[SignalOne] 8072 Final Tube

[Rodger Singley]

And to add to Don’s comment tube testers don’t test tubes RF operating frequency so even tubes that you can test in a tube tester often provide misleading results.  The 12BY7 used as a driver tube in many rigs is a classic example where one might test fine in a tube tester but fails miserably at RF.  The same is true of many tubes used as a converter or HFO in a receiver.  As Tektronix wisely puts it in many of their 500 series lab grade scope operating manuals the best test for a tube is whether it operates properly in the circuit.



A tube tester will often pass tubes that will fail to operate at the frequency of operation and/or tubes whose defect only shows up at full operating temperature which it will never reach in a tube tester.  Many tubes that have a short or leakage issue or secondary emission from a grid will only exhibit this fault after some time with all elements at their normal operating potential.



Tube testers often “fail” tubes that still operate perfectly in the circuit.



When troubleshooting symptoms and measurements lead me to suspect a tube I will first try replacing it with a new tube of the same type, second choice is an equivalent substitute, and third choice is to use a tester to render an opinion.  I seldom have to resort to the third choice.



Rodger WQ9E



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________________________________
From: signalone-bounces at mailman.qth.net <signalone-bounces at mailman.qth.net> on behalf of Don Merz via SignalOne <signalone at mailman.qth.net>
Sent: Friday, December 29, 2017 3:05:06 PM
To: signalone at mailman.qth.net; A Cass
Subject: Re: [SignalOne] 8072 Final Tube



This list is for discussions regarding collecting, repair, use and sale of Signal/One radios and accessories.

Documentation on Signal/One radios can be found at https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.hamanuals.com&data=02%7C01%7C%7Cca73a932c7cb4c45b27b08d54f0080b4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636501785932137776&sdata=mQsdSAb3wN8rjeEsjR6OCojX0Bt5I2ncOjj%2BdrTK%2FsM%3D&reserved=0 and several other sites on the Web.

.
 Transmitting tubes can rarely if ever be tested by commercial testers. Sometimes you can rig something. But usually the voltages and currents involved are higher than what a commercial tester will safely handle.
The 8072 is about as robust a tube as was ever made. The chances of it being bad are small enough that it is a pretty safe bet to just test it in use. Just my opinion. Your mileage may vary....
73, Don Merz, n3RHT

    On Friday, December 29, 2017, 3:51:07 PM EST, A Cass <cass44 at outlook.com> wrote:



This list is for discussions regarding collecting, repair, use and sale of Signal/One radios and accessories.

Documentation on Signal/One radios can be found at https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.hamanuals.com&data=02%7C01%7C%7Cca73a932c7cb4c45b27b08d54f0080b4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636501785932137776&sdata=mQsdSAb3wN8rjeEsjR6OCojX0Bt5I2ncOjj%2BdrTK%2FsM%3D&reserved=0 and several other sites on the Web.

.
I have a EICO 667 Tube Tester and the latest tube listing - no 8072 tube is listed.


Anyone know how this tube cam be tested?


thx


Alan, W4FBI
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