Saturday, 22 January 2011

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...

Saturday, 15 January 2011

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.


Monday, 10 January 2011

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.

Sunday, 9 January 2011


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.

Saturday, 8 January 2011

Shellac-ing the cabinet

First job was to start to lacquer the cabinet.

I could have easily bought a pre-lacquered cabinet, but what's the fun in that?

There are all sorts of forum posts about how to approach the lacquering, and I settled on the simple approach of using one coat of clear shellac to seal the edges and corners, and then a number of coats of amber shellac to give that vintage tone.

The clear shellac was easy to buy locally, and I found a reasonably cheap supplier of the amber online and placed an order.

I also read online that you can clean the brushes in denatured alcohol, and it's also useful to dilute the amber so that the color isn't so glaringly orange. So I put some on my shopping list.

The first coat was pretty easy. I took the cabinet apart (removed the speaker baffle, took off the handle and feet) and laid it all out on some newspaper, and proceeded to apply a coat of clear shellac.

It dries pretty quickly, so I was able to turn it all over and reach the parts I hadn't got to about an hour or so after the first pass.

Selecting a Champ kit

As I surfed around for a new guitar, I decided I wanted a vintage Fender Champ amplifier to go with it. It was high time to have some valves in my life.

As I Google-ed around for some information on which models were available in which years, and which years were considered better than others, I came across a very interesting forum post. Someone had built a Champ from a kit. Now there's an interesting idea!

I've always been a geek, and I'm somewhat proud of that. I used to de-solder pretty much anything and everything when I was a kid, so the idea of building a kit by following a set of instructions was not that daunting, and was definitely pretty exciting.

I channeled my Google activity away from vintage Champs, to vintage Champ kits. There are a number of companies out there that are putting these kits together, and most are clustered around the $500 price point for all the electronics, a speaker, and a chassis and cabinet for it all to live in.

The forums gently pointed me towards Marsh Amps, and this company also happened to offer some of the "options" that I was interested in. So I pulled the trigger on my order, and added an international power transformer (just in case I move back to Europe at some point), and also the Weber alnico speaker (which seems to get a pretty good writeup in the forums).

I also couldn't resist getting the Sprague capacitors. Even though I wasn't quite sure why I needed them.

It also seemed appropriate to get the "Marsh Amps" badge to put on the front. It wasn't right to put a Fender logo on there, and seeing as the good folk at Marsh had gone to effort of putting the kit together, their logo on the front was the right thing to do.

Marsh Amps provided me with the kit. Now all I have to do is build it.