So basically I have followed all step to a T, bear in mind I am quite new at this and I was using a soldering gun that had quite a large tip. I am doing this for a school project and it was due on Wednesday May 11th ...so it is late as I was not expecting problems. So any help advice would be greatly appreciated, thanks.
First Test - I get the expected results.
Second test - Boost Converter - I get the expected results.
Third Test - I hear the beep, but no display on the clock.
After searching on the forum, I think the problem lies with the transistor because I do not get any voltage on the base. Emitter - 4.6V Base - 0V Collector - 4.6V I read somewhere to short the transistor, so I tried with a wire and the display lights up but goes out, I have to keep fiddling with it but the display does light up and goes out. Please provide any advice as this project is overdue, thanks.
The soldering doesn't look bad (though I can't really tell as the joints aren't in focus) but you might want to check everything carefully and touch up any joint that doesn't look right (dull, cracked, etc)
I highly recommend a proper soldering iron with small tip - a standard 25 watt from your local electronics store will be OK - big soldering guns are not recommended for things like this, even though you seem to have done a fairly OK job with it, you might have damaged something. best not to use them.
I also see you have bent the leads on some components over quite far, this is not necessary, you really should actually keep them as straight as possible, only bending them enough to stop them falling out. When they are bent over that far, they can cause shorts (maybe not on this board which has a solder mask, but on others you might end up with problems)
The leads on the bottom should be clipped closer to the board to avoid potential shorts. There is also a very suspicious looking streak of something between two pins on the bottom of the VFD chip. It looks like a thin strand of copper?
It's NPN, it conducts if the base is low. The base is connected to pin 5 of the AVR, the VFDPWR line. If AC power is connected, it should be low, at or near zero. What worries me is that the VCC voltage is 4.6, not 5, that means something is drawing enough current to pull the power supply down below 5V.
It looks to me like you might have two wires shorted on the tube. One of them is one of the "non connect" pins, so it might not matter.
All the joints where the lead has been bent over and extends out further than the pad are 'bad' (potentially cause shorts) - but it probably won't matter in this case but you shouldn't do it that way.
It's not as easy to cut the leads short when they are bent over quite far as you have done, You only need to bend them over enough stop the component falling out. The more they are bent the harder they are to desolder as well.
Q3 is the correct device and it sounds like it is working. If shorting two leads that are already at the same potential causes the display to light intermittantly, it is probably because you have some bad solder joints in the area.
So are there any suggestions on what I exactly should do now?
Clip the long leads as several have suggested. And re-touch all the solder joints in the vicinity of Q3. Some of those do look a litle solder-starved in the photos.
You might also check the VBIAS at the tube to see if the voltage is getting there.
I have tried everything, I have shortened all the leads I could and retouched all pretty much all the soldier joints. Yet I am still in the same place the clock on lights up if I play around and start shorting out the transistor and then it only comes on for a second and then goes off. I have attached more pics if anyone can see anything I’m missing, my project is well overdue and I need to hand it in tomorrow so any suggestions will be welcome, thanks. (I’ll just go over the voltages I get again)
First Step: No MAXIM with MAXIM with MAXIM & Tube first pin 8.81V 8.81V 8.6 second pin 0V 0V 0V third pin 4.94V 4.94V 4.94V
Second Step (diode)
50.8V 13.92V 13.64V
All three times the voltages on the transistor are E = 4.6V B = OV C = 4.6V - when I short it the clock comes on and the values change to C = 4.6V B = 1.58 E = 4.34V (Not sure what side is collector and what side is emitter)
(Not sure what side is collector and what side is emitter)
There is a data sheet link in the parts list. You should tell us precisely which pins you are measuring and which pins you are shorting. We can't draw any useful conclusions based on arbitrarily labeled measurements.
Andy whay would shorting the source and drain that are already at the same potential result in any change?
I am quite new at this, so could you be specific and tell me what pins, or points you want me to measure voltages across based upon the symptoms I have. Also can you see any bad soldier joints or extra wire clipping I may need to do based on the updated pics.
Overall I just need any tips/suggestions anyone can recommend, thank you very much.
It would light up for a brief second when I measured the transistor and the probe would touch both the collector and base or both the emitter and base. Also when you mean short what exactly does that entail? Does it mean connect one end to ground? Thanks.