Some tips for modifying your system
We have discussed many schematics and have worked with many of you to improve system performance. We've all learned a lot in these back and forth discussions via telephone and email. Here are some tips based on these experiences.
The tab is LIVE with Vin!
Superpower SPJ and SPL have the mounting tab of the output transistor connected live to Vin. This is DIFFERENT from LM78xx devices, which have the power tab connected to ground. If you replace an LM78xx with SPJ or SPL, you must use an insulator to mount the output transistor to a heat sink.
Use cheap stuff first
Superpower are expensive. Yes, they are worth it but the last thing you want to do is replace one due to a careless meter probe short circuit! When you build or modify a regulator circuit for the first time, use a cheap monolithic part until everything is working as expected. If possible, tack solder a LM78xx, LM79xx or LM1117, measure the output voltage and even power up the system to be sure all is working as expected. This way, if there are any wrong connections the damage is to a low cost part not the Superpower. Then power down and solder in the Superpower.
Remove the spacer if you wish
The leads/pins/legs come with a black spacer. This is to keep the leads properly set when they are attached during manufacture. If you wish, remove it before you solder Superpower to its PCB.
Remotely mount the output transistor
SPJ regulators have a TO-220 case output transistor. This can be removed from the PCB and mounted to a chassis or heat sink, connected by 3 wires. Keep the wires as short as possible, but up to 5 or 6 inches (12 or 15 cm) should be OK. The emitter is the output pin and the load can be wired directly to the emitter rather than to the SPJ output pin. The mounting tab is live and connected to Vin so it needs a mica or Silpad® insulator. Mount a 100µF capacitor near the output transistor, from emitter to ground.
To remove the transistor, it's usually easier to use a flush cutter and clip the device leads, then remove the solder and pins from the holes. The epoxy on the front of the PCB protects the circuit while you do this.
Find more information on separate mounting of the output transistor here, including wiring diagrams to keep high current off the Superpower PCB.
Send us a schematic or a photo
If you have questions, send us a schematic or a photo. We've become good at long distance problem solving. Especially if you're replacing a LM317 or LM337, you can send a photo and we'll try to help with which resistor to remove and which one to short across.