[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]

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]

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

[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!

[spark-el]

You'll probably be alright, just make sure that each probe is only touching one terminal point (not shorting another that may be close to it). Before doing that, see if you can ring out your cable, i.e. test each conductor from one end to the other with the ohmmeter. If the female connector has small holes, you may have to use a paper clip or something smaller to get into it.
is this a 120V supply cable, or do you have another power supply?

[KIMFAB]

What are you using for voltages from what I can read that chip is a 74HC149 which is a 8 line to 8 line priority encoder I may have misread couldn't see the other chip type any way these 74xxxseries chips need exactly 5 volts to operate properly and they will also act flakey if your inputs or outputs are unterminated. try putting a terminating resistor maybe about 10 k or so to ground on your inputs

[Oldmanandhistoy]

What are you using for voltages from what I can read that chip is a 74HC149 which is a 8 line to 8 line priority encoder I may have misread couldn't see the other chip type any way these 74xxxseries chips need exactly 5 volts to operate properly and they will also act flakey if your inputs or outputs are unterminated. try putting a terminating resistor maybe about 10 k or so to ground on your inputs

There are two chips on the board both are MM74HC14N.

You have completely lost me with the resistors. Would it make a difference if I had something connected to the relays?

[skiddaw]

You might try grounding the control inputs or loading them with 1kohm to ground.

Unlike a 7404 the 7414 is a hysterisis device. A short noise spike into a 7404 might be passed as such but a 7414 will latch it until the lower threshold is detected. The 7414 is still the correct device to use but inputs need to be driven i.e. GND or 5V. If you are not using all of the relays then make sure unused control lines are loaded one way or another.

There was once a serial output port being used to drive a printer where the input was used for messaging. In one installation the serial cable contained both serial lines but only the printer line was required and the input line was left open circuit. Unfortunately the printer output was 'picked up' by the input line as noise. If you sent the right sequence of print characters they could look like a receive message .... which was then printed ...

[Oldmanandhistoy]

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?

I got the board via Ebay from brenthub, there is no indication of a manufacturer and I want to use the boards for my CNC routers.

I will just go and see what I get on my meter; could I damage anything if I test wrong points on the relays?

John