jim beam <nospam@example.net> wrote in
news:8rGdnT9Rm7_WIaDcRVn-hA@comcast.com:

> Jim Yanik wrote:
>> jim beam <nospam@example.net> wrote in
>> news:OKmdnSCDnfAdjKDcRVn-pw@comcast.com:
>>
>>
>>>Jim Yanik wrote:
>>>
>>>>jim beam <nospam@example.net> wrote in
>>>>news:iJCdnbXfNPhZGaHcRVn-rQ@comcast.com:
>>>>
>>>>
>>>>
>>>>>Jim Yanik wrote:
>>>>>
>>>>>
>>>>>>jim beam <nospam@example.net> wrote in news:gJednYm5v8lpW6bcRVn-
>>>>>>qQ@comcast.com:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Jim Yanik wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>"Howard" <howardh1951at@hotmail.com> wrote in
>>>>>>>>news:71u_c.96991$_h.12688@bignews3.bellsou th.net:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>It's your relay. Just replace the relay. Stop being so cheap or
>>>>>>>>>listening to all these cheapskates, just buy a damn relay and
>>>>>>>>>drive on. You'll never get your solder joints to last like the
>>>>>>>>>mfr's.
>>>>>>>>
>>>>>>>>
>>>>>>>>That's nonsense.(about their solder joints lasting longer)
>>>>>>>>If that's the sort of 'advice' you have to offer....
>>>>>>>>
>>>>>>>>And I can save $50 with such little labor.
>>>>>>>>
>>>>>>>
>>>>>>>fwiw, relay contact points burn out too.
>>>>>>
>>>>>>
>>>>>>When they are not selected properly for the application.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>when they're starting to go,
>>>>>>>they run hot, which probably accelerates/starts the solder
>>>>>>>problem in the first place. remember how bad car ignition used
>>>>>>>to be when they used old fashioned contact breakers and how they
>>>>>>>didn't last very long?
>>>>>>
>>>>>>
>>>>>>Yes,electrical engineering was not very advanced in those days.
>>>>>>Also,the buzzer type of ignition had to make/break contact many
>>>>>>times per second(thousands?),greatly increasing wear,and there was
>>>>>>also flyback arcing from the coil,which probably was the biggest
>>>>>>factor in contact burning.The Honda main relay only makes/breaks
>>>>>>when the ignition is turned on/off,once per trip.
>>>>>
>>>>>the back emf arcing is pretty much dealt with by putting a diode in
>>>>>parallel with the coil - it conducts the breakdown current rather
>>>>>than allowing the points to arc - and that's what these relays have
>>>>>built in.
>>>>> so that reduces the rate of contact point wear, but they still
>>>>> wear,
>>>>>and when they wear, they run hot. that's why the relay is of
>>>>>massive copper construction - to conduct some of the heat away from
>>>>>the contacts. the part of the relay that's running the fuel pump
>>>>>is also responsible for switching a big reactive load, which
>>>>>doesn't help. you can argue that the relay is not big enough for
>>>>>the job, but otoh, a 10 year relay's not bad in the grand scheme of
>>>>>things.
>>>>>
>>>>>
>>>>>
>>>>>>>relays are exactly the same type of electrical switch.
>>>>>>>
>>>>>>>in the long run, replacement /is/ the best policy. sure, a
>>>>>>>resolder job is a quick fix, and may even last a while, but if
>>>>>>>the contact points are already running hot, it's a temporary fix.
>>>>>>> i keep a resoldered spare in my glove box, but i use the new one
>>>>>>>i bought just to be sure.
>>>>>>>
>>>>>>
>>>>>>
>>>>>>That does not take into consideration bad batches from the
>>>>>>factory. These things are soldered on wave-soldering machines,and
>>>>>>it's easy to get solder problems and marginal solder joints.And
>>>>>>even humans can have a bad day.Like buying a car made on Mondays.
>>>>>>
>>>>>
>>>>>reject rates on machine soldered work are /way/ less than human
>>>>>soldered.
>>>>>
>>>>>
>>>>
>>>>
>>>>I bet the early coil/breaker ignitions did NOT have any diode to
>>>>proect from back EMF.
>>>
>>>no, but they had a condenser, which helps. you can't completely kill
>>>back emf on a contact breaker circuit because that's what creates the
>>>spark on the ht side of the coil.
>>
>>
>> Well,now we have diodes that can take the back EMF,back then we
>> didn't,had to use big stacks of selenium wafers for rectifiers,and
>> they were SLOW(in turn-off time,critical for flyback operation).Your
>> PC power supply works just fine using diode snubbers in the flyback
>> mode supply.They even make the switching transistors with
>> on-substrate diodes for this purpose.
>
> jim, sorry if i'm coming across as unclear.
>
> diodes on relays aren't used in normal forward conduct mode. think
> about it: if they conducted the current used to energise the coil, the
> coil would never activate. so they're oriented the opposite way.
> where's the benefit? well, when the magnetic field energy of the
> solenoid breaks down after switch-off, it changes rapidly. a rapidly
> changing magnetic field induces an electric current in the coil that
> just happens to be wrapped around it. depending on the number of
> turns & rate of decay, that current can have many thousands of volts.
> diodes break down and conduct reverse voltage at some level, and this
> level of breakdown can be carefully designed. so, the diodes used to
> protect relay circuits do this at some appropriate level - whatever -
> and so the voltage spike never goes beyond this, hence protection.
>
> the devices used in switch mode power supplies are a very different
> creature. unlike simple full wave rectifiers that conduct the whole
> waveform, switching devices need to be able to switch a forward
> current in the middle of a wave. this means a very large momentary
> power dissipation within the device, so to do this successfully,
> [semiconductors are not great power dissipators] the switch needs to
> be /fast/.

