SBE SB-1LA sweep tube Amateur Radio linear amplifier early 1960's walkthru + some SBE history

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.