[Heathkit] SB-200

[Kenneth G. Gordon]

On 1 May 2007 at 14:11, jeremy-ca wrote:

> > 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've never bought caps off Ebay, just dont feel secure with unknowns.

So far (so far) I have had good luck with what I have bought there. 
But I am pretty careful. Not being rich makes me very careful. :-)

> I
> use the CDE 381LX Series 105* C 330/450V Made In The USA; everything
> lines up like the originals so it looks neat.  I use the same caps in
> the SB220.

Sounds superior to what I do. I have rebuilt several HP-23(*) using 
those I bought off Ebay. I simply super-glue them to the original 
caps' mounting plates.

> Whats a Measures resistor?

I meant resistors that Rich Measures will sell from his website, 
www.somis.org. Here is a quote from there: "High-reliability, high-
stability MOF resistors for electrolytic filter capacitor equalizer 
R service. Matsushita, 100k-ohm, 3w, 500V max. matched within 
0.05%, part number 86, $0.48 each."

> I replace the 30K with 75K 5W MOX from
> Mouser. Cuts heat way down and with the tolerance quality of the caps
> the balance is excellent.

Measures does the same thing, for the same reasons, but uses 
100K resistors.

> Absolutely true. Its an unknown to some and others may just be too
> stubborn to admit it. Besides, the resistors in the Harbach kit are
> low quality junk that often blow apart under the surge. Some
> protection! In all my years with that amp Ive never heard of a surge
> related failure.

Thanks. It is nice to know that what I understood about the HK 
filament transformers is true. I wasn't sure, but it made sense to 
me.

> I build my own right off the bias winding AC, a handful of components
> and a 5 lug terminal strip.

I wouldn't mind seeing a schematic...

> Completely stripping HF and building as a 6M monobander is the ONLY
> way to go. Trying to change 10M to 6M is barely possible but it is
> terribly inefficient (cuts tube life way down), parasitic and
> oscillation prone. Several other components are way out of
> requirements for 6M.

Of course: like bypass cap values and RF choke inductances. Yes. 
Makes sense.

> Its way too much of a compromise....even for
> cheap hams!

I understand. Again, what you say makes perfect sense to me now.

> Here is a link which goes into more detail on 6M conversions.
> http://www.uksmg.org/1kw.htm

Thanks. I'll immediately take a look at it.

BTW, in another group with which I am involved, one of our 
members recently rebuilt an SB-200 for 600 meters. 750 watts 
output and very stable. He renamed it SB-600M.

Quite a range: 600 meters on the low end and 6 meters on the 
high. How many other rigs are known that can be made to cover a 
range of 1:100? :-)

Ken Gordon W7EKB