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eHam Forums => Mods And Repairs => Topic started by: WB8PFZ on February 11, 2023, 10:39:52 AM

Title: Tube tester question
Post by: WB8PFZ on February 11, 2023, 10:39:52 AM
I am testing a few 6SJ6C tubes from an estate sale. They both test good but the meter pointer has a little flutter. I've seen this before but not sure if this is signs of a bad tube or what? Thanks
Title: Re: Tube tester question
Post by: AC2EU on February 11, 2023, 12:13:28 PM
I am testing a few 6SJ6C tubes from an estate sale. They both test good but the meter pointer has a little flutter. I've seen this before but not sure if this is signs of a bad tube or what? Thanks

More like a bad tube tester! Too much ripple in the DC.
Title: Re: Tube tester question
Post by: WB8PFZ on February 11, 2023, 12:38:04 PM
I have tested many tubes and this is the first I have seen this.
Title: Re: Tube tester question
Post by: K4GTE on February 11, 2023, 02:25:24 PM
What type/model of tube tester ? I have multiple testers, I test a lot of tubes, and I haven't seen this issue before. I'm tending to agree with AC2EU that it's a DC problem in the tester, and not a tube issue.
Title: Re: Tube tester question
Post by: WB8PFZ on February 11, 2023, 03:24:37 PM
It is a Mercury model 1000 mutual conductance tester
Title: Re: Tube tester question
Post by: K8AXW on February 11, 2023, 10:08:01 PM
The first thing I would do is test some other tubes to see if the flutter was there. 
Title: Re: Tube tester question
Post by: WB8PFZ on February 12, 2023, 04:16:05 AM
I  have tested many tubes and this is the first I have seen this.
Title: Re: Tube tester question
Post by: W9WQA on February 12, 2023, 06:29:47 AM
pull tube
scope or meter the plate conn on socket
load it with a resistor to ground
test other tubes.

try tube in amp.

oh, it dont matter what kind of tester,and, you prob wont see ripple, only scope.

Title: Re: Tube tester question
Post by: W1VT on February 12, 2023, 07:51:00 AM
One possibility is that you have made an oscillator!  You should be able to see this on a spectrum analyzer or hear it on a receiver.
An oscillator requires an active element with gain to overcome the circuit losses.   Only a good tube can do this.
Normally there is enough resistive loading or losses to prevent this.
Title: Re: Tube tester question
Post by: AC2EU on February 12, 2023, 08:55:08 AM
One possibility is that you have made an oscillator!  You should be able to see this on a spectrum analyzer or hear it on a receiver.
An oscillator requires an active element with gain to overcome the circuit losses.   Only a good tube can do this.
Normally there is enough resistive loading or losses to prevent this.

I've seen this on older testers that didn't have choke beads on the wires. Occasionally some tube might take off oscillating in the RF spectrum, but no flutter was seen on the meter. Never seen one oscillate in the low audio region, though.