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#1
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Electronic keyboard repair (I hope)
New here ... Yamaha PSR-12, has maybe 72 keys, around 24 voicings, flexible-speed percussion, canned tunes, etc. About 20 years old. I turn it on lately, it works fine for 2-10 min., then freezes. The little light that is supposed to come on for beat 1 (when percussion accompaniment is running) locks on. That and the power led are the only things functional. The case has 2 halves. I workbench the thing turning the business end (with keys and most PCB's) up 90 degrees to tinker, and it plays OK for up to 3 hours (presumably lots longer). I figured the problem has to do with either gravity or heat buildup, but I just left it normally assembled and on for several hours and it didn't freeze up, so maybe heat isn't the problem. There are PCB's for power and switching, and 2 big PCB's presumably for tone generation, special effects, etc. I tried some ribbon cable connections: wouldn't budge. I'm afraid of breaking a board or connector or ?. It's gotta be repairable. I think. :-) Any/all help/advice much appreciated. Thx, Puddin' "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#2
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Electronic keyboard repair (I hope)
"Puddin' Man" wrote in message ... New here ... Yamaha PSR-12, has maybe 72 keys, around 24 voicings, flexible-speed percussion, canned tunes, etc. About 20 years old. I turn it on lately, it works fine for 2-10 min., then freezes. The little light that is supposed to come on for beat 1 (when percussion accompaniment is running) locks on. That and the power led are the only things functional. The case has 2 halves. I workbench the thing turning the business end (with keys and most PCB's) up 90 degrees to tinker, and it plays OK for up to 3 hours (presumably lots longer). I figured the problem has to do with either gravity or heat buildup, but I just left it normally assembled and on for several hours and it didn't freeze up, so maybe heat isn't the problem. There are PCB's for power and switching, and 2 big PCB's presumably for tone generation, special effects, etc. I tried some ribbon cable connections: wouldn't budge. I'm afraid of breaking a board or connector or ?. It's gotta be repairable. I think. :-) Any/all help/advice much appreciated. Thx, Puddin' Stuff with micros locking up, often is a heat problem to do with the power supply, especially if the item really is 20 years old, and more especially, if it makes use of a switchmode power supply. As a first move, I would feel inclined to pop a meter on the main 5v rail, and see where it's at, then leave it on there, and see if it's any different, when the unit locks up. A 'scope on there wouldn't hurt as well. The rail should ideally be no lower than about 4.85v and no higher than about 5.2v. The 'official' limits are a little wider than that, but it won't have been designed to run outside of the limits I've said. The rail should also be 'clean' with hash or ripple no higher than say 20mV. If there are any issues with voltage level or noise, look to caps and resistors in the regulator circuit, for your trouble. If the power supply turns out to be ok, the next place I would turn my attention, is to the system control processor's clock crystal. Old xtals sometimes get reluctant to oscillate, and will just stop after a short while, in just the way you describe. You can often 'prove the point' by taking the xtal out, and refitting it reveresed to its original orientation. Finally, I have a dim recollection of a keyboard having a problem like this, some years ago. As I recall, it too had a couple of large logic boards, and ribbon style interconnects looping the boards and power supply together. The 'launch' level of the power supply was fine at 5v, but by the time it reached the second board, having passed through tracks from one end of the board to the other, and the in and out board connectors, it had dropped to perhaps 4.8v, due no doubt to age-deterioration of the connector plating, and the large current that all this logic draws on the older stuff. Anyway, it was enough to cause the thing to keep locking up. Eventually, I decided that there was no particular need for the supply to the furthest board to loop through the nearest one, so I gave it its own heavy gauge wires straight back to the power supply, which cleared up its problems completely. Arfa |
#3
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Electronic keyboard repair (I hope)
Arfa Daily wrote:
