# Mini Heterodyne Receiver



## chongmagic (Apr 8, 2019)

First, my SMD soldering is still very much a work in progress. I just noticed that pins 12-15 on the CD4046 seem to not have any solder. However my voltages on the TL072 are way off. I had the hardest time soldering that chip so I quite possibly fried it. I tried the drag and drop method using a flux pen and for the most part it worked great, with the smaller TL072 it moved the chip a little so I had to get it back in place which probably fried it. 

I get bypass, the LED works, I just get hiss when the effect is turned on.

The TL072 voltages are reading 7.5 to 8v on all pins, so I know that is not correct. 









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If anyone sees anything else out of place let me know, I will troubleshoot it some more later.


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## Robert (Apr 8, 2019)

Don't feel bad.     I solder a _lot_ of SMD ICs but this one was pretty tough.   The TL072 is so small it's hard to hold it in place while soldering.
It might be worth using a tiny drop of super glue to hold it in place.

Check to see if pin 4 is still connected to ground.


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## chongmagic (Apr 8, 2019)

Yeah this is like my third attempt, I will test that. I tried to clean off the flux as much as I could. I probably went a little overboard with the flux.


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## chongmagic (Apr 8, 2019)

TL072 is connected to ground. Or at least the pad is, I'll have to try and reflow it. Still getting about 8 or 7.5 v on all pins. The other chips have a ground connection as well.


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## chongmagic (Apr 8, 2019)

Quick question, if pin 4 is not connected to ground would that cause the other pins to show the higher voltage?


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## chongmagic (Apr 8, 2019)

I got it working, I reflowed the TL072 and the voltages are more in line to what they should be. I am testing it out now and am getting some sound out of it so hopefully all is good. Is there any way to list the voltages of the other chips?


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## nosamiam (May 11, 2019)

To keep ICs from moving, I do the following:'

1) Apply a tiny bit of solder to Pad 1. You don't need a super-narrow tip for this. Just put a dab on the iron and touch it to the pad.
2)Add some extra flux on top of the cooled solder.
2) Line up the IC over the pads with Pin 1 on top of that dab of solder.
3) Heat up Pin 1 and the solder while pressing down with a finger so that it (hopefully) lands right over the pad.
4) If it needs minimal realignment simply nudge it over with Pin 1 still soldered in place. The pin will bend a little bit without causing issues. If it is pretty crooked, you can reheat the joint and scoot the IC over, then allow it to cool in the right position.
5) Solder Pin 8 (use extra flux to get the solder to wick underneath the pin). You IC should now be well aligned
6) If everything looks good, solder the rest of the pins using whatever method you prefer.


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