Defeat snatched from the jaws of victory... And rescuing it back (a tale of idiocy and woe)

So I totally forgot to write anything for a while. Not because i'd stopped doing anything, but more because good intentions, and then just forgetting to, and, well, a slight mishap...

Anyway I finished the build beginning of June? Or something like that. Bit more wires than the sloclone, but got there in the end, even drew some skull on cross bones ontop of some caps to remind myself not to be stupid and lick them.

It all mostly went well, apart from that just like on the slo, the OT anode wires were the wrong way round again, and I found a mistake on the layout vs the schematic that meant i had no signal to the power amp. Important lesson here, trust the schematic, double check against the layout.

I'd done pretty well with neat wiring up to that point, but then had to concede and do a bit of rewiring and de soldering, but eventually, it all worked. Big thanks to the oracle for not getting sick of me, as I asked a lot of questions in the depths of despair...

So yeah, it came out really cool. I had some preconceptions about it maybe being too nice, but i think having the option of 20v zeners as well as stock Friedman values nicely added a bit of aggression to the amp, and it was brilliant! All was well with the world, apart from total inability to do woodwork (you should see the ghetto chicken door i made, and even did it without losing fingers, but it's definitely not an oil painting...)

But then, yeah, I killed it. Wondering why it stopped working, i was poking around in the amp, and here, dear reader, follows a tale of caution, entitled "don't be this stupid, and put dowen the screwdriver"

So, i decided, in infinite wisdom, to go tapping power tube pins with the screwdriver. The input jack I figured was iffy as it had been loose, but after tightening, and poking the wires, it was still not responding. Patient was braindead, but still had a pulse (ie, pilot light came on, transformers humming, valve heaters working).

All good. But does it make sound from the power amp? How shall I test this? I know, lets tap a pin with the screwdriver to make it go "pop", that way I'll be able to know it's the preamp.

What happened next was a moment of idiocy. The idiocy being that I thought this was a good idea. There was no voice of common sense sitting on my shoulder screamning "noooooo" (he'd gone on holiday to a day spa or something) so I did it. In went the screwdriver, and then, slip went the hand....

Now, we all like firreworks, they are cool, we like bangs too. Just not in an amp you've just built. The screwdriver (i think) shorted the pins between high tension supply and heaters. One big blue flas, and small bang, and now, nothing. All dead. No pilot light. No hum of transformers.

Dead.

Really Dead.

Really really dead.

Having taken stock, and after a fairly long period of silence staring at the amp, I checked the fuse. OK, so that's gone, maybe that's it.

I replaced the fuse. Still nothing. Measured voltages, nothing coming in at all. 

I looked, and looked, stared, consulted the (by now probably fed up) Oracle, but all to no avail. My diagnosis? Fried Power Transformer.

And thus, I left it. It had lived, briefly, and then died. Life happened. I did things, worked, summer went, the days grew shorter and it lay there forgotten. To repair it, I needed a new Power Transformer, and there was other stuff to do.

Then when i tried to order, the guy who makes them was unavailable. So again, the wait. 

Finally, beginning this year, i put a large order in. Not only was I going to fix it, but i was going to finish the second BE100 build I'd started, one that was using the Russian PCB I'd got (don't worry, I'll do a quick post on this one, as it's much the same as the BE100 build, unless, of course, it goes hilariously wrong, in which case the story might be longer).

So, got the transformers, and then one evening, not too long ago now, set about replacing the fried power transformer.

I even got some xt60 connectors so i could just plug it in, instead of desoldering from the board. These are cool by the way, used in RC cars, and can handle stupid amounts of current.  

So, I then, having rewired it, turned the amp on. Nothing. Nothing again. At this point my heart sank. Have i screwed it that badly that it's silently taken out the new PT? So I checked the fuse. All fine. Really, what is happening here?

 

Then, the penny, it dropped. The penny that read "Hey Stupid" on it. I checked the fuse holder. Now, it has two places the fuse can go. One is difficult to put it in, one is not. So i took the fuse from the difficult place, and put it in the easy to put place. 

 

Then, turned it back on. It works! Lights on, yes!!!! Still no sound, but, closer!   

So, time to have a look, and there it was, the culprit. A strand of shielded wire grounding the input to the chassis. That's what the problem was that caused all this mess.

So, as a result, I am now (after watching a lee jackson amp mod video) putting heat shrink on all the ends of shielded cables now, to avoid that happening. A rather long winded lesson I must say...

So, you may ask, does that mean the other Power tranny was fried? Well, not to spoil too much, but the answer to that question may very well involve subject matter for some future (not too far in the future) blog posts!

Meanwhile, here's some pics of incorrect, followed by correct places to put a fuse in an integrated mains IEC plug. Enjoy, and remember, I've been dumb so you don't have to be...

Anyway, until next time, when I'll be introducing a new project, and explaining how I will be torturing myself with this one.