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Re: Reliability of electronics

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On 31/05/2022 2:08 pm, Trevor Wilson wrote:
> On 31/05/2022 2:02 pm, Phil Allison wrote:
>> Trevor Wilson wrote:
>> =================
>>>>
>>> **Good plan. FWIW: The Model 500 never overheated. Thermostat
>>> controlled, two speed fan cooled. Output devices were all mica/thermal
>>> paste mounted. Even after repair (using original output devices) the
>>> amps failed. Only after the output devices were substituted with
>>> Japanese types did reliability significantly improve.
>>>
>>
>> **   Were the SJs in steel or Aluminium paks?
>>
>> Early 70s Motorola TO3s had a big problem with thermal expansion of 
>> chip headers.
>> The silicon and the header had differing tempcos of expansion.
>> The end result was the chip developed micro cracks.
>>
>> Such devices were speced at a mere 5000 thermal cycles.
>> OK for some apps but not class AB audio.
>> Sudden, unaccountable failure was the norm.
>>
>> Aluminium paks got dumped and were never seen again.
> 
> **BTW: The Marantz Models: 240, 250, 250M, 1120, 1200/B, 140, 2270, 2275 
> all used Motorola aluminium cased To3 devices. All demonstrated 
> reasonable reliability. None were fan cooled like the Model 500. The 
> Model 500 ran much cooler than all those models under normal operation.

**Oh and with all those models, a visual inspection of the output 
devices would frequently and quickly reveal the problem - A tiny pinhole 
in the case, where, presumably, a piece of white hot silicon ejected 
itself from the header.

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Thread

Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-30 17:24 +1000
  Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-30 19:33 +1000
  Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 16:01 -0700
    Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 10:35 +1000
      Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 17:59 -0700
        Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 11:31 +1000
          Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 18:52 -0700
            Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 12:00 +1000
              Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 20:03 -0700
                Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 13:45 +1000
                Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 21:02 -0700
                Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 14:05 +1000
                Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 14:08 +1000
                Re: Reliability of electronics Trevor Wilson <trevor@rageaudio.com.au> - 2022-05-31 14:18 +1000
                Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 21:32 -0700
                Re: Reliability of electronics Phil Allison <pallison49@gmail.com> - 2022-05-30 21:26 -0700

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