DC on opamp outpin

[Swampy]

Yo team,


I'm working on a "Master" Solista 160 PA combo (pre/power amp and sub / mid / tweeter in the box) and can't iron out DC on the output of a LM4558 opamp in the preamp.

With all components connected to pins 7 and 6 disconnected I measure

9v DC on output (pin 7 )
+ and - 12 v rails on pins 8 and 4
0v / 0hms to ground on non inverting (pin 5)
0.5 v on inverting input (pin 6)


When I pull the IC I measure -25 mV on pin 7 and pin 6 (there are 'floating' resistors [half desoldered] connected to these pins.



No schem out there, the output of this IC goes to power amp in via 'main input' switching jack (which is lifted and have verified there is no DC on PA side.)

Cheers,
Matt

[soundguruman]

kind of high DC on output.
but you said no DC on PA side...
Is there a coupling cap? one may think so...
Why is something really wrong? Noise or hum in output? Or is it a normal kind of output?
Is something really malfunctioning? Or are you thinking so, without a schematic?

[J M Fahey]

(there are 'floating' resistors [half desoldered] connected to these pins.

Why is that?
The Op Amp does not work by magic or on its own, its pins are connected to different parts or points, including resistors, which in due turn are connected somewhere else.
Reconnect those resistors and repost measurements.