19-05-2024, 12:07 PM
Kinds of Valve tester
Simple Go/Fail
Hickock and very early AVOs
Very limited and may "fail" usuable valves. Only much use for parts and sockets.
I've used a couple of these. Horrible.
Advanced Go/Fail
Mullard High speed tester.
Very rapid but can't test anything not programmed, You can't do what if. Designed for production or testing stock or TVs. Not a great idea for home workshop.
Characteristic tester
The AVO models from mid 1950s. Later more advanced models added AC gain and electrode leakage tests. They are calibrated with direct manual separate controls for heater/filament, g1 volts, g2 volts and Anode. Usually have links that can be replaced by a resistor for magic eyes or pentode-triode or hexode-triode mixers. Can test any valve.
You can manually curve trace by writing it all down (or spreadsheet). Note a DVM will give a different reading to the built in knob legends except for heater / filamment as they may use a half wave unsmoothed supply.
https://www.radiomuseum.org/r/avo_valve_...met_2.html
Read the explination.
Probably the ultimate original tester. I had extended loan of a VCM163. I had to replace both meters and make new scales.
Also a lesser AVO where I replaced the nearly dead meters with easy to get cheap one and an op-amp driver.
A problem with old testers is failure of the rotary switches that select socket to voltage. On a self-build use two sets of 2mm wander plugs and sockets.
Meter failure or reduced sensitivity is common on old AVO testgear except the actual AVO meters.
The Sussex tester is somewhere between a Hickock and VCM163. It's really late 1960s home brew.
Curve Tracer
A microprocessor based tester is now the cheapest solution.
https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
There are now several versions. You can peer an unmarked valve and figure out possible connections, and measure for filament/heater and connect to a bench PSU (start at 0.5V) to see likely voltage. Filaments/ heaters vary from 0.7V (two hearing aid valves in series off 1.4V and a 22V anode) to 117V for some direct on USA mains rectifiers.
I made a mistake wiring mine like an AVO. I should have used a plug-in with the valve socket. The inductance is too high on some of the sockets and this reduces the heater voltage.
https://www.youtube.com/watch?v=JhNvdOW2zX4
On here http://www.radicalvalves.com/index/
Test in the equipment
This is simplest if the equipment voltages make sense. Tektronix argued this was the best way for repair shops.
Check value of cathode resistor, g2 resistor with set off.
Check all the socket voltages with valve unplugged (use separate socket and wires for series heater/filament). The g1 must be zero or less unless a car radio.
See volts on cathode resistor and calculate anode current.
Ad Hoc tester
A collection of PSUs, meters etc to test occasionally.
Next some PSU and leakage test ideas for Ad hoc testing.
Simple Go/Fail
Hickock and very early AVOs
Very limited and may "fail" usuable valves. Only much use for parts and sockets.
I've used a couple of these. Horrible.
Advanced Go/Fail
Mullard High speed tester.
Very rapid but can't test anything not programmed, You can't do what if. Designed for production or testing stock or TVs. Not a great idea for home workshop.
Characteristic tester
The AVO models from mid 1950s. Later more advanced models added AC gain and electrode leakage tests. They are calibrated with direct manual separate controls for heater/filament, g1 volts, g2 volts and Anode. Usually have links that can be replaced by a resistor for magic eyes or pentode-triode or hexode-triode mixers. Can test any valve.
You can manually curve trace by writing it all down (or spreadsheet). Note a DVM will give a different reading to the built in knob legends except for heater / filamment as they may use a half wave unsmoothed supply.
https://www.radiomuseum.org/r/avo_valve_...met_2.html
Read the explination.
Probably the ultimate original tester. I had extended loan of a VCM163. I had to replace both meters and make new scales.
Also a lesser AVO where I replaced the nearly dead meters with easy to get cheap one and an op-amp driver.
A problem with old testers is failure of the rotary switches that select socket to voltage. On a self-build use two sets of 2mm wander plugs and sockets.
Meter failure or reduced sensitivity is common on old AVO testgear except the actual AVO meters.
The Sussex tester is somewhere between a Hickock and VCM163. It's really late 1960s home brew.
Curve Tracer
A microprocessor based tester is now the cheapest solution.
https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
There are now several versions. You can peer an unmarked valve and figure out possible connections, and measure for filament/heater and connect to a bench PSU (start at 0.5V) to see likely voltage. Filaments/ heaters vary from 0.7V (two hearing aid valves in series off 1.4V and a 22V anode) to 117V for some direct on USA mains rectifiers.
I made a mistake wiring mine like an AVO. I should have used a plug-in with the valve socket. The inductance is too high on some of the sockets and this reduces the heater voltage.
https://www.youtube.com/watch?v=JhNvdOW2zX4
On here http://www.radicalvalves.com/index/
Test in the equipment
This is simplest if the equipment voltages make sense. Tektronix argued this was the best way for repair shops.
Check value of cathode resistor, g2 resistor with set off.
Check all the socket voltages with valve unplugged (use separate socket and wires for series heater/filament). The g1 must be zero or less unless a car radio.
See volts on cathode resistor and calculate anode current.
Ad Hoc tester
A collection of PSUs, meters etc to test occasionally.
Next some PSU and leakage test ideas for Ad hoc testing.
