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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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#1
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
I've never seen reference to this mechanism, so transcribed and placed
here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
N_Cook wrote:
I've never seen reference to this mechanism, so transcribed and placed here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? I'm sure modern health and safety departments would have kittens at the thought of an employee deliberately igniting plastics for the purpose of determining the resulting smell. Sylvia. |
#3
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Plastics failure mechanism
On Jun 5, 6:32*am, Sylvia Else wrote:
N_Cook wrote: I've never seen reference to this mechanism, *so transcribed and placed here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? I'm sure modern health and safety departments would have kittens at the thought of an employee deliberately igniting plastics for the purpose of determining the resulting smell. Sylvia.- Hide quoted text - - Show quoted text - Too true! To be fair, though, the common method of doing it is to poke the plasitc with a hot wire and see the effect and smell the odour, so one should not be creating clouds of smoke/fumes. How the plastic reacts to the hot wire is also a clue to its 'type'. I saw a description at one of the sites my wife was on about Jewellery as to the smells and effects on the plastics commonly used for orimental purposes such as Bakelite, Catalin, acrylic, ABS and so on, but I don't recall which one it was. Googling 'plastic jewellery' sould turn up something. Neil S. |
#4
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
Sylvia Else wrote:
N_Cook wrote: I've never seen reference to this mechanism, so transcribed and placed here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? I'm sure modern health and safety departments would have kittens at the thought of an employee deliberately igniting plastics for the purpose of determining the resulting smell. Yeah, same here. The closest I can recall seeing to that was a US army tech guide for identifying metals based on the kind of sparks you got when you hit it with an angle-grinder. -- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est ---^----^--------------------------------------------------------------- |
#5
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
Where I used to work , there was a flow-chart wall-chart for identifying
plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? My chart is from "Materials In Design Engineering", February 1959. It doesn't appear to be posted on the net anywhere. I could send you a scan. Alan |
#6
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
"N_Cook" wrote in message ... I've never seen reference to this mechanism, so transcribed and placed here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ http://www.boedeker.com/burntest.htm |
#7
Posted to sci.electronics.repair
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Plastics failure mechanism
Rick wrote in message
news "N_Cook" wrote in message ... I've never seen reference to this mechanism, so transcribed and placed here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ http://www.boedeker.com/burntest.htm Thanks for that, bookmarked and saved to disc -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#8
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
Alan Douglas adouglasatgis.net wrote in message
... Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? My chart is from "Materials In Design Engineering", February 1959. It doesn't appear to be posted on the net anywhere. I could send you a scan. Alan Arrived safely, I wonder what HCl smells like |
#9
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
N_Cook wrote:
Alan Douglas adouglasatgis.net wrote in message ... Where I used to work , there was a flow-chart wall-chart for identifying plastics by flame test, smell/smoke character when burnt and other basic characteristics, anyone know of a WWW version somewhere? My chart is from "Materials In Design Engineering", February 1959. It doesn't appear to be posted on the net anywhere. I could send you a scan. Alan Arrived safely, I wonder what HCl smells like Bit like Chlorine, and just as nasty. Sylvia. |
#10
Posted to rec.antiques.radio+phono,sci.electronics.repair
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Plastics failure mechanism
"N_Cook" wrote in message
... I've never seen reference to this mechanism, so transcribed and placed here. From (UK) Hacker GP42 record player of 1966, technical bulletin, not dated but probably close to '66 "Investigation over a period of time of reports of knob breakages have shown that the adhesive used to fix the chrome trim has affected the material and caused the knob to fracture after a period of time. A further investigation by the manufacturers disclosed that the material used in one batch of knobs was an incorrect type. DIAKON was the material specified and POLYSTYRENE was used in error. Unfortunately there is no way in which we can easily differentiate between these materials other than by a flame test. " I forgot to mention this in my earlier post. The causative mechanism is stress corrosion cracking. The solvent in the glue, in the presence of the stress caused by the tightening of the setscrew or by the stress caused by stretching the knob to fit over a push-on shaft, precipitates the shattering of the knob. While stress corrosion cracking in metals is well known, it also occurs in many plastics. A crack will start at the plastic surface and propagate perpendicular to the applied stress. In addition to solvents, ozone can cause stress corrosion cracking in many plastics. Gasoline will cause stress corrosion cracking of polyethylene terephthalate; this is the reason that you should never store gasoline in PET soft drink bottles. -- 73, Dr. Barry L. Ornitz WA4VZQ |
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