Well it was a long day of working on the amp yesterday. I intended to post this update last night but it was 11:30pm when I gave up and went to bed.
I got the entire amp wired up, switched it on.... No smoke, fire, sparks. Okay that's good.
The valves warm up nicely and a horrendous hum develops. Ahhh @#*@*##*!
After plenty head scratching I disconnected the base and treble pots, and used a single ECC83 to the volume controls.
Less of a hum, that's good. Not good enough yet.
Rigged a quick input line and plugged in my phone. Played some music, low output, distorted. Even more @#**#@#&.
Tested some voltages, valve bias is wrong. My dad managed to figure out a fix, switched it on, the hum is back...
Poked around with a screwdriver, found that the mains transformer hadn't been grounded properly! Set to work rectifying that.
Switched it back on, slight hum, much better. More than acceptable as you won't be able to hear any of it when it's playing audio.
Hooked up the input line again, music plays. Great stuff! Sounds very nice and smooth, the tone seem just fine too, since I don't have any tone control right now.
So I set about hooking up all my inputs and outputs, and switches for them.
The switch is used to switch between outputs, one way will play the audio through the speaker panel, the other through the 3.5mm jack.
Blurry photo sorry, it was really late at this point. Here you see the thick white cabling, that is screened stereo cable so that I don't pick up hum as it makes it way across the chassis past components.
After finishing both switches connecting the inputs and outputs I hooked it up to the mains, plugged in my phone through auxiliary cable and plugged in two speakers, time to test both amps at the same time!
Plugged in, switch on, music sounds great, I started to adjust volume of each speaker individually, hang on. One volume control set one speaker going fine, the second one altered the same speaker and distorted it like hell.
This was the point I went to bed, no rational decisions can be made with the tiredness.
Came back to it this morning with my dad, he discovered one of the 0.05 capacitors is pretty much dead, he made a slight adjustment to the circuit and I tested again, great sound through both speakers and independent volume controls working correctly!
Right now I'm just happy that it works. Several points I thought this entire project was going to fail.
Next steps are to get the tone controls included to the circuit and replace the dying capacitors.
When I bought a load of specific resistors needed from maplin it turned out half of them weren't rated nearly as high as I needed them, that's why you can see a lot of reused resistors from the donor radios.
Maybe in the time I have it at him I will cosmetically clean it up, I'm thinking a brushed finish on the chassis and need to cut down the length of the pots, clean up and paint the knobs, and so forth.
Now I'm travelling home (via my girlfriends) so when I get home tonight I will rig it up and do a video for you guys!