05-09-2023, 10:13 AM
The selenium diode stack gave inconsistent readings, so I have substituted a pair of 1N4007s.
I found a pair of AC128s and that restored the audio output. Setting the quiescent current is tricky now, the sliders are almost at the zero ends. In fact with them hard up against the stop there is still 0.8mA and it is impossible to get less than 2.2mA when they are moved away at all. I can live with that.
Difficult to arrange a heat sink, the XC131s are in their own dual heat sink that the AC128s will not fit. However running the set at high volume the transistors are still cold so I will just anchor them to the aluminium plate with hot melt.
Receives Gold on MW, twice! Nothing else and LW is silent. I suspect the twiddler has been here, the LW aerial trimmer is very loose.
I found a pair of AC128s and that restored the audio output. Setting the quiescent current is tricky now, the sliders are almost at the zero ends. In fact with them hard up against the stop there is still 0.8mA and it is impossible to get less than 2.2mA when they are moved away at all. I can live with that.
Difficult to arrange a heat sink, the XC131s are in their own dual heat sink that the AC128s will not fit. However running the set at high volume the transistors are still cold so I will just anchor them to the aluminium plate with hot melt.
Receives Gold on MW, twice! Nothing else and LW is silent. I suspect the twiddler has been here, the LW aerial trimmer is very loose.
Boater Sam.
