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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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dead microwave
Frigidaire, Professional Series PLMV169DCD
When plugged in, no clock is displayed. Nothing. No response to any buttons. No lights, no fan, no sound. It failed gradually. Starting from a few buttons that didn't work, then this. It is a combo microwave/range hood. I opened up the panel/keyboard. There's a layer of grease on the circult board, and some grease droplets dangling on wires and connectors. Some greenish(!) grease drips out of connectors. Could the grease cause the connectors to fail? I found on the internet a parts and schematic PDF for this model. Unfortunately, the schematic shows everything (relays, transformers, lights, fuses, magnetron, motors) but the controller board. Yet the controller board is where I want to start debugging since it houses the LCD display and hooks up to the keypad. Does anyone know where to get the controller board's schematic? BTW, there's a note inside saying "this device should not be serviced by a do-it-yourself repair person". I could understand if it says "this device should be serviced only by a qualified person". But why get personal? |
#2
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dead microwave
On Fri, 15 Oct 2010 10:56:04 -0700, james wrote:
Frigidaire, Professional Series PLMV169DCD When plugged in, no clock is displayed. Nothing. No response to any buttons. No lights, no fan, no sound. It failed gradually. Starting from a few buttons that didn't work, then this. Uh Huh. It is a combo microwave/range hood. I opened up the panel/keyboard. There's a layer of grease on the circult board, and some grease droplets dangling on wires and connectors. Some greenish(!) grease drips out of connectors. Could the grease cause the connectors to fail? Yep I found on the internet a parts and schematic PDF for this model. Unfortunately, the schematic shows everything (relays, transformers, lights, fuses, magnetron, motors) but the controller board. Yet the controller board is where I want to start debugging since it houses the LCD display and hooks up to the keypad. Does anyone know where to get the controller board's schematic? Controllers are usually replaced not serviced. BTW, there's a note inside saying "this device should not be serviced by a do-it-yourself repair person". I could understand if it says "this device should be serviced only by a qualified person". But why get personal? Because your health depends on you knowing what you are doing. What price are you willing to see yourself and others possibly pay for a more friendly message? -- Live Fast, Die Young and Leave a Pretty Corpse |
#3
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dead microwave
BTW, there's a note inside saying "this device should not be
serviced by a do-it-yourself repair person". I could understand if it says "this device should be serviced only by a qualified person". But why get personal? "I don't get no respect!" Why not start by simply cleaning up everything? The only thing you might have to worry about is electrostatic discharge damaging the controller or other electronic components. |
#4
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dead microwave
On Oct 15, 1:37*pm, "William Sommerwerck"
wrote: BTW, there's a note inside saying "this device should not be serviced by a do-it-yourself repair person". I could understand if it says "this device should be serviced only by a qualified person". But why get personal? "I don't get no respect!" Why not start by simply cleaning up everything? The only thing you might have to worry about is electrostatic discharge damaging the controller or other electronic components. I would suggest some naptha and a soft brush to dissolve the grease and clean the board. Do NOT use soap and /or water!!!! After everything looks clean and nice, let it sit overnoght before you plug it back in. That gives time for things to dry out reasonably well. |
#5
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dead microwave
wrote in message ... On Oct 15, 1:37 pm, "William Sommerwerck" wrote: BTW, there's a note inside saying "this device should not be serviced by a do-it-yourself repair person". I could understand if it says "this device should be serviced only by a qualified person". But why get personal? "I don't get no respect!" Why not start by simply cleaning up everything? The only thing you might have to worry about is electrostatic discharge damaging the controller or other electronic components. I would suggest some naptha and a soft brush to dissolve the grease and clean the board. Do NOT use soap and /or water!!!! After everything looks clean and nice, let it sit overnoght before you plug it back in. That gives time for things to dry out reasonably well. Surely, the most fundamental first move is to take a meter to the power supply, and see if there is at least some supply to the system control micro etc ? The fact that it's covered in grease may well be neither here nor there as far as the fault goes. Oils and greases are not known for being particularly conductive or corrosive. Dead is a positive problem, and one to which basic faultfinding techniques should be first applied, before going off on an 'if-then-maybe' exercise ... Arfa |
