I have found that into a Brazilian site...maybe some translation from a foreigner text.
If you have something to contribute, post it here.
Laws of Murphy applied in electronics
A - The possibility you have that a fuse will protect a transistor is smaller when the transistor is difficult to find or expensive.
B - The stock has a variety of components, except those ones you need now!
C - When you have the equipment schematic, the most confused part printed, or erased, is normally the part were you have the damage.
D – Power semiconductors, the possibility of them to explode and become unreadable, happens more when you do not have the schematic to discover the code numbers.
E - When you need a lot of components equal, defined as N, the amount that you have tend to be equal to (N - 1).
F - The more there are components in the equipment to make it work, there are more components to make it not work.
G - The right time to find out we forgot to install a small pcboard inside the equipment happens, usually, when the equipment is almost totally assembled
H - integrated circuits dedicated serve to facilitate the life of the designer, and ruining the lives of the repair man that will have to find substitution.
I - The possibility of being burned some integrated circuit is greater when it is not easy to find.
J - Understand the switching power supplies is easy when working fine..hard is to understand them when does not operate.
K – Switching power supplies turns our live easier?..
L – When the equipment smells bad, it is easy, the guilty is the transformer, be happy, untill you will realise that cannot install other in place… they do not fit, size is always a little bit different.
M – Optocouplers (Led and photo resistance) are difficult to burn; But they use to burn when there’s not substitution to the unit and it is unreachable.
N - When something metallic fall on top of the energized pcboard, will fall exactly into the most critical point of the circuit.
If you have something to contribute, post it here.
Laws of Murphy applied in electronics
A - The possibility you have that a fuse will protect a transistor is smaller when the transistor is difficult to find or expensive.
B - The stock has a variety of components, except those ones you need now!
C - When you have the equipment schematic, the most confused part printed, or erased, is normally the part were you have the damage.
D – Power semiconductors, the possibility of them to explode and become unreadable, happens more when you do not have the schematic to discover the code numbers.
E - When you need a lot of components equal, defined as N, the amount that you have tend to be equal to (N - 1).
F - The more there are components in the equipment to make it work, there are more components to make it not work.
G - The right time to find out we forgot to install a small pcboard inside the equipment happens, usually, when the equipment is almost totally assembled
H - integrated circuits dedicated serve to facilitate the life of the designer, and ruining the lives of the repair man that will have to find substitution.
I - The possibility of being burned some integrated circuit is greater when it is not easy to find.
J - Understand the switching power supplies is easy when working fine..hard is to understand them when does not operate.
K – Switching power supplies turns our live easier?..
L – When the equipment smells bad, it is easy, the guilty is the transformer, be happy, untill you will realise that cannot install other in place… they do not fit, size is always a little bit different.
M – Optocouplers (Led and photo resistance) are difficult to burn; But they use to burn when there’s not substitution to the unit and it is unreachable.
N - When something metallic fall on top of the energized pcboard, will fall exactly into the most critical point of the circuit.
Second part of the text...sorry, was made a google translator version from
Portuguese...not very good.. do not know if the original is in Portuguese or in other language.
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fake MOSFETs works beautifully until itself starts to believe they are not fake..then it burns alike a match on fire.
P - All electrolytic capacitors dry, but most gave the impression of being perfect, and are only identified after we have tweaked all the rest of the circuit.. then finally it is found.
Q - The chance of a grounding plug pin, founded as cutted by the user, will be proportional to the parts the repair man will touch receiving electrical shocks.
R - Resistores has two ways to burn till it turns an open circuit. One it will look perfect to drive you mad to find it…or it will be toasted, and the burned part will be in a such place you cannot find with eye observation… when you are lucky, it will reveal itself burning completelly, so entirelly burned, that you will never know the value it had before burn… when this happens, the schematic you have is
not clear exactly into this resistance point.
S - When you approach the nose to sniff a circuit board, trying to identify which component is smelling burned, the nose will automatically be attracted to a heat sink with live voltage, or overheated.
