Posts Tagged ‘Tube Tester Restoration’

Posted on April 7, 2018 - by DLandon

Weston 981 Type 3 Tube Tester

This is a Weston 981 Mutual Conductance tube tester that was not functional when I received it for calibration.  One of the electrolytic capacitors was shorted and blew a fuse when the line adjust was turned up.  This tube tester uses selenium rectifiers instead of vacuum tube rectifiers.  The selenium rectifiers should not be replaced with solid state diodes because this affects the calibration of the tube tester.  The tester was designed for the voltage drop across the selenium rectifier and is difficult to replicate with solid state diodes.  Luckily the selenium rectifier was not affected by the shorted capacitor.  The line adjust was pot was also bad and had to be replaced.  The line adjust pots in the old tube testers are wire wound pots with around 25 watt handling capability.  They are still available in NOS or as new units.

This tube tester is a mutual conductance tube tester and provides good quality testing of vacuum tubes.

Posted on April 7, 2018 - by DLandon

Hickok 752A Tube Tester

This is a Hickok 752A that I restored electronically and calibrated.  This is a very nice tester and is very clean.  The 752A has the ability to test a multi section tube without having to re-do the settings for the second section.  You just make the settings according to the tube chart, test the first section, then select the second section and make the tests in the second section.

The tester came to me with a blown Bias fuse so tubes could not be tested.  The Bias fuse is used to protect the Bias potentiometer if incorrect settings are made for the tube being tested.  When it is blown, the Bias voltage is not applied to the tube.

The 752A has the ability to test the older and newer tubes, including compactrons.

Posted on April 1, 2017 - by DLandon

Hickok 539C with Digital Meters

This 539C was not working because all three meters were bad.  The meters were replaced with digital meter replacements and the tube tester was calibrated.  Analog meters in tube testers that are 50 plus years old will have problems.  If they are working, they are most likely no longer calibrated and readings will be off.  The digital meters are very accurate and not prone to the mechanical issues with the older analog meters.  The micromho reading is read from the Gm meter as a percent of the selected scale.

Posted on February 12, 2012 - by DLandon

Restored and Calibrated Precision 912P For Sale – SOLD

This is a restored Precision 912P Tube Tester.  Included is a CD with a copy of the manual and tube test data. The deck is in very good condition and the cabinet is in excellent condition.  The finish is original and was restored – it was not refinished.  This is one of the nicest original condition Precision tube testers that I have seen. The tube tester is fully functional and has been calibrated.  The power cord was replaced, the proper fuses were installed, controls were lubricated, cabinet restored, hardware cleaned, and calibration performed. The 912P has battery testing capability. I do not restore the battery testing circuits because these older tube testers are desired for tube testing capability and not battery testing. Most of the time the battery testing circuits will work. This tester is for sale for $325.  I will only ship this unit to the lower 48 states because of the weight. Contact me by email at dlandon@vintagetubeelectronics.com if you are interested.

Posted on February 19, 2011 - by DLandon

Hickok 6000A Tube Tester

I picked up this tube tester as a trade for refurbishing an amplifier and a tuner. The history of this tube tester is that it was used by P & G (Proctor and Gamble) and then surplused out some years ago. The case shows some wear, but the deck and electronics appear to be in excellent shape. The original power cord is still in excellent condition. I checked the calibration and it was spot on and didn’t require any adjustments. This is a very nice tube tester that doesn’t appear to have seen much use.

The 6000A is a compact unit that tests the newer tubes like Compactrons and does not test the older 4, 5, and 7 pin tubes. I use this tube tester as my everyday tester for newer style tubes.

I especially like the shorts indicators. With a quick glance you can see if there are any shorts before testing the tube for quality.

Posted on February 19, 2011 - by DLandon

Hickok 750 Tube Tester

This is my “go to” tube tester. The Hickok 750 is a Mutual Conductance tube tester.  Mutual Conductance tube testers are the best for true vacuum tube performance.  When matching tubes, this is the best type of tester to use.

The meter movement on this tester has been replaced.  The original meter movement developed a mechanical problem.  The needle came unglued from the movement coil.  A quick fix got it going for the short term, but a new replacement movement was installed.

This tube tester is in pretty good shape.  A lot of the old Hickok tube testers were work horses and were used daily.  This resulted in a lot of wear on most of them.  The case on this particular unit is not too badly beat up.  There are a few nicks and scratches; overall the tester is in good condition.

There is no calibration procedure available for the 750, but several other models of Hickok tube testers are very similar and the calibration procedure can be used from these other testers.  I calibrated this tube tester using what information was available. The shorts testing circuitry was pretty far off.  Most every tube I tested before calibration showed a short.  It now works properly following the calibration.

What I particularly like about this tester is that I can check for overall tube quality and also check Mutual Conductance.

I have found a lot of tubes that will check good on an emission tester will test bad on the 750.

Hickok tube testers command a premium price these days, but overall this 750 is a nice tube tester and well worth the investment.

Posted on February 19, 2011 - by DLandon

Precision 10-12 Tube Tester

This is a very nice newer model 10-12. The serial number has a “D” prefix character, and you can see the difference in the knobs used on the deck. The electronics appear to be the same as the older style 10-12s.

Posted on February 19, 2011 - by DLandon

Precision 10-xx Solid State Prototype?

Does anyone know anything about this tube tester?

I believe it is a prototype Precision 10-xx that never saw production.  The meter is from a 10-12 tester.  The power supply uses a top hat solid-state rectifier instead of a #80 tube.  I can test tubes on this unit using the test data from a 10-12 tube tester.

The buttons for “W”, “X”, “Y”, and “Z” are individually pushed to make the connections to the tube rather than the lever switches like on the 10-12.  There is a knob that is pulled to clear the pressed buttons.

There is a “Gas” pushbutton that is not connected.  There must have been plans for a gas test in this tube tester.  A compactron tube socket has been added.

I would appreciate any information that anyone has about this tester. Email me at dlandon@vintagetubeelectronics.com  if you know anything about it.

Posted on February 19, 2011 - by DLandon

Precision 10-12 Tube Tester

This is a very nice older model 10-12.  It is in excellent condition. The meter movement was replaced with a newer meter movement.  The meter indicator is a pointer, rather than a line indicator.  The dial face attached with the same mounting holes.  This kept the unit as original as possible.  I even have the original warranty card for this tester.

Posted on February 19, 2011 - by DLandon

Precision 612 Tube Tester

This is a pristine example of a Precision 612 tube tester.  The Precision 612 is a basic Cathode Emissions tester with battery testing functionality.  It does not have any VOM functions.  Calibration was spot on and did not have to be changed.