09-04-2015, 03:54 PM
O.K., I've been putting a few hours into this project and I guess it's been a learning curve. The truth is this is hard radio for my actual level but nothing ventured, nothing gained.
Here is what I have found so far:
The AF117 transistors have a screen leak. I'm not quite sure how significant this will be as I figure there are other issues. The screen as far as I'm aware is colour coded black. I was getting some Ohms reading between the screen and the blue collector lead. Not an infinity resistance. And the same applies to the other AF117's. I was soon locking into vintage radio discussions on the AF117's and a lot of the guys were suggesting to cut the screen lead off but many experts are advising it's far better to remove the transistor and subject to a high voltage capacitor "blast".
Tests between the P/N junctions are reading fine. Between base and collector/emitter any reading only happens in a single direction. The other is infinity. So, my best is the transistors ought to be removed and the capacitor "blast" used to hopefully cure the screen leak. I don't have a capacitor but am wondering if any chance of using a battery in series to get 50 volts D.C. or around.
Sure I could ditch the transistors but it would really devalue the radio.
Something else very weird. I was using a PSU at 9 volts supply and the radio is now humming. However, I noticed the PSU voltage will just drop off and the neon light goes out. At that point it's output is a few millivolts. So, something very wrong there. I ask myself could the speaker coil be cancelling the voltage from the PSU or is it an internal short of the main power caps?
Anyway, I've still been feeling a bit discouraged over all of this as I ask myself have I wrecked this radio somehow? I think the truth is at my present level I'm not good enough yet to understand all the ins and outs of a circuit so have had to relay on notes and blindly put ear-jack wires back to where my sketches indicate. Perhaps there was a simple mistake somewhere? Or maybe what happened was it just briefly gave a last gasp.
Here is what I have found so far:
The AF117 transistors have a screen leak. I'm not quite sure how significant this will be as I figure there are other issues. The screen as far as I'm aware is colour coded black. I was getting some Ohms reading between the screen and the blue collector lead. Not an infinity resistance. And the same applies to the other AF117's. I was soon locking into vintage radio discussions on the AF117's and a lot of the guys were suggesting to cut the screen lead off but many experts are advising it's far better to remove the transistor and subject to a high voltage capacitor "blast".
Tests between the P/N junctions are reading fine. Between base and collector/emitter any reading only happens in a single direction. The other is infinity. So, my best is the transistors ought to be removed and the capacitor "blast" used to hopefully cure the screen leak. I don't have a capacitor but am wondering if any chance of using a battery in series to get 50 volts D.C. or around.
Sure I could ditch the transistors but it would really devalue the radio.
Something else very weird. I was using a PSU at 9 volts supply and the radio is now humming. However, I noticed the PSU voltage will just drop off and the neon light goes out. At that point it's output is a few millivolts. So, something very wrong there. I ask myself could the speaker coil be cancelling the voltage from the PSU or is it an internal short of the main power caps?
Anyway, I've still been feeling a bit discouraged over all of this as I ask myself have I wrecked this radio somehow? I think the truth is at my present level I'm not good enough yet to understand all the ins and outs of a circuit so have had to relay on notes and blindly put ear-jack wires back to where my sketches indicate. Perhaps there was a simple mistake somewhere? Or maybe what happened was it just briefly gave a last gasp.
