Digital piano repair : technics SX PX336 : help needed on PSU

[tepsamps]

Something on the board is shorted, at least to 104 ohms. You will have to follow the +15V trace to wherever it goes. Lift any jumpers or cut the trace to find where the short is. Could be a bad capacitor or chip.

It's D14, it has 100 R to ground,i did not suspect it, as i just changed it. So what? It has worked but it has given more than 18 V instead of just 15 V ?

[Helmholtz]

Not much sense measuring DCR at the output of a solid state circuit - especially if you don't observe polarity.

If D14 is an 18V zener, it's not involved in the 15V regulation and you should have the +15V without the zener.

[tepsamps]

especially if you don't observe polarity.

I know but i try to observe polarity,

If D14 is an 18V zener, it's not involved in the 15V regulation and you should have the +15V without the zener.

Yes, or much more and burn some parts... It works as a security, i understood like that...

Why did it short?

[Helmholtz]

Why did it short?

Does it measure 100R in both directions out of circuit?
Failure could have been caused by a mains transient (e.g. due to a lightning stroke). In very rare cases components even fail spontaneously, i.e. without an obvious reason.

Do you get the +15V without it and without load?

[tepsamps]

Does it measure 100R in both directions out of circuit?
Failure could have been caused by a mains transient (e.g. due to a lightning stroke). In very rare cases components even fail spontaneously, i.e. without an obvious reason.

Do you get the +15V without it and without load?

Yes 104 R in both directions...
I did not try yet without D14 and still without load. Tomorrow i put all back in place with a socket for D14.

[tepsamps]

Hey guys, it works!!! +15 and -15 V with or without load, and without D14 i'm happy to have this piano working fine.
So many thanks to Helmoltz and Dmeek for the support.
I learnt many things thanks to you and to this forum...

[Helmholtz]

Hey guys, it works!!! +15 and -15 V with or without load, and without D14 i'm happy to have this piano working fine.
So many thanks to Helmoltz and Dmeek for the support.
I learnt many things thanks to you and to this forum...

Seems the 18V zener served its purpose and self-sacrificed in order to protect the rest of the electronics.
Make sure to replace it.