Tube Tester Calibration
Tube tester calibration and repair of Hickok, Western Electric, Precision, B&K, Sencore, Triplett and other brands of tube testers. This is a description of the services provided. Contact me about a tube tester you’d like to have calibrated. I do some Military tube testers, but I don’t do Cardmatic tube testers.
Tube tester restoration labor is warranted for one year.
Mutual Conductance Tube Testers (Hickok, B&K, Triplett, Western Electric, Military)
Hickok tube testers are Mutual Conductance tube testers and are highly prized for their quality. If you want to match tubes, you need a Mutual Conductance tube tester. Some of these tube testers do not have enough resolution in the readings to match tubes. The Hickok 539 series, and the 750/752 series are some of the best for tube matching.
A functioning Bias potentiometer is required for a calibration. Since they were made custom for Hickok tube testers they are no longer available. If you have a tube tester with a bad Bias pot, consider it a boat anchor. The only source for a replacement Bias pot is from another tube tester.
The service consists of the following:
- Install proper fuse lamps.
- Clean controls and switches as necessary.
- Replace resistors and capacitors as necessary to insure accurate calibration.
- Verify proper meter operation.
- Check and calibrate shorts testing.
- Check overall calibration of the tube tester with various tubes – power, rectifier, and pre-amplifier.
- Transformer Plate Winding Impedance Matching for best symmetry between plate circuits—improves accuracy and consistency of test results.
Recommended Options:
- Replace vacuum tube rectifiers. The #83 tube is getting scarce and expensive. I recommend converting to solid state rectifiers on 539A/B/C models. Requires circuit modifications.
- Bias Fuse Lamp Protection to protect the bias circuit from shorts—avoids damage to Bias potentiometer on tube testers without this protection.
- Plate Current Mod allows direct measurement with an external digital voltmeter in place of an ammeter on Hickok 539A/B/C tube testers—ideal for precision tube matching and logging.
Services provided at additional cost:
- Repairs to get the tube tester operating properly.
- Replace shorts indicator.
- Replace line adjust potentiometer.
- Replace power cord.
- Replace meter.
Requirements for a tube tester calibration:
- The meter movement should be operational and within specifications.
- Bias control working. There are no replacements for the bias pot except a donor tester.
- Transformer not burned out.
- All knobs must be present.
- No broken controls.
Calibration starts at $220 for Mutual Conductance Tube Testers. The 539 and 752 series of tube testers start at $312.
Package properly and insure against loss or damage. Shipping damage is not our responsibility. If the tube tester is not repaired or calibrated there is a $65 diagnostics charge.
Use the Repair Form to let me know you are sending your Tube Tester.
Hickok 539C Digital Meters
I can convert your meters to Digital Meters. Digital meters are more accurate and robust, eliminating the overload conditions that burn out analog meters. Contact me for details.
Package properly and insure against loss or damage. Shipping damage is not our responsibility.
If the tube tester is not repaired or calibrated there will be a $65 diagnostics charge.
Emission Tube Testers (B&K, EICO, Precision, Sencore, Triplett)
Precision Tube Testers were manufactured by the Precision Apparatus Corporation from the 1940s to the 1960s. I have restored quite a few Precision tube testers, and I am quite impressed with the craftsmanship and quality in these vintage units. I really like the old wood cases.
They are all Emission type Tube Testers. Precision’s “Electronamic” design in some models of Tube Testers was an attempt to improve on the basic Emission tube testing principle.
Some of the models included VOM functionality. Precision called this “Set Analyzing”. I try the best I can to restore the VOM functions in these old testers. I have come up with modern replacement battery systems so the Ohm Meter functionality will work properly. It is amazing that the VOM functionality in these old testers is still quite accurate after all these years.
Most of the testers include battery testing functionality. I generally do not bother with this functionality. The value of having the battery testing feature is not worth the cost and effort to troubleshoot and repair. Most of the time it works properly anyway.
They have a one-year warranty that does not include burning out of the meter movement. Since meter movements are very delicate, they can be burned out very easily by testing a shorted tube, or from improper test settings. I find the most common functional failure with these old testers is bad meter movements.
I will purchase tube testers or parts. Contact me with what you have and I will make an offer. Let me know if the unit works and what parts are missing and send a picture so I can evaluate the unit.
The service consists of the following:
- Install proper fuses.
- Replace resistors in the tube testing circuit related to calibration. Especially carbon composition resistors that drift in value over time.
- Replace capacitor in shorts indicator circuit and resistors as necessary.
- Clean controls and lubricate push button/lever mechanisms as necessary.
- Verify proper meter operation.
- Verify calibration with known quality tubes – power, rectifier, and pre-amplifier.
Services provided at additional cost:
- Repairs to get the tube tester operating properly.
- Replace power cord and/or fused plug.
- Replace 4.5 volt battery for “Set Testing” operation in Precision testers.
- Replace rectifier tubes.
- Replace line adjust potentiometer.
- Replace grid/plate cap lead(s).
- Replace rubber feet on case.
Requirements for a tube tester calibration:
- The meter movement must be operational. I can source some Precision meters.
- The shorts indicator must be the proper one for the tube tester and working.
- All knobs must be present.
- No broken controls.
- Case not damaged. Ugly cases accepted if not damaged.
Calibration starts at $150.
Precision 920 and 10-12 Meter Replacement
I now have replacement meters for the Precision 920 and 10-12 tube testers. Send your tube tester and I will replace the meter, lubricate the controls, and calibrate the tester. You can extend its useful life by replacing the meter. The most common failure in the old tube testers is the meter. Because new meters are more robust, they can better tolerate incorrect settings of the tester.
The calibration with meter replacement is as stated above for the Precision Tube Testers.
Meter replacement and Calibration is $318.
Contact me and I can go over your options for repairing and calibrating your tube tester.
Package it properly and insure against loss or damage. Shipping damage is not our responsibility. If the tube tester is not repaired or calibrated there is a $65 diagnostics charge.
Use the Repair Form to let me know you are sending your Tube Tester.
