On Sun, 13 Sep 1998 14:01:30 -0700 zeitler@ibm.net writes:
>
>
>-----Original Message-----
>From: km1h@juno.com <km1h@juno.com>
>To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
>Date: Sunday, September 13, 1998 12:04 PM
>Subject: Re: [AMPS] Augmenting SB-220 power supply
>
>
>>
>>
>>On Sun, 13 Sep 1998 12:18:10 -0500 "Bob Hutchinson" <bhut@nol.net>
>>writes:
>>>
>>>This is a multi-part message in MIME format.
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>>>
>>>I notice that Peter Dahl has for sale replacement outboard
>>>transformers for
>>>the SB-220 that produce twice the normal 1A. current. The prices
>are
>>>not
>>>exactly Coke money. I have a couple of SB-220s and am about to come
>>>into
>>>more parts, including transformers.
>>
>>
>>I need an original xfmr in case you want to sell one.
>>
>>
>>>
>>>Is it feasible to improve of the current capability of the SB-220
>>>power
>>>supply by connecting two of the standard SB-220 transformers in
>>>parallel?
>>
>>
>>The stock xfmr will run fine in non-contest or RTTY modes. Increasing
>the
>>I rating gave them a bit better survivability in contests but the
>SB-220
>>is pretty much passe for that use today...at least DX contests unless
>it
>>has 160M added.
>>
>>Outboard xfmrs with higher voltage just increased the possibility of
>>bandswitch failure.
>>
>>The CBers buy a lot of the big Dahl xfmrs for that amp and even
>change or
>>add tubes.
>>
>>
>>>Perhaps with an outboard transformer augmenting the inside
>>>transformer.
>>>Would this technique provide a more robust power supply input
>>>capability?
>>>What would the ramifications to the rectifier, filter and other
>>>components
>>>be?
>>
>>The stock rectifiers should be changed to 1N5408's in any case....or
>just
>>buy a new updated PS board from Harbach Electronics.
>
>...an option is to bypass the middle man and get them directly from
>the
>source--Digikey. They have the caps, diodes, MOF resistors, etc..
Good point for the person not afraid to do some work. The only caveat is
that the filter caps are not matched to 1.5% as is Harbach so it may be
pure luck if you can use the 100K resistors.
Harbach will sell just the caps BTW and his prices competitive with
unmatched Mouser which I find to be a lot better priced than DigiKey.
73 Carl KM1H
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