Relay Identification - Help ;)

Thread Starter

fellsteruk

Joined Oct 21, 2023
2
Hey Everyone,
My mother in-law who's deaf has a door bell which is wired up to the mains supply and a normal household bulb above her door in the main room of her house, when the door bell is pressed the light flashes.

For the past few months this has been intermittently working and today i decided to try and troubleshoot, the box controlling this contraption dates back to the 70/80's and looking at it was clearly made by hand. All the components except one relay seems to be working fine, the relay is sticking and not working every time it's triggered.

My plan is to source a replacement and switch it out for the new one but im struggling to find what is a good replacement as it has limited markings, I've emailed IMO asking for help but nothing yet.

Any ideas?
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LesJones

Joined Jan 8, 2017
4,207
I think this is a home made device. You will need to trace out the scematic of the device so we can work out how it is designed to work.
I notice that the 3 pole double thow relay has a 6 volt AC coil so that is probable driven from the low voltage AC bell circuit. I think there is a second relay but none of your pictures show all of the board. I think the two T05 transistors will be part of a multivibrator that will cauase the lamp to flash on and off. A picture that covers all of the board and one of the underside of the board would be helpfull.
Does the 3 pole relay pull in when the bell push is pressed and drop out when it is released ?
Is it this relay that is sticking or the other one that is not shown fully ?

Les.
 
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Thread Starter

fellsteruk

Joined Oct 21, 2023
2
Thanks for the replies, the board, i think is glued into a project box which itself is glued to the wall so may be tricky to get an image of the reverse of the board but i'll take another look, it's also wired directly to the consumer under so i'll need to isolate and see if i can get it out to take some more picks. Not checked voltage yet.

It's the big one with A2 on it that's in question.

When the door bell is pressed you can hear the relay click on and off about four/ five times as it's doing this the lamp is flashing on and off. However it often get's stuck and just makes a buzz sound, you can flick it back into flicking on and and off with some pressure on the bit that's moves.

I also did some searching on eBay and found this which looks similar in build but appears to be different:
 

LesJones

Joined Jan 8, 2017
4,207
The relay in your link has the correct contact arrangement but it has a 110 volt AC coil You need a relay with a 6 volt coil. It may be easier to find a relay with a 5 or 6 volt DC coil and add a bridge rectifier. What is the wattage of the bulb it is driving and what is the mains voltage in your country. (Your profile does not say which country you are in.) It may be easier to find a relay with a lower current contact rating which is still suitable to drive the mains voltage lamp.

Les.
 

MisterBill2

Joined Jan 23, 2018
18,928
All of the detail photosare OK but I wonder what the whole thing looks like. It is quite possible to fix relay problems by sanding the contacts gently WITH THE POWER OFF!!. A strip of sanding cloth can remove the part making the relay stick, if that is actually the problem. With a picture of the entire package we should be able to solve the riddle.
 

LesJones

Joined Jan 8, 2017
4,207
Re-reading the first post I think the relay is sticking in the non actuated position. I think the first step is to verify that it is getting the full 6 volts AC on the coil. It is possible that the fault could be high resistance contacts on the bell push. If this relay is manualy actuated (Using something insulated to actuate it) does the light come on or does the other relay also need to be actuated ?
When the unit is in the working state does the 3 pole relay stay closed while the bell push is held pressed or does it pulse on and off in time with the flashing of the light ?
Max, The only place i can see information on the coil voltage in the Ebay advert is by selecting the fourth picture down which shows 110 V AC.

Les.
 
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MisterBill2

Joined Jan 23, 2018
18,928
Consider that there are two relays and some other circuit components involved in both the latching on and the flashing functions. And certainly the setup does include those functions.
The TS has already decided that the fault is in the six volt trigger relay, while if either relay chatters then the fault may also be elsewhere. But we are told that it must be in the trigger relay.
So why ask for help when the TS has already made a guess that is not backed up by analysis??

Consider that the actual operation probably includes the functions of #1 latching on the trigger relay, #2 flashing the mains powered light repeatedly, #3 after some short time, releasing the latched trigger relay.

This is another instance of telling us that we do not need to know any other details to provide assistance. Replacing that 3 pole relay will take some effort, and if it is not the problem then additional effort will be needed.
 

MaxHeadRoom

Joined Jul 18, 2013
28,759
Replacing that 3 pole relay will take some effort,
I don't see a problem, there are multiple makes and suppliers?

Max, The only place i can see information on the coil voltage in the Ebay advert is by selecting the fourth picture down which shows 110 V AC.
Les.
Les, I was just mentioning that Finder make the same relay with a 6V coil, available from a few vendors. ;)
 
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BobTPH

Joined Jun 5, 2013
9,116
Given that there is a flasher circuit driving the relay, I think it is likely driven by DC, not AC.

You really need to put a multimeter on the coil to get the actual triggering voltage. If it is AC, you will get a reading on the AC voltage setting. If DC, it should read near zero on the AC setting and a reasonable voltage in the DC setting.
 

MisterBill2

Joined Jan 23, 2018
18,928
There are eight solid wire connections with no service slack, and the TS had previously stated the board appeared to be glued in place.
If the coil is still OK, then a very small amount of contact sanding or filing will solve the problem, if that is in fact the problem. If a relay like that has a contact issue cleaning is the way to go. Or is this a collection of parts changers ?? Relay contact service, cleaning or filing has been a standard service activity for about a hundred years.
 

MisterBill2

Joined Jan 23, 2018
18,928
Do you mean to tell us, Max, that you have never restored a relay function by sanding or cleaning a contact???? Of course, the first effort would be to clean the contact with contact cleaner spray. Replacing the relay first is the way parts changers work, because they have no idea as to how anything functions.
 
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