INSTALLING THE INPUT TRANSFORMER
In this tutorial we are using an unusually small input transformer, the Lundahl LL1587. Granted, it happens to be the next shortest component after our 1/4″ connector and gain pot, and thus will be installed next. Most input transformers are taller, and so we would install the switches first. If this is true of your input transformer, then skip to the next step and return here later.
Some important precautions:
- Installing the input transformer in the correct position and orientation is crucial. Among the many overlapping transformer footprints on the DIY500 mkII PCB you will find an outline and set of holes which match your selected model. Using the transformers datasheet and labeling, locate its pin 1 or chassis pin and correlate with the PCB. Most of the PCB transformer footprints have a white circle printed around the hole for pin 1, perhaps with an arrow pointing to it and indicting the manufacturer. (e.g. “LUNDAHL_SM” for the smaller sized Lundahl footrpint)
- Unless your input transformer is particularly large and heavy (e.g. the Cinemag size “C” models, such as CMMI-2CPC), it is advisable to leave a small amount of space between the PCB surface and the transformer can. This will help to avoid accidental shorts from the transformer can to a PCB signal connection.
- Take extra care to make quick, light, and effective solder joints around your input transformer pins/wire leads. It it easy to damage an input transformer through excessive soldering and overheating, especially small and delicate packages such as our Lundahl LL1587.
Fig. 45 Locate your input transformer footprint and determine the correct pin orientation.
Fig. 46 Gently insert the input transformer.
Fig. 47 In the correct position, this is what our Lundahl LL1587 input transformer looks like.
Fig. 48 Turn over the PCB. Quickly and carefully solder the transformer pins, using no more solder than necessary.
Fig. 49 Nicely completed solder joints will look like this. There is no need to clip the leads.
Fig. 50 A side view of our successfully installed input transformer. Though there is no gap, we can see that the clear laminating wrap creates an insulating layer between the conductive transformer case and the PCB surface.
