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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
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Anyone replace pots with presets ?
Ten years ago I would have considered it impractical or even immoral.
But having to replace yet another effectively all plastic 12 mm pot because the wiper is almost invisible in thickness, perhaps time for a rethink. This type of pot has a metal covering but its only function is as a shroud for fixing to the board, not even earthed, it does not strengthen the pot body to restrain abuse at the other, user end. No longer are such pots fixed to the front pannel. I'm thinking that with the next one to replace it will be with a standard small 12 mm or so enclosed preset that takes a standard plastic shaft in the adjustment slot, fudging the other end of the shaft to take the knob and through pannel bearer. The internal mechanism is just a pro-rata scaled down conventional paxolin backed track with double wiper nibs. If this replacement physically breaks in use then that seems more justifiable than the modern flimsy wipers losing spring action or just aging of the lubricant inside to wedge under the wiper and loose contact or whatever their problem is, the tracks are always perfect (so little wiper pressure presumably). Are the resistive tracks of presets more frail/easier scoored than pot tracks, so for that reason cannot be used say for volume control ? Anyone any opinions? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
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Anyone replace pots with presets ?
"N Cook" wrote in message ... Ten years ago I would have considered it impractical or even immoral. But having to replace yet another effectively all plastic 12 mm pot because the wiper is almost invisible in thickness, perhaps time for a rethink. This type of pot has a metal covering but its only function is as a shroud for fixing to the board, not even earthed, it does not strengthen the pot body to restrain abuse at the other, user end. No longer are such pots fixed to the front pannel. I'm thinking that with the next one to replace it will be with a standard small 12 mm or so enclosed preset that takes a standard plastic shaft in the adjustment slot, fudging the other end of the shaft to take the knob and through pannel bearer. The internal mechanism is just a pro-rata scaled down conventional paxolin backed track with double wiper nibs. If this replacement physically breaks in use then that seems more justifiable than the modern flimsy wipers losing spring action or just aging of the lubricant inside to wedge under the wiper and loose contact or whatever their problem is, the tracks are always perfect (so little wiper pressure presumably). Are the resistive tracks of presets more frail/easier scoored than pot tracks, so for that reason cannot be used say for volume control ? Anyone any opinions? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I would have said that the description " preset " tells you all that you need to know on that score. These components are designed to be set and left, pretty much for the lifetime of the equipment, so I can't see them standing up to the rigours of regular use for long. Add to this that as they are not designed to be rotated repeatedly as a user control, the wiper / track interface has not been designed to be specifically quiet. I also think that the control will feel bad to a user, as it will not have that " stirring treacle " feel that a proper user control has, courtesy of the drag grease that the manufacturers put in the spindle bush. Why not replace controls with manufacturer's originals ? Most group amp builders supply spare parts. Failing that, there are plenty of reasonable quality pots available - even the range that Maplin keep are pretty fair quality - and if you really want to fit top quality pots, these are also available from audiophile outlets. Arfa |
#3
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Arfa Daily wrote in message
... "N Cook" wrote in message ... Ten years ago I would have considered it impractical or even immoral. But having to replace yet another effectively all plastic 12 mm pot because the wiper is almost invisible in thickness, perhaps time for a rethink. This type of pot has a metal covering but its only function is as a shroud for fixing to the board, not even earthed, it does not strengthen the pot body to restrain abuse at the other, user end. No longer are such pots fixed to the front pannel. I'm thinking that with the next one to replace it will be with a standard small 12 mm or so enclosed preset that takes a standard plastic shaft in the adjustment slot, fudging the other end of the shaft to take the knob and through pannel bearer. The internal mechanism is just a pro-rata scaled down conventional paxolin backed track with double wiper nibs. If this replacement physically breaks in use then that seems more justifiable than the modern flimsy wipers losing spring action or just aging of the lubricant inside to wedge under the wiper and loose contact or whatever their problem is, the tracks are always perfect (so little wiper pressure presumably). Are the resistive tracks of presets more frail/easier scoored than pot tracks, so for that reason cannot be used say for volume control ? Anyone any opinions? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I would have said that the description " preset " tells you all that you need to know on that score. These components are designed to be set and left, pretty much for the lifetime of the equipment, so I can't see them standing up to the rigours of regular use for long. Add to this that as they are not designed to be rotated repeatedly as a user control, the wiper / track interface has not been designed to be specifically quiet. I also think that the control will feel bad to a user, as it will not have that " stirring treacle " feel that a proper user control has, courtesy of the drag grease that the manufacturers put in the spindle bush. Why not replace controls with manufacturer's originals ? Most group amp builders supply spare parts. Failing that, there are plenty of reasonable quality pots available - even the range that Maplin keep are pretty fair quality - and if you really want to fit top quality pots, these are also available from audiophile outlets. Arfa I had not considered the feel, which agreed is very 'scratchy'. Squirting silicone oil in one and turning back and forth a hundred times is very much improved, and resistive track still ok. What is the point of the feather-light touch of the flimsy pots if the downside is they just don't last. I don't see the point of replacing with an exact match when the original is say one of 8 and has only lasted for use once a week for 2 years before internally failing , ie not abuse. In fact they seem to be the pots that are not used much if at all, that's why I suspect clumping or something in the lubricant. I'll try a 1000 times and re-measure to see if the track fails. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#4
