SBE SB1-LA 6 sweep tube linear amplifier all dressed up on the bench
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- Опубликовано: 29 авг 2024
- Finished with the SBE SB1-LA Linear Amplifier and giving her a quick test drive before she goes up on the shelf. I like this amplifier a lot. It's compact, its clean physically and electronically, it's built like a boat anchor but its compact, and it runs a solid clean 500 watts out with no problems and hiccups. What's there not to like about it?
Well, it does have a few quirks. One is, originally, it was made to mate with the early SBE radios of its day, the SBE 33 and 34. Those SBE radios sent +10 volts out to key this amplifier. Fine, but modern equipment grounds the keying relay in an amp rather than sending voltage to it. Hence, I did some slight relay rewiring in this and added an RCA jack out for keying the relay. Now a normal foot switch or a radio that grounds the keying circuit can be used. CB amps usually have a built in keying circuit that sniffs the watts coming in and then keys the amp. However, this was built in 1962-63 before CB which moved to 27mhz in 58 hadn't taken off yet. This amp also has only the 15-80 meter Ham Bands in it. No 10 meters. However an amp that will work on 15 meter will also work on 10 meters too. This one included. However, on 10, the output wasn't quite optimal, so the output tank coil was spread a little and is now broad enough to work on 10 and 15 meters with good results and the same with the other higher bands too. It doesn't have a tuned input, only a bunch of swamping resistors on the input grid, so no tuning on the input side.
The 2nd Power switch is basically a HV ON and relay standby switch. However, why this Power switch has Low for off and High for on I don't know. Even in the factory manual it explains that the switch puts the amp and HV in standby and hence has nothing to do with High and Low at all. Amp uses an RCA jack on the Input coming in instead of the normal S0-239. I left this stock and just got an RCA to S0239 adapter for the input.
Amp uses a 9 pin Octal type connector for the ac coming in and originally had a 2nd set of wires that would go to an SBE transceiver that would be the +10 line already mentioned to key the amp up. Since most amps have a RCA jack on the back of the amp for keying, I did mod it and added one to this one. Tried to make it look factory.
Other than recapping, spreading the 15 meter coil so it will work on 10 and 15, rewiring the relays so that grounding the key line will activate the relays, and adding an RCA jack in the back for a footswitch or modern radio keying, this amp is factory. Has the original blacktop 6mj6 tubes and though not mint, is very clean for its age which would be 60+ years old. Does around 500 rms and 700 peak. Someone said it could do more with more volts on the plate, but that would dirty up this cool clean running amp for a few more watts.
Here is a copy and paste from a Ham on the net:
The SB2-LA, and the earlier version SB1-LA, were some of the best "sweep tube" amplifiers produced. They employed six 6JE6 power pentodes in parallel. At the time, 6JE6's where rated at 24 watts plate dissipation and the bunch of them could do about 1000 watts PEP input on SSB. The power supply, which uses a separate filament transformer, was capable of higher power; thus, when the 6LQ6 became available, the amplifier could do an easy 1200 watts PEP input. It will tune the 17 & 24 meter bands without modification; but, is more efficient if the taps on the output PI network coil are changed for those frequencies
Though no big powerhouse, I give this amp a 9 on a 1-10 It does what it was designed to do and it does it very well. 
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Saving CB History, one unit at a time.
That's the plan.
Sweet looking piece of history !!
She’s a runner 💪🏻 I like it
Please sell it to me !
I Love this amp so its going to take 600 or a great trade for me to let it go.
@@tramdr
Yikes!
I have the matching SBE 33 transiever.
or a good trade, but as I said, I like this a lot too.
@@tramdr
How do i PM you?
Tramdr at Yahoo.com