Hi. When I push any contestant button, the quizmaster’s led lights up for as long as I hold the button down. This happens with all four contestant buttons. None of the other LEDs light up, and nothing stays on. LED polarity is correct. Any ideas what I might check next?
Thank you!
Most likely an assembly problem.
Did you test the unit ‘as-is’ i.e. no modifications or external buttons ?
Make sure none of the diodes are inverted.
Check resistor values.
Check for bad/forgotten/loose/touching solder joints and damaged PCB pads/tracks.
Thank you. I will give it another good inspection! 
Hi. I’m not too savvy in electronics so I’m hoping for a little more help. In another person’s post you suggested checking for certain voltages. When I did that I found some serious differences. But you didn’t say what it would mean if we didn;t find the voltages you suggested. So, I’m hoping you won’t mind writing a little tip about what to do if the voltages are not what you expected. Here is a little table of what I found. Hoping something will jump out at you. Thank you, I really appreciate it!:
part | you | me
T1
E | 8V75 | 8 (good)
B | 8V | 7.5 (good)
C | 8V75 | 8 (good)
R3/Btn 1 | 8V75 | 4 (problem!)
T6
E | 8v75 | 0 (problem!)
B | 8v75 | 7.5 (good)
C | 0 | 8 (problem!) (This T is mounted correctly)
T2, 3, 4, 5
E | 8v75 | 0 (problem!)
B | 8v75 | 1 V (problem!)
C | 0 | 1 V (problem!)
T7, 8, 9, 10
E | 0 | 4 (problem!)
B | 0 | 0
C | 8V3 | 0 (problem!)
These voltages look OK.
At this time we are unable to tell what might be the cause of troubles.
Make sure none of the leds or diodes are inverted.
Thanks for the response. Just one more thing in case it wasn’t clear. I edited my previous post to put the pipe character “|” between the voltages you recommended and the voltages I actually had. So the first voltage listed is what I should have, and the second voltage listed is what I actually have. Do you still think the voltages I have look ok? They look way off to me, and I’m thinking the formatting of my post may have caused confusion. 
No, it was not clear.
If T6 emitter is at zero volts, LD5 can never light, altough you say it does… very strange.
Can you post hi-res and sharp pics of both componenten and solderside ?
Use a free picture base, as this forum does not allow to post pictures.
I just wanted to get back to you in case others read this post looking for help. I actually bought two of these kits at the same time, and I also took a soldering lesson from my brother. I built the second kit with better soldering and it worked great! So someday I’ll have to go back and find out what my assembly problem was, but I am confident it’s my fault. I’m very happy with the kit!
Just a guess.
Did you verify that all of the transistors are in their proper place?
When I did that I found some serious differences. But you didn’t say what it would mean if we didn;t find the voltages you suggested.