NAD and BFD!! (Blown Fuse) Pics Inside

[notjonahbutnoah]

Welp, I acquired it over the last couple weeks, but didn't get around to taking pics until last night, so here she is:

 

Behold, The Heartbreaker.

 

 

 

 

 

I quite like it. It needs my OD pedal to get the gain juuust how I like it, but once it's there, it's probably my favorite Distortion I've ever heard. Cleans are also spectacular.

 

So some of you are aware of my footswitch antics, now I've got this other issue.

 

I ordered a set of Tung Sol EL34B's from Doug's, along with their Mesa tone kit (with an added 12AX7 because mine takes SEVEN!!!) and a JJ rec tube. GZ34 I believe.

 

Anyhoo, I installed them, did some living room jamming, some quite loud, and everything was good to go. Got to practice last night, warmed up for a bit, then literally on the 1st chord of our 1st song, POP! Fuse blew. (I actually remembered to check it once the amp just shut off because our bassist goes "Man, that blows"... EUREKA!)

 

Anyway, I am almost certain that it's the tubes. I think I've got em in wrong. See, it worked fine at last practice with the god-knows-how-old stock Mesa 6L6s, no problem. I think I've got them in their sockets wrong.

 

The Sockets have 10 holes(excluding the center one), the Mesa 6L6s have 5 or 6 pins, and these new EL34s have 9 pins. So, I could conceivably have them in the wrong holes...(I mean wrong holes for the pins on the tube, I might need to rotate them, not put them in different sockets) if this matters, does it? I don't even know. I'm used to EL84s. Same deal for the GZ34, just had to guess...

 

Anyone have any advice? I quite like this amp, and I DO NOT want to take it to a tech because there's really only one in town that's worth a damn that I know of and he takes MONTHS, from being so backed up all the time. HELP!

[Prages]

Tubes and tube sockets have a key on the center hole that will only allow you to insert them the right way.

 

EL34s and 6L6s aren't normally interchangeable either. They'll fit in the same socket, but the pins aren't wired the same. I don't know anything about that amp, but unless it's made to allow you to swap 6L6s for EL34s (which granted, some amps are), then the two tube types are not cross-compatible.

[thermionic geek]

Replace the fuse, Put the 6L6's back in and see if there is any other damage. If you put the EL34's back they should only go in one way. There is a guide pin with a raised portion that fits in a notch in the tube socket. Be sure that the Bias switch is set to the EL34 position. If you still blow fuses go to a tech.

[Prages]

Nevermind, I see that it is capable of handling either EL34s or 6L6s. Did you set the bias switch for EL34s?

 

Also, changing the rectifier type might have put too much voltage to the tubes. Did you use the same type of rectifier tube?

 

I'd replace the fuse, then put the old power tubes and rectifier back in. If the amp works with the old tubes, then I'd leave the old rectifier in and replace the power tubes with the new ones.

 

Rectifier tubes last a long, long time, so the old one probably still has plenty of life left in it anyway.

[notjonahbutnoah]

OK, all good info.

 

I've exchanged an email with Doug as well.

 

Yes, the bias switch is in the proper position. This amp can handle 6L6, EL34, and 6v6 tubes. Nice eh?

 

I think the rec tube is the same type, 5AR4s and GZ34s are the same type, like 12AX7 and ECC83.

 

Here, take a look at this:

 

 

Maybe that helps.

 

Also, I did make all the EL34s fit in the same way. As in the gap is in the same spot, but I picked it, as this was one of the pin-less holes with the 6L6s, and didn't notice a notch on the center plastic pin.

[notjonahbutnoah]

After a few emails, Doug thinks its a power tube short. Ugh. PITA!

[Doctor Morbius]

Congrats on the new amp. Hope you get things sorted out.

[JoeBoy]

Just think about getting it fixed. What a great amp.

[notjonahbutnoah]

Thanks ya'll.

 

Yeah, I'll figure something out. Probably just end up going back to the 6L6s.

[metal0822]

yea if you turn it on and the fuse blows shortly after you put it on standby, its power tubes almost every time. that being said, im not sure why the el34s caused that to happen. maybe the bias switch is messed up/not connected? any particular reason you wanted el34s and not 6l6s? i dont blame you, i would have done the same swap. o and HNAD, i hope you get it all figured out, working on amps really isnt that hard imo.

[notjonahbutnoah]

yea if you turn it on and the fuse blows shortly after you put it on standby, its power tubes almost every time. that being said, im not sure why the el34s caused that to happen. maybe the bias switch is messed up/not connected? any particular reason you wanted el34s and not 6l6s? i dont blame you, i would have done the same swap. o and HNAD, i hope you get it all figured out, working on amps really isnt that hard imo.

 

Fanks.

 

I swapped because our other guitarist plays a 6L6 based amp and I do all I can to have a solid but different tone. That and to brighten it up a little, which it did, but oh well.

 

As far as working on amps... I'd love to learn, but I need some courses on how electricity works. I'm awesome with my hands, and love to mess with stuff, but the actual science of electricity is f*cked up. I don't get it. Kinda, but not really. The big picture is VERY blurry at the moment.