But once the switching transistor turns OFF,there's still the flyback EMF
that has to be dealt with (on the primary side),otherwise the switching
xstr breaks down and fails due to those high voltages.That's where the fast
recovery diodes enter the picture.(along with other snubbing circuitry) The
fast diode allows less of the back EMF to reach the switcher xstr.

BTW,the switcher transistor only dissipates power when it is ON,when it's
off,it passes no current,thus no dissipation.That's why they use low ON-
resistance devices,to reduce dissipation inthe switcher xstr.
>
> the two operations are very different and there is no simple analogy
> between them.
>
>>
>>>>Also,I suspect there haven't been many -worn out- main relays that
>>>>were due to contact wear,if any. Just cracked solder joints due to
>>>>aging of the solder alloy itself,or thermal cycling unrelated to
>>>>current flow thru the contacts.The current drawn by the main relay
>>>>is not enough to heat up those contacts,especially with the low
>>>>make/break duty cycle.
>>>
>>>the contacts don't heat much when new, but after a while in
>>>operation, even with spark protection, the contact points get eroded.
>>> it may not look much to the naked eye, but reality is that the
>>>actual surface contact area decreases - you can see all the little
>>>hills & valleys that have been eaten away under a microscope. as the
>>>current per unit area increases [same current divided by less area],
>>>operating temperature increases.
>>
>>
>> Yes,and for the -main relay- we're discussing,how often does the
>> make/break happen? Not anything like a automotive ignition doing it
>> thousands of times per second,nor is there a high current.
>
> well, you're right that the switch count is not high, but take one of
> these relays apart, particularly if you get a chance to put it under a
> microscope, and you'll see the contact erosion. also, it's switching
> the fuel pump which has a fairly large coil in it....

And the inductance of the long wiring between relay and fuel pump windings
helps limit that.