#6
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dead microwave
Surely, the most fundamental first move is to take a meter to the power
supply, and see if there is at least some supply to the system control micro etc ? The fact that it's covered in grease may well be neither here nor there as far as the fault goes. Oils and greases are not known for being particularly conductive or corrosive. Dead is a positive problem, and one to which basic faultfinding techniques should be first applied, before going off on an 'if-then-maybe' exercise ... I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Of course, it takes just a few seconds to check the voltages. Couldn't hurt. |
#7
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dead microwave
james wrote:
Frigidaire, Professional Series PLMV169DCD When plugged in, no clock is displayed. Nothing. No response to any buttons. No lights, no fan, no sound. It failed gradually. Starting from a few buttons that didn't work, then this. It is a combo microwave/range hood. I opened up the panel/keyboard. There's a layer of grease on the circult board, and some grease droplets dangling on wires and connectors. Some greenish(!) grease drips out of connectors. Could the grease cause the connectors to fail? I found on the internet a parts and schematic PDF for this model. Unfortunately, the schematic shows everything (relays, transformers, lights, fuses, magnetron, motors) but the controller board. Yet the controller board is where I want to start debugging since it houses the LCD display and hooks up to the keypad. Does anyone know where to get the controller board's schematic? BTW, there's a note inside saying "this device should not be serviced by a do-it-yourself repair person". I could understand if it says "this device should be serviced only by a qualified person". But why get personal? That is an odd warning. Microwaves should just state "you will die if you open this, even if it's unplugged. |
#8
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dead microwave
"William Sommerwerck" wrote in message ... Surely, the most fundamental first move is to take a meter to the power supply, and see if there is at least some supply to the system control micro etc ? The fact that it's covered in grease may well be neither here nor there as far as the fault goes. Oils and greases are not known for being particularly conductive or corrosive. Dead is a positive problem, and one to which basic faultfinding techniques should be first applied, before going off on an 'if-then-maybe' exercise ... I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. Arfa |
#9
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dead microwave
I'd normally agree, but the fact the unit /slowly/ declined suggests
that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) |
#10
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dead microwave
"William Sommerwerck" wrote in message ... I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) Understood a rhet question, but I guess it still might need an answer for others following the thread. If a supply that's feeding a logic device such as a microcontroller becomes 'dirty' - that's either with excessive ripple from an analogue supply, or hash from a switch mode supply, and both cases potentially caused by a failing filter cap, - then operation of the micro can become 'flaky'. This can take the form of odd / unreliable behaviour, incorrect reset at power up, incorrect operation of any connected displays, and wrong operation of connected peripherals such as keypads, fault sensors etc. This is particularly true of devices which use A-D converter inputs with a ladder of resistors connected between buttons, to sense which button has been pressed, although it can also occur with matrix driven / sensed keypads. Arfa |
#11
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dead microwave
On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote:
I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Live Fast, Die Young and Leave a Pretty Corpse |
#12
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dead microwave
"Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa |
#13
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dead microwave
On Sat, 16 Oct 2010 14:41:02 +0100, Arfa Daily wrote:
"Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa Total failure as in front panel function could easily result from cleaning fluids, corrosive cooking vapors, condensation etc.. I don't recall if the OP mentioned the interior light working when the door was opened. -- Live Fast, Die Young and Leave a Pretty Corpse |
#14
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dead microwave
On Oct 16, 9:34*am, Meat Plow wrote:
On Sat, 16 Oct 2010 14:41:02 +0100, Arfa Daily wrote: "Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa Total failure as in front panel function could easily result from cleaning fluids, corrosive cooking vapors, condensation etc.. I don't recall if the OP mentioned the interior light working when the door was opened. -- Live Fast, Die Young and Leave a Pretty Corpse- Hide quoted text - - Show quoted text - Excellent point about the interior door/light, that is usually a combination of microswitches and a relay contact from the controller so the light goes on if the door is opened or if it is cooking. |
#15
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dead microwave
"Arfa Daily" wrote in
: "Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa grease infiltration into the keypad could be the first problem,and then grease making a conductive path and the HV shorting out and blowing the line fuse. I finally "retired" my 30 year old,$350USD Sharp MW,replaced it with a $99 GE from Wal-Mart;1.8Cu.Ft.,1100W. Had to return the first one,the turntable didn't turn.... then I realized how much the power had dropped on the older 700W Sharp. ;-) I don't expect the GE to last half as long as the Sharp did. -- Jim Yanik jyanik at localnet dot com |
#16
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dead microwave
"Jim Yanik" wrote in message
4... "Arfa Daily" wrote in : "Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa grease infiltration into the keypad could be the first problem,and then grease making a conductive path and the HV shorting out and blowing the line fuse. I finally "retired" my 30 year old,$350USD Sharp MW,replaced it with a $99 GE from Wal-Mart;1.8Cu.Ft.,1100W. Had to return the first one,the turntable didn't turn.... then I realized how much the power had dropped on the older 700W Sharp. ;-) I don't expect the GE to last half as long as the Sharp did. -- Jim Yanik jyanik at localnet dot com If it has GE on the front, you'll be lucky to make it past the first year. ESPECIALLY if you bought it at Wal-Mart. |
#17
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dead microwave
If it has GE on the front, you'll be lucky to make it past the first year.
My GE over-the-cooktop microwave is 11 years old, gets near-daily use, and is a-working still. |
#18
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dead microwave
On 10/18/2010 6:18 AM, William Sommerwerck wrote:
If it has GE on the front, you'll be lucky to make it past the first year. My GE over-the-cooktop microwave is 11 years old, gets near-daily use, and is a-working still. That's because it IS 11 years old. The reference was for the new ones being sold at Wal=Mart. Jeff |
#19
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dead microwave
If it has GE on the front, you'll be lucky to make it past
the first year. My GE over-the-cooktop microwave is 11 years old, gets near-daily use, and is a-working still. That's because it IS 11 years old. The reference was for the new ones being sold at Wal-Mart. I still have one of the last made-in-the US Littons, which I can pull out if the GE fails. Does anyone make a really good, reliable microwave? PS: There's a classic MAD spoof showing an Appalachian family (is that sufficiently PC) around their washing machine, which has been converted for alcohol production: "Our Mayjag is 18 years old, and it's a-working still!" |
#20
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dead microwave
On Sun, 17 Oct 2010 20:12:59 -0500, Klaatu wrote:
"Jim Yanik" wrote in message 4... "Arfa Daily" wrote in : "Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa grease infiltration into the keypad could be the first problem,and then grease making a conductive path and the HV shorting out and blowing the line fuse. I finally "retired" my 30 year old,$350USD Sharp MW,replaced it with a $99 GE from Wal-Mart;1.8Cu.Ft.,1100W. Had to return the first one,the turntable didn't turn.... then I realized how much the power had dropped on the older 700W Sharp. ;-) I don't expect the GE to last half as long as the Sharp did. -- Jim Yanik jyanik at localnet dot com If it has GE on the front, you'll be lucky to make it past the first year. ESPECIALLY if you bought it at Wal-Mart. 1100 watt GE here. Now 6 years old, works good as new. -- Live Fast, Die Young and Leave a Pretty Corpse |
#21
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dead microwave
On Sat, 16 Oct 2010 14:34:28 +0000 (UTC), Meat Plow
