A New 6 meter amplifier project..

[QUOTE=koØm;408896]I have built 2 GS-35b amps and, I have a third one that I have taken a sabbatical on building until things slow down around here. The first was a single tube / single band model. 4500 on the plate Ip was about 1.0 amps with 100 peak watts of drive produced upwards of 3000 watts on the Bird 43P. Second one was a 2 holer with 5000 on the plates that did over six easy. They worked great, but compared to your construction, I am humble, embarrased and not qualified to sweep the shaving from your shop floor.

I see that you are using the W4ZT bias type board, what the idle current one the tubes during zero-signal mode and, what the Ip and Ig under transmit?

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G'day Melvin, you are doing ok I would say...I idle my GS-35B around 150ma....Grid current loaded at 1kw is around 200ma and 1500 watts about 300ma...I don't put more than 3700 volts on the tubes as I sell these amplifiers to hams, experience unknown....I do find that individual tubes show different characteristics as far as grid current and general performance is concerned....Grid current really isn't an issue and I know many hams using these tubes don't bother putting in a grid meter..Overall I find the GS-35B a very rugged tube and you would have to do something really stupid to hurt one at ham power...The 8877 pales against these tubes with it's delicate grid structure and looking at the $ value most Russian tubes are excellent value...:cool2:

73...Bob..VK3ZL..




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Originally Posted by koØm

I have built 2 GS-35b amps and, I have a third one that I have taken a sabbatical on building until things slow down around here. The first was a single tube / single band model. 4500 on the plate Ip was about 1.0 amps with 100 peak watts of drive produced upwards of 3000 watts on the Bird 43P. Second one was a 2 holer with 5000 on the plates that did over six easy. They worked great, but compared to your construction, I am humble, embarrased and not qualified to sweep the shaving from your shop floor.

I see that you are using the W4ZT bias type board, what the idle current one the tubes during zero-signal mode and, what the Ip and Ig under transmit?

Attachment 5405

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Nothing wrong with that construction. I would say you are MORE than qualified to do Bob's floor. Hell, with all the $$ his making on his amps, he'll probably fly you to OZ on his nickel (or it's equivalent in Aussie currency) just to do it.

Both you guys do really nice work!
I've been toying with the idea of one of these myself. I've got a TenTec 425, uses a pair of 3CX800-A7's, and the tubes are getting pretty soft. I'm having a real hard time justifying the tube replacement cost on this one. Eimac tubes are about $1600/pair, and Chinese tubes are about $900/pair. On the used market, the entire amp is in the $1500 range with good tubes.

Anybody care to do some close collaboration on a conversion?

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Originally Posted by W5GA

Both you guys do really nice work!
I've been toying with the idea of one of these myself. I've got a TenTec 425, uses a pair of 3CX800-A7's, and the tubes are getting pretty soft. I'm having a real hard time justifying the tube replacement cost on this one. Eimac tubes are about $1600/pair, and Chinese tubes are about $900/pair. On the used market, the entire amp is in the $1500 range with good tubes.

Anybody care to do some close collaboration on a conversion?

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G'day Doug....If you are considering a conversion check out the UR4LL website for possible substitute tubes...From my experience, Russian tubes are generally tough, reliable and cheap...There are a couple of Russian triodes that you may be able to utilise...You would probably have to do a part re build of the RF deck and substitute the filament transformer...Some commercial linears lend themselves to conversion than others however...You would best Google around and look at work other hams have done...Start with the W4ZT site...There are also many Youtube videos to be found....

Good luck..Bob..VK3ZL..