22-12-2023, 04:51 PM
I've just tried replacing the EB91 with silicon diodes but it throws the IF tuning off quite a bit and there is even less DC and AF output. I'll try and get a replacement valve instead.
One thing I've noticed though is that when there is no RF signal then there is 450mV across the detector capacitor, but with the silicon diodes there is just a couple of mV. I wonder if it is some heater / cathode leakage in the diode, I cant measure anything when the vale is out of circuit, but there is no great hum either.
DC output with silicon diodes is 3.1 volts DC, with EB91 it is 5.3
The diodes I'm using are BAW62 - I could try 1N4148 or even OA81!
D
One thing I've noticed though is that when there is no RF signal then there is 450mV across the detector capacitor, but with the silicon diodes there is just a couple of mV. I wonder if it is some heater / cathode leakage in the diode, I cant measure anything when the vale is out of circuit, but there is no great hum either.
DC output with silicon diodes is 3.1 volts DC, with EB91 it is 5.3
The diodes I'm using are BAW62 - I could try 1N4148 or even OA81!
D
