What is the service history of the Honeywell unit? Any other experience with these things bursting into flames?
On a related note: What sort of connections does the ELT have with the aircraft power system? There is a flight deck test switch plus activation annunciation. Is this powered from the aircraft DC system? Any chance that it was connected to a 32 Vdc buss (most other applications are likely to be 28 Vdc).