gary Smith wrote:

> My .02 on this:
> I would update the 220 with the Harbach rectifier mod.  Have heard
> nothing but praise for his mods to the point he is sometimes 
> overwhelmed
> with orders for them.  To me, that speaks well enough.

The only problem that I have heard about is that his suppressors don't 
get hot enough at 28MHz to a decent job of suppressing VHF.  Adding 
more L to L-supp would fix this.

> 73
> Gary...wa6fgi
>
>
> John Adkins wrote:
>> My sb220 cooked one of the diodes on the pc board a couple of days 
>> ago.  I replaced the faulty one
>> with a 1kv piv 2.5 amp substitute that was in my junk box.  
>> Resoldered the wires back to the pc
>> board, reassembled it, and fired it up.  When I went to tune the amp 
>> up, with no exciter power, I
>> get a plate current of 200 ma instead of the 120 ma the manual 
>> indicates should be seen.
>>
>> HV is 2.2 kv on low power, 2.8 kv on ssb.
>>
>> The manual suggests that the zener may be blown.
>>
>> What do you think?  Should I just get the Harbach rectifier/metering 
>> board substitute for the
>> original pc board and eliminate the zener altogether?  Other 
>> suggestions for troubleshooting this?
>>
>> Thanks
>>
>> John
>> w4kv
>>
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>
>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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