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Starving Student PCB Help!! Pics

post #1 of 26
5/2/09 at 6:23pm
Thread Starter 
1st go at making a pcb, didnt seem to difficult using the laserprinter/photpaper method. The amp is built, but when turned on the tubes do not warm up and one cap (c1) just gets realy hot!
Turned off straight away, heres pics of my board;

PCB design, the cap that is heating up is C1;


schematic used;
http://img4.imageshack.us/img4/986/s...optionsgr6.jpg

Top;


Bottom;


I think maybe my pcb design is wrong somewhere, since it is my 1st go :-[
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post #2 of 26
5/2/09 at 7:09pm
Thread Starter 
anyone?
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post #3 of 26
5/2/09 at 7:13pm
Why do you have the gate resistors r3 tied to 48V and r9 tied to ground? Also, r8 and r10 should be connected in series. r3 should be connected between r2 and r4 and r9 should be connected between r8 and r10. I think it is best to scrap the pcb.
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post #4 of 26
5/2/09 at 7:31pm
Quote:
Originally Posted by Logistic View Post
Why do you have the gate resistors r3 tied to 48V and r9 tied to ground? Also, r8 and r10 should be connected in series. r3 should be connected between r2 and r4 and r9 should be connected between r8 and r10. I think it is best to scrap the pcb.
Agreed, I just looked at R8 and that was enough for me. R8 just goes to ground on that pcb. Why does the c1 cap get warm though? is it backwards? Its just a cap across the power supply, it should be the easiest part.
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post #5 of 26
5/2/09 at 7:42pm
What package are you using to layout the board? It is usually best to use something that uses a schematic to generate the board connections (Eagle, etc.), as this avoids this type of problem.

On the plus side, it looks like you did a nice job fabricating the board.
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post #6 of 26
5/2/09 at 7:56pm
Thread Starter 
Quote:
Originally Posted by Pars View Post
What package are you using to layout the board? It is usually best to use something that uses a schematic to generate the board connections (Eagle, etc.), as this avoids this type of problem.

On the plus side, it looks like you did a nice job fabricating the board.
I used PCBEXPRESS, looks like im gona start over on the board with eagle, any ways to fix this problem on the current board?

ps does express pcb support converting schematic to pcblayout?
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post #7 of 26
5/2/09 at 8:00pm
You can wire p2p the portions that are incorrect. However, that requires you to not only make sure you wire the p2p right, but that the erroneous traces on the pcb don't cause you trouble. It might be easier to refab the pcb.
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post #8 of 26
5/2/09 at 11:00pm
You can just cut any bad traces and point-to-point wire for now. No point making a new PCB until you know that you've found and corrected the problem.
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post #9 of 26
5/3/09 at 6:12am
Thread Starter 
Quote:
Originally Posted by Juaquin View Post
You can just cut any bad traces and point-to-point wire for now. No point making a new PCB until you know that you've found and corrected the problem.
what parts of the circuit need to be modified?

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post #10 of 26
5/3/09 at 8:35am
Thread Starter 
http://www.users.on.net/%7Erkwmd/Untitled-1a.jpg

this look any good?
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post #11 of 26
5/3/09 at 10:36am
Unless you can mount the tube sockets on the other side of the board, you'll have to trash your PCB, unfortunately. The tubes are wired backward. When you look at the basing diagram, the pin numbers are from the perspective of looking at the pins on the bottom of the tube. Thus, when looking down on the tube from the top (as when mounted on a PCB), Pin 7 is the first pin on the LEFT. Pin 1 is the first pin on the RIGHT.


Sorry about that.

EDIT: Those heat sinks won't do it, either. You need to leave much more room for much larger heat sinks, or plan on mounting them outside of the case. Sorry to be discouraging.
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post #12 of 26
5/3/09 at 12:47pm
Thread Starter 
looks like im gona have to start over
Any chance someone could make me a pcb from this schematic;
http://img4.imageshack.us/img4/986/s...optionsgr6.jpg
im sure there are 'experts' that could knock it together in no time, thanks guys
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post #13 of 26
5/3/09 at 7:39pm
Thread Starter 
been busy on new pcb, this look better?

P=Pot
A=Tube 1
B=Tube 2



Tubes and larger heatsinks are to be mounted externally this time around

ps how would I move the component name R1, R2.....etc. so it doesnt interfear with traces?
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post #14 of 26
5/6/09 at 11:39am
Thread Starter 
Built and tested today, same problem, C1 and C6 get very hot when i switch it on, I realy do not understand this, I have tested the voltages accross the caps and they are correct, and the right way round.
Iam giving up on the pcb method and going back to p2p, thats how I built my 1st one and worked fine, unless anyone can spot a flaw in the pcb design?
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post #15 of 26
5/6/09 at 1:22pm
Hmm, it looks okay to me. I can't find anything wrong with your pcb layout/traces...
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