[Amps] SB220 step start blows fuses

[donroden at hiwaay.net]

The problem with this approach is that with two 60-100 watt bulbs *IN SERIES*,
there is too much resistance to "wake up" the amp.

It's difficult enough to try to "fix" an amp over the internet, and  
even more difficult to publish a broad-stroke technique that applies  
to every amp or the technical experience of the owner.

Some amps, like the SB220  require straight 240 ( no requirement for a  
common 120 return ), but others do. Some amps like the Collins 30S-1  
use switches to control the filament and HV relays.  The light bulb  
technique won't work well on these amps until you use a high enough  
wattage bulb to pull in the relays.  Study the schematics and  
accommodate  accordingly.

For a 2340vac amp, I would use a single 150 watt bulb in series and if  
it popped..... no big deal.
But I would know that there was a serious problem, and that I probably  
saved an unobtanium switch on the front panel.  But that's just me.   
You may have a better idea, and if that works for you ...great.   Do  
what is within your experience level and test equipment on hand and  
learn from your troubleshooting.



Don W4DNR





Quoting Jim Thomson <jim.thom at telus.net>:

> Date: Mon, 10 Jul 2017 12:41:52 -0500
> From: "Gary Schafer" <garyschafer at largeriver.net>
> To: "'Joe'" <nss at mwt.net>, <amps at contesting.com>
> Subject: Re: [Amps] SB220 step start blows fuses
>
> Well, yes you would need a bulb in each side of the 220 circuit or two bulbs
> in series (rather than parallel) on one side,
> assuming that the amp is not a 4 wire amp that also uses 120 volts.
>
> If something in the amp shorts you would have 220 volts across a single bulb
> and the bulb would burn out.
>
> 73
> Gary  K4FMX
>
> ##  agreed.  This is also why, if you install a separate fuse in  
> each leg of the 240 line,
> each fuse has to be rated for 240 vac.  IE:  if only one fuse blows  
> open, you will
> have 240 vac sitting across the same open fuse.
>
> ##  Step start should consist of one resistor, or 2 in parallel,  in  
> just one leg of the
> 240 line.   Ditto if the amp is wired for 120 vac, step star goes  
> into the hot leg of the
> 120 vac line.
>
> ##  The drake amps used a separate breaker in each leg of the 240  
> line.  They too have to
> each be rated for 240 vac.   Same deal, if only one breaker opened   
> off, you have 240 vac
> sitting across the open breaker.
>
> Jim  VE7RF
>
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