24-10-2023, 04:50 AM
I think the AVO 163 is more impressive. That Mullard is really for factories or checking the huge number of valves in a TV. It's a high speed tester, hence the cards instead of switches. The later good AVOs can be used to test any valve if you have the data, you don't need the AVO setting chart. Or if you have the pin out and a good guess at the heater voltage you can use it to work out the data for a valve. I'm pretty sure some computers still used punched cards by the time the Mullard tester ended production. The original was released in 1950 and the first ForTran compiler was 1956.
https://mullard.org/blogs/news/1950-the-...ary-design
Here is it is again. Not sure if the same version. The "??" means the date is a guess and it's too late.
https://www.radiomuseum.org/r/mullard_hi...ester.html
Better info here:
http://www.thevalvepage.com/testeq/mulla.../vtest.htm
An AVO CT160, AVO VCM MkiV or VCM163 are more use.
I also fitted an interface to a VCM163 so an Tektronix Transistor curve tracer could trace valves. Avo used for socket, pin assignment, heater and g2 volts. My friend has both.
They are of limited use, but a time saver, if you have the working gear because you can measure the in circuit currents to know about emission, or leakage to a grid. A 400V capacitor leakage tester can be used to test electrode leakage, hot and cold.
However while I've never needed one to repair/restore a radio, record player, tape recorder or amp I'd certainly use one to test bought valves on arrival to stock if I was building and selling amps. I'd relied on one in the local friendly TV shop in the late 1960s and early 1970s initially as I'd not realized the device itself could be used to test the valve.
I had a loan of this: https://www.radiomuseum.org/r/avo_valve_...met_2.html Undoubtedly very good.
I replaced the meter in this, https://www.radiomuseum.org/r/avo_valve_...er_mk.html or something similar, for a friend by using an op-amp and resistor to simulate the original meter and drive a 1mA meter with a new scale made by scan & edit of the original. I didn't have a posh expensive low offset instrument op-amp to hand so I built a stand-alone supply and same op-amp to derive a dynamic offset (to allow for supply drift) at input of the meter drive amp. So mechanical zero of meter without power and then preset offset & gain (save having to use precision resistors) to calibrate meter. No noticeable drift after initial setup.
I also looked at an old Hickock or something, a basic go/no tester that was pretty useless because many old valves won't have original spec emission and yet will be fine in use. Even as low as 20% or 30% can give acceptable performance in loads of old gear and some are hardly available such as an EBL31. The old go/no tester was also very limited on valve bases and voltages compare to the later AVOs (Maybe CT160 and later).
A curve tracer (and these are cheap now for valves) is more use when designing new gear if you have only limited data on the valves, or the data only assumes a particular HT. It's a bit slow for testing valves. https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
I have version one of that.
https://mullard.org/blogs/news/1950-the-...ary-design
Here is it is again. Not sure if the same version. The "??" means the date is a guess and it's too late.
https://www.radiomuseum.org/r/mullard_hi...ester.html
Better info here:
http://www.thevalvepage.com/testeq/mulla.../vtest.htm
An AVO CT160, AVO VCM MkiV or VCM163 are more use.
I also fitted an interface to a VCM163 so an Tektronix Transistor curve tracer could trace valves. Avo used for socket, pin assignment, heater and g2 volts. My friend has both.
They are of limited use, but a time saver, if you have the working gear because you can measure the in circuit currents to know about emission, or leakage to a grid. A 400V capacitor leakage tester can be used to test electrode leakage, hot and cold.
However while I've never needed one to repair/restore a radio, record player, tape recorder or amp I'd certainly use one to test bought valves on arrival to stock if I was building and selling amps. I'd relied on one in the local friendly TV shop in the late 1960s and early 1970s initially as I'd not realized the device itself could be used to test the valve.
I had a loan of this: https://www.radiomuseum.org/r/avo_valve_...met_2.html Undoubtedly very good.
I replaced the meter in this, https://www.radiomuseum.org/r/avo_valve_...er_mk.html or something similar, for a friend by using an op-amp and resistor to simulate the original meter and drive a 1mA meter with a new scale made by scan & edit of the original. I didn't have a posh expensive low offset instrument op-amp to hand so I built a stand-alone supply and same op-amp to derive a dynamic offset (to allow for supply drift) at input of the meter drive amp. So mechanical zero of meter without power and then preset offset & gain (save having to use precision resistors) to calibrate meter. No noticeable drift after initial setup.
I also looked at an old Hickock or something, a basic go/no tester that was pretty useless because many old valves won't have original spec emission and yet will be fine in use. Even as low as 20% or 30% can give acceptable performance in loads of old gear and some are hardly available such as an EBL31. The old go/no tester was also very limited on valve bases and voltages compare to the later AVOs (Maybe CT160 and later).
A curve tracer (and these are cheap now for valves) is more use when designing new gear if you have only limited data on the valves, or the data only assumes a particular HT. It's a bit slow for testing valves. https://www.dos4ever.com/uTracer3/uTracer3_pag0.html
I have version one of that.
