Anybody noticed issues with Tayda L78l05 regs?

D

Diynot

Well-known member
Noticed during a troubleshooting session that with a 7.5v input (my test battery is dying), the bag of L78l05 I have were all spitting out 6.5-6.6v. Should be 5v, right?
Edit: secondary question, will feeding a pt2399 6.6v damage the IC or cause it to oscillate?
 
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Don’t L78 series regulators have a minimum input voltage, where if it drops below that it doesn’t regulate correctly? Could it just need a minimum voltage higher than you’re supplying?
 
Bricksnbeatles said:
Don’t L78 series regulators have a minimum input voltage, where if it drops below that it doesn’t regulate correctly? Could it just need a minimum voltage higher than you’re supplying?
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The thought did cross my mind, but wasn’t sure. Was going to test out a few more that I have in other circuits connected to a reliable power source, but work and all that….
 
What does your test circuit look like? I seem to recall that you need a load on the output of the regulator to get an accurate reading. I just looked on the datasheet and you need a minimum load of 1ma. The min input voltage is 7 volts.
 
tcpoint said:
What does your test circuit look like? I seem to recall that you need a load on the output of the regulator to get an accurate reading. I just looked on the datasheet and you need a minimum load of 1ma. The min input voltage is 7 volts.
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I had them on a breadboard with a 1n4148 across pins 1+3 and 47u cap to ground off pin 1. Those would not represent a load though. I think we’re good. I tested the ones I had in my Spirit Box build (from the same pink baggie) with an input of 8.9v and they were putting out 4.9-5v. I think @Bricksnbeatles was right, just not enough input voltage from dying battery.
 
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