Hi,
Need some advise before i blow up my OP AMP. I want to test my right hand DAC and OP AMP, the left channel is working fine. My plan is to use a ttl probe to compare both Input pins (1) i'm expecting to see a pulse signal from both. I plan to ground the probe on any main board ground. Will that work or do i risk any damage? Any suggestion on a better way to check the DAC and any tips on how best to check the OP AMP with a multimeter ? I was planning on checking the +5v supply to the op amp on pin 2 and 5, and then a volt reading or ttl probe indications from pin 1 and 7 of the op amp output? (i have obtained replacement DAC) as it seems a common failure point on this board)
Need some advise before i blow up my OP AMP. I want to test my right hand DAC and OP AMP, the left channel is working fine. My plan is to use a ttl probe to compare both Input pins (1) i'm expecting to see a pulse signal from both. I plan to ground the probe on any main board ground. Will that work or do i risk any damage? Any suggestion on a better way to check the DAC and any tips on how best to check the OP AMP with a multimeter ? I was planning on checking the +5v supply to the op amp on pin 2 and 5, and then a volt reading or ttl probe indications from pin 1 and 7 of the op amp output? (i have obtained replacement DAC) as it seems a common failure point on this board)
You will not blow the opamp up provided it is correctly supplied with power of the correct polarity and voltage limits.
A true TTL input logic probe may or may not work on data lines because it may load the data lines too heavily. Nothing bad will happen though.
Opamps obey simple rules and are extremely unlikely to be defective. Just measure the supply voltages and check the output pin is close to zero volts. You should not see any voltage on the inverting input as the opamp is configured as an I/V convertor.
A true TTL input logic probe may or may not work on data lines because it may load the data lines too heavily. Nothing bad will happen though.
Opamps obey simple rules and are extremely unlikely to be defective. Just measure the supply voltages and check the output pin is close to zero volts. You should not see any voltage on the inverting input as the opamp is configured as an I/V convertor.
The opamp outputs are the analog signal so these could be viewed on a scope.
A multimeter there doesn't tell you much except 'it's not broken'.
TTL probes on the digital pins will work but what do you expect to see?
These are also well checked with a scope where you can see the level and frquency and shape.
In these types of circuit, if you want to see anything meaningful, a scope is the instrument of choice.
At any rate, sit back and reflect on what signal is at those pins and what you expect to see/measure, then select the instrument you'd want to use.
Horse before the cart.
Jan
A multimeter there doesn't tell you much except 'it's not broken'.
TTL probes on the digital pins will work but what do you expect to see?
These are also well checked with a scope where you can see the level and frquency and shape.
In these types of circuit, if you want to see anything meaningful, a scope is the instrument of choice.
At any rate, sit back and reflect on what signal is at those pins and what you expect to see/measure, then select the instrument you'd want to use.
Horse before the cart.
Jan
Thanks jan.. I really appreciate the input. I agree a scope would be great and its something that I am considering. However my testing is only to validate if something is broken. I was expecting the probe to just flash randomly on the input side of the DAC and that would suggest the sound chip is outputting a digital single and its reached the DAC. For the OP AMP i was looking for any voltage on the output pins... i guess a simple compare with the working L channel. The power rail check is to just confirm 5v supply to the op amp / dac my concern is pins 3 and 5 is my lack of knowledge on current vs volts i dont know what to expect i'll see with a volt meter on 3 and 5 once I probe there as the board will be powered up.
Pins 3 and 5 are grounded and this ground is your point of reference. So you should see 0.00 volts on these two pins. Pins 2 and 6 and 1 and 7 should also show zero volts.