[govee]

I haven't turned this on for a while but recently when I did I discovered that when I perform the line test the meter pegs right. I Looked over the schematic and I am not seeing the reason for the issue. Regardless of line switch position the meter past off the meter is pegged. I have checked all resistors and all check ok with the exception of r107 which measures at ~45 ohms. Since r107 sits across the meter I disconnected the meter and I get ~270 ohms. High but not open. The meter measures 50 ohms. I decide to put a decade box in series with the meter and at about 500 ohms on the decade box the line test is able to be centered and the each of the positions of the line switch vary the meters response as expected. While that works I am not sure what the failure mode is or the effect the additional resistance would have on  tube testing results.


   

Andy

[govee]

While I was continuing to look for the culprit for my line voltage adjustment, I checked the meter resistance and it is 50 ohms. The meter checks electrically ok, but does get stuck some times. I had remembered when I was working on a EICO VTVM (this was a 221) that that meter was 50 ohms. I got the 221 and looked it over and except for the dial face its looked the same. I pulled it out of the meter and It is identical. I put the eico meter in the tube tester and its the same. unfortunately its the same meaning I still get the high reading, but it does solve the getting stuck issue.

Andy

[Radioroslyn]

My 2c. Tubetesters are a headache because of all of the switching it tough to follow flow of voltages.

R-107 is critical. It determines the amount of current that flows thru the meter. Never operate it with the meter in circuit and R-107 out. Use your decade box connected in parallel w/R-107. Start with a low resistance raising it till you get the meter to behave. Remove the meter from the circuit and measure the resistance of R-107 with the decade box connected. Replace R-107 with resistance just measured. R 104,5,and 6 are fairly critical too. I might take R-107's original value with a grain of salt. It may have had the meter movement replaced which would probably require a different value. Once the meter and the shunt (R-107) are working the other original resistor's values should work ok.

Now if this was a shop fixing this they would have a "test tube". It's a tube that has a known specification so when put into the suspect tester it can be tested to see if it's work properly. I don't know if you have a way of evaluating the accuracy.

[govee]

Thanks Terry. I will start looking at that approach.