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
"N Cook" wrote in message ... Arfa Daily wrote in message ... "N Cook" wrote in message ... Ten years ago I would have considered it impractical or even immoral. But having to replace yet another effectively all plastic 12 mm pot because the wiper is almost invisible in thickness, perhaps time for a rethink. This type of pot has a metal covering but its only function is as a shroud for fixing to the board, not even earthed, it does not strengthen the pot body to restrain abuse at the other, user end. No longer are such pots fixed to the front pannel. I'm thinking that with the next one to replace it will be with a standard small 12 mm or so enclosed preset that takes a standard plastic shaft in the adjustment slot, fudging the other end of the shaft to take the knob and through pannel bearer. The internal mechanism is just a pro-rata scaled down conventional paxolin backed track with double wiper nibs. If this replacement physically breaks in use then that seems more justifiable than the modern flimsy wipers losing spring action or just aging of the lubricant inside to wedge under the wiper and loose contact or whatever their problem is, the tracks are always perfect (so little wiper pressure presumably). Are the resistive tracks of presets more frail/easier scoored than pot tracks, so for that reason cannot be used say for volume control ? Anyone any opinions? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I would have said that the description " preset " tells you all that you need to know on that score. These components are designed to be set and left, pretty much for the lifetime of the equipment, so I can't see them standing up to the rigours of regular use for long. Add to this that as they are not designed to be rotated repeatedly as a user control, the wiper / track interface has not been designed to be specifically quiet. I also think that the control will feel bad to a user, as it will not have that " stirring treacle " feel that a proper user control has, courtesy of the drag grease that the manufacturers put in the spindle bush. Why not replace controls with manufacturer's originals ? Most group amp builders supply spare parts. Failing that, there are plenty of reasonable quality pots available - even the range that Maplin keep are pretty fair quality - and if you really want to fit top quality pots, these are also available from audiophile outlets. Arfa I had not considered the feel, which agreed is very 'scratchy'. Squirting silicone oil in one and turning back and forth a hundred times is very much improved, and resistive track still ok. What is the point of the feather-light touch of the flimsy pots if the downside is they just don't last. I don't see the point of replacing with an exact match when the original is say one of 8 and has only lasted for use once a week for 2 years before internally failing , ie not abuse. In fact they seem to be the pots that are not used much if at all, that's why I suspect clumping or something in the lubricant. I'll try a 1000 times and re-measure to see if the track fails. -- I'm actually really surprised that you seem to come across so many bad pots in group amps. I have been repairing these for many many years, and do lots of all makes and models, for a local shop, and I really don't have to replace many pots that aren't physically broken through taking knocks. I have found in general, that most manufacturers appreciate that this gear is going to last its owners for a lot of years, and tailor their design criteria, and component spec-ing to suit. I would agree that the pots fitted these days tend to be Japanese ( probably Chinese actually ) small-bodied types, which are not as good quality as say the large body Wellyns or the typical RS components pots that you used to find in them a few years back, but still, I don't seem to have that much trouble with them. If you really think that the problem is insufficient spring tension on the wiper fingers, just pile a bit more on. It's easily done with a pair of long-nosed pointy surgical tweezers. Arfa Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#5
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Arfa Daily wrote in message
... "N Cook" wrote in message ... Arfa Daily wrote in message ... "N Cook" wrote in message ... Ten years ago I would have considered it impractical or even immoral. But having to replace yet another effectively all plastic 12 mm pot because the wiper is almost invisible in thickness, perhaps time for a rethink. This type of pot has a metal covering but its only function is as a shroud for fixing to the board, not even earthed, it does not strengthen the pot body to restrain abuse at the other, user end. No longer are such pots fixed to the front pannel. I'm thinking that with the next one to replace it will be with a standard small 12 mm or so enclosed preset that takes a standard plastic shaft in the adjustment slot, fudging the other end of the shaft to take the knob and through pannel bearer. The internal mechanism is just a pro-rata scaled down conventional paxolin backed track with double wiper nibs. If this replacement physically breaks in use then that seems more justifiable than the modern flimsy wipers losing spring action or just aging of the lubricant inside to wedge under the wiper and loose contact or whatever their problem is, the tracks are always perfect (so little wiper pressure presumably). Are the resistive tracks of presets more frail/easier scoored than pot tracks, so for that reason cannot be used say for volume control ? Anyone any opinions? