help with ultra probe amplifier

I have not yet created the ultra probe amplifier myself yet, but maybe a point to start finding out what could be wrong, is measuring the DC voltages on various locations ? That way, you can find out if there is a possible short or open circuit in a component or trace ?

thanks Paul, I’ve .done that and do get power to probe and on board but not to green indicator. I know that the Ics are doing switching based on signal. so that is where I think I’m having issues.. the dilemma is that I’m not sure if the led would light if there is a problem with the probe ;adding another dimension to the troubleshooting. I have not had any way of testing probe . I was planning on using this to do so. optimistic I guess 😂  Ill keep working 

@jodonne22 It is hard to tell from what you say because there could be several things wrong with it, but you can do the following. Make sure your ICs are perfectly centered on their pads because odherside the traces running underneath them will most definitely short out, especially the big IC. Then make sure all pots have the right value on them and that you didn’t somehow mix them up. Also, does the base unit switch one LED on or the other as you switch from audio to RF using the designated switch? Also, make sure that you did not mix up resistor values or cap values in the wrong place.

Thanks so much for your reply. I’ve checked all resistors and caps several times and have double checked pots. the red LEDs switch correctly. I will remove the large IC and double check the position.

Will the green led light quickly when unit is turned on without the probe connected? the reason I ask is because I’m not sure that I don’t have a problem with the probe which I have not been able to test.

thanks again 

best regards 

@jodonne22 The Green LED will light up only if the probe picks up a signal, depending on the position of the 100K pot, which is responsible for the sensitivity of the LED peak detection of the signal. The LED’s illumination will fluctuate ”in sync” with the signal’s ”peak level” and as its intensity changes. In the absence of any signal, it wouldn’t /or shouldn’t light up unless the pot position is either near the max or at max.

@jodonne22 PS: There are potentially 2 mistakes. All your 1K resistors are 1.2K, and you have fitted (it seems) a zero-ohms blank jumper resistor instead of its designed value. Check your resistor values with the ones on the schematic. The ones that are attached to D1’s anode. Also, check all the diodes’ polarity. Also, check the voltage presence at the output of the v. regulator (which brings the voltage to the probe head. Take measurements first without the probe connected and then with the probe connected. You are supposed to be able to vary the measured voltage as you vary the corresponding pot. If you cannot vary the voltage, you either have a burned regulator IC or you have potentially purchased the wrong part number.  Also check if all your ground points have been connected through the board to the other side of the board.

thank you so much for taking the time to respond. I did catch the 1.2 k error the other day, but will check the jumpers. I will go through and check what you suggested. I’m new to all of this and your input is  very helpful. I’ll keep you posted on what I find.

best regards 😊

@jodonne22 Like I said:  test your resistors connected to D1’s Anode. One of them looks to be a blank (jumper) instead of a proper resistor value.

@ovi4 thanks, it was the large IC causing the issue, like you said a piece of solder shorting it out. I checked the resistor next to d1 and it is correct. i don’t know why those did not have any markings..

everything seems to be working correctly. once I’m done I’ll post some pictures. thanks for all your help.

best regards 

@jodonne22 Hi, I’m glad my advice worked. On the other hand, can you please ensure that you read the rules and regulations imposed by ”MCL himself”? In case you haven’t done so (as of yet). They are located all the way down on any page of this forum You’ll see a big black background (a footer area), and below the title LINKS, you’ll see the forum rules title. Clicking on it will take you to the forum rules you can read them. Please pay close attention to sharing certain information on this site.  Best regards

thanks for the heads-up, I just read them, is the picture the issue? I can understand that, I just saw other members sharing their pictures (i.e.-member two dogs) and thought it was ok. I will be conscious of this going forward. again thinks for everything.

@jodonne22 yes, that indeed could be a problem. I would suggest that you erase that from the Imgur account. You can still post pictures, but only the ones showing the finished product in the box or you can blur the parts you cannot show. is best to follow the rules. My 2 cents.

thanks I just deleted it .  

hi all, just a quick update and question. I have the ultra probe amplifier working, however I’m still having an issue.  I think the problem might be in the probe head . When I use the probe,  in order to get sound on the amp from my test sorce I need to touch the positive headphone wire to the metal on the bcn connector. I do get sound when tapping  on the probe head without touching the wire.

questions

1. when I turn volume up on amp and it’s set on detection I get a worble sound, is that normal.
2. should I be able to plug the probe bnc into my signal tracer and get sound as a test. if so I do not .

any suggestions on how to proceed would be greatly appreciated.

thanks