Find component for replacement

Thread Starter

CHARGED

Joined Nov 9, 2019
9
Dear electronics enthusiast,

A softstarter has stopped working after 6-7 years, the visible damage is a blown up resistor and capacitor lead.
Now I would like to replace these components.
A diode is connected in between the blown up resistor and capacitor. Therefore I am wondering if this diode should be replaced as well.
Problem with that is that I can not find the corresponding diode from the code which is written on the diode.
The diode code is:
LT9228
SIM

Attached is a picture, hope somebody can give me some advice.

Looking forward to any replies.

Best regards,

Twan
 

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dl324

Joined Mar 30, 2015
9,332
A diode is connected in between the blown up resistor and capacitor. Therefore I am wondering if this diode should be replaced as well.
You should test the diode to see if the junction is opened or shorted. Sometimes you can do this check in-circuit and sometimes you can't. If you lift one lead from the board, you can do a dead or alive check.
 

MisterBill2

Joined Jan 23, 2018
4,564
Certainly the diode need s to be checked, not only against being shorted or open, but also for reverse breakdown voltage. Then, in addition, you need to know why those parts failed in that manner. Parts seldom fail for "no reason", and so usually that reason is another failed part, or a short circuit caused by something. If you replace only those failed parts without removing the cause of their failure, you will shortly have more failed parts and a damaged reputation. Resistors fail because of excess current, capacitors mostly fail because of too much voltage. You need to understand what caused the failure and fix it before replacing the obviously damaged parts.
 

Thread Starter

CHARGED

Joined Nov 9, 2019
9
You should test the diode to see if the junction is opened or shorted. Sometimes you can do this check in-circuit and sometimes you can't. If you lift one lead from the board, you can do a dead or alive check.
Measuring on the pcb gives a voltage drop of 0,56 V across the diode, so that seems to be correct. Both sides of the diode are disconnected because the resistor and capacitor are removed, so there shouldn't be any interference with other components/traces.
 

Thread Starter

CHARGED

Joined Nov 9, 2019
9
Certainly the diode need s to be checked, not only against being shorted or open, but also for reverse breakdown voltage. Then, in addition, you need to know why those parts failed in that manner. Parts seldom fail for "no reason", and so usually that reason is another failed part, or a short circuit caused by something. If you replace only those failed parts without removing the cause of their failure, you will shortly have more failed parts and a damaged reputation. Resistors fail because of excess current, capacitors mostly fail because of too much voltage. You need to understand what caused the failure and fix it before replacing the obviously damaged parts.
Totally agree with finding what caused the failure, do you have any advice for this? Everything else seems to be totally fine.. from the outside at least..
 

MisterBill2

Joined Jan 23, 2018
4,564
If you are able to post the circuit we can proved a good evaluation and suggest things to check. One question now is what was being done just prior to the failure? Failures are generally caused by something, often an error of some kind.
 

dl324

Joined Mar 30, 2015
9,332
Measuring on the pcb gives a voltage drop of 0,56 V across the diode, so that seems to be correct. Both sides of the diode are disconnected because the resistor and capacitor are removed, so there shouldn't be any interference with other components/traces.
Then it would seem that there's no reason to replace the diode at this point.
Totally agree with finding what caused the failure, do you have any advice for this?
A schematic would be helpful.

Sometimes the bad component is the cause for the problem and replacing it fixes the problem. I've had cases like that.

Had a curve tracer that only produced one curve. Found a TTL IC that wasn't working correctly, replaced it, and the curve tracer worked.

Had a headlight switch burn up in my truck (luckily it didn't burn up the truck). Replaced the switch and was good to go.
 
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