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Re: 6as7 life continued...

Posted by Legendre (A) on February 15, 2005 at 09:53:53

In Reply to: Re: 6as7 life continued... posted by bryan on February 14, 2005 at 21:12:35:

>Thanks for the reply, Bill. For those that don't have access to what you have in the factory bench, it's more difficult isn't it?

If by 'the factory bench' you mean the old Philco, then I guess the answer is yes. This said, a simple emission-type tube tester (like the Philco) can be had for $25 or so at a Hamfest, or on eBay. Noting special about it, just make sure that the 6AS7 / 6080 is listed in the tube data for your tester - these tubes require 2.5A @ 6.3V for the filaments, and some cheap testers just don't have enough power supply for them.

When referring to 'plate voltage', it seems that you are actually referring to cathode current, derived from voltages measured across the cathode resistors? In this case, 50-80mA per section is pretty much nominal, and gives a good indication of the tube's DC characteristics.

Yes, it is quite possible for a tube to show good emission and DC characteristics, and still have poor transconductance. However, this is less likely with a simple triode than with a more complex (multi-grid) tube, such as a pentode.

I just had an idea; suddenly, I'm getting the itch to do a little bench work on this.. if I come up with any interesting results, I'll post them. For now, it's just an idea. I'll see how it pans out.

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