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[AMPS] Purpose of components on SB-1000

To: <amps@contesting.com>
Subject: [AMPS] Purpose of components on SB-1000
From: measures@vc.net (Rich Measures)
Date: Wed, 9 Jun 1999 23:08:49 -0700

>
>Gents,

?  [guffaw]

>The Heathkit SB-1000 amp has a very small (tiny) coil in series with the B-
>and also has a 1N5408 in parallel with the B- right after the tiny coil with
>the anode side to ground. Component designations are L401 and D401 on the HV
>PS board. What are they for?
>
?  D401 appears to limit the hv neg. potential to gnd during a glitch, 
hopefully protecting the grid-current meter from damage.  .  Because 
there should be no RF in this part of the circuit, I can see no purpose 
for L401 being there.  .  Since no peak current-limiting glitch resistor 
is used in the hv pos. circuit, I would be concerned that L401 might open 
during a glitch.  If I owned a SB-1000, I would add a glitch resistor, 
short out L401, and add a 25-ohm cathode NFB R, just for starters.  //  
It seems a bit curious that a separate meter is devoted to grid-current 
since the amount of grid-current plays no part in tuneup.  A filament 
voltmeter (and rheostat adj.) would have been way more useful than a 
grid-current meter.   //  Have you measured the filament-voltage in 
yours, Lane?



Rich...

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


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