Another stupid mistake on my part...

[Randy Magee]

I can't believe I've made so many stupid errors with this Express clone! First the mistake in the PI wiring that gave me no volume and a nasty distortion, now I discovered that I crossed up the wires from the tone controls to the tagboard! I've been wondering why I couldn't get the tone of this amp dialed in and I'd just kind of stuck it in a corner with my "great idea but didn't really pan out" projects and was actually thinking of tearing it down and making something else out of it. I noticed that my tone controls were working backwards and that what should be a treble control didn't exactly respond correctly even in backwards mode if that makes any sense. I rewired the mistake this morning and now the amp sounds incredible! Previously it had an annoying "ticking" sound to it at idle, but you wouldn't really hear it when you were playing it. It also had a bit more hiss than it has now... I'm sure happy that I didn't tear it down now!

[Zippy]

Kudos for 'fessin' up in the forum.

Bonus points for figuring it out!

Enjoy!

[Reeltarded]

Randy! Congrats on the discovery!

My most recent dumb move was when I was tweaking Martin's presonance control on 3 amps, and that third amp just wasn't doing it.. yeah, because even after looking 2 times, I missed that I didn't run a feed wire. Oh, that'd do that!

[Gibsonman63]

Since we are telling on ourselves here, I have been re-routing a bunch of wiring in my Marshall combo. Basically separating AC from DC and cleaning up the wire from the board to the tube sockets and testing as I go. All was fine until I got to the PI. No sound. Then I realized all the tubes were off except for one power tube. Yep, I forgot to solder one of the heater wire connections between the power tubes.

[cbass]

I spent a while trying to figure out why an amp I built was to bassy.After checking everything about a dozen times.I realized I had used a .047 cap instead of a .0047 on the tone control.

[M Fowler]

I heck I've made lots of screw-ups I just don't tell you guys

[leadfootdriver]

Cool!

[ampmike]

I thought I made a mistake once,But I was wrong?

[leadfootdriver]

I just modded my 4x12 with cliff jacks for a choice of 4 or 16 ohm operation. It works great now that I fixed it. But when began the job, I wired up the jacks outside the cab with wires out of the left and right speaker holes, instead of one side or the other. So when I was done, I couldn't get the jacks in the cab.

[Randy Magee]

This is helping me feel not so "dumb as a brick". ;^)

[Cliff Schecht]

Randy the only time I feel dumb about mistakes is if I've made them before. I treat every first mistake like a lesson learned and try not to repeat said mistake. I've noticed recently that this same ideology has made me a much safer motorcycle rider as well, I've had a few close calls but have learned my lesson and know what to watch out for on the road. I've never had a moving motorcycle accident in the past 10 years I've been riding. Too bad I can't say the same about having the piss shocked out of me!

The only time I feel really dumb is when I make the same mistake inside multiple amps. It's not something I've done in a while but when I built my first few amps (all gutted and rebuilt now, minus my second Express) I made all sorts of goofy mistakes that made the amps noisy and unsafe. If anything I try now to build amps that I know are safe (i.e. power is wired correctly, proper fuse, heavy duty switches, HV is anchored down well) and are easy to work on if I need to do so.

[don280z]

I remember my 1st amp build. I got it all together, powered it up, check voltages, etc. All was OK....
I plugged in my guitar and NOTHING. Dead quiet. I thought "crap...what did I do wrong???". I turned it around and discovered I had forgotten to put the tubes back in.

[Cliff Schecht]

I think we've all done that one. I've done it in pedals too. Build em up, flip em on and no sound. I've done it so many times that this and shorts in the 1/4" jacks are the first thing I look at instinctively.

I went through a short phase when I started building amps again this winter where I finished up a couple of projects but was hesitant to fire them on. Everything went together too nicely and I was expecting sparks on the first turn-on. I don't know what was causing my hesitation (it had been months since I'd even touched a tube amp at that point) but all of the amps passed my initial tests and worked just fine. I guess it just took me a little bit to work up the nerve to work around HV again after dealing with only low voltage stuff for a good few months.

Then I went the other way and started just turning on amps after I finished them. No tests, just flip it on and see what happens. That can be quite a thrill and it actually helped me verify my process for building amps. Not something I do constantly but it was fun the few times I did it .

Now I always hook a function generator up on the amps wall plug first (set for sine wave, max amplitude, 60 Hz) and test all of the windings as well as the B+ chain (plug in a SS rectifier if you have a socket for a tube rec). You can check that there is DC where it should be and that the power transformer is hooked up correctly. You can even back calculate what the voltage on each pin will be with 120/240V AC mains. I also like to calculate what the heater voltages will be with 117V and 125V just to figure out exactly what my wall voltage needs to be to get 6.3V dead nuts on the heaters.

I do this instead of a light bulb limiter. Since you aren't working with high current AC from the wall everything in the amp is safe to touch. This lets me poke and prod at the connections to make sure everything is down securely. Also you can safely measure that there is continuity down your B+ chain. Then I do a dry fire-on with no tubes, check that everything is still correct, drop in tubes and pray to the amp gods that all will go smoothly.