wrote: Total failure as in front panel function could easily result from cleaning fluids, corrosive cooking vapors, condensation etc.. I don't recall if the OP mentioned the interior light working when the door was opened. I was once asked to look at a heavily used microwave oven at a local residential facility. The description was similar, but the problem was obvious on first inspection. Long finger nails punching through the elastometric contact keyboard. Once the protective membrane on the front panel is punctured, all manner of liquids and gasses can cause damage. I've seen this problem other times, where the customer doesn't want to admit that they damaged the front panel, or somehow considers such damage as normal. It also applies to TV/hi-fi remote controls, printer control panels, calculators, where easily damaged flexible membranes are used in place of hard plastic buttons. While grease is usually non-conductive, having any grease in the various connectors will produce lousy connections. I suspect a good cleaning, and a low grease diet, might restore the oven to normal operation. The green crud (copper sulfate) does not necessarily signal the demise of the wiring, unless it's extensive. I would not replace any electronics until the keyboard and controller cards are baptized in solvent. It would also be interesting to determine how the grease entered the area. Probably a mechanically mis-aligned exhaust duct. Opinions: http://www.epinions.com/reviews/Frigidaire_PLMV169DC_Stainless_Steel_Microwave_Ove n This one is interesting: http://www.epinions.com/review/Frigidaire_PLMV169DC_Stainless_Steel_Microwave_Ove n/content_392811679364 The Bottom Line: Despite the top-flight brand name, attractive styling, and high price tag, this microwave is unreliable and extremely difficult to clean. Drivel: US DoE can't figure out how to measure microwave oven power output. http://www.federalregister.gov/articles/2010/07/22/2010-17773/energy-conservation-program-for-consumer-products-test-procedure-for-microwave-ovens-repeal-of Sigh. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#22
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dead microwave
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#23
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dead microwave
On Mon, 18 Oct 2010 09:34:05 -0700, Jeff Liebermann wrote:
On Sat, 16 Oct 2010 14:34:28 +0000 (UTC), Meat Plow wrote: Total failure as in front panel function could easily result from cleaning fluids, corrosive cooking vapors, condensation etc.. I don't recall if the OP mentioned the interior light working when the door was opened. I was once asked to look at a heavily used microwave oven at a local residential facility. The description was similar, but the problem was obvious on first inspection. Long finger nails punching through the elastometric contact keyboard. Once the protective membrane on the front panel is punctured, all manner of liquids and gasses can cause damage. I've seen this problem other times, where the customer doesn't want to admit that they damaged the front panel, or somehow considers such damage as normal. It also applies to TV/hi-fi remote controls, printer control panels, calculators, where easily damaged flexible membranes are used in place of hard plastic buttons. While grease is usually non-conductive, having any grease in the various connectors will produce lousy connections. I suspect a good cleaning, and a low grease diet, might restore the oven to normal operation. The green crud (copper sulfate) does not necessarily signal the demise of the wiring, unless it's extensive. I would not replace any electronics until the keyboard and controller cards are baptized in solvent. It would also be interesting to determine how the grease entered the area. Probably a mechanically mis-aligned exhaust duct. I've seen the corruption of membrane switch panels from users spraying things like window cleaners directly on them. Without any punctures. While talking to the customer I try to ask how they cleaned their stuff without trying to point blame. People don't like to readily admit to the over zealous spraying of cleaners that can and do eventually seep into membrane panels. I cringed in horror once watching my girlfriend cleaning my then 2 year old GE oven, She sprayed the front with copious amounts of window cleaner. I told her from now on she was to lightly spray it on a clean cloth first then wipe the membrane. On everything. Not too many realize this is a serious problem unfortunately. -- Live Fast, Die Young and Leave a Pretty Corpse |
#24
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dead microwave
In article ,
