LM1875 non funziona

[Mooly]

I bought some pcb already made, I mounted one this morning and the incredible thing is that this one doesn't work either, always with the same problem.

So maybe we should be suspecting your LM1875 chips. There isn't much else left...

 

[csdcar]

hello dear.I have used many, I don't think they can all be broken

 

[csdcar]

I bought them all from reputable sellers

 

[farley]

The capacitor circled in the attached image looks like it needs to move up one set of holes.

 

[Mooly]

hello dear.I have used many, I don't think they can all be broken

OK

So lets be logical in this. With the LM1875 you show on the PCB do have the correct DC voltages on all 5 of the pins?

Yes or no?

And if no then which are not correct.

 

[csdcar]

I'll try to move it even though I think it has to be right there.

 

[csdcar]

Si e' tutto ok,d'altronde e' un pcb moto usato e non penso di averlo montato male

 

[csdcar]

on that pcb i tried 4 different chips

 

[csdcar]

4 lm 1875

 

[Mooly]

And what about the DC voltages (see post #145)?

What have you got on all the pins. Are they all correct.

 

[farley]

It appears from looking at the provided top and bottom views of the PCB that the pads that cap are soldered to are connected together on the bottom side of the board.

The red circles show the two pads I believe that cap should connect to.

 

[csdcar]

Le tensioni sono corrette,e poi scusa cosa vuol dire , chip sono nuovi il cablaggio e' corretto, l'alimentazione c'e' ed e 34volt ogni binario 17volt .non puo essere alimentato male, l'altoparlante funziona.
Domattina ricontrollero' le tensioni ma penso che sia tutto ok

 

[csdcar]

farley I did not understand, how would you like to mount it?

 

[Mooly]

If you have doubts over connectivity then just measure continuity with your meter.

Everything initially hinges on the voltage reading I have kept asking for

 

[csdcar]

I left the pins a bit long and so it seems that they are not soldered

 

[csdcar]

.Mooly tell me exactly how I should measure the voltage.
once and for all.

 

[csdcar]

I'm going to do it now

 

[Mooly]

You put the black lead of the meter of the 0 volts line (which is ground) of the power supply. This point is where the two big power supply caps join together. Everything is measured from that point.

It will be tomorrow when I look in again.

 

[csdcar]

I can not understand well, try to explain it again, there. power supply ground ok but then which pins? have patience

 

[mjf]

It appears from looking at the provided top and bottom views of the PCB that the pads that cap are soldered to are connected together on the bottom side of the board.
The red circles show the two pads I believe that cap should connect to.

.........yes,looks like the elcap should be shifted one position "towards
the heatsink"