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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#41
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On Tue, 20 Jun 2017 20:16:48 +0100, "Ian Field"
wrote: diodes would be OK but die mounting and bond wires in some germanium transistors was well, err - a bit amateurish. Nowadays; suppliers pack *ANY* components in anti-static bags - it used to be some sort of clue which bits to handle with care. There's some unexpected parts on the vulnerable list, so maybe they have a point. molded semiconductors can be subjected to pretty much anything that doesn't break the case. IC sockets though? Why do they pack them in anti-static bags (Digi-Key)! They pack *EVERYTHING* in anti static bags - there was a time anti static bags alerted you to the need for special handling. All semiconductors need special handling. Usually I just wet my hands and ground myself. That is plenty. Wet hands cant cause static electricity. No other passive components need that (as far as I know). Tubes are safe too. |
#42
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![]() "Cursitor Doom" wrote in message news ![]() On Fri, 16 Jun 2017 21:48:37 +0100, Ian Field wrote: molded semiconductors can be subjected to pretty much anything that doesn't break the case. Are you the same Ian Field that has authored several books on UHF/VHF subjects? I rarely play with anything higher than a few MHz. The "pill" molded transistors in early TV tuners weren't so robust - they weren't exactly molded as such, they were 2 plastic shells glued together. |
#43
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![]() "John Robertson" wrote in message ... On 2017/06/16 1:48 PM, Ian Field wrote: "Cursitor Doom" wrote in message news ![]() On Tue, 13 Jun 2017 13:45:40 -0700, tabbypurr wrote: I'd first be mindful of mechanical damage from doing that. When was the book written? Germanium? NT Haha! I think even those old germanium diodes would easily cope with a four foot fall! diodes would be OK but die mounting and bond wires in some germanium transistors was well, err - a bit amateurish. Nowadays; suppliers pack *ANY* components in anti-static bags - it used to be some sort of clue which bits to handle with care. There's some unexpected parts on the vulnerable list, so maybe they have a point. molded semiconductors can be subjected to pretty much anything that doesn't break the case. IC sockets though? Why do they pack them in anti-static bags (Digi-Key)! They pack *EVERYTHING* in anti static bags - there was a time anti static bags alerted you to the need for special handling. |
#44
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![]() wrote in message ... On Tue, 20 Jun 2017 20:16:48 +0100, "Ian Field" wrote: diodes would be OK but die mounting and bond wires in some germanium transistors was well, err - a bit amateurish. Nowadays; suppliers pack *ANY* components in anti-static bags - it used to be some sort of clue which bits to handle with care. There's some unexpected parts on the vulnerable list, so maybe they have a point. molded semiconductors can be subjected to pretty much anything that doesn't break the case. IC sockets though? Why do they pack them in anti-static bags (Digi-Key)! They pack *EVERYTHING* in anti static bags - there was a time anti static bags alerted you to the need for special handling. All semiconductors need special handling. Usually I just wet my hands and ground myself. That is plenty. Wet hands cant cause static electricity. Wrong - your hands are essentially wet by default. Wet hands simply provide a lower impedance jump off point for that fat blue spark. Working on a PC - I rest my bare elbow on the metal case so I'm at the same potential as what the PC thinks is earth. Some people insist on unplugging the mains - but it makes no difference from the ESD point of view if you do it properly. Handling individual ICs, I breathe on them so the slight humidity provides a leakage path between the pins. I always plant my hand on the anti static mat before putting the chip down to make sure I'm at the same potential as where I'm putting the chip. Deploying the part is same as working on a PC - touch the ground plane while introducing the chip to its socket. |
#45
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On Tuesday, June 20, 2017 at 1:15:14 PM UTC-7, wrote:
On Tue, 20 Jun 2017 20:16:48 +0100, "Ian Field" All semiconductors need special handling. Usually I just wet my hands and ground myself. That is plenty. Not sure about the 'wet hands' part (your hands have lower skin resistance than a ground strap), and the 'ground myself' is likewise a problem. We all have to unclip from the leash at some point. Installing RAM, I generally unseal the package, then hold onto the computer chassis with my left hand while installing the module with my right. Earth ground is not a requirement, just that the conductive packaging, the installer, and the computer's groundable parts are all at the same potential. If you have groundstrap and conductive mat, you STILL need also to ground the computer. Sometimes, this is done with a dummy cord, ground-only, to the power supply, but that's just SO ugly: a power cord that doesn't connect power !!ick!! |
#46
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![]() "whit3rd" wrote in message ... On Tuesday, June 20, 2017 at 1:15:14 PM UTC-7, wrote: On Tue, 20 Jun 2017 20:16:48 +0100, "Ian Field" All semiconductors need special handling. Usually I just wet my hands and ground myself. That is plenty. Not sure about the 'wet hands' part (your hands have lower skin resistance than a ground strap), and the 'ground myself' is likewise a problem. We all have to unclip from the leash at some point. Installing RAM, I generally unseal the package, then hold onto the computer chassis with my left hand while installing the module with my right. Earth ground is not a requirement, just that the conductive packaging, the installer, and the computer's groundable parts are all at the same potential. If you have groundstrap and conductive mat, you STILL need also to ground the computer. Sometimes, this is done with a dummy cord, ground-only, to the power supply, but that's just SO ugly: a power cord that doesn't connect power !!ick!! You didn't change much from what I said. |
#47
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Cursitor Doom wrote:
One of the books I picked up on faultfinding and troubleshooting whilst in London the other day (title escapes me but I can find it if anyone cares) states that: a) A bipolar transistor may be permanently damaged by dropping it on a concrete floor from a height of over 4'. (I'm paraphrasing but that's the gist of it). Elsewhere it states that: b) static sensitive components can be damaged by careless use of air dusters, which can build up a static charge, in their vicinity. Whilst I'm prepared to place some faith in assertion b) I'm reluctant to do so in the case of a). However, I'm more concerned with b) because I recently purchased a fair sized air compressor for blowing dust out of the insides of test equipment which is of course considerably more powerful than the aerosol cans the author was thinking about when he asserted b). Has anyone ever caused damage to static-sensitive components through the use of compressed air? Is this something we really need to be mindful of? We had a pair of large (160 gallon) three phase air compressors at Microdyne. They ran the crimping tools, as well as supplying compressed air for two leased air nozzles with a radioactive element to prevent static buildup when cleaning flux from new circuit boards. -- Never **** off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
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