I've started to reverse engineer the circuit, from the photo's point of view I'm referring to the 1st pic in post#5.
It doesn't show all the valve sockets because of the two transformers, never the less there's four of them, all B4's, for the purpose of description I'll call them left to right V1, V2, V3 & V4.
V1 is unidentified, V2 is a Mullard PM2, V3 is a Mullard but its ID number is missing, V4 is a Mullard PM1 HF.
Filaments: All 2 volts, fairly certain of that, all the filament pin 3 connections are all connected together and connect via a 6 ohm rheostat to the + 4 V terminal on the front panel, there are no other connections to that terminal.
Both pin 4 filament connections of V3 & V4 are connected together and are connected to the T terminal on the front panel, from there is a connection to the - 4 V terminal, both V3 & V4 pin 4 filament connections also connect to a three position lever switch (leaf type), that switch has four poles, two contacts for each pole, for the purposes of description I'll call that switch S1, later on in this thread I'll try and refer to them as S1a, b, c & d.
V3 & V4 filaments are in circuit at all times irrespective of S1 settings.
With S1 lever in the up position V1 & V2 filaments are in circuit.
With S1 lever in the center position V1 & V2 filaments are not in circuit.
With S1 lever in the down position V1 filament is out of circuit and V2 filament is in circuit.
So....That's the filament circuit sorted...Hopefully.
This subject is also being aired on the UKVRR forum in order to increase the chances of an ID.
More to come.
EDIT: There's a wire connected to pin 4 (filament) of V1, that wire runs to outside the unit, there's no ID tag on that wire.
Lawrence.
It doesn't show all the valve sockets because of the two transformers, never the less there's four of them, all B4's, for the purpose of description I'll call them left to right V1, V2, V3 & V4.
V1 is unidentified, V2 is a Mullard PM2, V3 is a Mullard but its ID number is missing, V4 is a Mullard PM1 HF.
Filaments: All 2 volts, fairly certain of that, all the filament pin 3 connections are all connected together and connect via a 6 ohm rheostat to the + 4 V terminal on the front panel, there are no other connections to that terminal.
Both pin 4 filament connections of V3 & V4 are connected together and are connected to the T terminal on the front panel, from there is a connection to the - 4 V terminal, both V3 & V4 pin 4 filament connections also connect to a three position lever switch (leaf type), that switch has four poles, two contacts for each pole, for the purposes of description I'll call that switch S1, later on in this thread I'll try and refer to them as S1a, b, c & d.
V3 & V4 filaments are in circuit at all times irrespective of S1 settings.
With S1 lever in the up position V1 & V2 filaments are in circuit.
With S1 lever in the center position V1 & V2 filaments are not in circuit.
With S1 lever in the down position V1 filament is out of circuit and V2 filament is in circuit.
So....That's the filament circuit sorted...Hopefully.
This subject is also being aired on the UKVRR forum in order to increase the chances of an ID.
More to come.
EDIT: There's a wire connected to pin 4 (filament) of V1, that wire runs to outside the unit, there's no ID tag on that wire.
Lawrence.