Jeff Liebermann wrote: Drivel: US DoE can't figure out how to measure microwave oven power output. Jeff- My impression is that the referenced article refers to efficiency, not power output. It talks about such things as magnetron filament current and warm-up time. Somewhere on the web I found a procedure for measuring power. You heat a liter of water for a certain amount of time, measuring temperature before and after. Using a formula, temperature rise correlates to power output. I think such a procedure is basic, and don't see how it could be challenged other than for "hot spots" in an oven. In my case, the oven has a carousel to compensate. My old 900 Watt Sharp microwave actually puts out 650 Watts according to the procedure. I adjust cooking times meant for 1100 Watt units, multiplying by 1100/650. The food appears to be getting the right amount of heat. An old Sharp "Half Pint" is rated for 450 Watts. The above procedure agrees exactly. Fred |
#25
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dead microwave
On Mon, 18 Oct 2010 11:41:03 -0500, "David"
wrote: Drivel: US DoE can't figure out how to measure microwave oven power output. http://www.federalregister.gov/articles/2010/07/22/2010-17773/energy-conservation-program-for-consumer-products-test-procedure-for-microwave-ovens-repeal-of Sigh. Jeff Liebermann Your tax dollars at work, Sigh^2. David Yeah, it's really a tough problem. Never mind IEC-705 which has been around since 1990. http://www1.eere.energy.gov/buildings/appliance_standards/residential/docs/krtp1003.txt Place about a liter of water in the oven. Measure temperature. Apply power. Measure temperature again after a specific cooking time. Power = (Volume_of_water) x (Temp_rise) x 4.1868 / (Cook_time) 4.1868 is joules/calorie (specific heat of water) Power = Watts Volume = Cubic centimeters or Milliliters Temp rise = Celsius Cooking time = Seconds Every oven I've tested (6 ovens) with a liter flask and about a minute runtime has resulted in measurements of 15% to 30% less than the rated power. If a use more water and a longer runtime, even less (because the magnetron decreases in RF output as it gets hot). This is not because the manufacturers all lie, but because the IEC-705 standard method generates inflated results for power output. This might also offer a clue why the DoE can't seem to find a workable procedure that produces the same results as IEC-705. I've also measured the efficiency of these ovens. All are about 60% (using the above test procedure). Perhaps what's needed is a multi-million dollar research grant to study methods of measuring microwave oven power output. However, should such a study succeed, I'm certain the method will be ultra complexicated and designed to sell plenty of specialized hardware and certified testing labs. With luck, maybe even a bureaucracy to oversee the muddle. Hint: Don't use a big heavy Pyrex glass bowl as it becomes part of the thermal mass and wrecks the results. Use thin chemistry glassware or if really careful, light plastic bowls. A 10C to 20C temp rise is sufficient. No need to boil the water. Don't leave the thermometer inside the oven when running. Let the water temperature stabilize for 30 seconds or more at the end of a run as microwave heating is rather uneven. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#26
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dead microwave
In article ,
William Sommerwerck wrote: Does anyone make a really good, reliable microwave? We had a Kenmore which had lasted us almost 20 years. When it gave up the ghost, I replaced it with a Panasonic "inverter" model... one of the higher-end consumer-grade microwaves. This died early this year less than three years of service. Looking at the consumer-grade microwaves available at the time gave me no confidence at all. I bought an Amana "medium volume commercial setting" model (ALD10T) as a replacement. It's roughly twice the price of the better consumer-grade type, but does seem to have a substantially better build quality, and the magnetron has a 3-year warranty as opposed to 1 year (or less) for consumer-grade models. My hope is that it will have a substantially longer lifetime than today's race-to-the-bottom consumer junk. Biggest negative noted so far (from my wife'w point of view) is that the fan continues to run for 30 seconds to a minute after the cooking cycle is complete - this clears out the steam and odors from inside the oven, but she hates the noise. The companion model ALD10D has a mechanical timer and dial, and only a single power setting... less to go wrong. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#27
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dead microwave
On Mon, 18 Oct 2010 13:39:25 -0400, Fred McKenzie