T - Tantalum capacitors has greater tendency to have the mark of polarity confusing the greater the possibility of being used in a power supply line . Connect one o tantalum capacitor reversed in a power supply and you will know what I mean.
U – When the boss is inside the laboratory, the chances to have a short circuit, with smell and smoke increases 67 percent compared to the moments that no one, but you is inside the room.
V - Fuse components are of excellent quality, as they are always the last one to burn, they use to burn after everything already burn in fire…. Maybe because it was made to avoid fire.
W – Non connected wires found are difficult to occur, but happens much
more when we do not know where they are linked.
X – Intermittent, non good contact, such kind of failures stops immediattelly in front of the repair man..will re start to present problems when the equipment returns to the owner’s home.
Y - Contacts fixed using screw, will be loosen only if you do not have the tool to fix them or when the tool you have is not long enougth to reach them.
Z - If an earlier defective equipment, already repaired was plugged to be shown to the customer. It will stop immediately to operate… wait the owner leave the shop and them it will return to operate perfectly till the owner return to pick his amplifier. Better not to demonstrate, it there’s a change to smoke, it will happens with the owner watching.
Portuguese...not very good.. do not know if the original is in Portuguese or in other language.
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fake MOSFETs works beautifully until itself starts to believe they are not fake..then it burns alike a match on fire.
P - All electrolytic capacitors dry, but most gave the impression of being perfect, and are only identified after we have tweaked all the rest of the circuit.. then finally it is found.
Q - The chance of a grounding plug pin, founded as cutted by the user, will be proportional to the parts the repair man will touch receiving electrical shocks.
R - Resistores has two ways to burn till it turns an open circuit. One it will look perfect to drive you mad to find it…or it will be toasted, and the burned part will be in a such place you cannot find with eye observation… when you are lucky, it will reveal itself burning completelly, so entirelly burned, that you will never know the value it had before burn… when this happens, the schematic you have is
not clear exactly into this resistance point.
S - When you approach the nose to sniff a circuit board, trying to identify which component is smelling burned, the nose will automatically be attracted to a heat sink with live voltage, or overheated.
T - Tantalum capacitors has greater tendency to have the mark of polarity confusing the greater the possibility of being used in a power supply line . Connect one o tantalum capacitor reversed in a power supply and you will know what I mean.
U – When the boss is inside the laboratory, the chances to have a short circuit, with smell and smoke increases 67 percent compared to the moments that no one, but you is inside the room.
V - Fuse components are of excellent quality, as they are always the last one to burn, they use to burn after everything already burn in fire…. Maybe because it was made to avoid fire.
W – Non connected wires found are difficult to occur, but happens much
more when we do not know where they are linked.
X – Intermittent, non good contact, such kind of failures stops immediattelly in front of the repair man..will re start to present problems when the equipment returns to the owner’s home.
Y - Contacts fixed using screw, will be loosen only if you do not have the tool to fix them or when the tool you have is not long enougth to reach them.
Z - If an earlier defective equipment, already repaired was plugged to be shown to the customer. It will stop immediately to operate… wait the owner leave the shop and them it will return to operate perfectly till the owner return to pick his amplifier. Better not to demonstrate, it there’s a change to smoke, it will happens with the owner watching.
One more law (the recent one):
after you fried all samples you had of IRFP4321 you've discovered that there is more than one version of VN2222 with different pinouts...
after you fried all samples you had of IRFP4321 you've discovered that there is more than one version of VN2222 with different pinouts...
when repairing an expensive receiver for a finnicky customer, you will have N-1 cover screws.....
things which must be used together, are never shipped together..... (this is also one of Murphy's Laws of Combat)
the mechanical designer of the $10,000.00 receiver never stopped to think it may have to be repaired some day.
surround sound isn't......
you will find the open spot on the bias pot on your last little tweak that's supposed to get the bias perfect.
you always need scope leads N+1 inches long.
nothing is idiot proof, because idiots are so clever....
the expensive amp you worked 4 hours on comes back with major shipping damage, the cheap amp that you replaced a fuse on was in the same shipment, but it's fine......
backordered parts come in the day after the customer cancels the work order....