[metal0822]

ah, gotcha. i guess majoring in applied engineering with a focus in electronics/control systems helps a lot. but if i were you i would just dive into it. read what you can and watch youtube videos on draining your caps! for the love of god, you could die if you dont. now while that does sound scary, draining the caps is also simple as pie. AND, as long as you have one hand behind your back you're fine ( though you could get burned ) because the current cannot close a circuit from one hand through your chest (HEART!) to the other hand, to whatever else you are holding. just dont be an idiot and you should be fine. i mean yea you could cut your head off with a table saw too, but if you know thats possible and why it could happen, you wont let it happen. definitely read on how to drain your caps though.

[Wyatt]

 

The Sockets have 10 holes(excluding the center one), the Mesa 6L6s have 5 or 6 pins, and these new EL34s have 9 pins. So, I could conceivably have them in the wrong holes...(I mean wrong holes for the pins on the tube, I might need to rotate them, not put them in different sockets) if this matters, does it? I don't even know. I'm used to EL84s. Same deal for the GZ34, just had to guess...

 

 

I think you need to count again.

 

6L6, 6V6, EL34, 6550, KT66, KT88, 6CA7, etc. are all octal tubes...octal means eight.

 

There is no such thing as a nine-pin EL34.

 

I've never seen a 6L6G/GB/GC with less than eight pins...but it doesn't use two of them (pin 1 and pin 6), so a six-pin 6L6 is possible...a five-pin 6L6 is NOT.

 

An the sockets are octal sockets...eight holes for eight pins.

 

Now the rectifier tube, which also plugs into a octal socket, usually only have five pins.

 

As noted above, every very single octal tube should have a key guide, so you can't put them in wrong.

[Deadbeat Son]

To echo what's already been said, have you tried to put the 6L6s back in and set the bias switch back? The problem sounds like a defective EL34.

[notjonahbutnoah]

 

To echo what's already been said, have you tried to put the 6L6s back in and set the bias switch back? The problem sounds like a defective EL34.

 

 

Will do, this is the plan.

[Prages]

I've never seen an octal tube socket or tube that doesn't have the keyhole so you can't put it in wrong.

 

[notjonahbutnoah]

I've never seen an octal tube socket or tube that doesn't have the keyhole so you can't put it in wrong.

 

Welp, I believe you, however, mine either don't have that or I just lucked out and put em in right on a guess. I'll fiddle and report back later tonight or tomorrow. Thanks for all your help!!!!!!!!!

[Wyatt]

Welp, I believe you, however, mine either don't have that or I just lucked out and put em in right on a guess. I'll fiddle and report back later tonight or tomorrow. Thanks for all your help!!!!!!!!!

 

Trust us, it's there.

 

I have never seen a socket that lacked the guide, not even back to the '40's.

 

And all modern, mass-produced octal tubes have the center guide pin as well. You have to go NOS to some oddball brands not to find one. It's been the industry standard since before WWII.

[metal0822]

yes you just need to connect one end of an alligator clip if you got them, but any conductor will work really, to the post on the filter cap. ground the other side on the chassis and wait like 2 seconds. BUT! i would not do it this way as you will possible create a large spark and very unlikely you could damage something. so i like to put a power resistor somewhere in the path. so cap >---------

[notjonahbutnoah]

Ok so sure enough, that guide was there. I swear I just chose a spot in the socket where there was no 6L6 pin and slid them in. Crazy.

 

 

Anyhoo, I replaced the fuse, and everything is ok, 'cept I haven't cranked it like I can at practice. If another fuse blows then I'll switch back and go from there.

 

THANKS FOR ALL THE HELP AND ADVICE!!!!!!!!!!!!!! Lub you guys.

[metal0822]

cool, keep us updated either way

[notjonahbutnoah]

Will do, and thanks for the cap-draining advice. Probably won't reach the level where I will need to any time soon, but it's noted regardless.

[notjonahbutnoah]

So, last night we had practice again. Mondees 'n Thirsdees!

 

When I blew my fuse it was set up as follows:

 

-full voltage (not the tweed/variac setting)

-full wattage (all 4 as opposed to just 2 power tubes engaged)

-tube rectified (not the diodes)

 

Last night I started with the opposite of those setting ans worked my way up.

 

The thing worked fine, the only thing I didnt try was the full on power with the tube rectification... the fuse never blew, which leads me to believe it's a shoddy rec tube.

 

It's a JJ GZ34, bought it from Doug at DougsTubes. He doesn't speak too highly of the JJs, said that rec tube can be intermittent. Sheesh. So who knows. I guess next practice I'll try to blow the fuse again by using the tube recto in the full power mode.

 

Question: Is it true in EVERY instance of fuse blowing that it's another problem? I mean I know this is the general rule, but can a fuse just plain wear out?

[Prages]

I guess in theory a fuse can just blow...I mean, it operates basically like a light bulb, and they eventually blow.

 

I've never had one do that, but I guess it's possible.

[notjonahbutnoah]

 

I guess in theory a tube can blow...I mean, it operates basically like a light bulb, and they eventually blow. I've never had one do that, but I guess it's possible.

 

 

you meant fuse right? just to be clear here