[kmcdonou]

How reliable is the shorts test function of a B&K 747 tube tester? I have a tube that made popping noises when I put it in my Singlepower Supra. Everytime it popped I never had the headphones on my head so I couldn't tell what tube was shorting. It never popped continuously, just every so often. I would remove the tube I thought it was, put another in, and not hear popping. I would then put the suspect tube back in (since I wasn't sure what tube it was) and not hear popping. It was hard to find out what tube was shorting. Eventually it blew a resistor in my amp.

I found out our university has a B&K 747. I was playing around with it on Friday. When using the B&K 747 for the shorts test, it seems like you are only holding down the shorts button for a relatively short time (and according to the instructions, lightly tap on the tube). What happens if the tube has intermittent shorting. Can the tester determine if the tube is shorting if it doesn't do it during the brief test?

I just want to be sure if the tester doesn't indicate a short I can believe it.

Also, what happens if the mutual conductance test gives a reading in the questionable area (approximately 60%). Is this it worth using this tube or throwing it away?

 

[JKDJedi]

How reliable is the shorts test function of a B&K 747 tube tester? I have a tube that made popping noises when I put it in my Singlepower Supra. Everytime it popped I never had the headphones on my head so I couldn't tell what tube was shorting. It never popped continuously, just every so often. I would remove the tube I thought it was, put another in, and not hear popping. I would then put the suspect tube back in (since I wasn't sure what tube it was) and not hear popping. It was hard to find out what tube was shorting. Eventually it blew a resistor in my amp.

I found out our university has a B&K 747. I was playing around with it on Friday. When using the B&K 747 for the shorts test, it seems like you are only holding down the shorts button for a relatively short time (and according to the instructions, lightly tap on the tube). What happens if the tube has intermittent shorting. Can the tester determine if the tube is shorting if it doesn't do it during the brief test?

I just want to be sure if the tester doesn't indicate a short I can believe it.

Also, what happens if the mutual conductance test gives a reading in the questionable area (approximately 60%). Is this it worth using this tube or throwing it away?

Probably at one time the base was loose, got fixed and the wires sometimes touch at the bottom now.. get rid of it or fix it.

 

[JKDJedi]

How reliable is the shorts test function of a B&K 747 tube tester? I have a tube that made popping noises when I put it in my Singlepower Supra. Everytime it popped I never had the headphones on my head so I couldn't tell what tube was shorting. It never popped continuously, just every so often. I would remove the tube I thought it was, put another in, and not hear popping. I would then put the suspect tube back in (since I wasn't sure what tube it was) and not hear popping. It was hard to find out what tube was shorting. Eventually it blew a resistor in my amp.

I found out our university has a B&K 747. I was playing around with it on Friday. When using the B&K 747 for the shorts test, it seems like you are only holding down the shorts button for a relatively short time (and according to the instructions, lightly tap on the tube). What happens if the tube has intermittent shorting. Can the tester determine if the tube is shorting if it doesn't do it during the brief test?

I just want to be sure if the tester doesn't indicate a short I can believe it.

Also, what happens if the mutual conductance test gives a reading in the questionable area (approximately 60%). Is this it worth using this tube or throwing it away?

So I've had my tester for some time now and gotten some experience that might help better answer than my previous post. The BK747 is an excellent shorts and grid emissions tester, you can bet the bank on it for that. And yes tapping on the suspect tube and or even twisting the base a little will show up any shorts. AND... tubes up to 30% are usable. Heck I have tubes down to 20% I was using when I didn't have the tester. But now that i know, I draw the line at 30%, there's belief that some NOS tubes come out of the factory near the 60% mark due to grid imperfections or what not, but they are still NOS. If the tube looks great and in near mint condition, most of the time 99.9% it's a good tube.