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I would have said that the description " preset " tells you all that you need to know on that score. These components are designed to be set and left, pretty much for the lifetime of the equipment, so I can't see them standing up to the rigours of regular use for long. Add to this that as they are not designed to be rotated repeatedly as a user control, the wiper / track interface has not been designed to be specifically quiet. I also think that the control will feel bad to a user, as it will not have that " stirring treacle " feel that a proper user control has, courtesy of the drag grease that the manufacturers put in the spindle bush. Why not replace controls with manufacturer's originals ? Most group amp builders supply spare parts. Failing that, there are plenty of reasonable quality pots available - even the range that Maplin keep are pretty fair quality - and if you really want to fit top quality pots, these are also available from audiophile outlets. Arfa I had not considered the feel, which agreed is very 'scratchy'. Squirting silicone oil in one and turning back and forth a hundred times is very much improved, and resistive track still ok. What is the point of the feather-light touch of the flimsy pots if the downside is they just don't last. I don't see the point of replacing with an exact match when the original is say one of 8 and has only lasted for use once a week for 2 years before internally failing , ie not abuse. In fact they seem to be the pots that are not used much if at all, that's why I suspect clumping or something in the lubricant. I'll try a 1000 times and re-measure to see if the track fails. -- I'm actually really surprised that you seem to come across so many bad pots in group amps. I have been repairing these for many many years, and do lots of all makes and models, for a local shop, and I really don't have to replace many pots that aren't physically broken through taking knocks. I have found in general, that most manufacturers appreciate that this gear is going to last its owners for a lot of years, and tailor their design criteria, and component spec-ing to suit. I would agree that the pots fitted these days tend to be Japanese ( probably Chinese actually ) small-bodied types, which are not as good quality as say the large body Wellyns or the typical RS components pots that you used to find in them a few years back, but still, I don't seem to have that much trouble with them. If you really think that the problem is insufficient spring tension on the wiper fingers, just pile a bit more on. It's easily done with a pair of long-nosed pointy surgical tweezers. Arfa Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ The present problematic is a Carvin Pro Bass 100, PB100 which will come bouncing back next weekend. The new fault , could well be due to another pot failed, symptoms over the phone so far, the previous one I replaced is fine. I still have the previous original one lying around . No makers name , a logo like cross-section of a flying saucer, a thin elipse laid over a circle, just the outermost lineforms. The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it starts deflecting at only 12 grams pressure. Followup on my endurance test on a preset, I survived 1000 turns back and forth , whole track, as did the pot. No wavering on mid-track resistance readings. The rough feel has returned but I doubt that is due to the wiper action. Cracking it open, one obvious shiny, but not broken through to paxolin, track from one nib and vague partial thin trace from the other nib. I would estimate it could have done more than 10,000 rotations before both tracks were worn through. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#6
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
"N Cook" wrote in message ... Arfa Daily wrote in message ... "N Cook" wrote in message ... Arfa Daily wrote in message ... "N Cook" wrote in message ... Ten years ago I would have considered it impractical or even immoral. But having to replace yet another effectively all plastic 12 mm pot because the wiper is almost invisible in thickness, perhaps time for a rethink. This type of pot has a metal covering but its only function is as a shroud for fixing to the board, not even earthed, it does not strengthen the pot body to restrain abuse at the other, user end. No longer are such pots fixed to the front pannel. I'm thinking that with the next one to replace it will be with a standard small 12 mm or so enclosed preset that takes a standard plastic shaft in the adjustment slot, fudging the other end of the shaft to take the knob and through pannel bearer. The internal mechanism is just a pro-rata scaled down conventional paxolin backed track with double wiper nibs. If this replacement physically breaks in use then that seems more justifiable than the modern flimsy wipers losing spring action or just aging of the lubricant inside to wedge under the wiper and loose contact or whatever their problem is, the tracks are always perfect (so little wiper pressure presumably). Are the resistive tracks of presets more frail/easier scoored than pot tracks, so for that reason cannot be used say for volume control ? Anyone any opinions? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I would have said that the description " preset " tells you all that you need to know on that score. These components are designed to be set and left, pretty much for the lifetime of the equipment, so I can't see them standing up to the rigours of regular use for long. Add to this that as they are not designed to be rotated repeatedly as a user control, the wiper / track interface has not been designed to be specifically quiet. I also think that the control will feel bad to a user, as it will not have that " stirring treacle " feel that a proper user control has, courtesy of the drag grease that the manufacturers put in the spindle bush. Why not replace controls with manufacturer's originals ? Most group amp builders supply spare parts. Failing that, there are plenty of reasonable quality pots available - even the range that Maplin keep are pretty fair quality - and if you really want to fit top quality pots, these are also available from audiophile outlets. Arfa I had not considered the feel, which agreed is very 'scratchy'. Squirting silicone oil in one and turning back and forth a hundred times is very much improved, and resistive track still ok. What is the point of the feather-light touch of the flimsy pots if the downside is they just don't last. I don't see the point of replacing with an exact match when the original is say one of 8 and has only lasted for use once a week for 2 years before internally failing , ie not abuse. In fact