05-04-2018, 10:43 PM
The Dublin made Pye 69A had been performing very well until this week. The problem is instability in the IF amplifier. The fault turned out to be the 8mfd electrolytic capacitor across the HT supply, it had gone OC.
As an extra precaution against RF and IF instability a 0.1mfd capacitor has been connected across the HT supply to the FC and IF amplifier valves.
The 0.001mfd capacitor connected to anode to anode of the QP25 push-pull output valve was found to be open circuit, actually it was a brown Hunts make capacitor and it had simply disintegrated into bits.
Now the set performs better than ever on medium and short wavebands, not so good on LW.
Geordie McBoyne.
As an extra precaution against RF and IF instability a 0.1mfd capacitor has been connected across the HT supply to the FC and IF amplifier valves.
The 0.001mfd capacitor connected to anode to anode of the QP25 push-pull output valve was found to be open circuit, actually it was a brown Hunts make capacitor and it had simply disintegrated into bits.
Now the set performs better than ever on medium and short wavebands, not so good on LW.
Geordie McBoyne.
