I recently got a totally smashed (bloody touring) TC VoiceDoubler on my workbench, with very similar circuitry inside. After re-adjusting all metal panels and replacing screws I tried booting it up but constantly was given "DSP won't boot" and "Trying to reset..."

I also suspected the PSU, but after measuring all outputs from the PSU-card all voltages seemed to be correct. The issue lies in the DSP-chip (duh!) which is, in the VoiceDoubler at least, labeled with a white sticker. I gently pulled it out of the socket, cleaned the legs on the chip and the socket VERY gently with a q-tip and some isopropane, then pushed it back and made sure it was in place. Around 50+ reboots later there's no sign of DSP error and all patches are working properly.

So if you're still experiencing these issues, try pulling the DSP-chip and putting it back in, making sure it's firmly in place.

/Chris