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[AMPS] Tuned input

To: <amps@contesting.com>
Subject: [AMPS] Tuned input
From: measures@vc.net (Rich Measures)
Date: Mon, 9 Nov 1998 07:55:51 -0800
>
>'just did this and feel obligated to address the "safest" part too;
>1.) Know that the voltages in the SB220 will kill you given the opportunity.
>2.) After you "remote" the front panel and before you plug your amp in put
>electrical tape over the exposed high voltage areas, esp. in the feed through
>area.
>3.) Use only non conducting tuning tools.
>
Good advice, however, whereas the 3kV anode supply will knock an oaf 
across the room, the electric-mains potential (which is available under 
the chassis if the amp. is plugged in and switched Off) can prevent such 
a person from letting go, as in Fatal.   .  //  It should also be 
mentioned that the interlock spring must be bent down or removed prior to 
doing an input SWR adj..  Also, to avoid possible damage to the 0.82 ohm 
resistor and grid current meter, one should wait at least 5 minutes to 
bleed down the hv caps before removing the perforated cover.   Once the 
interlock spring is removed, this is no longer necessary.  
>
>Rich Measures wrote:
>
>> >
>> >I need to tune the input circuit on my SB 220.
>> >I have seen something about this in the past on the reflector.
>> >Please give me some idea's about the easiest/safest way of doing this.
>> >Thanks Will
>> >
>> Remove the front panel;  lengthen the metering leads ;  add a ground wire
>> between the panel and the chassis.  The Q of the stock tuned inputs is
>> too low for good swr with solid-state radios and should be increased to
>> approx. 2.  In other words, C-in and C-out needs to be increased, plus L
>> needs to be decreased on each band.  [See "Circuit Improvements for the
>> Heath SB-220 Amp[lifier" November/December, 1990 QST].
>>
>> Rich. Measures.  Web site:  www.vcnet.com/measures



Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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