Completed cabinet

I finished the cabinet today, and it looks pretty nice!

After the five coats of lacquer, I needed to drill a couple of holes which will eventually be used to mount the chassis. I had been wondering about how to find the right place to put the holes, as I only had one chance to get this right, and there wasn't much room for error.

Luckily I found a template online that I could print out and place over the cabinet to indicate where to drill. I was also able to borrow an electric drill from someone at the office.

After a glass of beer I had enough courage to give it a go. The holes went in cleanly, and in exactly the right place. Phew!

I put all the hardware back on (feet and handle), and then added the Marsh logo plate on the front.

Looking good!

Now back to the electricals and the chassis...

Working on the chassis

One of today's tasks was to start to prepare the chassis. This involves mounting the power transformer and input transformer to the back of the metal box, and then mounting other components such as the valve sockets, inputs, volume control, fuse and fuse-holder to the relevant holes.

This was a pretty straightforward exercise and it hasn't required much soldering so far.

The inputs require a little attention. There's a resistor soldered across the tabs of one of them, and then a jumper runs across to the other.

I've reached a minor hiatus in construction. The nut that holds the volume control in place was missing from my kit (so I'll have to wait until another is shipped out to me). And in addition, the screws that are supposed to hold two of the valve sockets in place just don't seem to want to go through their little holes (I've asked the kit manufacturers for some advice on that one).

So it's back to more lacquering for me.

Second coat of lacquer

I put the second coat of lacquer on the cabinet today. The second coat was a mix of clear shellac, amber shellac, and denatured alcohol. The idea is to start to give the cabinet a nice vintage look, without it getting too orange.

I had been wondering what sort of difference the amber shellac would make. It turns out that it has a very pleasing effect -- you can see the contrast between a "raw" and "cooked" cabinet in this picture. It should look pretty good when it's done!

I think I'll do one more amber-mix coat. And then top it all off with a final coat of clear.

Music while you work

I seem to be listening to a lot of blues while I construct this kit (for example, while lacquering the second coat on the cabinet, I was listening to "From the Cradle" by Mr Clapton).

My beautiful wife asked me a very sage (if a little grammatically clumsy) question: are you only listening to music played on that amp as you build your amp?

Maybe I'm already doing that subconsciously, but I think I'll try to stick to that assertion going forward.

Mojo.

How to mount the chassis in the cabinet

Something I'll have to work out sooner or later is just how to mount the chassis in the cabinet.

The chassis is the metal box that all the electricals are attached to (valve sockets, transformers, circuit board etc). It looks like I need to drill some holes in the cabinet, and then screw the chassis inside with some bolts... but the instructions don't mention anything about how to do this, or where exactly I need to drill the holes.

I still have some time to think about this part, as I have to finish the lacquering of the cabinet, and there's quite a lot more to do on the electricals side before it will all come together.

Jumpers

Next up was to wire up the jump leads from the edges of the board. These will eventually connect to the tube sockets, input jacks, speaker, etc.

The kit came with cloth covered wire for these jumpers, and as I cut the first piece to the right length I also tried to strip the end so I had some clean wire to solder. The cloth covering wasn't the most forgiving sheath to cut through, and I had little success in getting a nicely stripped end.

I looked on the RadioShack website for a wire stripper tool, and found one that looked reasonable. I planned to buy it the next day.

For some reason I decided to Google for tips on stripping cloth covered wire. I'm glad I did, because it turns out that you don't need to strip it at all! You just pull back the covering to expose the wire underneath. Easy!

I worked through each jumper connection, and the couple of under-board connections. This didn't take too long, but I found that I needed to refer back to the big circuit diagram that came with the kit to make sure that I was putting things in the right place.

Wiring up the first components

While the lacquer was drying, I started to "stuff" the circuit board. This involved locating the various components (resistors and capacitors) and poking their legs through the holes in the circuit board.

This was a pretty straightforward exercise, and proceeded quickly. The only marginally tricky part was to get the capacitors lined up pointing in the right direction (they require the positive end to point to the positive rail on the circuit). Nothing too complex, though.

Once all the components were in the relevant locations, it was time to see how good my soldering skills were after all these years.

I bought a 25W soldering iron from RadioShack. The low power seemed to be a good idea, as I didn't want to cook any of the components, and it might give me a semblance of control over the process.

As I worked from location to location soldering the joints, I was pleasantly surprised to find that I was able to produce a reasonable joint if I didn't rush.

I also found that the tip of the iron needed cleaning regularly, and used a damp Scotch Brite sponge to keep things flowing. The abrasive side was good at keeping the crud off the tip; and the spongy side acted like a classic soldering sponge.