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Posted: 5 Days 9 Hours ago by: Phil Allison================================> ** It does actually - you lying, POS IDIOT. ** No such thing is clear. noticed that as ** Testing is no proof of being genuine. ** I sure YOU can, but not me. ** Prove it. F
Posted: 5 Days 10 Hours ago by: ClockyThat does not mean they are immune to purchasing and selling recovered and remarked or fake parts. They are clearly faked or remarked used transistors, noticed that as soon as soon as I saw them - no need for testing. You can buy f
Posted: 5 Days 21 Hours ago by: ZilogBobSpecial birthday greetings for a couple of weeks ago to one of the stars of this group. He knows who it is! 😉
Posted: 13 Days ago by: Steven WhiteHello Group, I'm the owner of a few Ecommerce Electrical and Appliance Parts websites. Our Warehouse and Retail Parts counter is located Unit 2/68 Parramatta Road, Underwood 4119 QLD. We are open to the public. My main website is https:/
Posted: 13 Days ago by: Steven WhiteHello Group, I'm the owner of a few Ecommerce Electrical and Appliance Parts websites. Our Warehouse and retail counter is located Unit 2/68 Parramatta Road, Underwood 4119 QLD. My main website is https://electricalsuppliesaustralia.com.
Posted: 29 Days 2 Hours ago by: Daniel65Yes, you are quite correct!
Posted: 29 Days 7 Hours ago by: Phil Allison================> >>> ** Ha ha, no way is that true. What really happens is the Al feed wire ( aka fuse) from chip to TO3 emitter pin vaporises. This gives a path for a DC arc to jump from the pin to the inside top of the pak. A ne
Posted: 29 Days 7 Hours ago by: Phil Allison--------------------------------- ** The chip in a TO3 can heat in milliseconds - or at least a small part of it can. This is why excursions beyond SOA limits are often fatal. High Vces are the killer - aka "second breakdown".
Posted: 29 Days 7 Hours ago by: Trevor Wilson**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.
Posted: 29 Days 7 Hours ago by: Trevor Wilson**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 tha
Posted: 29 Days 8 Hours ago by: Trevor Wilson**Like all Motorola TO3 devices of the early 1970s, they were in those horrible aluminium packs. **Yep. I recall reading the RCA white paper on the issue. **Yep. Steel or copper is the way to go for TO3 devices. RCA won the argument
Posted: 29 Days 8 Hours ago by: Phil Allison================> > ** 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
Posted: 29 Days 8 Hours ago by: Trevor Wilson**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 outpu
Posted: 29 Days 9 Hours ago by: Phil Allison================> >>> ** I once used to see a lot of Phase Linear 400 mk2 amps. A revised version of the famous PL400 hi-fi model. Complementary MJ output devices and input op-amps on the pcb. These were all used in PA s
Posted: 29 Days 10 Hours ago by: Trevor Wilson**Will do. **Yep. **Point taken. When the Japanese devices were installed, the Model 500 became reasonably reliable. If I recall correctly, most amps failed at switch on, rather than under use. I could be wrong.
Posted: 29 Days 10 Hours ago by: Phil AllisonTrevor Wilson wrote: ================> >>> Designed in 1963, it used, unusual for the time, ** Measured with open base ? Not how they are used. ** If you do, put 100ohms between B and E. Makes at least a 10% increase .
Posted: 29 Days 10 Hours ago by: Trevor Wilson**Correct. All the US built Marantz models used Motorola devices with an SJ prefix. Even some of the early Japanese ones used Motorolas as well. Very unusual. I measured a few back in the day. As I recall none of the Model 500 output d
Posted: 29 Days 11 Hours ago by: Phil AllisonTrevor Wilson wrote: ** That assertion makes no sense. Facts: 1. Output transistors do not operate in Vceo mode. 2. They are only exposed to * half* the DC supply at idle or moderate volumes. ** MJ numbered power BJTs all e
Posted: 29 Days 11 Hours ago by: Trevor Wilson**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 fluctuat
Posted: 29 Days 13 Hours ago by: Phil Allison================> ** 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/50
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