Building a Tube Tester

Discussion in 'DIY' started by batriq, Dec 27, 2020.

  1. batriq

    batriq Probably has made you smarter

    Friend
    Joined:
    Oct 31, 2015
    Likes Received:
    888
    Dislikes Received:
    0
    Trophy Points:
    93
    I've been looking for a tube tester for a while, and my options were:
    • Buy an old tube tester. It would need to be calibrated, and I don't know who are the reputable sellers. Prices varied a lot -- this option is basically a crapshoot.
    • Buy an Amplitrex. Good but very expensive -- about $3000.
    • Build one. The two primary options I found are the uTracer and the eTracer.
    I opted for the 3rd option. The eTracer is a more complete kit with well-supported software. The only issue is that I didn't own a Windows machine. The eTracer with case, power supply, an extra top plate that I needed for 211 tubes, and shipping costs $1250. I opted to buy a Lenovo laptop during black Friday sales. The combo ended up costing me <$2000 (side note: I've been a mac user since 2003 -- Windows has come a long way, and I'm preferring this machine over my mac).

    First tube I tested after completing the build:
    [​IMG]

    Parts
    Here are the parts I ordered from the site:
    • PC control software $500
    • Built and tested PCB: $350
    • Model-01 chassis with accessories: $200
    • Extra Top-B-3 blank top plate for customizing sockets: $20
    • Mean Well EPP-200-27 internal power supply: $30
    • + Shipping $80 and PayPal fees $70
    While it comes with all the tube sockets, I decided to replace the Octal and 9-pin miniature sockets with NOS ones I had at hand. I wish I had UX4 and UX5 NOS sockets that fit the existing openings on the top plate, so the ones provided would have to do (they're fine -- in retrospect, I needn't replace any sockets).

    There are some extra parts that are needed besides what comes with the kit. Below are the parts and links to the ones I bought:
    I already had a soldering iron, solder, silicone, (optional) heat shrink, (optional) techflex, (optional) heat gun. For silicone in builds, I use RTV silicone. The kit comes with 600V stranded Teflon coated wire. The wire is high-quality, but I prefer solid wire for point-to-point connections. For that I use Belden milspec 1kV wire.

    Finally, I use 311B tubes, and I needed a connection for the grid cap. I already owned a ceramic tube cap, and I appropriated a banana plug for the terminal connection:

    [​IMG]

    To be continued with build, tests, and a tube configuration file.
     
  2. batriq

    batriq Probably has made you smarter

    Friend
    Joined:
    Oct 31, 2015
    Likes Received:
    888
    Dislikes Received:
    0
    Trophy Points:
    93
    Build

    The eTracer comes with a manual that outlines the build. It's actually a 3-part manual, one for the chassis, one for the board, and one for the software. You need to read the first two for the build. A few more pictures would have been very helpful. I took pictures during the build and I provide them below with descriptions.

    Mounting

    The two images below show all the parts mounted. You can mount the tubes in different orientations, but I chose the setup below to make it easier to connect all the tube pins to each other among the sockets.

    [​IMG]
    [​IMG]

    The first step was to install the two side walls:

    [​IMG]

    Power

    Next I wired up the power. This includes power from the IEC connector to the PS, and from the PS to the board. The first image shows the crimped power connectors covered in heat shrink (the long wire with the bare connector is ground, it's the cable's drain wire covered in heat shrink). I used a Belden internal wiring power cable I had left over from another build -- it's not necessary, the wires that come with the kit are sufficient:

    [​IMG]
    [​IMG]

    Note that IEC ground connects to the chassis:

    [​IMG]

    LEDs

    Creating the LED assemblies took time (these wires come with the kit). Once done, I kept them neat with some techflex:

    [​IMG]
    [​IMG]

    Terminals

    The wires connecting the terminals to the board must be cut at different lengths. Make sure to measure everything first. Here they are measured (1st pic), then soldered (2nd pic). I stripped enough wire to connect the identical terminals rather than connect them with separate wires:

    [​IMG]
    [​IMG]

    Catch Tray

    This is how the catch tray looks like once done:

    [​IMG]

    Completed Chassis

    At this point the chassis was ready, except for the top plate:

    [​IMG]
    [​IMG]
     
    Last edited: Dec 27, 2020
  3. batriq

    batriq Probably has made you smarter

    Friend
    Joined:
    Oct 31, 2015
    Likes Received:
    888
    Dislikes Received:
    0
    Trophy Points:
    93
    The Top Plate

    The top plate takes a long time. Every other wire has to have a ferrite bead attached to it. These are kept in place with RTV silicone. I took the extra step of covering them with heat shrink. In fact, I color coded each pin with different color heat shrink for easier debugging in case anything went wrong. These point-to-point connections is where I used the solid core Belden wire rather than the provided stranded wire (I used stranded wire everywhere else in the chassis -- crimping it is much easier). The first 5 pins I used white wire, and the next 5 I used black wire.

    Each pin is connected in series among the sockets then I soldered the sequence is soldered. Here are the first 4 pins. Once these are connected, you can test any UX4 tube, and it's a good opportunity to check that everything is working so far.

    [​IMG]

    And all the pins connected:

    [​IMG]
     
    Last edited: Dec 27, 2020
    Cspirou, Lyander, Empyah and 9 others like this.
  4. batriq

    batriq Probably has made you smarter

    Friend
    Joined:
    Oct 31, 2015
    Likes Received:
    888
    Dislikes Received:
    0
    Trophy Points:
    93
    Testing Tubes

    The software manual is quite elaborate, so I won't go into too much details, but I'll show some examples of tested tubes.

