HI ,
Mooly:hbeat:
Hi, I have a 1970s British amplifier Ferrograph f307. I need help. Please help me. The voltage of the gold sealed tube thrust triode of this machine is 55v. What is the static voltage of the emitter R506? thank you,
I would replace that ancient Mullard light blue electrolytic first before it pukes all over the board and writes the amplifier off!
The Quiescent Current is between 25 and 35mA. that equates to between 7.5 and 10.5mV across R500 adjusted by varying the value of R518.
The Quiescent Current is between 25 and 35mA. that equates to between 7.5 and 10.5mV across R500 adjusted by varying the value of R518.
And I'd also have some close look at thal small resistor next to the big 100 k one. Both apparently are replacements, and the smaller one's wattage might not be apt.
Btw, I'd really be interested in having a look at the schematics of this unit. Are there two germanium transistors beneath R506 and it's neighbour?
Best regards!
Edit: Found the schematics!
Btw, I'd really be interested in having a look at the schematics of this unit. Are there two germanium transistors beneath R506 and it's neighbour?
Best regards!
Edit: Found the schematics!
Yes, I directly separated the collector of the triode, plugged in the ammeter, adjusted the fine adjustment, adjusted 35mA on both sides, and the sound was great. When the machine came back, the value of the replaced RS old electrolytic capacitor was the same as the original. I detected the voltage value, which was the same as the other side. The state was very good, the sound improved a lot, and the working state was great. The green line in the picture was the fine adjustment of the current, which was specially shown in the picture, Show it to friends who want to help. Thank you,
Yes, both are germanium transistors. I carefully compare the capacitors on the other side. In fact, they are electrolytic capacitors with the same capacity and voltage. It's great. The voltage on both sides is the same, the sound is the same, and the bias current on both sides is the same. Thank you for your help,