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Re: Fairchild? (Large F ) transistors of 1970s

I was checking for data on an FT5154 transistor of 1976 kit.

> An old German transistor data manual showed it equivalent to 2N5154. > A straight block of 50 or so others listed in that manual from FT1724 to > FT5154 showed the same 2N equivalence. > Anyone know of a general rule ? > FT??? in hundreds don't seem to have direct number 2N equivalents > > -- > Diverse Devices, Southampton, England > electronic hints and repair briefs , schematics/manuals list on >
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> > > >

Sometimes the mfrs make a line of transistors having very similar characteristics, differing in only a few specific elements, such as Vce, Ic(max), etc. They might have numbered them sequentially, but there is (was) no requirement or guideline to do that. Part numbers are arbitrary in most cases, and have no correlation between manufacturers. If a manufacturer second sources a part, then it's good sense to assign the same or very similar part number, but again, no specific requirement.

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Dave M
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DaveM
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Sometimes they took the same transistor and tested it. Depending upon the results, it became one part or the other.

Back when the IBM PC first came out you could buy memory that cycled at 200, 150, 125 or 100 ns. There was only one production line.

Each chip was tested at 100ns (10mHz), if it passed it was maked -100 and sent off to be packaged. If it passed at 125ns (8mHz) it was marked

-125, and so on. If it did not pass at the lowest speed the chips were sold at it was tossed.

Now the chips that failed would be sold on eBay as "untested". :-)

Geoff.

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Geoffrey S. Mendelson

1-215-821-1838

Replaced FT5415 with 2N5415 and working fine

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
n cook

Really? Then explain the 4164 chips of various brands marked 300 that tested to 150 or better on my RAM tester. I repaired a LOT of Commodore 64 computers, and bad or slow memory was one of the biggest failures. I salvaged thousands of used 4164 and 41256 chips from Unisys mainframe memory boards. All that were still good (over 99%) tested at least one level faster than they were marked. They told me that they bought millions of RAM chips, speed tested them, and then sold the slower culls to the IBM clone makers and on the spot market.

Reply to
Michael A. Terrell

Did you test them at worst case conditions? The manufacturer ensures they meet spec at all legal conditions, the slowest conditions would typically be low voltage (-10%?) and high temperature (often 70degC, maybe even 100degC?) so if you're testing them at room temp and nominal voltage they'll run considerably faster.

Mike.

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The RAM tester checked the memory at three different voltages, (VCC-10% VCC and VCC+10%) and had a calibrated, adjustable clock to set the test speed. Most of my testing was done at either room temperature of 85 to 90 degree Fahrenheit, or at full operating temperature when socketed chips were pulled from a working motherboard. I was repairing hundreds of Commodore C64 computers, and early IBM clones with 4164 and

41256 RAM. I know there was fancier test equipment available, but I could test or verify bad RAM in seconds. Some that were marked 300 would test at under 100, while others in same the batch tested close to the guaranteed 300 under the same test conditions. 
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Michael A. Terrell

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