Okay, now for some some shitty webcam pics:
The PCB was made at home using this tutorial:
http://thomaspfeifer.net/direct_toner_pcb.htmThis method is as simple as it gets, and cost me around 10 euros. Since i never tried something like that before, it actually surprised me how well it works.
If you want to try this too, i want to add a thing or two:
If the transfer process didnt go well, and you have disconnected traces but dont want to repeat the whole printing/ironing, you can just repair errors by painting them over with a waterproof marker, like an "edding". Just make sure you paint over multiple times, so the layer gets thick enough to resist the etching. If you use sodium persulfate, it is best to keep the etching bath at around 45°C, this way the whole process doesnt take too long.
The tricky part is to get the two layers eactly on top of each other, as you can see i wasn't very sucessful. At least the offset is much smaller on the greater part of the board, i hope it wont be a problem as long as i solder carefully enough.
I've done about half of the resistors so far, im really slow because i try to be as pedantic as possible about checking each resistor with the layout before soldering. This way i hope to eliminate possible remaining errors.
I've never worked with tubes before, so maybe you can help me on the following. Im not sure if i overlooked some problem:
My idea was to change the tube heaters to 6.3V paralell. This is done by an additional resistor in the heaters power supply, pin 5 and 4 are connected to 6.3 volt and pin 9 is grounded. The reason for this is that i want to use russian 6n2p tubes, wich are equivalent to ecc83 except they only accept paralell heating (ecc83 accept both 12.6 and 6.3 volts). The power supply i got is a 12vac/1A, so it should handle the extra current. My only concern so far is that the bigger heating curretn adds more noise to this already noisy machine. Of course you can say its a bit pointless, since you can get ecc83's easily, but i have a couple of 6n2p-ev's lying around, i'm a cheapskate, and i like the irony of playing hippie music on some kind of good old russian military equipment.
I also got a question about the transformer. Blackbunny stated you could use a 15/230 trafo instead of the hard-to-get original 15/250. I think he is right, and maybe im a bit too pedantic, but the 15/230 has about 8% less winding ratio. So i want to use a 12/230 and reduce the primary voltage a bit with a resistor to be as close to the original as possible. What do you think? Do +/- 10% in the tube voltage even matter to the sound?
If you want to take a look at it, theres the modified layout and a simulation of the tube power supply i did out of curiosity in the attachments. Youll need a program like ltspice to open and run it.
Thanks to everyone who helped bringing this projects alive!
by ssmc » 05 Jul 2011, 04:22 
and in a week or so I plan to have this PCB made.
)
. I had many errors to trace and correct, no errors in the circuit or the layout (as far as i can tell), but many due to my almost non-existant soldering skills.
