wiring for ST35

[MLVA123]

OK, so the board is stuffed!
Next up is to finish off my chassis fine tuning. I have decided to go with the AC power inlet (mouser #161-0707-1-187) rather than the cord - this saves all that hassle with the "D" grommet. Just have to go widen that hole in the chassis for it, then I can prime, paint, and decorate.

I do have some wiring questions though. I saw on another DIY tube amp site about the virtues of twisting some wiring to avoid interference. I also noticed in the pics that Shannon posted that there was some kind of shielded wiring used there. Any guidelines or suggestions from the group on do's and do-not's for wiring?

-Michael

[Shannon Parks]

I'll throw in a couple obvious ones:
-Don't let any wires 'rest' on the side edges of the board where the filament AC is at.
-Make sure your input signal lines aren't touching any AC going to the ON-OFF switch.
-Also, make sure any chassis mounted hardware (eg rca jacks, speaker ground) gets grounded directly to the PCB instead of relying on just a chassis ground.

I'd like to hear some folks' suggestions for hook-up wire. Any cheap local suppliers for 18GA teflon coated wire?

Shannon

[EWBrown]

I've seen it advised to twist together all AC leads at least for teh power trannie. Twist the two (or 4) primary wires in one pair, and similarly, twist filament wires into their own pairs, and HV AC into its own pair/trio.
This will reduce any unwanted AC E or H field coupling.

The audio inputs should be shielded (ideal) or twisted pairs, and definitely keep them away from any AC wiring, to reduce or eliminate any AC hummmmmmmmmmm.

At least for my first unit, I plan on keeping all transformer leads at the original length, just in case I decide to relocate everything into a larger steel chassis at a later date.

/ed B in NH actually at work, where I should be working and not screwing off on the internet) :twisted: :lol: :shock:

[MLVA123]

I was looking through the new pics this morning - excellent job! I have a couple of questions. I noticed that there was some kind of sealant "goo" around the switches on the inside of the chassis. Is that silicone caulk? The other question pertains to the wiring - it appears that you chose to use the solderless connectors - did you just crimp those on or did you also solder them and then crimp them on? Can you use pliers for the crimping or do I have to cough up the $$ for one of them fancy crimping tools?

[Shannon Parks]

Hmm - the photos were supplied to me so I'm not sure about the silicone goo. Possibly it was meant to keep any rock or rattle out of it. I'll take a better look at the pix.
As per the connectors, I just use a pair of el-cheapo crimpers from my local hardware store (the wire stripper/crimper combo) with the compression spade terminals. Saw some yesterday for $2.99. No tinning necessary. I use the red collared spade terminals for most everything. The screws on the terminal blocks are #6. I have an empty box right here, and it says:

Ace Insulated Spade Terminals, 16-14AWG, 4-6 stud, 10pcs

The awesome thing about the amp I just posted was that it does indeed use these connectors 100%. You could disassemble the whole thing in a few minutes, paint the chassis and then reassemble it a couple weeks later (after the last coat of enamel has dried). Try that with point-to-point! :wink:

Shannon