Break out board help needed please.

[Oldmanandhistoy]

Hi all,

I have a problem with a couple of BOB’s that I bought a while back and have just got around to using them.

In the doc that came with the board it says once power is supplied you should hear the relays click. What I am getting from both boards is a loud buzzing noise from the relays. If you look at the pictures; when I touch any of the points marked in red with a finger the buzzing stops and when power is switched on and off the relays click as they should. I can get the buzzing to stop also when I move the boards about but this is hit and miss.

Any ideas or solutions will be very much appreciated.

John

[Al_The_Man]

It sounds like armature noise (the moving part of the relay that is attracted by the coil).
Normally there are two reasons, too low a voltage or bad seating of the armature, but this is usually prevalent in AC relays.
Do you have 24vdc on them?
As even raw DC (unsmoothed) does not cause this, unless maybe 1/2 wave rectified DC.
Just for kicks you could put a 100 to 500µfd across the coil to see if it stops , observing polarity, but make sure it is DC!.
Al.

[Oldmanandhistoy]

Hi Al Thanks for your input.

The boards come with a 6Vdc switch mode psu. There is a 470uF cap across the terminals of the psu connecting blocks. If I touch ever wide of the cap the buzzing stops also.

[spark-el]

Could be a cold solder joint or a crack in the foil path within the board.
If you're pressing on those points and the relays come in, then I would suspect the negative common not making good connection somewhere on the board. If you can isolate the point you may be able to solder a small
guage wire across it at the nearest two terminal points. Usually when a relay or starter vibrates like that, it is due to one side or the other not passing enough current to bring it all the way in and hold.

[Oldmanandhistoy]

Originally Posted by spark-el Could be a cold solder joint or a crack in the foil path within the board. If you're pressing on those points and the relays come in, then I would suspect the negative common not making good connection somewhere on the board. If you can isolate the point you may be able to solder a small guage wire across it at the nearest two terminal points. Usually when a relay or starter vibrates like that, it is due to one side or the other not passing enough current to bring it all the way in and hold.

Hi spark-el,

This problem is the same on both the boards I have; would that still imply a cold solder joint?

John

[sailandoar]

Do you have a schematic as part of the documentation and if so have you done any basic meter testing to see if voltages are present and proper as specified. Unlikely but possible that you have or can get test point data for the board. (i.e. go to this place and look for that voltage and/or signal)

[Oldmanandhistoy]

Originally Posted by sailandoar Do you have a schematic as part of the documentation and if so have you done any basic meter testing to see if voltages are present and proper as specified. Unlikely but possible that you have or can get test point data for the board. (i.e. go to this place and look for that voltage and/or signal)

Hi sailandoar,

Please keep in mind I am at best a beginner in electronic and would not know where to start.

John

[spark-el]

Could be, if they've seen some abuse or excessive vibration. Follow what
oar and sail says and you may be able to isolate the problem. Check your
voltage across each coil, use an analog meter if possible, the needle will
show vibration if the voltage is fluctuating.

[Oldmanandhistoy]

Originally Posted by spark-el Could be, if they've seen some abuse or excessive vibration. Follow what oar and sail says and you may be able to isolate the problem. Check your voltage across each coil, use an analog meter if possible, the needle will show vibration if the voltage is fluctuating.

Unfortunately I only have a digital meter; would I still be able to isolate the problem? I have to say it sounds to me that all the relays are vibrating.

As stated this problem is affecting both boards, does that imply they both have a cold solder joint?

John

[Oldmanandhistoy]

Another thing to consider is that if I touch the ground point on the parallel cable connection plug it also stops the vibration.

[spark-el]

It could also be a low voltage problem. See what you read across the coils of the relays with your digital meter. The fact that it stops when you press on those locations is what points to a bad connection. Check across each
relay. Are they all chattering? Who is the mfr of the boards, and what are
they for?

[spark-el]

Yes, could be a bad cable also. Kind of hard to help you over the internet, I just think it is a low voltage problem caused by a bad connection somewhere.
Only time I've ever seen a relay buzz is due to either a bad holding contact or the voltage driving them fluctuating. Good luck!