09-09-2020, 09:38 AM
The ways things are going with my Murphy V659X another line output transformer will have to be found and fitted.
The set works OK for an hour or so but if left on longer than an hour the left side of the picture becomes compressed and the oil filled transformer can becomes very hot, in fact too hot to touch.
The set has an ultrasonic remote control system. The channel change has never given any problems but the sound muting has never worked, this week I decided to sort out the sound control in the remote control receiver.
For starters the mute button on the remote control handset had jammed. Dismantle and reassemble the handset. but that doesn't solve the mute function fault. The remote control receiver is tuned to 43.6Kc/s for channel change and 46.6Kc/s for the muting. The channel change system has never given any problems but there's never been any activity in the sound control channel. The tuning coil coil was found to have green spot corrosion on the tags of the coil assembly. That fixed a pulse of 20volts is available at the grid of the relay driver valve V23A (6/30L2)
But still the mute function doesn't work. The relay wasn't responding to to signal from the remote control although the pulse signal is present at the anode of the valve. Just a sticky relay which responded to little adjustment. Finally, the sound muting switching contacts needed attention, that done the sound can now be controlled from the remote control handset. On the Murphy the level of the sound can be adjusted by a pre-set control situated at the back of the receiver.
Fully muted or the sound level of choice.
As you would expect from Murphy the remote control handset is a beautiful piece of over-engineering.
Geordie McBoyne.
The set works OK for an hour or so but if left on longer than an hour the left side of the picture becomes compressed and the oil filled transformer can becomes very hot, in fact too hot to touch.
The set has an ultrasonic remote control system. The channel change has never given any problems but the sound muting has never worked, this week I decided to sort out the sound control in the remote control receiver.
For starters the mute button on the remote control handset had jammed. Dismantle and reassemble the handset. but that doesn't solve the mute function fault. The remote control receiver is tuned to 43.6Kc/s for channel change and 46.6Kc/s for the muting. The channel change system has never given any problems but there's never been any activity in the sound control channel. The tuning coil coil was found to have green spot corrosion on the tags of the coil assembly. That fixed a pulse of 20volts is available at the grid of the relay driver valve V23A (6/30L2)
But still the mute function doesn't work. The relay wasn't responding to to signal from the remote control although the pulse signal is present at the anode of the valve. Just a sticky relay which responded to little adjustment. Finally, the sound muting switching contacts needed attention, that done the sound can now be controlled from the remote control handset. On the Murphy the level of the sound can be adjusted by a pre-set control situated at the back of the receiver.
Fully muted or the sound level of choice.
As you would expect from Murphy the remote control handset is a beautiful piece of over-engineering.
Geordie McBoyne.