    45

    This example shows the main 3 tests on a 45 tube: Quick scan, full trace, and corners test:

    [​IMG]

    You can see that this tube passes corners test, tests ~100% for transconductance, plate resistance, mu, and about 71% for plate current (25.8mA vs the 36mA reference).

    6SN7

    Here are the traces for two Tungsol tubes, one with matched sections and one without. What's really nice is you can save the results and load them later as I did below:

    [​IMG]
    [​IMG]

    300B

    Here we can see that my JJ tubes are no longer matched after the many years of use, while my EMLs remain matched:

    JJ (faint lines around the mean):
    [​IMG]

    EML:
    [​IMG]

    311B

    The eTracer does not come with tube configuration for testing 311B tubes. I created one based on the data sheet, and ran it by Chris, the creator of eTracer. Below is a test based on the final iteration of the pentode-mode file:

    Note, I forgot to save the full scan data, but here is the quick scan data for two tubes:
    Tube 1:
    current:32.50 mA, reference:33.00 mA, percent:98.5%
    gm:2994 umhos, reference:2800 umhos, percent: 106.9%
    Tube 2:
    current:32.38 mA, reference:33.00 mA, percent:98.1%
    gm:3060 umhos, reference:2800 umhos, percent: 109.3%

    You don't need to try hard to match these WE 311B tubes, these are two NOS ones I picked. I'll upload a full trace file next time I test.
     
    Last edited: Dec 27, 2020
    Azteca, memoryerror, ogodei and 10 others like this.
  5. ogodei

    ogodei Headphone Heaven Gatekeeper

    Friend
    Joined:
    Feb 9, 2016
    Likes Received:
    1,939
    Dislikes Received:
    5
    Trophy Points:
    93
    Location:
    Chicago
    Great build. You should make sure to include the Gas Tester. I built mine before it was added to the design, its the only thing I still use my old tester for now.
     
    Last edited: Dec 29, 2020
  6. YMO

    YMO it's not drinking alone if you're on Zoom

    Friend
    Joined:
    Apr 1, 2018
    Likes Received:
    6,213
    Dislikes Received:
    37
    Trophy Points:
    113
    Location:
    DUVALLL-904
    This is fucking cool. @purr1n front page plz.
     
    purr1n and Zampotech like this.
  7. ogodei

    ogodei Headphone Heaven Gatekeeper

    Friend
    Joined:
    Feb 9, 2016
    Likes Received:
    1,939
    Dislikes Received:
    5
    Trophy Points:
    93
    Location:
    Chicago
    Once you get the hang of it you can create testing configurations for just about any tube, you just need to have a data sheet. You can also create custom-target configs to get quick readings of whether a tube matches your specific standards. I'm filtering my 6N1P tubes for Stellaris to get the vaunted 'ruby tiger' specs.

    The matching feature (last image in post #4 above) is very cool, you can store named outputs for multiple tubes & then find matches. Good for when you have multiples of tubes bouncing around.
     
    CEE TEE, dBel84 and batriq like this.
  8. Cspirou

    Cspirou They call me Sparky

    Friend
    Joined:
    Sep 27, 2015
    Likes Received:
    6,015
    Dislikes Received:
    6
    Trophy Points:
    113
    Location:
    Northwest France
    I'll pay special attention to tubes from @batriq in the FS section
     
    tranq, Gazny, JK47 and 1 other person like this.
  9. Pogo

    Pogo Friend

    Friend
    Joined:
    Jun 14, 2018
    Likes Received:
    642
    Dislikes Received:
    9
    Trophy Points:
    93
    Location:
    SoFla
    That's a great write up,thank you.
    What I'd like to build is a time machine,take me back to the early 60's when my Dad used to take me to the Rexall drugstore which had a tube tester in the back. He'd have a bag of tubes from our Zenith tv and from his ham radio.
    Would but that I had paid more attention to what he said on these trips, he knew his shit having been a radio officer in the merchant marine during his war. At least I still remember the morse code he drilled into me. Sort of.
     
    batriq likes this.
  10. iFi audio

    iFi audio MOT iFi Audio

    Joined:
    Oct 3, 2017
    Likes Received:
    1,428
    Dislikes Received:
    36
    Trophy Points:
    93
    Location:
    Many places.
    Home Page:
    Dang, now that's serious! Great project!
     
  11. ogodei

    ogodei Headphone Heaven Gatekeeper

    Friend
    Joined:
    Feb 9, 2016
    Likes Received:
    1,939
    Dislikes Received:
    5
    Trophy Points:
    93
    Location:
    Chicago
    batriq, atomicbob and gurubhai like this.
  12. atomicbob

    atomicbob dScope Yoda

    Friend BWC MZR
    Joined:
    Sep 27, 2015
    Likes Received:
    15,237
    Dislikes Received:
    4
    Trophy Points:
    113
    Location:
    On planet
    His explanation of how to use an oscilloscope, signal generator and Analog RMS Voltmeter to make audio measurements is excellent! This is definitely worth reading. He has an older Audio Precision, however he explains very well how to obtain a lot of information without one.
     
    batriq and Azteca like this.

Share This Page