they seem to be the pots that are not used much if at all, that's why I suspect clumping or something in the lubricant. I'll try a 1000 times and re-measure to see if the track fails. -- I'm actually really surprised that you seem to come across so many bad pots in group amps. I have been repairing these for many many years, and do lots of all makes and models, for a local shop, and I really don't have to replace many pots that aren't physically broken through taking knocks. I have found in general, that most manufacturers appreciate that this gear is going to last its owners for a lot of years, and tailor their design criteria, and component spec-ing to suit. I would agree that the pots fitted these days tend to be Japanese ( probably Chinese actually ) small-bodied types, which are not as good quality as say the large body Wellyns or the typical RS components pots that you used to find in them a few years back, but still, I don't seem to have that much trouble with them. If you really think that the problem is insufficient spring tension on the wiper fingers, just pile a bit more on. It's easily done with a pair of long-nosed pointy surgical tweezers. Arfa Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ The present problematic is a Carvin Pro Bass 100, PB100 which will come bouncing back next weekend. The new fault , could well be due to another pot failed, symptoms over the phone so far, the previous one I replaced is fine. I still have the previous original one lying around . No makers name , a logo like cross-section of a flying saucer, a thin elipse laid over a circle, just the outermost lineforms. The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it starts deflecting at only 12 grams pressure. Followup on my endurance test on a preset, I survived 1000 turns back and forth , whole track, as did the pot. No wavering on mid-track resistance readings. The rough feel has returned but I doubt that is due to the wiper action. Cracking it open, one obvious shiny, but not broken through to paxolin, track from one nib and vague partial thin trace from the other nib. I would estimate it could have done more than 10,000 rotations before both tracks were worn through. In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa |
#7
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Arfa Daily wrote:
In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) |
#8
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
"Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa |
#9
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Ron(UK) wrote in message
... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) I should have said the failed original in the 0.6mm was 2 wipers , the metal is split into 2 wipers and nibs, absolutely no trace of wear on the track. I have a few hundred Piher presets that have an enlarged slot to take rod extenders with pair of pauls to engage the back of the slot, quite strong enough to be used as unabused pots. The very light action of the originals I would have thought were a disadvantage, on stage, as you could easily dislodge a neighbouring pot. Some of these Piher presets are log tracks, agreed unusual but useful -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#10
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Arfa Daily wrote:
"Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa Ah ok, Piher do a range of shafts for their min presets. I`ve used them on radio mike receivers etc. to replace the output level and squelch controls, invariably because the user has been heavy handed with them. The combined cost of preset and shaft is quite high compared with a normal pot. Personally I like the Omeg ECO plastic pots for replacements on gear that takes standard quarter inch bore knobs, Rapid Electronics stock the pots with the monkey metal slotted and splined short shaft that fits a lot of the Chinese product Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com |
#11
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
"Ron(UK)" wrote: Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Never IME. Graham |
#12
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Ron(UK) wrote in message
... Arfa Daily wrote: "Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa Ah ok, Piher do a range of shafts for their min presets. I`ve used them on radio mike receivers etc. to replace the output level and squelch controls, invariably because the user has been heavy handed with them. The combined cost of preset and shaft is quite high compared with a normal pot. Personally I like the Omeg ECO plastic pots for replacements on gear that takes standard quarter inch bore knobs, Rapid Electronics stock the pots with the monkey metal slotted and splined short shaft that fits a lot of the Chinese product Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com If you mean the Vishay 12/13mm footprint pots then they are the right size but the manufacturer's pdfs don't give the wiper dimensions , if of thickness of a coarse human hair , 150 microns, then little point in using, as will be back to square 1 in a few years. |
#13
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Anyone replace pots with presets ?
N Cook wrote:
Ron(UK) wrote in message ... Arfa Daily wrote: "Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa Ah ok, Piher do a range of shafts for their min presets. I`ve used them on radio mike receivers etc. to replace the output level and squelch controls, invariably because the user has been heavy handed with them. The combined cost of preset and shaft is quite high compared with a normal pot. Personally I like the Omeg ECO plastic pots for replacements on gear that takes standard quarter inch bore knobs, Rapid Electronics stock the pots with the monkey metal slotted and splined short shaft that fits a lot of the Chinese product Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com If you mean the Vishay 12/13mm footprint pots then they are the right size but the manufacturer's pdfs don't give the wiper dimensions , if of thickness of a coarse human hair , 150 microns, then little point in using, as will be back to square 1 in a few years. I didn't, I meant Omeg, but the Vishay pots will certainly be better than anything fitted as an original part by the vast majority of manufacturers. Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com |
#14
Posted to sci.electronics.repair
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Anyone replace pots with presets ?