>
>>
>>>tin/lead solders don't "age",but as stated by randolph, solder has
>>>poor mechanical properties. thermal cycling & mechanical stress can
>>>easily fatigue it. soldered joints not subject to these conditions
>>>can last virtually forever.
>>>
>>>
>>
>>
>>
>>
>
>



--
Jim Yanik
jyanik-at-kua.net

 

jim beam <nospam@example.net> wrote in
news:8rGdnT9Rm7_WIaDcRVn-hA@comcast.com:

> Jim Yanik wrote:
>> jim beam <nospam@example.net> wrote in
>> news:OKmdnSCDnfAdjKDcRVn-pw@comcast.com:
>>
>>
>>>Jim Yanik wrote:
>>>
>>>>jim beam <nospam@example.net> wrote in
>>>>news:iJCdnbXfNPhZGaHcRVn-rQ@comcast.com:
>>>>
>>>>
>>>>
>>>>>Jim Yanik wrote:
>>>>>
>>>>>
>>>>>>jim beam <nospam@example.net> wrote in news:gJednYm5v8lpW6bcRVn-
>>>>>>qQ@comcast.com:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Jim Yanik wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>"Howard" <howardh1951at@hotmail.com> wrote in
>>>>>>>>news:71u_c.96991$_h.12688@bignews3.bellsou th.net:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>It's your relay. Just replace the relay. Stop being so cheap or
>>>>>>>>>listening to all these cheapskates, just buy a damn relay and
>>>>>>>>>drive on. You'll never get your solder joints to last like the
>>>>>>>>>mfr's.
>>>>>>>>
>>>>>>>>
>>>>>>>>That's nonsense.(about their solder joints lasting longer)
>>>>>>>>If that's the sort of 'advice' you have to offer....
>>>>>>>>
>>>>>>>>And I can save $50 with such little labor.
>>>>>>>>
>>>>>>>
>>>>>>>fwiw, relay contact points burn out too.
>>>>>>
>>>>>>
>>>>>>When they are not selected properly for the application.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>when they're starting to go,
>>>>>>>they run hot, which probably accelerates/starts the solder
>>>>>>>problem in the first place. remember how bad car ignition used
>>>>>>>to be when they used old fashioned contact breakers and how they
>>>>>>>didn't last very long?
>>>>>>
>>>>>>
>>>>>>Yes,electrical engineering was not very advanced in those days.
>>>>>>Also,the buzzer type of ignition had to make/break contact many
>>>>>>times per second(thousands?),greatly increasing wear,and there was
>>>>>>also flyback arcing from the coil,which probably was the biggest
>>>>>>factor in contact burning.The Honda main relay only makes/breaks
>>>>>>when the ignition is turned on/off,once per trip.
>>>>>
>>>>>the back emf arcing is pretty much dealt with by putting a diode in
>>>>>parallel with the coil - it conducts the breakdown current rather
>>>>>than allowing the points to arc - and that's what these relays have
>>>>>built in.
>>>>> so that reduces the rate of contact point wear, but they still
>>>>> wear,
>>>>>and when they wear, they run hot. that's why the relay is of
>>>>>massive copper construction - to conduct some of the heat away from
>>>>>the contacts. the part of the relay that's running the fuel pump
>>>>>is also responsible for switching a big reactive load, which
>>>>>doesn't help. you can argue that the relay is not big enough for
>>>>>the job, but otoh, a 10 year relay's not bad in the grand scheme of
>>>>>things.
>>>>>
>>>>>
>>>>>
>>>>>>>relays are exactly the same type of electrical switch.
>>>>>>>
>>>>>>>in the long run, replacement /is/ the best policy. sure, a
>>>>>>>resolder job is a quick fix, and may even last a while, but if
>>>>>>>the contact points are already running hot, it's a temporary fix.
>>>>>>> i keep a resoldered spare in my glove box, but i use the new one
>>>>>>>i bought just to be sure.
>>>>>>>
>>>>>>
>>>>>>
>>>>>>That does not take into consideration bad batches from the
>>>>>>factory. These things are soldered on wave-soldering machines,and
>>>>>>it's easy to get solder problems and marginal solder joints.And
>>>>>>even humans can have a bad day.Like buying a car made on Mondays.
>>>>>>
>>>>>
>>>>>reject rates on machine soldered work are /way/ less than human
>>>>>soldered.
>>>>>
>>>>>
>>>>
>>>>
>>>>I bet the early coil/breaker ignitions did NOT have any diode to
>>>>proect from back EMF.
>>>
>>>no, but they had a condenser, which helps. you can't completely kill
>>>back emf on a contact breaker circuit because that's what creates the
>>>spark on the ht side of the coil.
>>
>>
>> Well,now we have diodes that can take the back EMF,back then we
>> didn't,had to use big stacks of selenium wafers for rectifiers,and
>> they were SLOW(in turn-off time,critical for flyback operation).Your
>> PC power supply works just fine using diode snubbers in the flyback
>> mode supply.They even make the switching transistors with
>> on-substrate diodes for this purpose.
>
> jim, sorry if i'm coming across as unclear.
>
> diodes on relays aren't used in normal forward conduct mode. think
> about it: if they conducted the current used to energise the coil, the
> coil would never activate. so they're oriented the opposite way.
> where's the benefit? well, when the magnetic field energy of the
> solenoid breaks down after switch-off, it changes rapidly. a rapidly
> changing magnetic field induces an electric current in the coil that
> just happens to be wrapped around it. depending on the number of
> turns & rate of decay, that current can have many thousands of volts.
> diodes break down and conduct reverse voltage at some level, and this
> level of breakdown can be carefully designed. so, the diodes used to
> protect relay circuits do this at some appropriate level - whatever -
> and so the voltage spike never goes beyond this, hence protection.
>
> the devices used in switch mode power supplies are a very different
> creature. unlike simple full wave rectifiers that conduct the whole
> waveform, switching devices need to be able to switch a forward
> current in the middle of a wave. this means a very large momentary
> power dissipation within the device, so to do this successfully,
> [semiconductors are not great power dissipators] the switch needs to
> be /fast/.

