Fender 5e3 build keeps blowing fuses and light doesn't come on

[Vonchampz]

When I built this amp it worked perfectly. However it was my first build and i didn't really solder everything perfectly and there was a lot of wiring that could have been done better. So last week i basically took out the board and re did all the connections. Everything. However now it turns on for a second the light comes on for a second an then my fuse blows every single time. I disconnected the secondaries and took the tubes out and the fuse does not blow. So its not the power transformer correct? Also, I thought i had the power switch, standby and fuse wired differently the first time, but i wasn't sure so I used the robrob diagram and i believe this is what the wiring diagram shows. I've enclosed 2 photos with the secondaries reconnected after i tried that test, as well as a photo of the rest of the inside of the amp. Am I hooking up all the switches and fuse correctly? Am I not putting in the right fuse? would that cause this to happen? Any help would be appreciated. Thanks!

 

[corliss1]

Alright, so we need to isolate.

First of all, it would be good to have a light bulb limiter or current meter so you aren't blowing through fuses.

You don't have the secondaries hooked up. Let's hook up just the heaters and see what happens? Fuse holds? Cool. Then hook up the high voltage with the power tubes removed. Fuse holds? Cool. Put tubes in? Fuse blows? Bad power tube.

Just a process of elimination to figure out what's drawing the current that's blowing the fuse.

 

[Jasonpatrick]

Clean up that rats nest and pair the wire together that go together before moving forward so you don’t accidentally kill yourself if something makes contact with something else and then follow what dude said above! PS— you don’t need a standby switch on a 5e3 and with that being said removing it out of the circuit will also remove some excess wire in the chassis

 

[Jasonpatrick]

Light not coming on sounds like the light harness is grounding out somewhere which the cheap ones included in kits have been known to do out of the blue.

 

[corliss1]

@Jasonpatrick - I was assuming he meant the light doesn't come on, as in now power at all because the mains fuse is blowing, but yes, it would be good for the OP to clarify

 

[Jasonpatrick]

@Jasonpatrick - I was assuming he meant the light doesn't come on, as in now power at all because the mains fuse is blowing, but yes, it would be good for the OP to clarify

Haha yeah that probably what they meant but I also wanted to add this just in case!

 

[Jasonpatrick]

Also check to make sure you are using the correct fuse. Slo blo and whatever the correct amperage is for that, I think it’s 2A, because if you are using just a regular fuse and you pop that standby switch it’s gonna go pop.

 

[King Fan]

By all means check you're using slow-blow fuses, but let's assume you have a short.

I'll double down on the advice from @corliss1 . A light bulb limiter is cheap, simple to build, and vital right now. (Use a 40-100W *incandescent* bulb -- you want the current limiting effect of a smaller bulb here.) Not only will it help you localize your short, and confirm when it's fixed, but while testing it'll protect your amp against the side effects of the short. It'll also save you buying and replacing lots of fuses, but that's the least important benefit.

One you have the limiter, you can use it to localize the short using the test sequence outlined by @corliss1 but substituting 'bright bulb' for blown fuse and 'dim bulb' for fuse holds.

Details: with the limiter and a small-ish bulb, you want to see the bulb go bright for a few seconds during startup (current inrush, basically charging get filters) and then go dim. If it stays bright, you have a short. After the short is fixed, *remove the LBL* from the circuit -- the limiter effect will alter both measured voltages and amp sound.

 

[King Fan]

Oh, and FWIW, here's a Rob-style 5E3 minus standby; as mentioned, an unnecessary complication in this amp. With respect, I'll admit I can't trace your wiring; those bare green wires are freaking me out a little. Removing standby isn't vital right now, but seeing what's going on is. I'd humbly suggest if your wire routing -- and length -- looked more like this, it might simplify troubleshooting.

 

[dan40]

Also, I thought i had the power switch, standby and fuse wired differently the first time, but i wasn't sure so I used the robrob diagram and i believe this is what the wiring diagram shows.

Everyone has given great advice above so i'll just add one thing...Rob's layout is great but you have to be certain that it matches your amp correctly. The power transformer wire colors in his layout are for the PT that he recommends for the 5e3. If you purchased a different PT, and it appears that you did, your wire colors may not match the layout's wire colors which will cause a wiring error. Verify that your PT's primary and secondary wire colors correctly match the PT that Rob used in the layout.

 

[Vonchampz]

Alright, so we need to isolate.

First of all, it would be good to have a light bulb limiter or current meter so you aren't blowing through fuses.

You don't have the secondaries hooked up. Let's hook up just the heaters and see what happens? Fuse holds? Cool. Then hook up the high voltage with the power tubes removed. Fuse holds? Cool. Put tubes in? Fuse blows? Bad power tube.

Just a process of elimination to figure out what's drawing the current that's blowing the fuse.

So I hooked up the secondaries and the fuse blows. I forgot to mention that

 

[Vonchampz]

i think i might not be using slo blo fuses, so im going to grab a pack. Concerning the light, when I know i had a slo blo fuse because it was the same fuse that i used when it was working, i would turn it on, the light would come on for a second and then shut off and i realized it had blown the fuse. So i reconnected all the wires and im going to get a slo blo and then troubleshoot from there, because i'm realizing that the pack i bought doesnt say slo blo... Thanks for the help and i'll update in a day or two. Thanks!

 

[JPKmusicman]

I'd use a multimeter set to ohms and start checking the filament and HV circuits for shorts. Discharge all caps first.

 

[corliss1]

So I hooked up the secondaries and the fuse blows.

Did you do them one at a time? And yes, make sure you have a slow-blow fuse.

 

[King Fan]

OK, I gotta ask. What are these two green wires? Where do they come from and why are they bare?

 

[corliss1]

@King Fan - that's from when he disconnected the secondaries

 

[JPKmusicman]

You probably created a short to ground on the filament or HV circuit after re-flowing things with your iron. Get out the multimeter.

 

[dan40]

i'm realizing that the pack i bought doesnt say slo blo.

The fuse should have the letter "T" stamped on it right next to the amperage rating. The "T" stands for "timed" which indicates that the fuse is a delayed or slow blow type. If you don't see this stamped right next to the amperage rating then you have a standard fast blow fuse.

 

[Vonchampz]

So i did have the wrong fuse in there and finally went out and bought a slo blo fuse. Turned it on, no sound at all. Used a wooden stick to poke around, nothing. Made sure the input jacks and speaker jack are correctly connected. Turned it on again, noticed that the rectifier tube was way hotter than any of the other tubes and at that moment, my output transformer started smoking. Obviously I turned it off, but the OT is fried. What would cause the OT to fry like that? and What should my next steps be in terms of trouble-shooting? I Obviously don't want to throw another OT in there and kill it without first finding the problem. I built this maybe almost a year ago and everything was great. However this all happened after I replaced most of the wire inside because I used really thin cheap plastic coated wire for everything initially. I will post some high-res photos when I get back home, but I really could use some help on where to go from here. Thanks!

 

[corliss1]

Parts fry - resistor, tube, OT, doesn't matter - because of too much current. This is likely caused by a short somewhere in your rework of the wiring.