[Heathkit] SB-200

[Kenneth G. Gordon]

On 30 Apr 2007 at 13:56, jeremy-ca wrote:

> > QST, Jan. 1969, page 44 has a mod for converting SB-200 to 6 meters.
> 
> Try it, it doesnt work; I get several in here to undo the mess and do
> it correctly. Often times the tubes have been destroyed from
> oscillation. Ive yet to see a decent "conversion" article in any ham
> rag.

"Mods" which actually IMPROVE most rigs are definitely in the minority!

> > Power Supply upgrade, soft-key mod, in-rush current upgrade approx
> > cost is between $100-150 from Harbach Electronics.
> 
> PS: If it aint broke dont fix it. Besides when the time comes you can
> get the parts from Mouser a lot cheaper.

Yup. Or off Ebay as I have done. 470 uf 450 VDC 105degree C caps 
cost me about $1.00 each and they were NIB. I would buy Rich 
Measures resistors though, which you can also buy from Mouser.

> In Rush: Totally unecessary and just adds another potential failure
> point.

Yup. The FILAMENT transformer in the two Heathkit amps, SB-200 and 
SB-220, already have inrush current limiting for the filament built into 
them, as far as I know.

> Soft Key:  Only if the TX/XCVR driving it cant switch -125VDC

A $5 relay from Radio Shack,  a 9 V battery, and a small piece of perf 
board (if you really think you need it) will do the job.

> I've converted over 300 SB200's to 6M over the past almost 40 years.
> With over 10,000 built its not exactly a collector item. Try and find
> a 700W 6M amp for that kind of money.

Good point. Building one from scratch as I mentioned would probably 
cost a lot more money, and would certainly take a lot more time.

Carl, I am curious though: when you convert an SB-200 for 6 meters, do 
you remove all the lower HF band stuff too? It seems to me that 
converting the 10 meter band switch position to cover 6 meters would 
be a lot less intrusive.

Can you fill us in a little?

Ken Gordon W7EKB