Are you disappointed that there are no longer any good 811A tubes available? If so, read more! I’ve discovered that NOS tubes are still available from the factory that made the Svetlana 811A that was quite popular with hams and enjoyed a good reputation. As a bonus, they’re cheaper than current production Chinese 811A tubes!
The tubes are the Ryazan G-811, here is the datasheet: Ryazan G-811
The tube in the picture on the Ryazan website is actually the Svetlana 811A product, which is now no longer manufactured. The NOS Ryazan tubes have a black base and no plate cap insulator (which was never needed), but are otherwise identical. Read more for the full story!
I’ve recently been overhauling an Ameritron AL-811 Amplifier, and one of the things required was a new set of tubes. This unfortunately, has been one of the hardest parts about getting the amplifier operating in perfect order.
The first set of tubes I tried were Shuguang 811A tubes. They turned out to be a pretty poor choice. After 15 hours testing into a dummy load at low power (my test cycle is JT65 transmissions), they developed cracks in the anodes. The tubes were carefully tuned to ensure the anodes never glowed more than a dull red, but in the end 3 out of 4 cracked along the reinforcement folds on the anodes… the cause? Scratches from the sheet metal bending on the production line!
Dismayed by the lack of alternatives, I did a bunch of research, with surprising results! I noticed that the Svetlana 811As, long out of production, had the Ryazan logo printed on them!
A quick search on eBay proved fruitful; Ryazan tubes are still available at very low cost NOS from Eastern Europe! In fact, at the time of writing $70 USD will get you a set of 4! As a bonus, as with all paypal purchases there is a fantastic warranty process!
The Ryazan tubes are known as ‘G-811’, and are often advertised along with the letters ‘OTK’ which really just means they have passed Soviet quality control. A close examination of photos shows that they are identical internally to Svetlana 811As. In fact, the only difference is that Svetlana dressed up their product with a white ceramic base, and white insulator on the plate cap!
More evidence of the superior quality of Ryazan G-811 tubes compared to the current production Chinese tubes is the fact that Ryazan (and Svetlana) tubes are manufactured without the use of a flash getter during pump down. This is proof that the plant was able to ‘pump down’ to a very hard vacuum – they didn’t have to rely on the use of a getter during manufacture to ensure good performance.
So far, the NOS Ryazan tubes have proven perfectly serviceable. The tubes I obtained had a date code of March 1985, and they had no issues with perished glue on the anode caps or base.
Naturally, I will provide updates as testing continues, but so far so good. I’m quite pleased to have discovered that Ryazan was the manufacturer of the Svetlana 811A, and that a better quality alternative is available to the current production Chinese tubes. Best of all? Ryazan G-811 tubes are also cheaper than the Chinese tubes, at least for now!
If you own an 811A based amplifier like an Ameritron AL-811 or AL-811H, do yourself a favour and get a set of Ryazan G-811 NOS tubes – aka the Svetlana 811A – before they run out and you are once again stuck with inferior Chinese tubes!
Lastly, here is a photo of both the Svetlana 811A & Ryazan G-811. Note the Ryazan ‘P’ logo on both of them!