Steve:
Most of the outright failures I have experienced (aside from stupid abuse/misoperation) have been with SS amps, not tube amps.
SS:
1: Musical Fidelity X-A1 integrated amp (one power section dead following < 1200 hours of usage - too bad as it sounded very nice with efficient speakers).
2. Musical Fidelity AS-100 power amp (loud hum following < 5 hours usage - returned to Audio Advisor).
3. Hafler DH-500 power amp (power cord interface became brittle and broke < 5 years from manufacture - this was an easy 5 minute diagnosis/fix once I popped the cover). Primarily for PA use, but nice with Hi-fi also.
4. Quad 303 power amp (caps and some of the resistors shot < 8 years from the manufacture date (too much of a hassle to repair per a friend/tech).
5. Quad 33 preamp (same as the 303 power amp above - I ended trading both units, with full disclosure, for a painting:-).
6. Advent 300 receiver (never a problem with sporatic usage over a 9-10 years period).
7. Phase Linear 400 power amp (had a tendency to shut down when continuously operated for approx. 6+ hours whether it be PA or Hifi use - otherwise reliable for lesser periods - bought it new and used it for a couple of years - preferred Dynaco ST-70's in mono mode for PA use as they sounded better and they did not shut down).
Tube Amps:
1: Various RCA, Emerson, etc., stereo console integrated, power and preamps (5-10 years old @ time of usage and no problems with Hi-fi use - blew up a few using them as guitar amps - 10 years old and clueless @ the time).
2. Eico HF-81 integrated (no problems and recapped after 10-12 years - standard maintenance for most any amp).
3. Dynaco Stereo 70 power amps (owned 4 of these and no problems other than having 2 people run/crank a signal through 2 of them w/o a load/speakers being connected, this caused major damage to one of them and it is a case of misuse - recapped the remaining three after 10 years, or so).
4. Mac 30 mono block power amps (never a problem and recapped once approx. 20 years after manufacture).
5. Dyanco Pas3X and Dynaco Pas3 preamps (no problems - had one of them modified with the tone controls being removed from circuit - caps reformed well and were never replaced)
6. Dynaco SCA-35 integrated amp (not mine, but on long term loan - had it recapped/refurbished even though it sounded/performed fine as the caps were original and 15+ years old).
7. Audion Silver Night 300B SET amp (no problems other than the chassis ground being miswired @ the factory, per the US rep, an easy fix).
8. Pilot 690A tuner/preamp (tuner section damaged in transit, but the preamp section is fine - reformed instead of replaced original caps, no problems with this 40 year old piece).
9. Pilot 232 power amp (replaced a single ceramic resistor, otherwise no problems with this 40+ year old piece - reformed original caps).
10. Pilot 240 integrated amp (no problems - 40+ years old - reformed original caps).
11. Bottlehead Foreplay preamp kit (2+ years old - I'm the second owner - no problems).
12. Bottlehead Paramour 2a3 SET mono block kits (same info as Bottlehead Foreplay).
From my experience tubes get the nod for reliablity and I did not even list the tube guitar amps I have owned in the past (not a problem with one). I also plan to recap the old Pilot units eventually if I decide to keep/use them long term (only had them for a couple of years now).
Most of the outright failures I have experienced (aside from stupid abuse/misoperation) have been with SS amps, not tube amps.
SS:
1: Musical Fidelity X-A1 integrated amp (one power section dead following < 1200 hours of usage - too bad as it sounded very nice with efficient speakers).
2. Musical Fidelity AS-100 power amp (loud hum following < 5 hours usage - returned to Audio Advisor).
3. Hafler DH-500 power amp (power cord interface became brittle and broke < 5 years from manufacture - this was an easy 5 minute diagnosis/fix once I popped the cover). Primarily for PA use, but nice with Hi-fi also.
4. Quad 303 power amp (caps and some of the resistors shot < 8 years from the manufacture date (too much of a hassle to repair per a friend/tech).
5. Quad 33 preamp (same as the 303 power amp above - I ended trading both units, with full disclosure, for a painting:-).
6. Advent 300 receiver (never a problem with sporatic usage over a 9-10 years period).
7. Phase Linear 400 power amp (had a tendency to shut down when continuously operated for approx. 6+ hours whether it be PA or Hifi use - otherwise reliable for lesser periods - bought it new and used it for a couple of years - preferred Dynaco ST-70's in mono mode for PA use as they sounded better and they did not shut down).
Tube Amps:
1: Various RCA, Emerson, etc., stereo console integrated, power and preamps (5-10 years old @ time of usage and no problems with Hi-fi use - blew up a few using them as guitar amps - 10 years old and clueless @ the time).
2. Eico HF-81 integrated (no problems and recapped after 10-12 years - standard maintenance for most any amp).
3. Dynaco Stereo 70 power amps (owned 4 of these and no problems other than having 2 people run/crank a signal through 2 of them w/o a load/speakers being connected, this caused major damage to one of them and it is a case of misuse - recapped the remaining three after 10 years, or so).
4. Mac 30 mono block power amps (never a problem and recapped once approx. 20 years after manufacture).
5. Dyanco Pas3X and Dynaco Pas3 preamps (no problems - had one of them modified with the tone controls being removed from circuit - caps reformed well and were never replaced)
6. Dynaco SCA-35 integrated amp (not mine, but on long term loan - had it recapped/refurbished even though it sounded/performed fine as the caps were original and 15+ years old).
7. Audion Silver Night 300B SET amp (no problems other than the chassis ground being miswired @ the factory, per the US rep, an easy fix).
8. Pilot 690A tuner/preamp (tuner section damaged in transit, but the preamp section is fine - reformed instead of replaced original caps, no problems with this 40 year old piece).
9. Pilot 232 power amp (replaced a single ceramic resistor, otherwise no problems with this 40+ year old piece - reformed original caps).
10. Pilot 240 integrated amp (no problems - 40+ years old - reformed original caps).
11. Bottlehead Foreplay preamp kit (2+ years old - I'm the second owner - no problems).
12. Bottlehead Paramour 2a3 SET mono block kits (same info as Bottlehead Foreplay).
From my experience tubes get the nod for reliablity and I did not even list the tube guitar amps I have owned in the past (not a problem with one). I also plan to recap the old Pilot units eventually if I decide to keep/use them long term (only had them for a couple of years now).