What would a short during testing do?
« on: February 06, 2021, 07:25:29 PM »
I’m currently troubleshooting a SoundSkulptor MP5.66 tube mic preamp. I was taking measurements to send to JPK (their owner) to see if I had gotten the right replacement for an OpAmp that I had broken. Pardon my lack of proper terminology but the OpAmp is an 8-DIP IC (IC with 8 legs) and despite JPKs endless warnings about shorting it while getting the measurements, I’m 75% sure that the probe made contact between pins 2 and 3. I’m not positive that this did anything horrific but I’ve been trying to check the circuits continuity and when I connect the cables to 0v and V+, I get the tone and then it’s gone. If I wait and test again, same thing so with my minimal knowledge I’m assuming it’s a bad capacitor? Is that possible? I’m guessing that the test signal is going through the circuit but then the capacitor maxes out/fills (can’t think of term) and so the test tone stops? Then when I test again after the capacitor drains the same thing happens again? I could be wayyyyy off on this.


Re: What would a short during testing do?
« Reply #1 on: February 06, 2021, 07:33:22 PM »
Nevermind. I think I was just working with some crappy test leads.

Potato Cakes

Re: What would a short during testing do?
« Reply #2 on: February 09, 2021, 11:52:39 AM »
I’m currently troubleshooting a SoundSkulptor MP5.66 tube mic preamp. I was taking measurements to send to JPK (their owner) to see if I had gotten the right replacement for an OpAmp that I had broken. Pardon my lack of proper terminology but the OpAmp is an 8-DIP IC (IC with 8 legs) and despite JPKs endless warnings about shorting it while getting the measurements, I’m 75% sure that the probe made contact between pins 2 and 3. I’m not positive that this did anything horrific but I’ve been trying to check the circuits continuity and when I connect the cables to 0v and V+, I get the tone and then it’s gone. If I wait and test again, same thing so with my minimal knowledge I’m assuming it’s a bad capacitor? Is that possible? I’m guessing that the test signal is going through the circuit but then the capacitor maxes out/fills (can’t think of term) and so the test tone stops? Then when I test again after the capacitor drains the same thing happens again? I could be wayyyyy off on this.

Do the test without the IC. Also, what is the IC in question? All of the DIP-8 op amps I know of have voltage on pin 4 and either pin 7 or 8, depending if it's single or dual. Shorting pins 2 and 3 shouldn't do anything unless you had the IC in backwards, which would ruin an IC chip. You may also have a bad solder joint or misplaced component.

Thanks!

Paul


 

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