[SixClub] SB-200 6 meter conversions

[Bill Dzurilla]

Nice looking amp, Roger.

Since everyone is talking about HF amp conversions, thought I'd mention a homebrew single 3-500Z 6 meter amp I recently bought.  It is powered by a transformer from an SB-200, with a Harbach board for the rest of the power supply.

It seems to work OK, but maximum output is only about 400 watts, and even this requires excessive drive and plate current.  Safe and clean output is probably 300-350 watts.  In contrast, I once owned a converted AL-80B, which also uses a single 3-500Z, but which put out 900 watts on 6.  The reason is that the AL-80B's power supply provides 3000v on the plate, while the SB-200's supply is close to 2000v under load.

The maximum plate voltage on a GI-7b is 2500v, so if using a power supply from an SB-200 or similar amp, you should get better results with a GI-7B than a 3-500Z.   

73, Bill NZ5N

> From: "Roger (K8RI)" <50mhz at rogerhalstead.com>
> Sent: Monday, May 24, 2010 8:19 PM
> To: <doc at kd4e.com>;
> "World Wide Six Meter Club" <sixclub at mailman.qth.net>
> Subject: Re: [SixClub] SB-200  6 meter conversions
> 
> > On 5/24/2010 10:02 PM, kd4e wrote:
> >> Nice piece of work!
> >>
> >> I have a GI-6b that I believe is identical to the
> GI-7b
> >> except not good up into the 2m and above range -
> fine on
> >> HF and 6M.  $35. including std USA shipping.
> >>
> >> doc
> >>
> >> KB0NLY wrote:
> >>
> >>> I had an amp on 6m running 572b's, while it
> would make
> >>> power it seemed to oscillate and tuning was
> very touchy.
> >>> After a while of fighting it and talking to
> many other
> >>> conversion owners I determined it was the best
> I was
> >>> going to get out of it.  The tubes just
> aren't worth a
> >>> darn at 6.  They glow red at 10m, pushing
> them higher in
> >>> frequency they would look hot enough to
> melt.  I tried a
> >>> new set of tubes, Taylor 572b's, and they did
> a little
> >>> better, some more mods and adjustments helped
> some of the
> >>> problems.  Eventually I got fed up with
> it and sold it.
> >>>
> >>> I then had the opportunity to operate a
> station that used
> >>> a SB-200 converted to a single GI7BT russian
> triode.
> >>> Tuning was nice, clean output, very stable and
> easy to
> >>> use.