"Puddin' Man" wrote in message ... New here ... Yamaha PSR-12, has maybe 72 keys, around 24 voicings, flexible-speed percussion, canned tunes, etc. About 20 years old. I turn it on lately, it works fine for 2-10 min., then freezes. The little light that is supposed to come on for beat 1 (when percussion accompaniment is running) locks on. That and the power led are the only things functional. The case has 2 halves. I workbench the thing turning the business end (with keys and most PCB's) up 90 degrees to tinker, and it plays OK for up to 3 hours (presumably lots longer). I figured the problem has to do with either gravity or heat buildup, but I just left it normally assembled and on for several hours and it didn't freeze up, so maybe heat isn't the problem. There are PCB's for power and switching, and 2 big PCB's presumably for tone generation, special effects, etc. I tried some ribbon cable connections: wouldn't budge. I'm afraid of breaking a board or connector or ?. It's gotta be repairable. I think. :-) Any/all help/advice much appreciated. Thx, Puddin' Stuff with micros locking up, often is a heat problem to do with the power supply, especially if the item really is 20 years old, and more especially, if it makes use of a switchmode power supply. As a first move, I would feel inclined to pop a meter on the main 5v rail, and see where it's at, then leave it on there, and see if it's any different, when the unit locks up. A 'scope on there wouldn't hurt as well. The rail should ideally be no lower than about 4.85v and no higher than about 5.2v. The 'official' limits are a little wider than that, but it won't have been designed to run outside of the limits I've said. The rail should also be 'clean' with hash or ripple no higher than say 20mV. If there are any issues with voltage level or noise, look to caps and resistors in the regulator circuit, for your trouble. If the power supply turns out to be ok, the next place I would turn my attention, is to the system control processor's clock crystal. Old xtals sometimes get reluctant to oscillate, and will just stop after a short while, in just the way you describe. You can often 'prove the point' by taking the xtal out, and refitting it reveresed to its original orientation. Finally, I have a dim recollection of a keyboard having a problem like this, some years ago. As I recall, it too had a couple of large logic boards, and ribbon style interconnects looping the boards and power supply together. The 'launch' level of the power supply was fine at 5v, but by the time it reached the second board, having passed through tracks from one end of the board to the other, and the in and out board connectors, it had dropped to perhaps 4.8v, due no doubt to age-deterioration of the connector plating, and the large current that all this logic draws on the older stuff. Anyway, it was enough to cause the thing to keep locking up. Eventually, I decided that there was no particular need for the supply to the furthest board to loop through the nearest one, so I gave it its own heavy gauge wires straight back to the power supply, which cleared up its problems completely. Arfa It`s just possible that a reset to factory settings might help[1]. There`s a list of Yamaha reset procedures here http://www.yamaha-europe.com/yamaha_...ist/index.html I dont see one for the PSR-12 but it`s possible that one of the other PSR resets would work. [1] It`s a long shot but it might work! Ron(UK) |
#4
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Electronic keyboard repair (I hope)
On Wed, 12 Dec 2007 09:33:11 GMT, "Arfa Daily" wrote:
Stuff with micros locking up, often is a heat problem to do with the power supply, especially if the item really is 20 years old, and more especially, if it makes use of a switchmode power supply. As a first move, I would feel inclined to pop a meter on the main 5v rail, and see where it's at, then leave it on there, and see if it's any different, when the unit locks up. A 'scope on there wouldn't hurt as well. The rail should ideally be no lower than about 4.85v and no higher than about 5.2v. The 'official' limits are a little wider than that, but it won't have been designed to run outside of the limits I've said. The rail should also be 'clean' with hash or ripple no higher than say 20mV. Here's some additional info: The specs say "rated voltage - 9v dc". I have only 19 yr-old $10 meter. I don't expect accuracy, but rather ballpark readings. Directly from the 120v converter connector, it *looks* like 15v dc. The switch/volume board has a 2 element wire that appears to feed the 2 main boards. There I measure 2v dc both with the unit functionaing -and- when it is frozen. Did that make any sense? Thanks, P "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#5
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Electronic keyboard repair (I hope)
On Wed, 12 Dec 2007 11:16:07 +0000, "Ron(UK)" wrote:
