Standard through-hole construction usually begins by soldering in the lowest-height parts first, following by remaining parts in gradually increasing heights. This is done with the method I use - the pine board - because I place the part, turn the PCB over and then press down on the PCB and board while soldering. This ensures the part is soldered flush to the PCB, without purchasing one of those expensive Panavise units. However, it does mean you need to progress linearly with the height of the parts. That doesn't mean I don't make a mistake and solder something out of order - as you will see - but it helps.
Using that strategy then, the first parts to go in are the small diodes, D1 and D2 -
Next up are the heater rectifier snubbers, just like the final tweak on the Torpedo I. In the case of the Torpedo III, bridge rectifiers are used, so only two snubbers are needed. As with the Torpedo I, these are on the bottom of the PCB. As with any SMD soldering, the first step is to tin one of the pads for each of the snubber caps, as you see in this pic:
And as follows with DIY-SMD soldering, melt the solder you just placed on one of the pads and while holding the iron keeping it melted, use your other hand (holding the SMD part with tweezers) to move the SMD cap in position. Then while continuing to hold the chip in position with the tweezers, remove the soldering iron. This allows the solder to cool on that one side and the SMD chip is locked in place. Go back and add solder to the other pad and you've soldered the SMD part! It's a lot easier than it sounds. You can re-heat to your heart's content until you get the SMD chip correctly positioned - as long as you don't solder the other pad. When you're happy with the position, then solder the other side. Here we are with them soldered:
Next up in the part height sequence are the V-D resistors (Vishay-Dale). The V-D resistors on the Torpedo III are all RN-55 size, so no worries about different sizes. However - as always - please, please solder the V-D resistors with their ohms value clearly on top. Unlike traditional resistors, V-D resistors are not color-coded. If you have to go back and trouble-shoot, and the ratings of the resistors are not top-oriented, you are at a loss to perform one of the easiest trouble-shooting checks: whether the resistors are mixed up. Measuring is often not productive, either, because many resistors may be in parallel with something else, complicating any reading you might make with a DMM.
There are basically four rows of V-D resistors in various orientations (one all by itself) as shown -
Next are the higher-wattage resistors -
Finally, there are a few 2W resistors that are even larger:
There are basically two rows of these resistors and one by itself, for a total of 9.
Finally, there are three large diodes:
Be certain to match the orientation of the diodes on the silkscreen. I must've not been paying attention and soldered two of them in backwards. De-soldering braid to the rescue!
That finishes it for resistors, diodes, and other small parts ... Wait!! I forgot something, as usual:
Just as with the Torpedo I, the Torpedo III can be configured for either 110V or 220V. This is accomplished by soldering jumpers at the Power Transformer (PT) position. The jumper pads are labeled A, B, C, and D:
- To configure for 110V house voltage, solder two jumpers, one from A to B and one from C to D.
- To configure for 220V house voltage, solder only one jumper from B to C.
I'm in the United States, so the photo shows the two jumpers that will configure the PT for 110V mains.
By the way, you may notice some extra diode positions on the PCB: D7, D8, D9, and D10 are not populated. The Torpedo III is complete without them.