Building the Expression Kit — Part 6
by Mark ~ June 2nd, 2008. Filed under: Amplifiers.
At the end of this step we should, in theory, have a working amplifier. The step mainly involves straight one-to-one wiring of the main-board leads to the pots and tube sockets, as well as wiring the power supply leads to the appropriate main-board turrets.
This photo shows the final wiring, after I upgraded the yellow Mallory 150s supplied in the kit to Orange-Drop 600V polyester capacitors. I found the 150s bright/brittle sounding and noticed in my tweaking that they are quite microphonic as well. The orange drops should be the 6PS type from Vishay/Sprague or SBE or the PVC type from Mallory. You don’t want the 715 series polyproplyene capacitors.
You might also notice a grid resistor on the 2nd triode of V1. In my debugging I had played with a grid resistor here to help stabilize the amplifier a bit (keep it from easily breaking into oscillation). A grid resistor is a common tweak seen in real Trainwrecks as well, a common result of the tweaking process. I don’t think I need this resistor anymore, but felt it did no harm to leave it in place.
Another, earlier, overview shot of the main-board wired in place. Definitely refer back to the Francesca wiring pictures for this phase of the project (see Part 1)! You want to make sure that you get the lead dress (wire routing and shaping) correct here!
After completing all the amp wiring, check and double-check the finished product against your layout diagrams and wiring photos. It may help to take a break from the project and come back to do your final checks with fresh eyes. Resist rushing to plug it in and ’smoke test’ the device… you might get smoke! Next time we’ll talk about power up and debugging.
September 28th, 2008 at 10:56 pm
Hey Mark, Where ya been lately?
How’s your Ceriatone unit doing? I just created a directory post for DIY effects & amp resources, and included a link to Ceriatone. Just curious if that’s turned out to be good stuff for you.
Don’t be a stranger ok!
cheers!
jp
September 29th, 2008 at 9:42 am
Hi JP,
Thanks for the ‘nudge.’
I took the summer off, focused on learning guitar, but I need to get back to posting and finish this series in particular.
I found having this unfinished series stifled my ability to post on other topics (guilt)… (memo to self… don’t start 9 or 10 part series no matter how interesting it seems at the beginning).
The Ceriatone worked out great, and I’d have to say that the Trainwreck Expression inspired amplifier is one of the best documented projects on the web, given the new material on AmpGarage.com recently.
I need to add power scaling and rewire the bright switch according to some new findings on the forum.
Despite my silence, I’m a regular reader of your blog… lurking there via my Snarfer RSS feed. Everybody should check out: http://stratoblogster.blogspot.com/
-mark.
September 30th, 2008 at 10:55 pm
Mark,
Glad to know you’re out there breathing ok and all. Thanks for the tip on AmpGarage.com! I’m adding that to my DIY/BYO resource directory. Also good to know your Ceriatone stuff is working well!
Hope to see you back blogging whenever you can!
Glad you’re a regular reader at Stratoblogster too– hope all the excitement isn’t too overwhelming!;)))
cheers!
jp
February 28th, 2009 at 12:58 am
Hi JP,
and we made sure to do our 1st youtube videos with a Strat! http://www.youtube.com/watch?v=Ipj20-EKhlc
Took me longer than I thought! Here’s why: http://tubenexus.com/2009/02/27/my-fet-dream-drove-me-to-distraction/
Got a new site for you to check out… cepedals.com (if you couldn’t tell
Hope you like it!
-mark.