Line 6 SpiderII No speaker output

[Tech. Tom]

Hello:
I am working on this Line 6 SpiderII 150W amp head.

I have no output at the speaker jacks but the headphones work.
I have a good signal on pin 3 of both output IC's. I have the positive and negative
supply voltages but no signal on pin 14...the output pin. I replaced the output IC's
and have the same problem.

Any suggestions would be appreciated.
Tom

[Randall]

Can you post the schematic?

[Jazz P Bass]

Check the 'Amp Mute' line.
Pin 10 of the TDA7293.
The pin must rise above 2.5Vdc to 'unmute'.

It's source appears to be the +VA low voltage rail, through a RC time delay (10K & a 10Uf cap to ground)(Pg 4)
It then enters the power amp board through a 10K resistor to pin 10.(Pg 6)



http://www.st.com/web/en/resource/te...CD00001887.pdf

I have attached the Spider II 75 as that is all that I have.

[Tech. Tom]

I checked for a short on the mute line and there was none, so I applied about 4 volts to
pin 10 and I got output from the speaker jack. You're right, from pin 10 it goes through a 10K resistor
then to the digital board via the PS board and ends up at Q1. This is a surface mount transistor that for the life of me
I can't find on the schematic. It appears to be open in one junction. I think the number on it is 12W..do you know what that is.

[Jazz P Bass]

12W may be a mosfet.
http://www.s-manuals.com/pdf/datashe...2n7002_nxp.pdf
Or
A zener diode.
http://www.s-manuals.com/pdf/datashe...es_central.pdf

Surface mount markings suck

Marking of electronic components, SMD Codes 12, 12-, 120, 1200P100, 1200P40, 1200P60, 1203P100, 1203P40, 1203P60, 120N03MS, 121, 122, 1225, 1225B, 1225C, 123, 123N08NS, 123N10LS, 12A, 12C, 12V, 12W, 12Y, 12p, 12t. Datasheets 1.5SMC12AT3, 2N7002, BSC1

I would suggest that you measure the 3 pins of the 12W & report back.

[mozwell]

In spider II HD75 amp mute line from pin 10 of power amp chip to R14 10k, to connector H1 pin 2, to connector H7 pin 2 to C20 10uf to 0V & R41 10k to +VA, which comes from the power supply Q3 2N5551 & D14 10V zener. VA looks to be approx 9.4VDC
What voltage do you have on each end of R41 ?

In the service manual, theory of operation it says the mute line goes to R68 & Q1, which level translates from the 3.3V used by the micro, to the VL level (7V), but i cant find them on the schematic anywhere

12W would appear to be a 33V smt zener on 2N7002