need help w/ wine cooler component ID

[billbyrd1945]

I have two diodes that I believe to be zeners. The schematic uses that symbol but gives no value. One of them is marked C11 ST while the other one is C7V5 ST. I want to replace them both but would prefer something more than a guess if possible. Testing the C11 with a bench power supply, I get about 11.5volts, the C7V5 measures about 7.5volts. I haven't found listings for those exact part numbers. There will always be accompanying numbers or letters that, I assume, affect their value. I've tried looking at various datasheets, but I'm not sure what data confirms whether the component referred to is what I need. Unfortunately, all I know about the boards is that they ultimately output 8volts and 12.5 volts and they receive input from thermistors attached to the cooing units. Any help would be appreciated.

[soldar]

I have an unexplainable hunch that C11 is an 11 volt zener and C7V5 is a 7.5 volt zener.

https://uk.farnell.com/nexperia/bzx79-c11/diode-zener-11v-500mw/dp/1097214

https://www.nexperia.com/products/diodes/zener-diodes/BZX79-C7V5.html

[DaJMasta]

So is there something wrong with it?  Sounds like you know the parts and they're reading the correct value.... so what's the fault?


Sounds like the outputs are about a diode drop more than the zeners, which could be easily accomplished in a few ways with the zeners configured as shunt regulators, maybe biasing an output power transistor, but it sounds to me like they're working.

[billbyrd1945]

"Is there something wrong with them?"

Leads damaged when removed for testing.

[fzabkar]

You need to ensure that the wattage of your replacements is fit for purpose. You can do that by calculating the diode current from the circuit components in the vicinity.