But once the switching transistor turns OFF,there's still the flyback EMF
that has to be dealt with (on the primary side),otherwise the switching
xstr breaks down and fails due to those high voltages.That's where the fast
recovery diodes enter the picture.(along with other snubbing circuitry) The
fast diode allows less of the back EMF to reach the switcher xstr.

BTW,the switcher transistor only dissipates power when it is ON,when it's
off,it passes no current,thus no dissipation.That's why they use low ON-
resistance devices,to reduce dissipation inthe switcher xstr.
>
> the two operations are very different and there is no simple analogy
> between them.
>
>>
>>>>Also,I suspect there haven't been many -worn out- main relays that
>>>>were due to contact wear,if any. Just cracked solder joints due to
>>>>aging of the solder alloy itself,or thermal cycling unrelated to
>>>>current flow thru the contacts.The current drawn by the main relay
>>>>is not enough to heat up those contacts,especially with the low
>>>>make/break duty cycle.
>>>
>>>the contacts don't heat much when new, but after a while in
>>>operation, even with spark protection, the contact points get eroded.
>>> it may not look much to the naked eye, but reality is that the
>>>actual surface contact area decreases - you can see all the little
>>>hills & valleys that have been eaten away under a microscope. as the
>>>current per unit area increases [same current divided by less area],
>>>operating temperature increases.
>>
>>
>> Yes,and for the -main relay- we're discussing,how often does the
>> make/break happen? Not anything like a automotive ignition doing it
>> thousands of times per second,nor is there a high current.
>
> well, you're right that the switch count is not high, but take one of
> these relays apart, particularly if you get a chance to put it under a
> microscope, and you'll see the contact erosion. also, it's switching
> the fuel pump which has a fairly large coil in it....

And the inductance of the long wiring between relay and fuel pump windings
helps limit that.

>
>>
>>>tin/lead solders don't "age",but as stated by randolph, solder has
>>>poor mechanical properties. thermal cycling & mechanical stress can
>>>easily fatigue it. soldered joints not subject to these conditions
>>>can last virtually forever.
>>>
>>>
>>
>>
>>
>>
>
>



--
Jim Yanik
jyanik-at-kua.net

 

I had a similar problem and you may want to check your timing belt. If your
car has jumped time, it will be hard to start at different times, but there
can be horerendous engine damage if the situation is not corrected in time
in the form of bent valves and wrecked pistons.

lackej1971

 

I had a similar problem and you may want to check your timing belt. If your
car has jumped time, it will be hard to start at different times, but there
can be horerendous engine damage if the situation is not corrected in time
in the form of bent valves and wrecked pistons.

lackej1971