21-03-2015, 09:45 AM
(This post was last modified: 21-03-2015, 09:57 AM by kevin.Hoyland.)
Alan,
The Advance 77B is the 4th valve volt meter I have. The other 3 are Marconi TF428B, Heathkit AV-3, Aerovox 77. To cut a long story short, none have probes with them. I keep reading that 99% of VTVM or VAVM HAVE IDENTICAL CIRCUIT inside. However, all have a different probe that needs to be shielded. So, back to the 77B. The manual says it has two probes a PL50 with a screened hood or a low capacity probe PL45. So Alan did you end up with a probe or not from the seller. I have a manual for the Heathkit AV-3 David sent to me. It shows the Probe with no screening, resistor or capacitor in it. It can be used for 1 to 300 volts, but with the other meters I have to say if you do not have a probe with shielding, you will not isolate low resistance from the meter movement, from the circuit that has been measured.
Kevin
The Advance 77B is the 4th valve volt meter I have. The other 3 are Marconi TF428B, Heathkit AV-3, Aerovox 77. To cut a long story short, none have probes with them. I keep reading that 99% of VTVM or VAVM HAVE IDENTICAL CIRCUIT inside. However, all have a different probe that needs to be shielded. So, back to the 77B. The manual says it has two probes a PL50 with a screened hood or a low capacity probe PL45. So Alan did you end up with a probe or not from the seller. I have a manual for the Heathkit AV-3 David sent to me. It shows the Probe with no screening, resistor or capacitor in it. It can be used for 1 to 300 volts, but with the other meters I have to say if you do not have a probe with shielding, you will not isolate low resistance from the meter movement, from the circuit that has been measured.
Kevin