It`s just possible that a reset to factory settings might help[1]. There`s a list of Yamaha reset procedures here http://www.yamaha-europe.com/yamaha_...ist/index.html I dont see one for the PSR-12 but it`s possible that one of the other PSR resets would work. [1] It`s a long shot but it might work! Anything's worth a shot. But I'm having trouble interpreting such as: PSR220 Press [+/YES], [-1/NO] + Power on There's no +, -, YES, NO on the keyboard. There are 2 pairs of buttons with only up/down settings: pitch and beat. When the unit freezes, these buttons have no effect. Thx, P "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#6
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Electronic keyboard repair (I hope)
Puddin' Man wrote:
On Wed, 12 Dec 2007 09:33:11 GMT, "Arfa Daily" wrote: Stuff with micros locking up, often is a heat problem to do with the power supply, especially if the item really is 20 years old, and more especially, if it makes use of a switchmode power supply. As a first move, I would feel inclined to pop a meter on the main 5v rail, and see where it's at, then leave it on there, and see if it's any different, when the unit locks up. A 'scope on there wouldn't hurt as well. The rail should ideally be no lower than about 4.85v and no higher than about 5.2v. The 'official' limits are a little wider than that, but it won't have been designed to run outside of the limits I've said. The rail should also be 'clean' with hash or ripple no higher than say 20mV. Here's some additional info: The specs say "rated voltage - 9v dc". I have only 19 yr-old $10 meter. I don't expect accuracy, but rather ballpark readings. Directly from the 120v converter connector, it *looks* like 15v dc. The switch/volume board has a 2 element wire that appears to feed the 2 main boards. There I measure 2v dc both with the unit functionaing -and- when it is frozen. Did that make any sense? Yes...and no. The 2 volt reading is meaningless unless you can determine that it was measured at the point where supply voltage enters that particular board. There might be some sort of marking at the terminal...perhaps "+5v" or "B+" or "Vcc". That the voltage does not change when frozen is irrelevant. That said, if it *is* the main supply terminal, it is probably low, and the unit is just barely limping along with reduced voltage even when functioning. The 15vdc reading from the 'unloaded' (IOW not connected to anything) supply is also irrelevant. The relevant reading is taken when the supply is actually supplying current to the keyboard. You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. jak Thanks, P "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#7
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Electronic keyboard repair (I hope)
On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote:
You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#8
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Electronic keyboard repair (I hope)
"Puddin' Man" wrote in message ... On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote: You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "+5D" will be the 5v digital supply - ie the 5v supply for the digital electronics, and "+5A" will be the 5v analogue supply. "DG" and "AG" are the corresponding digital and analogue ground returns for those two supplies, so will be the references to measure the supplies against. You really need to be able to measure the +5D supply with a reasonable amount of accuracy - to at least 0.05v. Arfa |
#9
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Electronic keyboard repair (I hope)
On Thu, 13 Dec 2007 01:11:59 GMT, "Arfa Daily" wrote:
"Puddin' Man" wrote in message .. . On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote: You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "+5D" will be the 5v digital supply - ie the 5v supply for the digital electronics, and "+5A" will be the 5v analogue supply. "DG" and "AG" are the corresponding digital and analogue ground returns for those two supplies, so will be the references to measure the supplies against. That's a big help. I had no idea how they code such stuff. You really need to be able to measure the +5D supply with a reasonable amount of accuracy - to at least 0.05v. To what extent will such an accurate measuring device empty my po' wallet? Goes without saying that if I get 5v from +5D when it plays and 0v when it freezes, I've likely found my problem? Thanks, P "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#10
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Electronic keyboard repair (I hope)
