05-21-2014, 11:42 AM
Your tube line up smells a lot like a AC / DC set, would like to hear more.
My experience is, the older tubes get and are still working well the less likely they are to go bad. If the manufacturer could pull a perfect vacuum and make a perfect seal they would last forever. The Getter inside the tube scavenges oxygen left inside after manufacture to help with less than perfect.
The mini tubes used in amplifiers for the first undersea ATT telephone cable from AL to WA (in 56 I think) was still working the last I had contact in area of ATT. The tubes were manufactured in lots of 10K and I forget the long burn in schedule. Any tube failed the entire lot was scrapped.
Watch hooking up the common lead on any AC powered test equipment. Measure the chassis common to common voltage first. Oldies plugs were not polarized and AC / DC units often had hot chassis.
First let admit I LOVE tube testers. They are most likely the first test equipment I ever got to operate. They were free to use at drug stores and supermarkets. Most places had a step stool to get up to set the switches, knobs and levers. Plug in a tube and actually see a meter move when the "test" was done.
My EICO has been home here for more than 30 years. The Hickok less than a year, just because I have wanted one for years, but never gotten around to buying.
Next: Jerry's' & Codefox statements that the radio (or whatever) is the best tube tester is spot on. Jerry's experience with tested tubes echoes mine. Your 7A tubes require Loctal sockets
A tube tester will tell you if the filament is good or there are pins shorted that shouldn't be.
You will get an indication if the tube may or not be good. In general if a tube tests in the "good" range it will work and if it is way down in the "poor" it probably won't. But that is only an indication as far as consumer affordable testers were concerned.
A tube may not work for V1, but works fine for V5 no mater what your tester indicates.
Tube testers are powered from 60 Hz. Most have B+ from a full wave supply which is 120 Hz. Not close to actual application frequencies.
TA - Thanks for the information on the Weston & HeathKit units. Didn't know about them and YOU BET it would be better. Something new on my want list.
As Ron says tapping the meter is often necessary. I remember doing it standing on a stool to get high enough to use a tester in a drug store.
My choice of beginning test equipment again echoes Jerry's (subject to reordering priority at any time).
1. DVM The cheepie from rat shack / harbor freight is more accurate than a mortal could afford in the 50's. A small warning if you are fortunate enough to have an old manual with voltage readings. Old VOM had nominal 20K / V input while DVM are in the meg range. If you find a lower voltage you have a problem, higher probably not.
2. Soldering / desoldering equipment. This is one area to spend more at the get go.
3. Scope, 10X leads and isolation transformer. Old is fine for broadcast radios. Many would place the scope in last place because of the learning curve.
4. Signal generator.
5. Lumped as depends on what you are trying to accomplish. Tube tester, inductance meter, cap meter, decade resistance box, decade capacitance box, lab power supply, dip meter, frequency counter
I readily admit I am a test equipment junkie.
My experience is, the older tubes get and are still working well the less likely they are to go bad. If the manufacturer could pull a perfect vacuum and make a perfect seal they would last forever. The Getter inside the tube scavenges oxygen left inside after manufacture to help with less than perfect.
The mini tubes used in amplifiers for the first undersea ATT telephone cable from AL to WA (in 56 I think) was still working the last I had contact in area of ATT. The tubes were manufactured in lots of 10K and I forget the long burn in schedule. Any tube failed the entire lot was scrapped.
Watch hooking up the common lead on any AC powered test equipment. Measure the chassis common to common voltage first. Oldies plugs were not polarized and AC / DC units often had hot chassis.
First let admit I LOVE tube testers. They are most likely the first test equipment I ever got to operate. They were free to use at drug stores and supermarkets. Most places had a step stool to get up to set the switches, knobs and levers. Plug in a tube and actually see a meter move when the "test" was done.
My EICO has been home here for more than 30 years. The Hickok less than a year, just because I have wanted one for years, but never gotten around to buying.
Next: Jerry's' & Codefox statements that the radio (or whatever) is the best tube tester is spot on. Jerry's experience with tested tubes echoes mine. Your 7A tubes require Loctal sockets
A tube tester will tell you if the filament is good or there are pins shorted that shouldn't be.
You will get an indication if the tube may or not be good. In general if a tube tests in the "good" range it will work and if it is way down in the "poor" it probably won't. But that is only an indication as far as consumer affordable testers were concerned.
A tube may not work for V1, but works fine for V5 no mater what your tester indicates.
Tube testers are powered from 60 Hz. Most have B+ from a full wave supply which is 120 Hz. Not close to actual application frequencies.
TA - Thanks for the information on the Weston & HeathKit units. Didn't know about them and YOU BET it would be better. Something new on my want list.
As Ron says tapping the meter is often necessary. I remember doing it standing on a stool to get high enough to use a tester in a drug store.
My choice of beginning test equipment again echoes Jerry's (subject to reordering priority at any time).
1. DVM The cheepie from rat shack / harbor freight is more accurate than a mortal could afford in the 50's. A small warning if you are fortunate enough to have an old manual with voltage readings. Old VOM had nominal 20K / V input while DVM are in the meg range. If you find a lower voltage you have a problem, higher probably not.
2. Soldering / desoldering equipment. This is one area to spend more at the get go.
3. Scope, 10X leads and isolation transformer. Old is fine for broadcast radios. Many would place the scope in last place because of the learning curve.
4. Signal generator.
5. Lumped as depends on what you are trying to accomplish. Tube tester, inductance meter, cap meter, decade resistance box, decade capacitance box, lab power supply, dip meter, frequency counter
I readily admit I am a test equipment junkie.
