Re Learning Something All the Time

I suppose I should just open a beer and sit back and have a laugh at myself, but I haven't convinced myself yet that its all that funny.  So a coffee will have to do while I contemplate a waste of about 5 hours.

I was working on 1 of 3 booster amp boards I've previously built for the Lets Build Something project.  There was a modification to be done which involved cutting a trace and putting in a jumper.  Basically it rerouted  a resistor and capacitor that was loading down the collector of the transistor rendering the circuit inoperable. Fortunately Ken, VA3ABN found the problem and reported his findings.  What makes this even more interesting is Franks circuit works without making any changes.

Where my day begins is testing the board as is before making the modification.  Somewhere along the line of soldering on last minute connectors and cables, I forgot about the mod and went about testing the board after those final touches. Of course the circuit didn't work and I even thought I let the smoke out of the smt transistor I was using.  I'm sure that only pushed the mod even further out of mind.  So after removing a solder bridge, thought I found the problem #1, re tested the board, no luck.  Testing the pot revealed a problem and eventually had to re-solder that component, thought I found the problem #2.  No luck again and this time testing proved that the transistor was not turning on at all. Replaced that smd with another one, thought I found the problem#3. No luck.  By this time I'm questioning my abilities as a homebrewer and double checking the schematic saw no errors.  This is a really simple circuit, 1 transistor amplifier, what could go wrong?  Well lets put in a through hole 2N3904 transistor and that should work as the 2nd smd transistor was not turning on either. Thought I found the problem #4. Nope not that either. If I can't make a 1 transistor amplifier work, then maybe I should give up and take up knitting. Or in the end, go get the original artical, make a coffee, get some left over Halloween candy, sit down and read up on the circuit.  I must be missing something.

A funny thing happen on the way back down the shack, arms full of crap, I realized what the problem was, I didn't complete Ken's mod. No wonder the board didn't work. Cut the trace, added the jumper, circuit works.  Not sure yet the details on how well it works, but happy that I now can see an signal on the output.

Trace cut circled in black and jumper beside it.

Coffee tastes better now.  I think I'll go work on my tower for a change of pace.

73, Peter