Arfa Daily wrote:
"Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa It's really a moot point though. One can still buy very high quality pots from a reputable manufacture. That's the route to take rather than trying to hack in something different. A good pot will last the life of most equipment. I use Bournes pots in arcade game controllers, they seem to hold up well to the abuse. |
#15
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Anyone replace pots with presets ?
"James Sweet" wrote in message news:tUgph.3163$Br.1752@trndny08... Arfa Daily wrote: "Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa It's really a moot point though. One can still buy very high quality pots from a reputable manufacture. That's the route to take rather than trying to hack in something different. A good pot will last the life of most equipment. I use Bournes pots in arcade game controllers, they seem to hold up well to the abuse. Hi James. That was my original feeling also, but as I said further up, I repair lots of group equipment, and really don't seem to suffer that much from bad as opposed to broken pots, anyway. Arfa |
#16
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Anyone replace pots with presets ?
Arfa Daily wrote:
Hi James. That was my original feeling also, but as I said further up, I repair lots of group equipment, and really don't seem to suffer that much from bad as opposed to broken pots, anyway. What do you mean by "Group equipment"? BTW, http://potentiometer.com/ carries high end commercial & military grade pots in the US. -- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida |
#17
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Anyone replace pots with presets ?
"Michael A. Terrell" wrote: Arfa Daily wrote: Hi James. That was my original feeling also, but as I said further up, I repair lots of group equipment, and really don't seem to suffer that much from bad as opposed to broken pots, anyway. What do you mean by "Group equipment"? Musical Instrument amplifiers and the like. Graham |
#18
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Anyone replace pots with presets ?
James Sweet wrote in message
news:tUgph.3163$Br.1752@trndny08... Arfa Daily wrote: "Ron(UK)" wrote in message ... Arfa Daily wrote: In that case, go for it. I would be interested to know how you get on with such transpants, and which presets you ultimately find most suitable. Also, how quiet they are in actual practical usage. Arfa I'm interested to know how the OP plans to reliably connect a standard shaft to a preset, I`m presuming his idea of a preset and mine concur. One other point, presents don`t normally come in log tapers, do they? Ron(UK) Hi Ron. That is a very good point, and one that I hadn't even considered when thinking about his original plan to use these. If you look in the post that started the thread, he says that he is intending using the presets that you can get a 6mm shaft for that turns them into a ( semi ?? ) user control - I'm sure you've seen the idea on stuff where there is an adjustment that would be a good idea to have available to the user, but not in a way that encourages him to *use* it. The shafts that I've seen usually have a lightly splined finish so that they can be gripped, and a screwdriver slot in the end. I think he intends to pass one of these through a panel mount shaft bush, and then persuade the knob to fit. Arfa It's really a moot point though. One can still buy very high quality pots from a reputable manufacture. That's the route to take rather than trying to hack in something different. A good pot will last the life of most equipment. I use Bournes pots in arcade game controllers, they seem to hold up well to the abuse. The thread concerns 12/13 mm footprint pots (sub miniature), no problem with 17mm miniature or 21mm standard size ones. I doubt game controllers use subminiature ones. |
#19
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Anyone replace pots with presets ?
N Cook wrote:
The thread concerns 12/13 mm footprint pots (sub miniature), no problem with 17mm miniature or 21mm standard size ones. I doubt game controllers use subminiature ones. One thing that concerns me about using a preset as a user control is the 'end stop' arrangement. Is the mechanism that prevents a user from turning the control past it`s fully on or fully off position rugged enough on a preset to to the job considering what heavy handed users there sometimes are in the music business. Also, if the end stop IS strong enough, is the mounting arrangement of a preset strong enough to withstand the turning force of a typical death metal guitarist after several pints of Krugermeister? Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com |
#20
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Anyone replace pots with presets ?
"Michael A. Terrell" wrote in message ... Arfa Daily wrote: Hi James. That was my original feeling also, but as I said further up, I repair lots of group equipment, and really don't seem to suffer that much from bad as opposed to broken pots, anyway. What do you mean by "Group equipment"? Er, equipment used by groups ? Like bands ? Beatles, Rolling Stones ? Do you not call them "groups" your side of the pond ? Never heard the term "groupies" for the girls that follow them around ? In terms of this thread, we have been talking specifically amplifiers for musical instruments, but in general, at least over here, "group equipment" covers anything that a group or band may be using on stage ( or off-stage ) to make their sound or image, so amps, mixer desks, effects units / pedals, wireless mics, lighting effects and so on. I know from our past - errr ... 'conversations' shall we say - that you have been involved in the repair of this equipment, so I'm sure that you probably have a valid opinion on the substituting of panel-type pots with presets made into panel mounting types ?? Back to you, friend ... Arfa |
#21
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Anyone replace pots with presets ?
