Sewing it all together: Wirings, nest stage and a prerequisite of concentration

So, last I posted I'd done all the heater wiring and put in the transformers. A lot has happened since then, and I've got a fair bit of catching up to do with regards to posts about it all...

Anyway...

So, armed with a chassis now populated with transformers, heaters wired up, jacks in place the next stage is mounting all the rest of the things, input jack and pots, and running the ground bus wire through the ones that need it, and not through the ones that don't (on some of the pins). The casings themselves will be grounded via the chassis, which is why all that effort was spent with a dremel stripping the powder coating from the chassis many moons ago. This bit s pretty quick, just making sure you don't put the pot in the wrong place, and that you make sure the isolation washers are used on the input jack, FX send/return and if you haven't already, the output speaker jacks. The slave out and footswitch don't need them, so safe there. I also didn't bother with putting heatshrink over the exposed ground bus wire across the pots, as it really is pretty unnecessary there.

At this point it's also a fairly good idea to wire the mini toggle switches, and i found a good way to do this for the two swtiches connected to each other was to reverse mount them so they stick out the chassis which then allows you to wire them and maintain the distance they naturally have without needing to fiddle about in the chassis. So I did that, and wired them with all the "extras" sticking of ready to be joined to ground wires and pots et all, then reversed it back into the chassis and bent all the bits in place so they'd fit.

Right, that done, time to quickly wire any caps and components that sit across the pots themselves, which is pretty quickly achieved as well.

Next up, channel select wiring, this runs from a mini switch on the front panel to the footswitch jack and then to the board. For this I decided to do twisted wiring for neatness, and picked a different colour combination to the heater wires as to easily see what is what. I also did another twisted wire pair for the bas control in, again, different colour combination of wires. Colours are good, helps you see where the hell things are going and coming from. Imagine I'd wired it all up with the same colour, it'd be like staring into the gates of hell wondering whether it's a ground or live or signal wire... admittedly, if i did this again I'd also colour code the wires to preamp valves as well, with one for

fixed voltage connections and rails, the other for sinal/output etc, just so it makes more sense to look at. Again, hindsight.

Now comes the wiring all the bits together, starting with the power board. Ok, simple enough, figure out all the connections to the power board, twist the wires leading to it that are of any same colour together and attach them. This is actually pretty easy, with the only slightly confusing part the whole standy/HT fuse/where do we go now phase which is over pretty sharpish and wiring the board up is fairly simple. Then add the wires leading off the board. At this stage there's plenty of wire left from the transformers after cutting the wires to length to reuse for the power connections to the preamp PCB and such, so that's cool. Also a good idea at this point was to wire in some leads to the star ground for use, as once everything is in, this area gets a little bit crowded. I also ended up grounding the power and standby switch casings out of paranoia to the star ground even though this technically isn't necessary as they should be grounded via the chassis.

So I did that, and wired all the controls together and wired on the leads which will lead to the preamp board. All good so far, but starting to get chaotic, so cable ties to tie wires together in groupings is a fairly decent idea keeping them out of the way until you're ready to attach them to where they need to go.

Now, the next bit is kind of fun, and can be done when the heaters are wred to the transformer and initial hookup of power board is done. Basically, turn the thing on so you can see the power light come on. I found it a nice thing to do, just to reaffirm that everything so far is wired correctly, at leas insofar as heaters go. It's cool to see the pilot light come on for the first time as well. I also sneakily popped a few valves in just to see them glow, then took them out again, but it was cool to see!

Right, moving on and now it's time to attach wires to all the preamp tube pins. I did it this way and left a lot of wire so as to then attach to the preamp board. In honesty, and hindsight I would actually connect all the wires that attach to the preamp board to the preamp board next time, and then solder to the valve pins and front panel controls. Call this a learning process if you will, but it would have probably avoided a few errors which I'll be blogging about later. With all the wires attached it does look a bit like a birds nest and at this stage it's advisable to really tie things together that belong together for the sake of sanity.

Also this point is a very good point to wire up the input to the first preamp tube, and also any other shielded wires that go to the front panel controls. I also wired up the shielded cable destined for the preamp board. However, this s a mistake insofar that it becomes harder to work with. Wire it to the preamp board, and cut to length based on placing the board in place and leaving a bit of play and allowing for the connecting to be straight onto the pin as we want it at 90 degrees to the chassis so it doesn't go near the heater wires. Again, this is from experience debugging the amp and needing to fix things later on...

So, what we're now left with is a bird's nest of wires and we now need to add in the preamp board and just start attaching wires as we go...

First stage is leave all the power amp/ power from power PCB etc etc well alone as they'll be easy to do once the front is done, and we want to keep signal wires as short as possible on the preamp. Not too short, but with just enough play in them not to have stupid stuff happen later down the line (again, this is hindsight, with so much of it I'd not be surprised if it being 20/20 by now is an understatement and that it's actually giving superman a run for his money)

So, take the wiring diagram, and slowly, from V1->V5 (right to left) start wiring it all up one wire at a time. Measure length, strip, feed into preamp bard, solder. This took longer than i though as well, that with it being incredibly fiddly to attach the shielded wire from FX send and V2/3 gain stages etc at this point. The inner core is fragile, hence best soldered to the preampboard first and THEN  soldered to things like valve pins.

At this point I'd also like to add that the shielded wire i got has been and still is an utter pain to work with. It's stiff, not very flexible, and wire strippers do not work on it, and so I've been using an exacto knife to cut it to length, expose the shield, and expose the core. Tedious long winded process that is still so. I'd get more flexible stuff in the future to be honest, preferably with a thicker signal wire in it tat is less flimsy and prone to snapping. Another tip I should have listened to from the beginning was to not use the shield as a connection, but rather solder a bit of bus wire round it, and ten use that to solder to wherever the shield goes. Trust me, doing it the way that seems more complicated and perfectionist actually saves you time and a lot of hassle later on by a significant margin.

Right, anyway, once you've wired up the front panel stuff and tubes, then just attach the power wires from the second 6.3vac supply to the switching circuit, again, twisting for neatness, attach the signals to the power valves ad then ground wire to the ground star and a few other wires from the power supply. Attach the bias pot to where I didn't solder on the trim pot (used a pot that can be adjusted without removing the amp from it's chassis) and finally hook up the send wire to the FX loop.


And then, voila, fully wired amp. Now all that's left is to see if it'll actually switch on fully. The next bog post will be about actually turning it on with full HT voltages across the valves, biasing it and actually seeing if the whole thing works

I have to admit this was also the stage where I started wondering "what if I've just built an expensive mess that doesn't produce sound" etc, and anxiety starts to creep in as well as excitement and hope. You just want it to switch on, plug a guitar in, and then celebrate glory with a massive shit eating grin. I'll come to that story and how that panned out next time, but for now all wiring is done, attached and everything is in place for the moment of truth...