300B Tube Reliability

[Raymond P.]

My recent experience with 300B tubes has me wondering about their reliability. Between 1-3 months of usage I had three 300B's go bad. One stock Electro-Harmonix tube had a failed heating filament, another stopped producing sound (although filaments were still glowing), and one ebay purchased Electro-Harmonix GOLD started producing hissing noises (luckily, the seller agreed to a warranty replacement.)


So I'm wondering if EH tubes have reliability issues in general or did I just have very bad luck. Based on your experiences, what brand(s) or 300B tubes do you consider to be most reliable (let's ignore sound quality for now)?

[Paul Birkeland]

That is incredibly bad luck. For years Doc B. had 18 300B tubes running in his system at once and they all lasted a very long time.  If proper precautions aren't taken with shipping, however, the filaments can get damaged.  I have had this happen twice, but only ever from eBay sellers (not actual tube dealers).

[Doc B.]

IME EH tubes have been very reliable, as PB notes. If you keep having failures in the same amp it might be prudent to check voltages, particularly filament and cathode voltages of the 300Bs.

[Raymond P.]

Paul and Doc, thanks for the reassurances. The three failures happened between my BeePre and Kaiju, one in the right channel and two in the left, although I can't remember the exact occurrences for each amp. Re-checking voltages is a good suggestion.

[jjvornov]

I had a BeePre 300B die on me a month or so ago, a stock EH. Fortunately, I had a spare and swapped it right in. I think it was the heater, as there was no glow or heat.

James

[Doc B.]

Can you tell us how long it ran before dying?

[jjvornov]

It was about 6 months. I was using a pair of Psavane in it until the Kaiju was built, then I switched in the EH I had already

James

[Raymond P.]

Update: I was able to revive one of the bad 300B's. It was the one that mysteriously just stopped making sound, but still had glowing filaments. I saw a youtube video that suggested heating the cathode for a few hours (it was a 300B). So I applied 5Vdc across the filament pins for about 5 hrs, plugged the tube back in, and the 'fix' worked! I'm glad I didn't toss the tube when it went bad. Hoping my tube is 100% recovered. We'll see.