you're always out of stock on 2N2222's (the most common transistor on the planet) when you need one.
the receiver that needs to have it's setup or reset done through a remote, never comes in with the proper remote.
microprocessor based equipment has two little known processor instructions. 1>BRTP branch when technician present and 2>BROP branch when owner present....
yes, the amplifier DOES know that the warranty has expired.
the likelihood of a crack in a circuit board is proportional to the number of traces that can be broken.
the likelihood of a surface mount component failing is directly proportional to the number of pins it has and exponentially related to the pin pitch.
if you can't remember, the ribbon cable IS plugged in backwards
things which must be used together, are never shipped together..... (this is also one of Murphy's Laws of Combat)
the mechanical designer of the $10,000.00 receiver never stopped to think it may have to be repaired some day.
surround sound isn't......
you will find the open spot on the bias pot on your last little tweak that's supposed to get the bias perfect.
you always need scope leads N+1 inches long.
nothing is idiot proof, because idiots are so clever....
the expensive amp you worked 4 hours on comes back with major shipping damage, the cheap amp that you replaced a fuse on was in the same shipment, but it's fine......
backordered parts come in the day after the customer cancels the work order....
you're always out of stock on 2N2222's (the most common transistor on the planet) when you need one.
the receiver that needs to have it's setup or reset done through a remote, never comes in with the proper remote.
microprocessor based equipment has two little known processor instructions. 1>BRTP branch when technician present and 2>BROP branch when owner present....
yes, the amplifier DOES know that the warranty has expired.
the likelihood of a crack in a circuit board is proportional to the number of traces that can be broken.
the likelihood of a surface mount component failing is directly proportional to the number of pins it has and exponentially related to the pin pitch.
if you can't remember, the ribbon cable IS plugged in backwards
I would add 1N400x/1N4148 to that list.
And I can never find a LM317T to save my life,when I need it. 🙄
One more:
When you're in need of a certain part,and you think, "Ohh,I've got a bunch of those..somewhere" ... and can't ever find them!!
You take the PCB, position the part that is the hardest to reach, holding things with your tongue, teeth and all available fingers... you grab the soldering iron with the other hand... DOH!!!! forgot to switch it on...
To add to Jed's post....
If you make something idiot proof, they will simply make a better idiot...
To add to Jed's post....
If you make something idiot proof, they will simply make a better idiot...
A circuit measures perfectly until you listen to it.
A circuit sounds perfect until you measure it.
A circuit sounds perfect until you measure it.
When u realize the SMD ICs u replaced were fake, it's too late for the copper tracks
Gajanan Phadte
Gajanan Phadte
guys !!!!!
i think that you forgoten the most importand ......
by murphy's law all amplifiers presented in this forum are working and tested devices ready to be produced and perform the very best in any use or abuse
this is also guaranteed by two very importand people :
Murphy and the designer ......
i think that you forgoten the most importand ......
by murphy's law all amplifiers presented in this forum are working and tested devices ready to be produced and perform the very best in any use or abuse
this is also guaranteed by two very importand people :
Murphy and the designer ......
HEhe ohh ;.D I will put this up at my workbench at work (I work in an aftersales electronics repair place).. because the next bench has the ordinary "murphys law" sheet on it 🙂
"A circuit sounds perfect until you measure it"
Or to paraphrase the late JLLH:
The circuit that sounds bad suddenly sounds o.k. once you've measured it.
Brian.
Or to paraphrase the late JLLH:
The circuit that sounds bad suddenly sounds o.k. once you've measured it.
Brian.
unclejed613 said:
😀 😀 😀 Oh yes!! Yours actually got out of the workshop then.
A colleague had just spent a couple of days on a real pig of a fault on an all singing all dancing music centre. You know what it's like, it's so intermitant it keeps getting put on one side until the day comes "It's got to fixed" And fixed it was, and he was so pleased he jumped up and with the scope lead wrapped round his legs, pulled the whole lot on the floor.
Great folks!
Other one:
We are ready to spend a lot of money to buy a FET, but we use to save the money to the protective zener... and because the zener missed, the FET goes to outerspace.
