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Re: Reliability of electronics

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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.

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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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