"Puddin' Man" wrote in message ... On Thu, 13 Dec 2007 01:11:59 GMT, "Arfa Daily" wrote: "Puddin' Man" wrote in message . .. On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote: You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "+5D" will be the 5v digital supply - ie the 5v supply for the digital electronics, and "+5A" will be the 5v analogue supply. "DG" and "AG" are the corresponding digital and analogue ground returns for those two supplies, so will be the references to measure the supplies against. That's a big help. I had no idea how they code such stuff. You really need to be able to measure the +5D supply with a reasonable amount of accuracy - to at least 0.05v. To what extent will such an accurate measuring device empty my po' wallet? Goes without saying that if I get 5v from +5D when it plays and 0v when it freezes, I've likely found my problem? Thanks, P Weeeelll, yes ... But more likely, it would be something like 4.9v when it's working ie just limping along on the lowest threshold that the micro can work at, and 4.7v when it's wrong. With digital electronics, particularly older garden variety such as this, a few decimals of a volt are enough to make the difference, which is why you need a meter that can read to half a decimal. Such a meter is not expensive, and if the one you have, even if it is a $10 job, is digital, then it should be capable of this level of resolution. The trick is how *accurate* it actually is, and that is something that you can't really know without comparing it to a 'standard' or someone else's much more expensive meter. I am shortly to be away for a few days, so will only get back on here another time or two. There are lots of others on here who should be able to help you through this. Good luck with it, and hope you manage to get a result. Arfa |
#11
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Electronic keyboard repair (I hope)
On Thu, 13 Dec 2007 09:42:34 GMT, "Arfa Daily" wrote:
"Puddin' Man" wrote in message .. . On Thu, 13 Dec 2007 01:11:59 GMT, "Arfa Daily" wrote: "Puddin' Man" wrote in message ... On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote: You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "+5D" will be the 5v digital supply - ie the 5v supply for the digital electronics, and "+5A" will be the 5v analogue supply. "DG" and "AG" are the corresponding digital and analogue ground returns for those two supplies, so will be the references to measure the supplies against. That's a big help. I had no idea how they code such stuff. You really need to be able to measure the +5D supply with a reasonable amount of accuracy - to at least 0.05v. To what extent will such an accurate measuring device empty my po' wallet? Goes without saying that if I get 5v from +5D when it plays and 0v when it freezes, I've likely found my problem? Thanks, P Weeeelll, yes ... But more likely, it would be something like 4.9v when it's working ie just limping along on the lowest threshold that the micro can work at, and 4.7v when it's wrong. With digital electronics, particularly older garden variety such as this, a few decimals of a volt are enough to make the difference, which is why you need a meter that can read to half a decimal. Ouch. Such a meter is not expensive, and if the one you have, even if it is a $10 job, is digital, then it should be capable of this level of resolution. It's analog. I spotted a Sears Craftsman dig. meter on sale $30 but sez "DC accuracy to 0.7 percent for accurate measurements." Not sufficient for the job? The trick is how *accurate* it actually is, and that is something that you can't really know without comparing it to a 'standard' or someone else's much more expensive meter. I am shortly to be away for a few days, so will only get back on here another time or two. There are lots of others on here who should be able to help you through this. Good luck with it, and hope you manage to get a result. Your help is -very- much appreciated. I continue to try to measure differential voltage between the ekb when working and when "frozen". Just measured both putting the meter under the microscope of my eyeball. If there was any difference at all, there was a snatch-hair more voltage when "frozen". Reading was like 4.9 v. Dunno where to go from here. Any help most welcome. Cheers, Puddin' "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 |
#12
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Electronic keyboard repair (I hope)
Puddin' Man wrote in message
... On Thu, 13 Dec 2007 01:11:59 GMT, "Arfa Daily" wrote: "Puddin' Man" wrote in message .. . On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote: You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "+5D" will be the 5v digital supply - ie the 5v supply for the digital electronics, and "+5A" will be the 5v analogue supply. "DG" and "AG" are the corresponding digital and analogue ground returns for those two supplies, so will be the references to measure the supplies against. That's a big help. I had no idea how they code such stuff. You really need to be able to measure the +5D supply with a reasonable amount of accuracy - to at least 0.05v. To what extent will such an accurate measuring device empty my po' wallet? Goes without saying that if I get 5v from +5D when it plays and 0v when it freezes, I've likely found my problem? Thanks, P For some odd reason it is often difficult to find a 0 ground point on music keyboards. Usually the battery negative is usable for that. Unpowered of course I would undo and remake any ribbon connections and closely inspect all surface mount chips with a powerfull magnifying glass and bright light , followed by looking at all solder joints. then powered Use an empty plastic ball point pen barrel to push all chips, tap other lumps ,waggle wires etc while powered up to see if anything changes , with a note engaged by sticky tape. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#13
