Troubleshooting to Victory

Right, in my last post I had everything wired up ready to go, so, why no victory look at how awesome my first time skillz are etc etc post?

Because quite frankly it didn't work.

Let me set the scene, our hero, with confidence boosted by how nice it all looks and having caught a few errors here and there from the layout and fixing them, intrepidly surveys his work and in supreme confidence flicks the switch, guitar in hand, ready for the 80's montage with high fives, winks and other awesome poses.

Yeah, so you can guess how that turned out... cur long face, toys thrown out of the pram and infinite sadness. It just didn't work, no apparent sound at all, back to the drawing board time, or more specifically troubleshooting.

So, I started, first thing to check was whether I had wired up all the valves/controls properly, so I went about that. Luckily i had a voltage chart supplied by The Oracle that I could use to see if the voltages i had in the amp where correct, so starting with the power amp and moving my way through that and checking the preamp valve voltages I found that for some reason all the voltages on V5 were wrong. Traced that through to two of the leads having been swapped, so proceeded to put them in the right place.

Turned it on again, now had some signal coming through the OD channel, but nothing through crunch/clean, and also a weird oscillation sound when turning up the master volumes. Oh, and I'd somehow swapped them around as well. Another thing to fix.

Anyway, so first up the oscillation, which turned out isa symptom of the output transformers being connected the wrong way round. Luckily this is an easy fix as you can just swap around the signals that go to the grids of each pair. Would have been nice to have it wired all like the diagram, but wasn't to be, besides, it's just one pair of crossed wires, and a clean fix too.

Next up figuring out what was wrong with the channels and switching. For this went round measuring the optocoupler voltages on each setting to find the funny thing that 2 of them just read weird voltages when engaged. This caused a hell of a lot of head scratching until i found a little strand of solder jumping from the track it was on onto another creating a short. Cleaned and resoldered and sorted. Voltages all correct, but still no sound from the clean and but a faint one from the OD channel.

*sigh* not going well this, and it's this stage with multiple problems that is frustrating and time consuming and not fun.

Following that I was advised to check all my shielded cable runs, so I did, and then found the way I'd wired the FX loop was incorrect, as the amp layout schematic was wrong, so following a rewire I was kind of hoping that'd be my problem. However, this turned out not to be the case. I check all the shielded cables, checked for continuity, checked to make sure it wasn't grounding to the shield, over and over again.

Anyway, so now I have a faint OD (as in really really really faint) still and no second channel. Not good and pretty frustrating.

So, next step, trace through everything from the beginning. I started with the switches and input, making sure the input was isolated, all good, then got hold of a picture of how the bright/clean/od switch configuration should be wired.

Another mistake.

So, one rewire later (which has now made it look messier which is crap, but i should have done it right first time) and i now can can a very very faint clean and still have bugger all volume. Frustrating again.

So, I jumped the FX loop and it all sprang to life, victory I though, I rewired the shielded cables to the preamp board, did a quick test, and all good, volume at long last, brilliant! With that I screwed down the board, and prepared to go get some glorious tones!

Only to be greeted by false dawn version 2.0. I'm now also 3 days into trying to get it all to work, having sacrificed all my spare evenings, going to sleep trying to figure out what to try next. So this isn't good.

So, time to remove the preamp PCB again and start checking the rear/front for problems.

And lo and behold, it all works again. Annoying as hell.

So I then by mistake discover that prodding the PCB and moving it a tad with my plastic stick towards where it needs to be mounted cuts out the sound. So something somewhere isn't right... Frustration at maximum with not knowing what the hell is wrong, another night of sleep and wondering. To cap it all I've just found out the mid control pot is broken as well, so will need a replacement for that. All in all it's just adding to my annoyance and sense of some kind of impeding failure.

Anyway, next day, I have replacement pot incoming, and it's time to figure out what's wrong. So on advice i mount the board loosely, no sound, and then start pulling at wires gently with a bit of wood (chopstick is ideal or anything as long as you're not near the high voltages) and I finally find the culprit, one bad wire near the input that when it is stretched cuts out. I replace said wire and there I am, victory oh sweet victory!

On the one hand supremely frustrating, on the other I did learn a lot by having it not work first time, a hell of a lot in fact, so it's been kind o a double edged sword. Just need to replace that mid pot now, and that's the last of the issues.

In summary, this stage is properly frustrating and involved a hell of a lot of patience and asking for advice from Th Oracle, amp forums and going of intuition and just trying things out. The worst part is not knowing how long it'll take, the best, finally being finished! The advice I got to just keep at it and eventually you'll find the issue rings true, and as long as you kind of know what bits are what you can just slowly work your way through it.

Anyway, I'll leave you with the video I recorded at that point, a sort of semi victory, but one none the less! I've also found this amp has way more gain than I expected it to as well, so am pleased already, just need to fix that one last thing!