Ron(UK) wrote in message
... N Cook wrote: The thread concerns 12/13 mm footprint pots (sub miniature), no problem with 17mm miniature or 21mm standard size ones. I doubt game controllers use subminiature ones. One thing that concerns me about using a preset as a user control is the 'end stop' arrangement. Is the mechanism that prevents a user from turning the control past it`s fully on or fully off position rugged enough on a preset to to the job considering what heavy handed users there sometimes are in the music business. Also, if the end stop IS strong enough, is the mounting arrangement of a preset strong enough to withstand the turning force of a typical death metal guitarist after several pints of Krugermeister? Ron(UK) -- Lune Valley Audio Public Address Systems Hire Sales Maintenance www.lunevalleyaudio.com Thanks for that, I had not considered the end stops. The original one, with the flimsey wiper, had quite manly endstop nib on the shaft and housing moulding. These presets have similar sized physical end stops, the weakest point would be the two plastic pauls on the shaft that engage with the slot, about 3 x 1.5mm each in cross section. I would mount the body to pcb with hot melt glue. Guitarists and pot problems is usually the guitar controls where the fascia is plastic so no reliable mounting, so the nuts loosen and pots are then twisted round and round , windlassing the wires into a broken mess. That problem I cure by heavy-soldering a thick copper strip between all the pots, replacing the wire grounds between the pots -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#22
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Anyone replace pots with presets ?
Arfa Daily wrote:
"Michael A. Terrell" wrote in message ... Arfa Daily wrote: Hi James. That was my original feeling also, but as I said further up, I repair lots of group equipment, and really don't seem to suffer that much from bad as opposed to broken pots, anyway. What do you mean by "Group equipment"? Er, equipment used by groups ? Like bands ? Beatles, Rolling Stones ? Do you not call them "groups" your side of the pond ? Never heard the term "groupies" for the girls that follow them around? Groupie is a group of enthusiastic fans of any type, in the US. In terms of this thread, we have been talking specifically amplifiers for musical instruments, but in general, at least over here, "group equipment" covers anything that a group or band may be using on stage ( or off-stage ) to make their sound or image, so amps, mixer desks, effects units / pedals, wireless mics, lighting effects and so on. They referred to them as bands, and their electronics as "Band Amps", "Musical equipment" or "Guitar amps" when I was doing that work in the '70s & '80s. Most repairs were done by part time techs at music stores, but there was usually a shop that specialized in amp repair in bigger cities. I even saw a few british amps, back in the '70s when some clueless wanabes were trying to copy one band or another, right down to the brand of wire and connectors for their cables. The only thing they forgot was to learn how to play music, sing, and perform in front of people who want good music. ;-) I know from our past - errr ... 'conversations' shall we say - that you have been involved in the repair of this equipment, so I'm sure that you probably have a valid opinion on the substituting of panel-type pots with presets made into panel mounting types ?? Back to you, friend ... As far as I am concerned, panel mounted controls are the only way to go for any application that involves rugged service. PC mounted are ok for internal adjustment, but nothing beats a mil spec made to last for 25 years of daily use. -- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida |
#23
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Anyone replace pots with presets ?
The thread concerns 12/13 mm footprint pots (sub miniature), no problem with 17mm miniature or 21mm standard size ones. I doubt game controllers use subminiature ones. What difference does it make? Cheap pots are cheap pots. I was originally using ones from Radio Shack, but those were not holding up even to home use. |
#24
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Anyone replace pots with presets ?
Seems kind of unlikely that equipment like that would get a lot of wear
from the pots being adjusted back and forth. Could it be that vibration from the speakers is tearing up the pots in the head? Maybe the PC board and front panel lack the mechanical dampening to protect this from happening. N Cook wrote: The present problematic is a Carvin Pro Bass 100, PB100 which will come bouncing back next weekend. The new fault , could well be due to another pot failed, symptoms over the phone so far, the previous one I replaced is fine. I still have the previous original one lying around . No makers name , a logo like cross-section of a flying saucer, a thin elipse laid over a circle, just the outermost lineforms. The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it starts deflecting at only 12 grams pressure. Followup on my endurance test on a preset, I survived 1000 turns back and forth , whole track, as did the pot. No wavering on mid-track resistance readings. The rough feel has returned but I doubt that is due to the wiper action. Cracking it open, one obvious shiny, but not broken through to paxolin, track from one nib and vague partial thin trace from the other nib. I would estimate it could have done more than 10,000 rotations before both tracks were worn through. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P |
#25
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Anyone replace pots with presets ?
