04-01-2012, 02:46 PM
It's bitten me, ungrateful sod 
I decided that I'd have to tidy up my shambolic wiring - you'll have noticed that I haven't posted a picture. So, I moved things around and dressed the cables to keep the Aerial wires away from the PSU and Output wiring, and gave it a better Earth. It was then a lot happier, with no hum that I could detect. Injecting an af signal into the Gram Socket via a couple of Caps produced a nice sounding output and monitoring V3 Anode showed a nice clean Sin wave. It's quite sensitive. 100mV RMS in gives a good solid output. What was the Output and Impedance of a 1930s Pickup? In the midst of this, as I was trying the Volume Control to see if it would oscillate, I caught the back of my hand on one of the PSU Caps. That made me jump, but fortunately there was no other damage.
It's all looking a lot better now, so next the rf stage. I measured the Resistance between the Main Chassis and the PSU Negative and it looks OK as the Volume Control is rotated, so next the valve. I hope I don't have to take the Volume Control/Reaction Assembly to bits 'cause that looks to be a bit of a sod. We'll see, but first a new R10 I think, just to see what difference it makes.
By that stage it was coming on to rain, I was hungry and I couldn't feel my feet, so I knocked off.
Alan
I decided that I'd have to tidy up my shambolic wiring - you'll have noticed that I haven't posted a picture. So, I moved things around and dressed the cables to keep the Aerial wires away from the PSU and Output wiring, and gave it a better Earth. It was then a lot happier, with no hum that I could detect. Injecting an af signal into the Gram Socket via a couple of Caps produced a nice sounding output and monitoring V3 Anode showed a nice clean Sin wave. It's quite sensitive. 100mV RMS in gives a good solid output. What was the Output and Impedance of a 1930s Pickup? In the midst of this, as I was trying the Volume Control to see if it would oscillate, I caught the back of my hand on one of the PSU Caps. That made me jump, but fortunately there was no other damage.
It's all looking a lot better now, so next the rf stage. I measured the Resistance between the Main Chassis and the PSU Negative and it looks OK as the Volume Control is rotated, so next the valve. I hope I don't have to take the Volume Control/Reaction Assembly to bits 'cause that looks to be a bit of a sod. We'll see, but first a new R10 I think, just to see what difference it makes.
By that stage it was coming on to rain, I was hungry and I couldn't feel my feet, so I knocked off.
Alan
