I recently finished my Compact Tube Hybrid (CTH) amp for my K702 and it turned out great. This project improved my skills troubleshoot a complex circuit on a small board, there were some mistakes while building this amp but for the most part it turned out great. So, when I placed everything on the table, I had the following:
And a close up of the board.
The webpage for the amp covers the building and testing process very carefully, but on top of what was on the website, I found a few things to look out for. Reading the resistors that came with the kit was a little challenging at first because it wasn’t the conventional color bands, the most important thing to realize is that the first three numbers of the resistor is the value and the forth digit is how many zeros are behind the value. Ie 1003 is 100 x 10^3 which is 100,000. You have to be especially careful with resistors with less than 100 because you have the R in the value. For example, 22R1F is 22.1 Ohms, not 220… that was one of the things that messed me up and it’s hard to unsolder components on this tight board.
Check all the components before you solder, Bill left out my 1k resistor but being in EECE, I had tons of 1k resistors in my kit; you might not be so lucky.
Follow the build order listed on Alex’s website, as in solder each component in the order he specified. If you solder a couple of capacitors and then some heat sticks in random order you will most likely get to a component that will be extremely difficult to solder.
Double check each resistor in tombstone placement to make sure that they are in the right place. Because you have so few resistors left when you do the tombstone placements, you might get too jumpy and that’s how I switched by R8 and R9 and got the LED to go from Green to Green instead of Red to Green (ie. e12 not working).
The number of capacitors did create doubts if I soldered things in the right place, but I hope my picture will help you out and remember to use your WIMA caps if you purchased them (edit: I think they come standard now)! Often times, if the components fits the white outline, it most likely is in the right place.
I will clean up the wires in the near future and put the top casing on, will upload more pictures when I finish that.
