Burnt Pin On 11 Pin Relay-Need Major Help

[Prototyper-Brian]

Hello Everyone,
I have a benchtop injection molding machine and I keep burning relay switches. This is what I can tell you, the fuses are not blowing but one of the pins melts and causes trouble in the machine. Any ideas of what would cause a burnt pin. I can send you pictures, I believe these are timer relays as well.

 

[Gryd3]

pictures help.
Heating can be caused by excessive current, or materials degrading. As some materials degrade, the resistance goes up which in turn can generate more heat. Poor connections also generate heat from the added resistance.

More info is always welcome

 

[Prototyper-Brian]

pictures help.
Heating can be caused by excessive current, or materials degrading. As some materials degrade, the resistance goes up which in turn can generate more heat. Poor connections also generate heat from the added resistance.

More info is always welcome

Thanks for the reply.
I was able to do some trouble shooting tonight. No matter what relay I put in the machine the same pin melts, so I believe its not a directly related to a relay. This machine is from the 1960's and I got it for free basically (barter deal) and runs like a champ.

The picture is of the relays, number 2 relay is the one giving me problems.

The relay is potter & brumfield 115v 50-60 C kap14a. 11 pins

I can't find any of these relays on ebay so tomorrow I am going to my local electrical shop.
Could I buy a higher amp relay as long as its rated lower than the fuse coming off of the drop down DC transformer.

When I put swap relays around I can only get one cycle out of the injection molding machine before it fries the pin so I'm not under a huge load over time.

 

[Prototyper-Brian]

I'm not too smart on electrical diagrams so I took a picture of the one on the relay itself.

 

[davenn]

hi Brian

I'm assuming its the connection between the base pin and the socket that's the problem ?
rather than the contacts inside the relay cover ?

if its the relay contacts ... that's suggesting a high current drawing load .... ie. a fault in the load that the relay is switching
and it wont matter how many relays you replace ... until you find and fix the external fault, you will continue to kill relays

I see no indication in the datasheet that these are any sort of timer relay
or your latest posted pic ( whilst I was typing


cheers
Dave

 

[Prototyper-Brian]

Hello Davenn,
Yes its the base pin and the socket that's the problem.

 

[davenn]

OK right ... that's an important clarification

My first instinct would be to replace the octal base socket .... again you will just keep burning pins on the replacement relays
as the base socket contacts are still damaged and will arc

Dave

 

[Prototyper-Brian]

Will do Dave, I will call the electrical shop tomorrow.

 

[Prototyper-Brian]

This may be a hard picture to see but I have a replacement relay. The wiring diagram is the same for both but the one on the right has a box with a line through it and the other squiggle line. Can I interchange these relays? I'm searching right now for a base.

 

[davenn]

..... both but the one on the right has a box with a line through it and the other squiggle line

That's just 2 different ways of showing the relay coil ... no worries there


D

 

[Gryd3]

Thanks for jumpin' in Dave.

OK right ... that's an important clarification

My first instinct would be to replace the octal base socket .... again you will just keep burning pins on the replacement relays
as the base socket contacts are still damaged and will arc

Dave

Is stated above, the socket could be generating the heat due to a poor connection to the relay. If they are cheap, buy a second as a spare and pay close attention to the operation after you swap it out. If it still gets hot and melts you may have a problem further down the line causing excessive current draw. If this is the case, don't put the spare in until you dive deeper down the line to find out what it could be.

Keep us up to date

 

[(*steve*)]

On the other hand, if the contact was very poor and only at a point (which would be the cause of the melting pin) then perhaps with a new socket the old relays will continue to have a long serviceable life.

Of course this depends on whether you still have them and whether the pin is still intact enough to make good contact.

 

[Gryd3]

On the other hand, if the contact was very poor and only at a point (which would be the cause of the melting pin) then perhaps with a new socket the old relays will continue to have a long serviceable life.

Of course this depends on whether you still have them and whether the pin is still intact enough to make good contact.

Can those pins be repaired or resurfaced? I thought of putting a dab of solder on them... but it sounds like a bad idea. I don't have any reason to call it a bad idea other than it might end up soldering itself to the socket.

 

[(*steve*)]

I was thinking that you could solder a wire inside the pin, pass it through the socket, then attach a spade connector, then finally plug that in to a mating connector. It wouldn't allow rapid removal of the relay, but it might reduce the demands on the socket.

Naturally there will be other connections (at least one other) carrying the same current. What current is this and what are these sockets rated for?

The fact that it's just a single pin rather than two suggests the socket is significantly degraded.

Of course, as you point out, if the heat can melt the metal, it will certainly melt solder. Yes, it may solder the pin to the socket (which might actually resolve the problem) but it would more likely drip balls of liquid solder over whatever is under the socket.

I've seen a fault in an electrical switchboard drip balls of copper in this manner, and the result was very nearly catastrophic for the house. The main switch was off, but was bridged by (presumably) liquid copper.

 

[Prototyper-Brian]

After work today I noticed there is a lot of dust/powder/debris inside the controller box. I got compressor air and blew all of the dust out and am going to use some contact cleaner and clean everything up. Will give an update later down the road.

 

[JoeM]

I read most of this thread and my thoughts are as follows. The relay may not be your problem, it may be a symptom of the true problem. So fixing the relay, or making parts heavier than the original was may produce a bigger, messier failure. You might want to measure the current going through the relay, if the relay doesn't destroy itself while you try doing that.
Relays don't usually burn up unless the current being pulled through its contacts is much moire than they can handle. Once it gets hot, it will also get soft and add to the mess it causes. It may catch fire. The cirecuit should have been protected by a fuse, or breakers. It would be a poor design to have your relay be the week link.
So, yes, replace the socket and other failed parts, but be careful when you turn it back on, or add a fuse to the circuit. The fuse should not allow more than half of what the relay contact can handle. Someone else might have other suggestions for that fuse.

If you had a schematic, or other circuit diagram of the machine, you should be able to see what the relay does, and how much power should be passing through it. One thing is for sure, the power should never be allowed to be greater than the relay can handle without destroying itself.

 

[elebish]

Thanks for the reply.
I was able to do some trouble shooting tonight. No matter what relay I put in the machine the same pin melts, so I believe its not a directly related to a relay. This machine is from the 1960's and I got it for free basically (barter deal) and runs like a champ.

The picture is of the relays, number 2 relay is the one giving me problems.

The relay is potter & brumfield 115v 50-60 C kap14a. 11 pins

I can't find any of these relays on ebay so tomorrow I am going to my local electrical shop.
Could I buy a higher amp relay as long as its rated lower than the fuse coming off of the drop down DC transformer.

When I put swap relays around I can only get one cycle out of the injection molding machine before it fries the pin so I'm not under a huge load over time. View attachment 15168

"Transformers only work when ac or pulsating dc is applied!" Whatever load is being drawn through the relay contacts that is getting the pin burned, is your problem or the supply voltage is too high. Ed.