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SBE SB-1LA sweep tube Amateur Radio linear amplifier early 1960's walkthru + some SBE history
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- เผยแพร่เมื่อ 13 ก.ค. 2024
- Old Amateur Radio sweep tube amp from the early 1960's era. The SBE model SB-1LA. It uses 6 6MH6/6LQ6 sweep tubes all finals, no drivers. It is 15-80 meters only. No 10 meters which is interesting as in the 60's there wasn't much happening with CB at all, especially with linear amplifiers. However, this was made to mate with the SBE-33 and 34 radios from back during that era and those SBE radios don't have 10 meters either.
Here is a cut and paste of a little SBE history from the net:
SBE Est. 1962 , closed 1975 | USA
SideBand Engineers was founded by the founder of Gonset, Mr. Faust Gonset in 1962. Its goal was to create ideal mobile equipments with latest transistor technology and advanced design.
In 1963, SBE started to sell their first model, SBE SB-33 transceiver. It is known as the first practical transistorized rig; one of the important milestones of the amateur equipment history. The SBE SB-34 followed in 1964.
In 1970s, all of the U.S. amateur equipment manufactures were under attack of the Japanese made rigs. SBE started to sell the SBE SB-35 and SBE SB-36 which were manufactured in Japan, but they could not save the company. Reportedly very few SBE SB-35 manufactured.
SBE withdrew from the amateur market in late 1970, but kept manufacturing high quality - high performance CB radios and scanners for a while. Sometime later however the company completely disappeared from the consumer radio equipment market
I didn't know that the founder of Gonset was the founder of SBE until I looked up some history on the net. SBE stood for SideBand Engineers and always strived to make better equipment and I think they did.
So back to the SB1, though I think it looks cool and is nice and compact, it is not just a show pony. When you pick it up, you will know it's got a lot of weight for its size. Maybe not built like a tank but built like a truck. As you can see in the video, it's got a lot of stuff packed in its smaller footprint. Internal power supply with separate filament and high voltage transformer, 2 HV diode and cap banks in series, 15-80 meter bands, big resistor bank on the input to get the input matching down, Tetrode 'Turbo' mode grid driven with voltage on the screen and -bias.
This amp does have a few strange? things. As many early amps had back in the day, the main power switch is actually marked Filament On/Off. That's not strange but the 2nd power switch is marked Hi and Low. However, that switch has nothing to do with high and low, but it turns On and Off the HV transformer only. Why not mark it like other amps did, HV On/Off? Also the so called power Hi/Low switch on this amp is tied to the relay keyer, so with the switch on Low, the HV transformer is off and te relay won't key. This is in the manual, and on Low, the amp is in standby. On 'High' the amp is fully operational with the HV transformer now on and the keyer now ready too.
Another quirk is no parasitic chokes on the plates. The Ham's say there is a parasitic on the input grid, but I don't see one. On the HV, it uses 2 voltage doublers in series. The Hams say that the four 200uf caps it uses in the HV are not near enough. I found this out the hard way. I originally replaced the 200's with new 220's. They worked, but as the Hams said, I had a lot of ac hum. I ended up taking out the nice, neat, pretty 220's I just put in and then wired in some big old 470uf snap caps. Interesting that I had to more than double the caps uf's to get rid of the hum, but from the net, a couple Hams said you need to go up to 800's.
This amp is set to work with the SBE 33 or 34 transceivers. They would key the amp by sending +10 from the transceiver to the amp to key it. Fine if you are running a SBE radio, but if not..... So, I ended up lightly modding this so the keying circuit would work like most other amps. I used the -15 which was right there and ran it to the hot side of the 2 relays and then ran the cold side of both relays out to the relay jack. Now a foot switch of radio will just need to switch to ground to key this amp. Hams on the net mod it different. They would just ground the -120 Bias line and the T/R relay to key this amp. That works, but you now have a dangerous -120 going out to your footswitch or radio. Not good. Just because everyone else is doing it doesn't make it right. Coming soon, going to show this in action, It runs the HV pretty low at around 800v, so it should run clean but not make crazy watts. I expect around 700 peak watts out of the 6 6mh6 tubes. It will need about 65 watts drive.
