Author Topic: Temperature controller failed...any experience of likely repair?  (Read 410 times)

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Offline FaringdonTopic starter

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Temperature controller failed...any experience of likely repair?
« on: September 29, 2023, 05:55:20 pm »
Hi,
We have a CAL 3200 PID temperarture controller...

https://uk.rs-online.com/web/p/temperature-controllers/0730004?redirect-relevancy-data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

Its failed.
Do you know if they have common failure modes?

I took it apart....the isolating flyback SMPS was a cheap discrete one and its main NPN had blown up and primary coil was toast.

Secondary had a '2951 5V regulator....so i shovelled a 6V PSU i had lying about into it and it got working again. (at  least the Forge 39G LED letter display was  lighting.)

But then it failed again...i noticed the Atmel EEPROM chip on the 5V rail was very hot, and must have been taking the 5V rail down...so i removed it, and got the 5v back....but it still wont work. No LED letters.

The main chip seems to be a philips P87C51R which i presume drives the display etc.

Any ideas?

I suspect the  isolating SMPS possibly overvoltaged the sec side and overvoltage-weakened the chips there....if so i think we've had it...but  do you know any other failure modes which may be fixable?
'Perfection' is the enemy of 'perfectly satisfactory'
 


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