DC offset; Does it increase over time?

[3-way]

This may sound like a silly question but...
One of my Yamaha AX-900u integrated amps reads 10.0mV LEFT & 8.0mV RIGHT at the speaker outputs. Another AX-900u of mine reads 21.0mV & 27.0mV.
Did the amps leave the factory with those numbers or did that happen over the course of 38+ years?

 

[coonmanx]

Either way those numbers are not bad at all.

 

[Powertech]

Yes the DC offset values can drift a little over time. Especially if a power amp has a longtailed pair at it's input any gain drift in these can cause a drift in the DC offset as can drifting values in their surrounding components. Eitehrcase may occur over time. The drift we're talking about should only be a few milliamps though. If an amp has a differential voltage stage, then you would expect there to be gain stage imbalance. If the change in measured value experienced is above 20mV or so, I would be looking at definite reasons why this is happening.
The values you have measured are fine..

 

[3-way]

I can't think of a single thing that can escape the effects of time, HaHaHa! but I didn't want to assume. I bought quite a few of the 900's back when you could pick one up for next to nothing. Thanks for the input, it is greatly appreciated.

 

[RVT1K]

This may sound like a silly question but...
One of my Yamaha AX-900u integrated amps reads 10.0mV LEFT & 8.0mV RIGHT at the speaker outputs. Another AX-900u of mine reads 21.0mV & 27.0mV.
Did the amps leave the factory with those numbers or did that happen over the course of 38+ years?

I'm curious to know what the spec in the service manual calls for?

It is almost a certainty that they came from the factory different from one another. And I'm willing to bet that those numbers have in fact drifted from when they left the factory.