Chassis drilling and layout and transformer mounting - Don't put the cart before the horse

So I spent last night lugging home some rather hefty transformers from inMADout all excited thinking I would just drill the mounting holes, drill a hole each for the wires to go into the chassis and do a load of work on the amp. Exciting!

However, this is not how it panned out.

Anyway, we'll start with the good stuff. Firstly the inMADout transformers are cool as hell looking, I got them with matte black covers and they look mean! There are also a hell of a lot of wires poking out the power one, and a fair amount out of the output one. They also have all the wires out of one side, which I've been told is the "vintage" way of doing things. Anyway, I reckoned less holes, right?

Next I decided to revisit the tactic of making cardboard templates for the transformers so I could place them where I want to drill and be able to line them up nicely. All good as well, just grab a piece of cardboard, trace around the transformer, colour in the holes so you know where to drill, and then to get your blue peter badge, cut around the outline ad bingo, one template.

The first consideration when figuring out placement was whether the bolts from the power transformer would not get in the way of the capacitors on both sdes of the power board. Now as you may remember, this board is a tight fit, and there is no room where the capacitors are so the bolts needed to avoid them. Next consideration was to leave at least 20mm space from each edge so that when it goes into the headshell it'll slide past any brackets on it used for mounting grills.

All good so far.

pcb mount screw hidden under transformer - countersunk

So, I start drilling, get the holes for the transformers done pretty quickly and cleanly. Then decide to go and countersink the holes for the PCB mounts and earth and tag boards, as screws sticking out just does not look as good. All went well apart from I broke my HSS M3 drill bit by attaching the countersink sleeve bit to the twisty drilly bit of the shaft rather than the shafty bit of the shaft (yes yes, technical terms and all that, i know, lacking). Anyway, all cool, and good thing I did, as one of the PCB standoff mounts is right inder the output transformer so needed to be countersunk. Also I got away with all the holes for M4 screws just about. I wouldn't have been able to contersink anything larger (M5 and above)

The I decided to look at the choke. Now this is mounted between the power and preamp PCBs on the inside of the chassis. So first thing to check was placement, and I am happy I did. So i lightly attached the preamp board with 2-3 screws, and just slotted the power board on, and then went to position the choke. Very very tight fit. And a lesson learned almost badly. I was lucky there was just enough space with it almost flush against the power board leaving a decent enough gap between it and the preamp board (I hope). Still, if I had moved the boards by about 20mm closer together it would not have fit at all and I'd have had to drill a load of new holes in the chassis to move the boards.

So here is the first lesson:
- No matter how exciting it is, do not do chassis prep until you have the transformers, choke, and ALL components to be mounted on or under it.

Anyway, a lucky escape.

So, next I though I'd just drill holes for the wires to fit through. I had some grommets, and I reckon the wires would fit through them. So I drilled my pilot holes, all good, then drilled larger holes, all good, tried the grommet, larger hole required, so out come larger and larger drill bits until I hit the 10. Ugly ugly process, and I would not advise using a normal drill bit for anything above M5/M6 holes, probably 5...

Right, holes drilled, grommets in, transformers positioned on chassis, start poking the wires through the grommets. Simple right? Wrong. First thing, the holes and grommets were too small. I could ust about get 6 wires through, maybe 7, but then getting them through pulled he grommet through. So, grommet and hole too small. Frustration. So at this point I stopped realizing that I was just going to get really annoyed really quickly.

So, I needed a plan. First plan was to use the countersink bits I had, which are large enough, to slowly drill it out both sides, but luckily a friend pointed out the existence of a step drill bit, which after watching a quick video tutorial pretty much seems like one of the most useful things on the planet, and something that can be used to punch tube socket holes if I ever get a blank chassis (although seeing how I am hating working on the chassis (more likely because this is the first time) I may not go that far).

So here come the next lessons:
- Drilling with mounted components vibrates all the screws nuts and bolts loose. Do all the drilling before you put stuff in the chassis.
- Get the right tools for the job.
- Go and youtube how to do stuff instead of figuring you already know how to. Or ask someone.
- Be patient. very patient. No matter how much you want to do something, it's not worth the anger and frustration because you rushed and did things out of order...

So, basically I am now waiting for larger grommets to turn up and a step drill bit and a deburring tool. As I don't like slicing myself open on the sharp edges of holes I've drilled, and the dremel does not work well on getting rid of them, at least not the one I have.

Amp chassis with transformers loosely mounted

And in conclusion: Chassis work is a pain in the arse, certainly for a first time build and I'd recommend getting one prepunched if it's the first time doing this as you can spend more time on the fun stuff. However, if you can't, then at least make sure you have the following before you start:

- HSS drill bits from M3-M4
- Step drill bit (that can do metal sheeting)
- Countersink bits or attachments you can put on drill bits
- Dremel, get the real thing, and get the right angle converter, it'll make getting rid of coating where you need to much easier, and less dangerous than the way I did it. Just spend the money.
- Deburring tool so you don't go all Emo and cut yourself all the time
- Templates of all the tings you need to drill
- Tape to tape the templates down
- Some kind of device to measure right angles so you can line everything up easily
- A good plan

Anyway, after what seemed like a bit of a failed evening with excitement turning into frustration, I decided a bit of zen like painting was required and proceeded to paint all the screws that will be visible on the top the chassis black. Matte black. To match the transformers. A god way to end the evening and feel like I'd at least done something right.

Bit of a tight squeeze with the choke!

Then I did a quick test mount of transformers, power and preamp PCBs and choke to make sure nothing is in the way of anything else. All worked out well enough, so at least it didn't turn into a disaster!

Anyway, I'll have to finish all the drilling before I hookup all the heater wires and power wires to the tubes as drilling loosens screws, so another delay kind of, but I think part of this life experience is to learn patience and order like some kind of zen like lesson for which I am sure I do not possess the correct outfit/uniform...