wrote: In article , Jeff Liebermann wrote: Drivel: US DoE can't figure out how to measure microwave oven power output. Jeff- My impression is that the referenced article refers to efficiency, not power output. It talks about such things as magnetron filament current and warm-up time. Yep. I measure the power input to the microwave with a Kill-a-watt power meter. The power output is using the calorimetric water heater method. I can throw in defrost, pre-heat, warm-up, cool-down, and such if you insist. Somewhere on the web I found a procedure for measuring power. What was dropped was: http://www1.eere.energy.gov/buildings/appliance_standards/residential/docs/krtp1003.txt http://www1.eere.energy.gov/buildings/appliance_standards/residential/pdfs/home_appl_micro_oven_tp_fr.pdf They're measuring "useful cooking energy" which is similar to the exaggerated numbers produced by "peak music power" in hi-fi. You heat a liter of water for a certain amount of time, measuring temperature before and after. Using a formula, temperature rise correlates to power output. http://www.gallawa.com/microtech/output.html http://www.ebsciences.com/papers/microwave_quality.htm http://www.zyra.info/micropwr.htm I think such a procedure is basic, and don't see how it could be challenged other than for "hot spots" in an oven. In my case, the oven has a carousel to compensate. I was borrowing an FLIR i7 infrared camera to do some unrelated (and paying) tests. http://www.flir.com/thermography/americas/us/content/?id=24072 What got my attention was the rather bizarre pattern of heating on a small pizza in the microwave oven. Of course, the carousel and stirrer fan help reduce hot spots, but it still takes time for the heat to move around in a liter of water. My old 900 Watt Sharp microwave actually puts out 650 Watts according to the procedure. I adjust cooking times meant for 1100 Watt units, multiplying by 1100/650. The food appears to be getting the right amount of heat. My cheap junk Welbilt something oven claims 950 watts and delivers 800 watts. An old Sharp "Half Pint" is rated for 450 Watts. The above procedure agrees exactly. That's because IEC-705 was designed to inflate the ratings. See first paragraph at: http://www.gallawa.com/microtech/output.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#28
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dead microwave
On Mon, 18 Oct 2010 10:52:53 -0700, Jeff Liebermann
wrote: Yeah, it's really a tough problem. Never mind IEC-705 which has been around since 1990. http://www1.eere.energy.gov/buildings/appliance_standards/residential/docs/krtp1003.txt New and improved IEC-705 is now IEC 60705: http://global.ihs.com/doc_detail.cfm?currency_code=USD&customer_id=21254 82C3B0A&shopping_cart_id=282758232F4950244D595D582 40A&rid=Z56&input_doc_number=iec%20705&mid=5280&in put_doc_number=iec%20705&country_code=US&lang_code =ENGL&item_s_key=00133560&item_key_date=930931&inp ut_doc_number=iec%20705&input_doc_title=&org_code= IEC For only $143, you too can learn how governments rate microwave ovens or maybe P-IEC 60705 {Ed.3.2} http://www.iec.ch/cgi-bin/procgi.pl/www/iecwww.p?wwwlang=e&wwwprog=cat-det.p&progdb=db1&wartnum=035873 http://www.iecchallenge.net/cgi-bin/procgi.pl/www/iecwww.p?wwwlang=english&wwwprog=pro-det.p&progdb=db1&He=IEC&Pu=60705&Pa=&Se=&Am=1&Fr=& TR=&Ed=3 for $170. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#29
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dead microwave
"Meat Plow" wrote in message
news On Sun, 17 Oct 2010 20:12:59 -0500, Klaatu wrote: "Jim Yanik" wrote in message 4... "Arfa Daily" wrote in : "Meat Plow" wrote in message news On Sat, 16 Oct 2010 03:57:47 -0700, William Sommerwerck wrote: I'd normally agree, but the fact the unit /slowly/ declined suggests that something other than a voltage loss is going on. Well, not really. Analogue power supplies, such as the ones in microwave ovens usually are, will die gracefully as a result of bad electrolytics getting worse. I've never seen this, but I sure don't know everything. Anyhow, what about the fact that some buttons "failed" before others? (That's a rhetorical question.) The microwave as I understood was above a stove and was probably cleaned frequently because of its location. I've seen many control panels permanently damaged by cleaning fluids on not only microwaves but also other home appliances and electronics. This fact can certainly account for button failure. -- Agreed. I was just thinking of a scenario that would account for both progressive failure of buttons, and then ultimately (apparent) total failure of the unit to operate at all. Arfa grease infiltration into the keypad could be the first problem,and then grease making a conductive path and the HV shorting out and blowing the line fuse. I finally "retired" my 30 year old,$350USD Sharp MW,replaced it with a $99 GE from Wal-Mart;1.8Cu.Ft.,1100W. Had to return the first one,the turntable didn't turn.... then I realized how much the power had dropped on the older 700W Sharp. ;-) I don't expect the GE to last half as long as the Sharp did. -- Jim Yanik jyanik at localnet dot com If it has GE on the front, you'll be lucky to make it past the first year. ESPECIALLY if you bought it at Wal-Mart. 1100 watt GE here. Now 6 years old, works good as new. See Jeffery Angus' reply. Try to keep up..... |
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