.................................................................................................
Then, your multimeter battery gone.... you remove the old battery and put it over the table.... very near you have the new one, same brand.... then the telephone rangs.... when you hold the battery to install it in place you put the wrong one... the discharged one!.... but this is not all the stuff.... then you start to believe that "new" battery is defective... and to be sure you hold the "used" one (in the reality the new one!) and put it against your tongue to check if it is discharged... after feel that annoying taste into your tongue you discover, once again, that you are human and Murphy law exists...if something can go wrong..for sure it will go wrong.
Carlos
Other one:
We are ready to spend a lot of money to buy a FET, but we use to save the money to the protective zener... and because the zener missed, the FET goes to outerspace.
.................................................................................................
Then, your multimeter battery gone.... you remove the old battery and put it over the table.... very near you have the new one, same brand.... then the telephone rangs.... when you hold the battery to install it in place you put the wrong one... the discharged one!.... but this is not all the stuff.... then you start to believe that "new" battery is defective... and to be sure you hold the "used" one (in the reality the new one!) and put it against your tongue to check if it is discharged... after feel that annoying taste into your tongue you discover, once again, that you are human and Murphy law exists...if something can go wrong..for sure it will go wrong.
Carlos
A wire cut to size will be short.
A fast acting fuse will be protected by the adjacent transistor it was designed to protect.
A fast acting fuse will be protected by the adjacent transistor it was designed to protect.
The electrolitic condenser you have installed with all your attention and care
The one you gave a tripple check!.... is inverted!
regards,
Carlos
The one you gave a tripple check!.... is inverted!
regards,
Carlos
this one actually happened. i worked for a company that had a contract refurbing WYSE RS-232 terminals, which consisted of a monochrome monitor and a digital board. there was hardly ever anything wrong with the digital board, but the monitor section always had dried out electrolytics. the refurb process had been streamlined down to two basic steps:
1> recap the monitor
2> repair whatever other components had blown as a result of caps drying out
there were about 8 revisions of the monitor board with letter codes A-H. there were only minor differences in the capacitor kit between revisions, most of the revisions were layout changes, etc...
all of the cap positions were marked with a "half moon" symbol indicating polarity. the first time i saw a "rev C" board, i replaced all of the caps as usual, and tested for shorted transistors, vertical output chip, diodes, etc... the first time i powered it up the power supply made a large CHIRP!!!! so i shut the power off and checked again for shorted devices. there were none so i powered the terminal up again to see what components would get hot. after having it powered up for about 10 seconds, and the power supply chirping loudly and constantly, about 5 caps launched with a loud POPPOPPOP!!!...... as it turns out, the difference between rev C and rev D was that rev C had ALL of the half moon symbols reversed (rev D was a corrected version of rev C).
1> recap the monitor
2> repair whatever other components had blown as a result of caps drying out
there were about 8 revisions of the monitor board with letter codes A-H. there were only minor differences in the capacitor kit between revisions, most of the revisions were layout changes, etc...
all of the cap positions were marked with a "half moon" symbol indicating polarity. the first time i saw a "rev C" board, i replaced all of the caps as usual, and tested for shorted transistors, vertical output chip, diodes, etc... the first time i powered it up the power supply made a large CHIRP!!!! so i shut the power off and checked again for shorted devices. there were none so i powered the terminal up again to see what components would get hot. after having it powered up for about 10 seconds, and the power supply chirping loudly and constantly, about 5 caps launched with a loud POPPOPPOP!!!...... as it turns out, the difference between rev C and rev D was that rev C had ALL of the half moon symbols reversed (rev D was a corrected version of rev C).
More the years u have worked on electronics, more the silly mistakes u will make.
Gajanan Phadte
Gajanan Phadte
Specially for diy ... - Nothing ever gets built on schedule or within budget - It is impossible to make anything foolproof because fools are so ingenious - A valuable dropped item will always fall into an inaccessible place - You will always find something in the last place you look ... and finally A knowledge of Murphy's Law is no help in any situation
artQuake
artQuake
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