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Electronic keyboard repair (I hope)
In article ,
Puddin' Man wrote: On Thu, 13 Dec 2007 09:42:34 GMT, "Arfa Daily" wrote: "Puddin' Man" wrote in message .. . On Thu, 13 Dec 2007 01:11:59 GMT, "Arfa Daily" wrote: "Puddin' Man" wrote in message ... On Wed, 12 Dec 2007 15:42:10 -0600, jakdedert wrote: You need to find the main power supply board, and trace forward from where there. That board (or portion of the main circuit board where the DC adapter connects) is where the excess voltage is regulated down to a level that the actual circuits use. Power supply board: Takes input from batt. or converter Connections: Black wire - screws to alum. kb frame "to HP" - 3 element, goes to speaker "to DM" - 4 element, goes to 1684 PN1 (lg. board) elements are labeled DG +5D AG +5A +5D and +5A measure 5v DC to black wire "to SW" - 8 element, goes to switch/volume board elements are labeled E 5v B T M S E E M measures 15v DC to black wire The two large boards (2 x 12+ ") are labeled 1684 PN1 and 1684 PN2 with markings for the voicings, various effects. Any help? Thx, P "+5D" will be the 5v digital supply - ie the 5v supply for the digital electronics, and "+5A" will be the 5v analogue supply. "DG" and "AG" are the corresponding digital and analogue ground returns for those two supplies, so will be the references to measure the supplies against. That's a big help. I had no idea how they code such stuff. You really need to be able to measure the +5D supply with a reasonable amount of accuracy - to at least 0.05v. To what extent will such an accurate measuring device empty my po' wallet? Goes without saying that if I get 5v from +5D when it plays and 0v when it freezes, I've likely found my problem? Thanks, P Weeeelll, yes ... But more likely, it would be something like 4.9v when it's working ie just limping along on the lowest threshold that the micro can work at, and 4.7v when it's wrong. With digital electronics, particularly older garden variety such as this, a few decimals of a volt are enough to make the difference, which is why you need a meter that can read to half a decimal. Ouch. Such a meter is not expensive, and if the one you have, even if it is a $10 job, is digital, then it should be capable of this level of resolution. It's analog. I spotted a Sears Craftsman dig. meter on sale $30 but sez "DC accuracy to 0.7 percent for accurate measurements." Not sufficient for the job? The trick is how *accurate* it actually is, and that is something that you can't really know without comparing it to a 'standard' or someone else's much more expensive meter. I am shortly to be away for a few days, so will only get back on here another time or two. There are lots of others on here who should be able to help you through this. Good luck with it, and hope you manage to get a result. Your help is -very- much appreciated. I continue to try to measure differential voltage between the ekb when working and when "frozen". Just measured both putting the meter under the microscope of my eyeball. If there was any difference at all, there was a snatch-hair more voltage when "frozen". Reading was like 4.9 v. Dunno where to go from here. Any help most welcome. Cheers, Puddin' "Well, there's two trains runnin'. Ain't neither one goin' my way. One run at midnight, the other run just before day." - from "Still A Fool", Muddy Waters, maybe 1949 I think the 0.7% meter will be accurate enough. Arfa mentioned .05V at a 5V level; that's 1%. As others have mentioned, loose or corroded cable connections and cracked solder joints are usual suspects in any electronic failure. Beyond that, not only are your diagnostic skills going to come into play, but also your soldering skills in removing and replacing defective or suspect components. A voltmeter may or may not be the only piece of test equipment you need to troubleshoot this. You may want to formulate a flow chart to help yourself maintain some clarity about when you decide to take it to a professional. If you're dedicated to shooting it yourself as a learning experience, a schematic will be helpful. |
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