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Tube Testing Services  

We have invested considerably in our tube testing capabilities to improve the performance and reliability of our products. 

With our extensive high quality testing abilities, we now offer our vacuum tube testing as a service for customers.

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To read more about our tube testing program, see our page on tube testing details:

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If you are interested in our tube testing service, contact us with your needs (tube types and quantities). We will be happy to work up a quote.

  • Once we receive your tubes, we will begin testing.

    • Any known quote adjustments will be communicated

  • We complete most tube testing requests in two weeks

Preamp Tube Testing

1. Health Check

 

Tubes are first electrically tested for shorts, grid current (gas or contaminants on the grid), and continuity. Once the tube passes these checks, it will move onto curve tracing.

 

Note: If there is an issue with the health check, we will clean and deoxidize the tube pins and any debris on the socket that may cause leakage between pin. This usually fixes most issues, but if the tube still fails, it will be put aside.

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2. Curve Tracing

 

For preamp tube testing, we use our curve tracing abilities to plot datasheet plate curves of each tubes. For dual triodes (12AX7, 12AT7, 12AU7, 6SN7, 6SL7 etc...) we test both sections simultaneously so you can visually see the section to section matching.

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We then will measure the tubes performance parameters around the operating bias point defined by the datasheet for easy numeric tube matching.

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Test Results Include:

  • gm (transconductance)

  • Mu (gain)

  • Rp (plate resistance

  • Ia (plate current)

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Printouts of both the tubes plate curves and the operating point values for tube matching are included. Tubes are assigned an sequence number with a sticker on the box, which matches the number found on the data printouts. 

 

From this info, tube can be easily matched between each section of a dual triode, or between tubes.

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Cost:  $7.50 / tube

Due to setup time of our equipment, this price is for a minimum of 4 tubes of any one tube type

A $5 surcharge is added for each tube type where there are fewer than 4 units to test.

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Note: This includes the printouts of the tuber curves and performance metrics at the datasheet specific operating points so you can be confident in how the tube performs in any circuit.

Power Tube Testing

1. Health Check

 

Like our preamp tube testing, power tubes are first electrically tested for shorts, grid current (gas or contaminants on the grid), and continuity. Once the tube passes these checks, it will move onto step 2.

 

Note: If there is an issue with the health check, we will clean and deoxidize the tube pins and any debris on the socket that may cause leakage between pin. This usually fixes most issues, but if the tube still fails, it will be put aside.

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2. Static and Dynamic Testing

 

We use our calibrated and extremely accurate Hickok Model 700 to test and measure power tubes to datasheet test conditions which are also used by the original tube manufacturer. We setup a high power static DC bias point on the tube to allow the tube to heat soak as it would in an amplifier. We then capture the the tubes static parameters, plate and screen current (Ip & Is), before measuring the dynamic transconductance (gm).

 

We then apply sticker to the tube base with the tubes sequence number. On the tube box, a sticker with the same number lists the test condition and the results, allowing tubes to be quickly compared for matching.

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Test Conductions Include:

  • Vp - Plate Voltage

  • Vs - Screen Voltage (for pentodes)

  • Vg - Grid Voltage

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Test Results Include:

  • Ip - Plate Current

  • Is- Screen Current

  • gm - Transconductance in mA/V

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This testing provides the real performance of the vacuum tube and can be directly compared to the values found on the datasheet.

 

This is in direct contrast to nearly every other analog tester (Hickok included) where the tube is tested under pulsed, low power conditions. In these testers, readings are then scaled by the testers meter to attempt to match the real test result. Many other dynamic mutual conductance testers will have their own lookup table for acceptance values for each tube type with an arbitrary scale (0-100).

 

This makes these testers useless since the results cannot be verified on another tester. This also leads to some nefarious practices by tube sellers.

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Cost:  $6.00 / tube

Due to setup time of our equipment, this price is for a minimum of 4 tubes of any one tube type

A $5 surcharge is added for each tube type where there are fewer than 4 units to test.

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Note: This includes datasheet printout for each tube type submitted for testing showing the test conditions and the nominal new specifications.

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