03-14-2021, 03:57 PM
From what I understood the original phonograph had an electromagneic pickup, as the transformer is 0.2 Ohm to 5,500 Ohms.
The transformer was omitted, probably due to the V-M phonograph having the piezo pickup.
I re-did the wires with proper grounding, both the motor and the phonograph chassis (via the Phono cable). Also installed new RCA cables, both males with the F-F RCA slug in between them.
The grounding scheme is as follows:
The RCA pigtail from the radio has the shield as the GND and the centrai wire as the signal; the turntable has twin shielded wire; Both shield and one wire are connected at the shell; then the signal and the wire go to teh cartridge while the shield only connects to the turntable's chassis, therefor avoiding GND loop.
The phonograph plays fine, and this with the old needle.
But. At a decent volume the hum is pronounced.
I did an experiment: disconnected the turntable with no reduction in hum, shorted the Radio's pigtale RCA, also with no reduction and then shorting the Phono input right at the tube socket - same result.
Significant reduction to very acceptable level occurs with me touching the chassis or simply connecting it to Earth GND.
I intend to use a 3-prong Earthed plug for this reason only.
The transformer was omitted, probably due to the V-M phonograph having the piezo pickup.
I re-did the wires with proper grounding, both the motor and the phonograph chassis (via the Phono cable). Also installed new RCA cables, both males with the F-F RCA slug in between them.
The grounding scheme is as follows:
The RCA pigtail from the radio has the shield as the GND and the centrai wire as the signal; the turntable has twin shielded wire; Both shield and one wire are connected at the shell; then the signal and the wire go to teh cartridge while the shield only connects to the turntable's chassis, therefor avoiding GND loop.
The phonograph plays fine, and this with the old needle.
But. At a decent volume the hum is pronounced.
I did an experiment: disconnected the turntable with no reduction in hum, shorted the Radio's pigtale RCA, also with no reduction and then shorting the Phono input right at the tube socket - same result.
Significant reduction to very acceptable level occurs with me touching the chassis or simply connecting it to Earth GND.
I intend to use a 3-prong Earthed plug for this reason only.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
