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Intermittent problem - help needed

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brunofunchas

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Intermittent problem

Hi,

This components can cause an intermittent problem?

- Transistor. Even if it checks ok with analog multimeter?

- Resistor. If it goes up in its value?

- Integrated circuits

- GND track with noise. How can we solve this problem? Soldering a wire between ground points?

Or "only" cold joints, capacitors, etc can cause this type of problem?

Thanks,
Bruno
 

brunofunchas

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Re: Intermittent problem

I have a DC drive that changes the velocity of the motor intermittent.

I have checked the power supply and it is ok. It is an old board that has a lot of analog in it. It has a lot of transistors and resitors.

Best regards,
Bruno
 

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pauloynski

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Re: Intermittent problem

Is it a double or single sided pcb? How much time does it stay malfunctioning? Try to freeze some portions of the circuit using a spray.
Some hints:
1- Resolder all components. Soldering points tend to degrade with age, even if you can´t see this (always happens in single sided boards, depending on age).
2- Older ceramic capacitors show intermittent shorts. Sometimes they work well when heated or resoldered but fail again after some time.
3- Resistors (mainly 1W or more) show intermittent failures.
4- In rare ocasions a bjt also fails intermittently.
5- xtal oscillators, diodes, zenners, etc also ....
Regards
 

brunofunchas

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Re: Intermittent problem

It is a single sided PCB.

Thanks for the tips / Obrigado pela ajuda,
Bruno
 

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pauloynski

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Re: Intermittent problem

Single sided boards ALWAYS have problems with soldering after some years. I strongly suggest your resoldering all components.

Added after 6 minutes:

Search for solder joints like the one in the attached image.
 

brunofunchas

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Re: Intermittent problem

Hi,

It was a transistor with an intermittent problem.

Thanks for the tips.

Best regards,
Bruno
 

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