[bhjazz]

Well, no smoke and no blown caps today!

The Tread is connected to the Pimeta, and is adjusted at 24VDC. All standard tests seemed to be fine, except for a little oddity with OPALR. In referencing Nate's discussion here, I noticed he had a measurement of 0 where I have -.058 on pins 2 and 7.


Is that good or bad? Or is it ok? (or is this due to Class A biasing?)


Here are the measurements.

OPAG

1 0_________ 5 0
2 0_________ 6 12.04
3 0_________ 7 0
4 -11.97_____ 8 0


BUFG

1 -11.97_____ 5 12.04
2 0__________ 6 12.04
3 0 _________ 7 0
4 -11.97_____ 8 0


BUFL

1 -11.96_____ 5 12.04
2 0 _________ 6 12.04
3 -11.95_____ 7 0
4 -11.97_____ 8 0


OPALR

1 -11.94_____ 5 12.04
2 -.058______ 6 -11.94
3 0__________ 7 -.058
4 -11.96_____ 8 0


BUFR

1 -11.96_____ 5 12.04
2 .005_______ 6 12.04
3 -11.94_____ 7 .006
4 -11.96_____ 8 -11.96


IL to IR 88.8K
IL to IG 44.5K
IR to IG 44.1K

Thanks for any help!

 

[tangent]

Quote:

Originally Posted by bhjazz I noticed he had a measurement of 0 where I have -.058 on pins 2 and 7.

Not enough information. (And also, your right hand side pin numbers are backwards. They're numbered counterclockwise from the upper left. So, you mean 2 and 6 -- the inverting inputs.)

The biggest question I have is, why are you worried about this? Is the amp not working? It's an inherent property of op-amps that there will be some offset from the ideal of +IN being equal to -IN. The only thing that bothers me is that the two values are apparently equal. Which leads me to:

What meter are you using to make these measurements? If it's a poor quality meter, it explains why it doesn't have enough resolution to make a differentiation between the two channels, and also why the values seem to be high.

Quote:

IL to IR 88.8K IL to IG 44.5K IR to IG 44.1K

Please give units! K-whats? K-ohms...K-volts....K-bytes?

 

[bhjazz]

Quote:

Originally Posted by tangent The biggest question I have is, why are you worried about this?

As stated, I was referencing Nate's post regarding his own measurements, and he had posted zeros for that pin. As I did show a small amount of voltage there, I wanted to make sure I did not have a wrong resistor in somehwere, or perhaps had the casocdes in the wrong places. I simply did not want to risk inserting the actual chips in there and cooking them because I was in a hurry to listen. If it's okay (and it seems to be) then I'll move on.
Quote:

Originally Posted by tangent It's an inherent property of op-amps that there will be some offset from the ideal of +IN being equal to -IN. The only thing that bothers me is that the two values are apparently equal. Which leads me to: What meter are you using to make these measurements? If it's a poor quality meter, it explains why it doesn't have enough resolution to make a differentiation between the two channels, and also why the values seem to be high.

It's a Fluke 112 with DC resolution of 1mV and DC accuracy of ± (0.7%+2). I thought that hundredths of a volt would be enough (-0.058)!!!