Hello, I'm working on a Helios RAT, nearly to spec. I'm trying to get it to run and, testing it with an audio probe, can't get past C2 per schematic.
My readouts are currently as such:
1: 6.74
2: <4 (draining)
3: 4.02
4: 0
5: 0.18
6: 3.3 (drains)
7: 8.9
8: 7.9
Any idea why 2 pins would be draining? As I understand on the LM308 these are the negative input and the output.
Pics
Aion Helios RAT - No signal past chip
-
pervyinthepark
- Breadboard Brother
-
deltafred
- Opamp Operator
I don't understand what you mean by "draining".
An opamp takes the difference in voltage between the + and - inputs and amplifies it by the open loop gain and that voltage appears on the output pin. Adding feedback components (everything connected to pins 2 & 6) modify this behaviour so it predictable and useful.
The way it is configured (non inverting operational amplifieramplifier - look it up to see how it works) in this circuit it will try and maintain the 2 inputs at the the same potential, which looking at your voltages it is doing quite effectively. Putting your meter on the pins will probably alter the voltages which will account for the differences.
It is pretty pointless measuring signals directly on the input pins as these are classed as "virtual earth". What are you getting on the output pin is the important part. If there is a signal the opamp is most probably working, no signal you probably have one or more of the following - faulty opamp, open or short circuit resistor or cap, wrong resistor or cap value, short between tracks or cold/dry solder joint.
An opamp takes the difference in voltage between the + and - inputs and amplifies it by the open loop gain and that voltage appears on the output pin. Adding feedback components (everything connected to pins 2 & 6) modify this behaviour so it predictable and useful.
The way it is configured (non inverting operational amplifieramplifier - look it up to see how it works) in this circuit it will try and maintain the 2 inputs at the the same potential, which looking at your voltages it is doing quite effectively. Putting your meter on the pins will probably alter the voltages which will account for the differences.
It is pretty pointless measuring signals directly on the input pins as these are classed as "virtual earth". What are you getting on the output pin is the important part. If there is a signal the opamp is most probably working, no signal you probably have one or more of the following - faulty opamp, open or short circuit resistor or cap, wrong resistor or cap value, short between tracks or cold/dry solder joint.
Politics is the art of so plucking the goose as to obtain the most feathers with the least squawking. - R.G. 2011
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
-
pervyinthepark
- Breadboard Brother
Hm. If it was a faulty opamp it wouldn't, would my voltages be so close to typical?
-
deltafred
- Opamp Operator
The DC biasing seems right but the AC signal is not getting through so something is wrong.
Difficult to say what without having it on my bench.
Difficult to say what without having it on my bench.
Politics is the art of so plucking the goose as to obtain the most feathers with the least squawking. - R.G. 2011
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
-
pervyinthepark
- Breadboard Brother
I'm posting on DIYstompboxes too and, well, heres my compiled stats so far:
Voltages, IC in:
1: 6.74
2: 1.44
3: 4.03
4: 0
5: 0.22
6: 1.48
7: 8.98
8: 8.01
IC out
1: 0
2: 3-4v? (Last time I checked this had 0.03v! What?? I havent even changed anything!!
3: 4.36
4: 0
5: 2-3v?? from 0????
6: 2-3v? (same?)
7: 9.7
8: 0
C12: 9.7 R10: 9.7/4.8 R11: 4.8/0
"So I got normal readings with IC in but with it out, everythings whacky... I havent changed anything but values have since I last took the IC out... a lot...
I feel like either my PCB or chip are broken."
It sounds like I have a major problem
Voltages, IC in:
1: 6.74
2: 1.44
3: 4.03
4: 0
5: 0.22
6: 1.48
7: 8.98
8: 8.01
IC out
1: 0
2: 3-4v? (Last time I checked this had 0.03v! What?? I havent even changed anything!!
3: 4.36
4: 0
5: 2-3v?? from 0????
6: 2-3v? (same?)
7: 9.7
8: 0
C12: 9.7 R10: 9.7/4.8 R11: 4.8/0
"So I got normal readings with IC in but with it out, everythings whacky... I havent changed anything but values have since I last took the IC out... a lot...
I feel like either my PCB or chip are broken."
It sounds like I have a major problem