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Fine piece of history, Doc. SBE serious back then, ample bypass caps to ground under tube sockets. Had the SBE Sierra 23 Ch transceiver (1973-4) that had the same 9-pin octal AC plug setup, Enjoyed your circuit walk through, thanks for posting. n2eye
You are welcome and agreed. SBE made some great performing radios, especially with the audio.
Interesting old amp. Never saw one like that before.
It caught my attention too. When I was looking up info on this, I saw one that was even more interesting to me. The Trio 'Kenwood' TL-911 5 sweep tube amp from Trio which is early Kenwood and looks like a stereo component. Now I have to find one of those too.
Before 1969, Sideband Engineers only manufactured American made amateur radio equipment like this amp and the SB-34 transceiver. Sometime in 1969 the company decided that the CB radio market was far more profitable than the amateur radio market... but only if they sold imported radios from Japan.
The SBE Console base and Sidebander mobile, both sharing the same circuit board as the new Midland 13-880B, entered the market along with a line of AM only rigs in 1970.
And, the rest was history.
I never knew these existed !
Me either until I saw this on Ebay. However, after looking it up, the early SBE amateur radio equipment was fairly common back then and rated pretty well too. Funny how Hams hate sweep tubes so much now.
@@tramdr yep. And sweep tubes are the ones that got em where they are now. I only own sweep tube amps except this 3cx 3000 a7 amp. I rarely use it
Interesting, thank you.
You're welcome
I like the engraved front facia and colour scheme, very retro!👍 That power switch is just stupid, though.
Thanks and agreed.
I was going to tell you the reason no 10M- but I can see you figured out that the SB-33 did not have 10M and this amp matches that rig. The SB-33 with a Shure 444c mike was one of the nicest sounding radios on the air that I have ever used- but I've only been a ham since 1976- that's when we (My Dad and Family) gave up on CB. Thanks for your video.
I should clarify the "gave up on CB" statement- I don't mean to denigrate CB in any way; we just found Ham Radio which is more interesting than CB. For example, my Dad liked rag chewing and operating- OTOH, I liked designing and building radios and antenna systems... a lot more opportunities for both with licensed ham radio.
Sure, but why not do both? My Elmer as a kid did in the 60's. I bought his estate when he went silent, both CB and Ham in the 90's. He and I both felt there were some things we liked about CB best and others we liked about Ham best.
The faceplate is engraved and painted. That cost a bit much more than a silkscreen panel. Nice amp for your collection.
Thanks!
When you are explaining the soft start, even though the small fuse is taken out of the circuit when in TX mode, F1 looks as though it's in circuit so shouldn't it blow if there is an issue?
Very cool walkthrough, thanks Doc.
True and good thinking, but what is also true is that F2 is a 3 amp fuse which is the right size to protect the HV if there is a glitch. When you tx, you are bypassing F2 and F1 though it is in circuit, it is a 15 amp fuse. Much harder for that to pop. Makes no sense to me. The very reason glitch fuses or glitch resistors are added to amps is to help protect the HV tranny. Why would you bypass that during TX?
I own one of these also Doc.. mine has been modded with a johnson roller inductor in place of the band switch. 600+ w out is about what it will do, my tubes may be going soft...
@@tramdr
🤔 I guess you could add a glitch fuse?
I think they meant to have a HV switch cernter off and low on 1 tap with 1 doubler and high on another tap or both the doublers? why not 1 doubler like the heathkit sb220? and it didnt make it to the final production for some reason
Could be on the center tap. On the 2 doubler problem, my best guess is cost again. The very reason manufacturers use a doubler instead of a full wave is transformer cost. It costs a lot less to make a 250v 2a transformer than it does to make a 500v 1a transformer even though both put out 500 watts. Heathkit even said so, that they used the doubler because the transformer is smaller, lighter, and cost effective vs a full waver. Hence, I'm guessing the dual output 2 doubler scheme is even cheaper. IMHO, its always about the money.
those are 6MJ6, super tough tubes. 6 of them would swing 1000 if the power supply was up to it
they got 2 straps giong to the plate too not just 1 wire on the plate cap. D&A used those too
Yes, but this amp is made to run clean, not made for max aka mo watts.
Plate straps? Well they run the straps tube to tube on this one. Actually, that is not ideal at all. It is better to run the straps to a center point of the tubes and make all the taps equal length which will help the tubes balance better.
@@tramdr the straps inside the tube
OK you right on that one. Good One.