K8021 zener

Hi,… my amp works good,…some times…
Can you tell me what is the correct voltage in the zener diode near 7805. In one side is +/- 35V, V+.
And in the other side, the input of the 7805?


ps - some times all the leds goes, off

Please tell me wish zener diode, ZD???
The voltage over a zener must always be his (or max) his zener voltage.

If power LED fails, check transformer cables and solderjoint on your PCB.

Hi,… as i know this kit only have one zever. A 20V zener in series with 7805.
In one side i have 35V and in the other side, the input ou 7805 regulator i have 34.5V

It is possible tho have the diagram with voltages in all circuit?

Thanks, Luís

The Kit is the K8040 High Class Amplifier, not the K8021.

35V or 34.5V is OK.

Sorry, no diagram with voltages.

Ok, are you saying that the input voltage of the LM7805 are 35V? It is not a great value for the 7805?


No, this is not correct.
You can only measure 35V at the input if the zener is defective or inverted.

ok,… may it from the zener.
But if the zener is working good, what is the voltage in one side and the other side relative to ground?
One side V+ 35V. And in the other side, or input of 7805? - That is my question.


+35V - 20V…

+35V (v+) - 20V (zener) = +15V (input of LM7805)


Your math is quite good…