When I powered it on, I noticed the power transformer got very, very hot - hot enough to burn one’s fingers, and so hot that it began to smell.
I quickly disconnected the power and began to do some rudimentary probing of the board using a digital multimeter.
Right away, I discovered that the DC resistance between the Gnd terminal and V+ terminal was less than 1 ohm. In contrast, the DC resistance between the Gnd terminal and the V- terminal is much, much higher (several mega-ohms). I would assume that the resistance would be more similar, if not the same.
I’ve checked a bunch of the components in the power supply section of the board, replaced both Zener diodes and the 1k resistors, as well as both transistors, but the same issue continues.
I’ve also checked the capacitors that sit next to each IC and tie V+ to Ground, and neither one is shorting.
Do you have any suggestions? Am I incorrect to assume that this very low resistance between Gnd and V+ is a sign of a problem?
I can’t believe that the transformer’s extreme temperature is to be expected.
Not sure what is wrong specifically with the soldering.
It may look messier than really it is in the photo, because I scratched away some of the flux that accumulated between the pads that are closest together, to make sure there was no bridging occurring. Maybe this is making it look like the solder joints are very rough. There is a bit of ‘flux-dust’ scattered around.
Or is there too much solder on each junction? Should I desolder and re-solder all the joints and try to use less this time?
I will go back over it again and check for bridging. One thing that would be really helpful would be if I could get a photo or an illustration of the underside of a clean, unpopulated K8084 board.
Is that something you could share with me?
Next time I build a kit, I’m going to scan both sides of the board before I build it, but in this case, it’s already too late.
