[AMPS] Heath SB-230

[w8jitom@postoffice.worldnet.att.net]

> So now I see a lot of big bang warnings about the SB-230 posted. Since I
> have a virgin factory built unit that I've been using only on 40 meters
> with no problems, I'd like to know what the story is with the amps'
> problems. I'll have a look at some of the web pages to see any additional
> info also.

I looked at the SB-230 for Heathkit, as a contract engineer. 

The problems the 230 has is:

1.) It has no grid protection circuit, making it possible to easily 
overdrive and damage the grid.

Add a FAST electronic  grid overload protection circuit.

2.) It has too low an ESR in the supply line, allowing momentary 
internal arcs to damage the tube.

Add a twenty five ohm 25 watt energy absorbing resistor in the B 
plus lead. 

3.) It has insufficient heatsinking to prevent over temp operation. 
The thermal overload switch trips after the tube is too hot because 
of the thermal resistance and thermal lag in the switch.

Add a fan

> I'd hate to dial this thing up on another band and  watch it go up in
> smoke... Other than a very noisy T/R relay, it's been a really nice unit.

And easy to convert to 160.
 
73, Tom W8JI

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