Novice 5e3 Build Pops fuse & has low hum/no output

[Apocrathia]

Got my first 5e3 built last night, everything went great in putting it together and I had no problem with it. Between the schematic, layout diagram, and a slew of pictures; I pretty much had it finished before I even opened the box. 1:30AM last night I got everything finished, I made a triple check that everything was in the right place, good solder joints, (I noticed a resistor i had left out, put that in), etc... I went to plug it in, flipped the power, the amp lights up and I let it sit to warm for a few seconds. I go grab a guitar, plug it into normal input 1 throw standby off and all I got was a low hum with no output from the guitar at all and then after about 15 seconds, the fuse popped.
Heres where I'm looking for suggestions. I am going to go out to radio shack and buy a box of 2.5A 250V SloBlo's and take out all the tubes, remove the load, and see if it pops another fuse. I will also take readings off of a multimeter later on when my roommate gets back since he has it on him right now.
Can anyone give me any ideas of what to do? I want to send it back to bruce and let him take care of it for me, but at the same time; I built it and I should learn how to fix it.
When I can I will post some pictures of the internals (its a bit of a mess >.<) to see if someone can spot something I can't.

[drlowlow]

You are on the the correct path there. Isolate the possible problematic circuits and test them one at a time in comprehensive logical steps. I do this before I even try to fire up a build. start up the amp with no tubes in it, test the filiment voltages, move it into on from stanby and test the AC voltages, put in the rectifier and test the DC, Put in the Power tubes and check for proper voltages and charectoristcs, add the tubes one at a time moving posterierly (electrically) to anterierly. If you follow those steps you will likely find the symptoms of your problem and then you can make an educated guess and find how to test for possible causes of the symtoms. A multimeter is a powerful tool and when combined with a solid electronic fundamentals understanding can locate most problems to at least get something functioning again. You could send it to someone to repair, but if you follow the steps you might solve it faster and you will learn alot more. Plus being able to troubleshoot your own build only increases the satisfaction when you bang chords through it.

[Apocrathia]

I just got back from radio shack with a bag of fuses, pulled all of my tubes out and I noticed that the 12ax7's 1st pin was bent out of socket. Popped a new fuse in and im letting it sit for right now and everything is working fine. I learned a trick from gerald weber about using a chopstick to test for lose connections, bad resistors, etc. and so far so good. im about to go pop the tubes back in and hook up the load and I will get back to you all.

[Apocrathia]

Okay so I popped everything back in, and its no longer popping fuses, however, the 5y3 is now glowing bright red with a light blue glow in the top of the tube and is burning hot. only one of the 6v6's light up and as far as i can see the preamp tubes are still cold. Any ideas? turns out my roommate left his multimeter at his house 500 miles away so im about to go see if a friend has one.

[macdillard]

First off go to www.paulrubyamps.com , go to the technical section and read the article on how to first start up an amp. Will save you a lot of hard work. Next go to Harbor Freight and purchase a $15 or less meter..You don't have to have a $250 Fluke but you really need a meter to read contunity and voltage. Sounds as though you probably have something wired wrong.

Checking Harbor Freight they have a meter for $5 that would probably get you by.

[Apocrathia]

got a hold of a multimeter and started testing voltages, is the PT supposed to put out a ~630v off of the red leads going to lugs 4 & 6 of the 5y3?
there is either a problem with my 5y3 or something it is glowing BURNING red with a light blue glow in the top of the tube, I am about to take a ton of pictures of everything so that everyone can get an idea of whats the wiring in my amp looks like and see if they can spot any problems.
I really think i've isolated the problem down to the tubes, because everything appears to be perfect without them.
I have a tube tester at my parents house, but I'm not about to drive a couple of hundred miles this weekend from my dorm to my house, lol. I will probably see if a local music store has a tube tester that I can use.

[drlowlow]

the rectifier glowing like described is a serious problem. obviously something is drawing too much current, something has a resistance much lower than it is supposed to. try to pull all the tubes besides the rectifier and see if it still does it. add tubes first power than individual PI and preamp tubes. you should be able to find the problematic circuit with that technique and then you should use a multimeter to isolate it further (when you have the equiptment of course). I wouldn't run it for long period at all with the tube glowing like that, it is alot of strain for the tube and the transformer which are exceding their rated maximum current.



I would guess the 6V6 that is staying lit is the one closest to the rectifier. I would look for a loose conection on the filement windings between the 6v6s. you can troubleshoot the filement line without the rectifier tube being in the circuit. I think it would be a safe bet to say it will likely be something you can see if you look for it (perhaps a missing wire).

Good luck

[cminor9]

+100 on the post advising you to check out Paul Ruby's first power-up checklist.

As for the 5Y3, not sure what kind you have. I have a few. One, an old from a Hammond organ doesn't glow as you describe. The sovtek, on the other hand, does glow because the heater is actually the rather large (1/4" dia) metal tube in the center of the tube. It's the brightest tube in my 5E3 by far. "burning red" is a bit subjective. But as another poster said, it could be a problem. You really need to measure those voltages and know what's happening.

If only one 6V6 is lighting up, then maybe try swapping the two to eliminate a bad tube. If it isn't the tube, check your heater wires and connections to the tube sockets. Also, are the 12ax7's glowing?

If it's not a bad tube, it's going to be awfully hard to do much else without a MM.

Finally, if your internals are a mess, then it'd be in your best interest to get that taken care of. Once you get this thing working, if you have bad lead dress, then you'll likely have other problems like hum, etc. Make sure you have nice clean solder joints, shortest possible leads (within reason, some thing you may need longer leads to route away from something else) with AC and DC lines intersecting each other at 90 degrees, tightly twisted heaters, etc. I'd recommend taking the time to so this while building, else you'll just spend it troubleshooting later.

Hope you get it working, and you will in time.

[Apocrathia]

Well I have a multimeter now and ive been testing voltages, I mentioned this in my previous post.

I put the rectifier tube in (5y3) with no other tubes and got the exact same thing. Can I try putting in tubes without the rectifier? This is a NOS Silvertone 5y3, so it's possible that it's just a bad tube. Any way that I can verify that its working with my multimeter? I don't have access to a tube tester, I just went to an electronics store up the street and asked them for if they had a tube tester I could use to test my tubes with and the owner claimed to have one in the back of the shop burried under a mountain of shit that he hadn't even touched in 40 years.

[Apocrathia]

Thus far, going by paul ruby's checklist, everything if fine, It's the rectifier tube... but thats as for as I can tell
If anyone knows how to test a 5y3 with a multimeter, that would help (^o^) but so far I think I have it isolated to that tube, im transferring pics to my computer now..

[Apocrathia]

Here are some pictures so far... sorry if some of them are blurry, i dont ahve the greatest camera.
Something I just thought of, my filter caps are not all facing the same way, could this be a problem??? are they all supposed to be positives on the bottom? if this could be a part of my problem, let me know and I will go ahead and reverse this.








I am also going to link this thread to harmony-central and see if anyone over there has any other advice (^o^)

[Apocrathia]

few more pics:

[Apocrathia]

Alright! I got the recto tube to stop glowing by correcting the direction of my filter caps. There is still no sound coming from the amp though and not all of the tubes light up.

[TD_Madden]

that was my frist thought on seeing the pics!

Two of the filter-caps and the cathode bypass cap.....

Your preamp electrolytic caps are also reversed.....

[TD_Madden]

check the wiring on the preamp heater-pins......(4,5 and 9)