Sony XM-475GSX

[mike49504]

I got another one of theese in for repair..

Someone has removed all of the outputs in the amp..


I know they use 540's in the amp

Does anyone know if they use all 540's or do they use both 540's and 9540's ?

[Perry Babin]

Do you read ~0 ohms between the drain pads for all of the outputs in the channel?

Do you read ~0 ohms between the source pads for all of the outputs in the channel?

[mike49504]

Between the drain pads i get 5.43 m ohms

Between the source pads i get:197.7 k ohms

[Perry Babin]

Are the source resistors in the circuit and within tolerance?

[mike49504]

Yes

[Perry Babin]

If there are direct connections (~0 ohms) between half of the drains to half of the sources, the amp likely uses all N-channel FETs.

[mike49504]

Well before i stick any outputs in i powerd the amp up to see if there were any other problems..


The amp will not power up for some reason..


Heres what i get on the 494


Pin 1:13.20
Pin 2:1.22
Pin 3:4.80
Pin 4:0.40
Pin 5:1.65
Pin 6:3.68
Pin 7:0
Pin 8:3.07
Pin 9:0
Pin 10:0
Pin 11:3.07
Pin 12:3.07
Pin 13:2.23
Pin 14:2.22
Pin 15:0.54
Pin 16:0.05

Any ideas?

[Perry Babin]

Check Q901.

This amp uses both 540s and 9540s. You should have found a direct connection between the source pads (via the source resistors) for the outputs in each channel.