Vox Pathfinder 15R head hum - not output

[beedoola]

There is a constant hum, volume control does not effect it. Looking at the schematic and PCB - VR4 is the master volume and since that does nothing it's gotta be after it. Looking at IC4. I tested the voltages and they are as follows:

Pins:
1: 0v
2: -2v
3: -20v
4: -2.3v
5: 20v

This seem correct?

[Enzo]

Real TDA2030 are hard to find, but LM1875 fits, I'd try one.

[Jon Snell]

Pin 4 of IC 4 must be around zero.
Try and avoid fleabay!

[Jazz P Bass]

When attempting to diagnose a fault on these 'all in one' output ic's I find it best to look at the input signal going to the IC..
If the power rails are good & the input is good but you have a bad output, it is highly probable that the output IC is bad.

[vintagekiki]

Temporarily disconnect the reverb at W4.
Improvised solder on W4 connector, cable with 6.3 mm female guitar jack.
Connect the guitar to the 6.3 mm jack.
Set the VR4 on 5 to 8, and VR7 to max.
If you hear a clear and loud guitar tone the IC4 (TDA2030) is correct.