The quiet before the storm. Note the pile of baggies from Tube Depot...most handy!
So the previous week, in an effort to have everything ready for assembly, I order the remaining parts. This amounted to all the resistors, capacitors and diodes that make up the circuits on the board. Finally, I needed tubes of course. I ordered from these folks:
- Tube Depot – They have all kinds of manufacturers in stock, and the shipping is fast and high quality. Each component arrived in its own ziplock baggie with a decent label. Very cool for a newbie like me.
- Eurotubes – I decided to go for a 6V6 in the output section and Eurotubes was the only place I could get a JJ 6V6 in a one lot. Every other place wanted to sell only pairs, and their prices were high anyway. Naturally this site is a big proponent of JJ, but others online have sung their praises. If these work out I may retube my 2204 with a set from these guys.
Before starting I laid everything out on my dining room table, and made sure I had plenty of light. To ensure accuracy I had both the schematic and the layout diagram available. And so as to maintain diplomatic relations with my significant other (i.e. not burn the table), I used a print out of the AX84 theory document for the P1eX as an “earth friendly soldering station”. Fitting, really.
So, now it was time to begin attaching stuff to the turrets. I started with the wires that go under the board as this made total sense (and the guide told me to). I had already drilled holes next to the appropriate turrets so that I could keep the solder joints above the board, but still route the wire underneath. Apart from the build guide recommending this, I was also keen to never have to remove the board once built as having previously repaired my Marshall 2204 it was a royal pain to have to remove the PCB to de-solder components.
A wire routed underneath the board surfacing to attach to the turret
Bare turrets with adjacent holes waiting for wires. The larger hole is for the chassis stand-off.
After all these were in place, and making sure I had marked these as ‘done’ with a hi-lighter on the layout diagram, I started on the right hand side of the board with the power supply diodes. As I worked my way through the layout I was troubled by a few things:
Progress. The first few joints drank solder like it was going out of fashion.
Is there a “rule of thumb” to help decide where/how to solder a component? i.e. do you put caps/resistors/diodes inside the turret, and wrap wires around the turret? Or is it the other way round? I did both as I saw fit, but it’s not particularly neat and tidy.
- Do you wrap as many components around each turret all at once and then apply solder? Or do you do them one by one? Again, I did both, but the latter meant components were heated multiple times, therefore went under more thermal stress.
- How do you stop the turret itself wicking all the solder away? Early on I found that if the turret got too hot it would wick solder until you filled it up. And in fact when I turned the board over there were quite a few lumps of solder that had fallen through and pooled on the paper I was using as an ad hoc insulating surface. I think this is down to technique. Later on I got better at keeping the heat on the parts as little as possible which meant I could minimize the amount of solder. This must’ve been due to the lower part of the turret remaining below solder melting temperature, thus no wicking.
- The ground bus along the top of the board cried out for a single wire to be connected from turret to turret. I decided to use my 20 AWG solid core wire (as I had been using that all along) but it didn’t come out looking especially nice. I’ll do it differently next time…perhaps thinner wire?
The board with a few missing/incorrect bits. Note the wiggly copper ground bus along the top
Along the way I realized I had screwed up my order to Tube Depot. A missing component here, a slightly-wrong component there etc. Never mind, I can go to Radio Shack during the week as it is only 5 minutes walk from the office, whereas from home it’s a 20 minute drive. Normally this would’ve irritated me, but I still had plenty of interesting stuff to do after soldering all the remaining components and wires.
So time to put the board aside and do some work on the chassis. The day before I had sprayed the amp’s chassis with a black ‘Rustoleum’ hammered-finish paint. It came out surprisingly well seeing as I was rushing (over excited) and humidity and temperature weren’t ideal. 24 hours later the paint was dry so I started adding pots and lights etc. This part was easy as I had already ‘dry fitted’ the parts a couple of weeks ago. I definitely did not want to have to drill anything out again once assembly had begun.
Once I had the transformers in place I decided to proceed with the filament wiring. I had some green and black solid core wire, so I used that to make the connections. Twisting the green wires from the power transformer wasn’t so easy as they are stranded. Stranded wire doesn’t seem to like keeping its form once twisted. We’ve all experienced a neatly coiled wire that transforms into a tangle once you let go of it. Luckily though the run from the PT to the pilot light is short. Twisting the black/green solid core was a breeze in comparison and I soon had plenty of wire to connect the pilot light to the output tube and the first preamp tube.
Green wires from the PT, to the pilot light, then my green/black wires going to the tube sockets.
Filament wiring at the output tube socket.
Overall I was very pleased with the weekend’s progress. It’s really starting to look like an amp now! I’ll have the missing/wrong components in order this week, and I might even be able to get some sound out of it within a couple of weeks, time allowing.
The PT and OT in their new homes. You can see the full effect of the hammered black paint.
Chassis so far. I must order some proper knobs for it.