Modify SB-200 for 6 meter

[KA5LQJ]

Hi All from the =Flyin' S's Ranch!

Well, if things go right, I'll have my 2 gigs of PC-2700, non EEC RAM soon. That means
I'll be changing to Debian 6 (Squeeze) to work with my Icom 706 MarkII-G transceiver
for digital work and my SB-220 for HF ssb. I heard there is something, an interface, that
goes between the rig and amplifier to help with the keying circuit.

Now, someone is bound to have this set-up and going so I'll need th know the particulairs.
Where do I get on, or can I build it myself?

Thanks for looking,
Regards,

Don/KA5LQJ

[KA5LQJ]

I agree, much easier. The SB-1000 is very similar to an Ameritron AL-80 series amp. The 3-500Z will run 800W PEP output on six meters. I've modified two AL-80Bs for 50 MHz and they both worked perfectly.

Hey Steve?

I'll look you up when I get mine, LOL!
GOD BLESS,
73,

Don/KA5LQJ

[WB2WIK]

Hey Steve?

I'll look you up when I get mine, LOL!
GOD BLESS,
73,

Don/KA5LQJ

I'd be happy to send you very detailed instructions; I wrote them up years ago and have them saved in a Word file. They work perfectly.

[WA6MHZ]

I have been searching for a SB-1000 but they are scarce as Hen's teeth! and AL-80s go for nearly $1000 bucks!
Meanwhile, I scored this SB-200 for $125!

[KM1H]

There is no reason to use a vacuum variable at that voltage or power level; Ive converted literally hundreds of single and dual 3-500 amps over the past 40+ years and Steve is well aware of this.

What works well is an air variable of similar construction that can be modified for a low minimum C by removing plates. The caps in the SB-1000 are made in the US by Oren Elliot Products and are copies of the EF Johnson and Cardwells going back to the 50's. The Johnson/Cardwell 154-11 works well without changes. The OEP's come apart and if you remove many plates you need more spacers to compensate.

Something similar from Europe can be used if you mount so it aligns with the tuning vernier on the front panel and has good grounding of the cap frame to the chassis.

Carl

[W1QJ]

There is no reason to use a vacuum variable at that voltage or power level; Ive converted literally hundreds of single and dual 3-500 amps over the past 40+ years and Steve is well aware of this.

What works well is an air variable of similar construction that can be modified for a low minimum C by removing plates. The caps in the SB-1000 are made in the US by Oren Elliot Products and are copies of the EF Johnson and Cardwells going back to the 50's. The Johnson/Cardwell 154-11 works well without changes. The OEP's come apart and if you remove many plates you need more spacers to compensate.

Something similar from Europe can be used if you mount so it aligns with the tuning vernier on the front panel and has good grounding of the cap frame to the chassis.

Carl

On the other end of the spectrum, I have been experimenting with a conversion of an SB-200 to a mono band 160 meter amp. I've been working on this project for about 4 months to perfect it. I am a firm believer that any amplfier converted to a mono bander should and will do quite a bit more power than the same amplfier on the same band as it does as a multi band amp. This has been proven with conversions of SB-220's and SB-200's to 6 meter mono banders. It's not at all unusal to obtain 70% efficeincy if all precautions are taken and all parameters are considered in the operating environment. Getting everything perfect takes time. mathmatical calculations of input ciruits and tank circuits are fine to get you in the ball park. Those values are affected by the surrounding enviroment and stray capacitance and inductance. A proper input circuit is just as important as a tank circuit to pull everthing into the realm of 70% efficiency. My initial whack at this yielded about 55% which in an SB-200 is about 575 watts. I knew it had to do more. Over the last 4 months I was looking for the missing power I knew should be there. Lately I was a little more enthusted about completing this project or scrubbing it altogether. Just today I found the missing link and was absolutely overwhelmed with the finished product. When everything pulled together I got the 70% I was looking for. 100 watts drive, 650ma plate current, grid current 80% in the white area. Load voltage about 2000 volts. That is a mere 1300 watts DC input. Output power 920 watts. Eff % = 70% on the button. To check for dissipation I dropped a 920 watt key down carrier for about 15 seconds, the tubes showed no color at all. Not to say someone will operate in these parameters but you can see it will loaf at 800 watts PEP SSB and will run cool as a cucumber at about 700w CW for DXIng purposes on the top band. I'll be offering this conversion along with the others as part of my line up as I begin to stock up on the needed parts to make the conversion. I'll have WW2DX do a youtube demo on this amplifier as soon as I can get with him. Oh..... Vac variables are in no way needed for 6 meter conversons. That I know.

[KM1H]

Ive had a 160M SB-200 monobander here since the power restrictions were lifted (1979 maybe??) since all I had at the time was a 60's NCL-2000. It does use a vacuum variable for Tune and the efficiency is high, never measured it exactly but output was around 800W with 80W drive. Its hard to get more than that with most tubes as the 572 is already in compression which you can see when adding more drive....the output no longer follows in a linear progression.

This was with Cetron tubes, some Chinese are constructed differently and have higher outputs....for awhile.

Carl

[W1QJ]

Ive had a 160M SB-200 monobander here since the power restrictions were lifted (1979 maybe??) since all I had at the time was a 60's NCL-2000. It does use a vacuum variable for Tune and the efficiency is high, never measured it exactly but output was around 800W with 80W drive. Its hard to get more than that with most tubes as the 572 is already in compression which you can see when adding more drive....the output no longer follows in a linear progression.

This was with Cetron tubes, some Chinese are constructed differently and have higher outputs....for awhile.

Carl

What is grid current, plate current at your 800w output?

[KM1H]

Its been ages since I used it but grid current should never exceed mid scale for any version of a SB-200 and Ip around 600ma and Ep roughly 2000V key down iffn I remember.

Carl