That explains the problem. What he needs to do is follow the group out
to the "Gig". He doesn't need to be there from the start, rather at the end when the group finishes up by smashing their guitars and mike stands into his rental amplifiers! Eeyore wrote: "Michael A. Terrell" wrote: Arfa Daily wrote: Hi James. That was my original feeling also, but as I said further up, I repair lots of group equipment, and really don't seem to suffer that much from bad as opposed to broken pots, anyway. What do you mean by "Group equipment"? Musical Instrument amplifiers and the like. Graham That explains the problem. What he needs to do is follow the group out to the "Gig". He doesn't need to be there from the start, rather at the end when the group finishes up by smashing their guitars and mike stands into his rental amplifiers! -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P |
#26
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Anyone replace pots with presets ?
**THE-RFI-EMI-GUY** wrote in message
... Seems kind of unlikely that equipment like that would get a lot of wear from the pots being adjusted back and forth. Could it be that vibration from the speakers is tearing up the pots in the head? Maybe the PC board and front panel lack the mechanical dampening to protect this from happening. N Cook wrote: The present problematic is a Carvin Pro Bass 100, PB100 which will come bouncing back next weekend. The new fault , could well be due to another pot failed, symptoms over the phone so far, the previous one I replaced is fine. I still have the previous original one lying around . No makers name , a logo like cross-section of a flying saucer, a thin elipse laid over a circle, just the outermost lineforms. The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it starts deflecting at only 12 grams pressure. Followup on my endurance test on a preset, I survived 1000 turns back and forth , whole track, as did the pot. No wavering on mid-track resistance readings. The rough feel has returned but I doubt that is due to the wiper action. Cracking it open, one obvious shiny, but not broken through to paxolin, track from one nib and vague partial thin trace from the other nib. I would estimate it could have done more than 10,000 rotations before both tracks were worn through. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P Its not a wear problem , in my opinion. There is absolutely no wear on the track , the problem is due to too flimsy a wiper, half an ounce of pressure is enough to start lifting the wiper, ie only age-thickened lubricant grease inside is enough to do that. |
#27
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Anyone replace pots with presets ?
"N Cook" wrote in message ... **THE-RFI-EMI-GUY** wrote in message ... Seems kind of unlikely that equipment like that would get a lot of wear from the pots being adjusted back and forth. Could it be that vibration from the speakers is tearing up the pots in the head? Maybe the PC board and front panel lack the mechanical dampening to protect this from happening. N Cook wrote: The present problematic is a Carvin Pro Bass 100, PB100 which will come bouncing back next weekend. The new fault , could well be due to another pot failed, symptoms over the phone so far, the previous one I replaced is fine. I still have the previous original one lying around . No makers name , a logo like cross-section of a flying saucer, a thin elipse laid over a circle, just the outermost lineforms. The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it starts deflecting at only 12 grams pressure. Followup on my endurance test on a preset, I survived 1000 turns back and forth , whole track, as did the pot. No wavering on mid-track resistance readings. The rough feel has returned but I doubt that is due to the wiper action. Cracking it open, one obvious shiny, but not broken through to paxolin, track from one nib and vague partial thin trace from the other nib. I would estimate it could have done more than 10,000 rotations before both tracks were worn through. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P Its not a wear problem , in my opinion. There is absolutely no wear on the track , the problem is due to too flimsy a wiper, half an ounce of pressure is enough to start lifting the wiper, ie only age-thickened lubricant grease inside is enough to do that. But surely that's the age-old problem of any pot ? Isn't that why we all squib decent quality switch cleaner into pot bodies ? The volatile component of this dissolves and washes out the hardened grease, whilst the lubricant component recoats the track. Thinking about your statements regarding wiper pressure. The wiper has to have reasonably light contact with the track in a user-intended control, otherwise constant adjustment, would wear the track. It seems to me that a half ounce of contact pressure, is quite a lot ? For sure, the big old clunky pots that were fitted to gear 40 years ago, probably had a wiper the size of your hand that pressed on a track as thick as your finger with a pressure of half a pound, but times and manufacturing techniques move on. Just exactly what problems do you seem to get with all these pots, that won't fix with a shot of Electrolube ? With the shaft encoders that many hifi's use now for volume control, I've found that the grease which appears on the encoder disc, and stops then from working, is the treacle-stir-feel grease that they put in the shaft bearing, which has migrated down into the main body. The wipers in these devices are like feathers, and very delicate, but once they are cleaned out, and relubed with a proper contact lubricant, they don't give any more trouble - in fact I can't recall ever having one thus treated, bounce back on me. Arfa |
#28
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Anyone replace pots with presets ?
N Cook wrote:
Its not a wear problem , in my opinion. There is absolutely no wear on the track , the problem is due to too flimsy a wiper, half an ounce of pressure is enough to start lifting the wiper, ie only age-thickened lubricant grease inside is enough to do that. It`s the age old problem of cheap nasty low cost components being used, even in some equipment perceived as being of high status. You CAN buy decent pots if you shop around, or use normal replacement pots and add a drop of electrolube to the track before you solder it in. I wouldn`t advise changing too many components in some muso`s vintage gear, some of these valve amp afficionados get shirty if you replace faulty resistors with modern types that 'don't look right' I hate to think what they`d say if you added a bodged up pot Ron(UK) |
#29
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Anyone replace pots with presets ?
