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Re: Reliability of electronics

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On 31/05/2022 9:01 am, Phil Allison wrote:
> Trevor Wilson wrote:
> =================
>>
>>
>> Model 500. 100% failure rate. In fact, each Model 500 usually required
>> service several times during it's warranty period. I budgeted 10 hours
>> to repair each one. As a consequence, of the 3 amplifiers imported by
>> Marantz, only to were sold to the public. It was cheaper to bury the
>> last one in landfill. I negotiated a price and I still own the beast. It
>> is a highly desirable amplifier. The Absolute Sound reported: "The
>> Marantz Model 500 would be issued with our 'best power amplifier ever'
>> if only we could manage to get one to operate for more than six weeks
>> without blowing up. Designed in 1963, it used, unusual for the time,
>> full complementary symmetry outputs. Unfortunately, the Voltage rating
>> on the output devices was marginal.
>>
> 
> ** The model 500 dates from 1973.
>     Each channel used 8 x TO3 transistors with SJ prefixes (  SJ2404 and 2405)
>     So specially selected types made by Motorola.
> 
>     https://www.hifiengine.com/manual_library/marantz/500.shtml
> 
>     Rated power was 250W at 8ohms, so 8 devices should be plenty.
>     Weight was 83 pounds  -  which is absurd.

**If you've downloaded the service manual, you can see the complexity of 
the beast. SOA adjustments are very comprehensive. The fault with the 
amp lay with the VCEO of the output devices. There was very little 
margin for mains fluctuations. Marantz finally solved the problem by 
specifying 200 Volt, Japanese output devices, rather than the Motorola 
ones originally fitted.

BTW: The Model 500 would typically deliver well over 300 Watts @ 8 Ohms. 
As I recall, around 320 Watts, both channels driven.

Yeah, it's a heavy sucker. Fan cooled too, so heat sink mass is not 
huge. Big power transformer and 4 huge main filter caps.

It was replaced by the Model 510/M, which was far more reliable, more 
compact, lower mass and sounded like shit. Series/parallel output 
devices. Yuk.

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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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