Tube Tester Restoration
Precision Tube Testers
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. Batteries are tested with a load resistor and will show the condition of a battery under load. I generally do not concern myself 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.
Sometimes I have tube testers for sale. These units include written manuals and updated tube test data. They have a one-year warranty that does not include burning out of the meter movement. Tube tester meter movements are very delicate and 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 meter movement burnout.
I will also purchase any Precision Tube tester or parts you may have. Email me at email@example.com with what you have and I will make an offer. Let me know if the unit works and what parts are missing. Include a picture so I can evaluate the unit.
- Clean all switches and controls with contact cleaner.
- Replace any missing, broken, or incorrect buttons and knobs.
- Replace capacitors.
- Replace out of spec resistors – especially in the tube testing circuitry.
- Replace power cord.
- Replace Elmenco fused plug if missing.
- Verify/replace fuses for proper protection.
- Test and replace neon shorts indicator lamp if necessary.
- Restoration of VOM functionality if possible. I do not repair or re-calibrate the VOM features. This functionality is not worth the cost or effort to restore. Usually a new battery will get the Ohms functionality working.
- Replacement of bad meter movements if possible. Many of these testers have modern meter movement equivalents. This is expensive and I try not to do it unless the tester is in really good shape and is worth the expense. Replacement of a meter movement in a tester with VOM functionality will change the circuitry enough so the VOM features will no longer be accurate. Tube testing can be re-calibrated.
- Calibration using a 6L6 tube of known emission.
- Verify roll chart is working. I don’t try to update the roll chart. I have printed documentation for all these testers for older and newer tubes that I use when testing tubes. I don’t want to take the time to position the roll chart when I need to test a tube, and I’d prefer not to damage the chart from over use.
- Refinish wood cabinets. Tube testers were used by radio and TV Repair shops and saw a lot of use. The wood cabinet finishes are all badly worn, and many have damage to the wood itself.
- Recondition all cabinet hardware. The cabinet hardware is cleaned and oiled so it will work properly.
- Replace rubber feet.
- Replace handle if missing or broken.
Precision Tube Tester Manuals and Data Charts can be downloaded at Chris’s Old Radios.
Hickok Tube Testers
Hickok tube testers are mutual conductance type tube testers and are highly prized for their quality. If you want to match tubes, you need a mutual conductance tube tester. Some of the Hickok tube testers do not have enough resolution in the readings to match tubes. The Hickok 539 series, and the 750 series are some of the best for tube matching. We restore some Hickok tube testers and can discuss with you the cost to repair and calibrate your tube tester. Your tube tester cannot be repaired if the Bias potentiometer is bad. They were made custom for Hickok tube testers and are no longer available. If you have a tube tester with a bad Bias pot, consider it a boat anchor. It cannot be repaired unless you salvage a Bias pot from another tube tester.
Contact me at sales@VintageTubeElectronics.com and I can go over your options for repairing and calibrating your tube tester.
Posted on November 27, 2016 - by DLandon
The Heathkit IO-102 is a transistor based oscilloscope. I replaced the electrolytic capacitors and some transistors that were very temperature sensitive and caused the unit to drift badly. This unit is used regularly on my test bench. I built one of these from a kit many years ago, but not this one.
Posted on November 27, 2016 - by DLandon
This Precision EV-10A was brought to me by a Customer wanting to get it fixed and working again. When this tester was made, they installed .01 uf RF filter capacitors across the AC line and ground. The paper capacitors used then were not made to withstand the 110 Volt 60Hz power line voltage and the […]