Power supply troubleshooting

Thread after thread after thread are being hijacked by repetitive questions about minor power supply issues. These discussions often displace the original discussion about the amp or preamp. I asked about this but was met with silence from moderators et al. Let's try this:

Please post power supply troubleshooting questions here. Be sure to include any relevant/needed photos.

Hopefully the members who generously give troubleshooting information will continue to be willing to do it here.