I'm coming round to thinking that as these pots are easily openable and
there is no wear at all on the tracks, then clean out all the lubricant with meths or something, coat the wiper with something to stiffen it up a bit and re-assemble, with no lubricant at all, maybe just "dry lubricant" of fine graphite powder laid in the track area instead. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#30
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Anyone replace pots with presets ?
Arfa Daily wrote in message
... "N Cook" wrote in message ... **THE-RFI-EMI-GUY** wrote in message ... Seems kind of unlikely that equipment like that would get a lot of wear from the pots being adjusted back and forth. Could it be that vibration from the speakers is tearing up the pots in the head? Maybe the PC board and front panel lack the mechanical dampening to protect this from happening. N Cook wrote: The present problematic is a Carvin Pro Bass 100, PB100 which will come bouncing back next weekend. The new fault , could well be due to another pot failed, symptoms over the phone so far, the previous one I replaced is fine. I still have the previous original one lying around . No makers name , a logo like cross-section of a flying saucer, a thin elipse laid over a circle, just the outermost lineforms. The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it starts deflecting at only 12 grams pressure. Followup on my endurance test on a preset, I survived 1000 turns back and forth , whole track, as did the pot. No wavering on mid-track resistance readings. The rough feel has returned but I doubt that is due to the wiper action. Cracking it open, one obvious shiny, but not broken through to paxolin, track from one nib and vague partial thin trace from the other nib. I would estimate it could have done more than 10,000 rotations before both tracks were worn through. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason." "Follow The Money" ;-P Its not a wear problem , in my opinion. There is absolutely no wear on the track , the problem is due to too flimsy a wiper, half an ounce of pressure is enough to start lifting the wiper, ie only age-thickened lubricant grease inside is enough to do that. But surely that's the age-old problem of any pot ? Isn't that why we all squib decent quality switch cleaner into pot bodies ? The volatile component of this dissolves and washes out the hardened grease, whilst the lubricant component recoats the track. Thinking about your statements regarding wiper pressure. The wiper has to have reasonably light contact with the track in a user-intended control, otherwise constant adjustment, would wear the track. It seems to me that a half ounce of contact pressure, is quite a lot ? For sure, the big old clunky pots that were fitted to gear 40 years ago, probably had a wiper the size of your hand that pressed on a track as thick as your finger with a pressure of half a pound, but times and manufacturing techniques move on. Just exactly what problems do you seem to get with all these pots, that won't fix with a shot of Electrolube ? With the shaft encoders that many hifi's use now for volume control, I've found that the grease which appears on the encoder disc, and stops then from working, is the treacle-stir-feel grease that they put in the shaft bearing, which has migrated down into the main body. The wipers in these devices are like feathers, and very delicate, but once they are cleaned out, and relubed with a proper contact lubricant, they don't give any more trouble - in fact I can't recall ever having one thus treated, bounce back on me. Arfa I'm not sure that aerosol lubricant would reliably get into these pots , there certainly isn't any slots and I would say the injection mouleded 2 components of the housing are tight fitting. There is still the sludgy lubricant grease inside. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#31
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Anyone replace pots with presets ?
"N Cook" wrote in message ... I'm coming round to thinking that as these pots are easily openable and there is no wear at all on the tracks, then clean out all the lubricant with meths or something, coat the wiper with something to stiffen it up a bit and re-assemble, with no lubricant at all, maybe just "dry lubricant" of fine graphite powder laid in the track area instead. Ah ! Same post appeared ( accidentally I guess ) in your "speaker power" thread, so I say the same here - There ya go then ! I also agree with Ron in respect of subbing parts in musos' gear. Looking for trouble with some of them ... Arfa -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#32
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Anyone replace pots with presets ?
Arfa Daily wrote in message
... "N Cook" wrote in message ... I'm coming round to thinking that as these pots are easily openable and there is no wear at all on the tracks, then clean out all the lubricant with meths or something, coat the wiper with something to stiffen it up a bit and re-assemble, with no lubricant at all, maybe just "dry lubricant" of fine graphite powder laid in the track area instead. Ah ! Same post appeared ( accidentally I guess ) in your "speaker power" thread, so I say the same here - There ya go then ! I also agree with Ron in respect of subbing parts in musos' gear. Looking for trouble with some of them ... Arfa -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Rushing around to go to a pyrotechnics lecture. Interesting demonstratiion of a developemental stage pyrotechnic strobe light, for chemistry , amazingly sharp cut-off, re-ignition, of about 4 flashes per second, intense flare strobe action |
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