Amp tech question

[DanF]

Hey guys, well this is certainly a bummer since I just posted how happy I am with my tube amp a few weeks ago.

I was playing last night and standing up walking around and I took one step too far and yanked the cord. I heard the cord pull then the amp started sqealing and stuff. So I walked over and hit the standby switch and let it cool off for a bit while I checked out the cord and swapped a different one in. I turned the amp back on and started playing with no output from the amp (:() So after freaking out a bit I decided to make like a scientist and hit the channel switch over to distortion, started playing and everything sounded normal. But nothing on the clean channel. I turned up the clean channel to about 3 (hey, I play pretty quietly usually) and I could get sound out of the clean side too.

My question is, did I blow a tube or something? Why do I have to turn it up louder to get any sound now? I have a repair center here I just wanted to get an idea of what it was before I went down (if I go down)

-Dan

[EricV]

Bring it to the repair center, really. If you´re not sure how much it´s gonna be ask them whether they could just check and tell ya how much a full repair would be... that check shouldn´t cost too much.
The reason why I am saying this is: I had the EXACT ! SAME ! THING! happening almost 10 years ago with a JCM 900 ( to be precise, a 4500 model... Hi Gain Dual Reverb 50 W ).
It was during some rehearsal, and I stepped on the cord that was between my stompbox and the input of the amp. All of a sudden there wasn´t a sound coming out of it anymore.
The dad of a friend of mine worked for a big music store back then, and that store had a really good amp tech. He told me that by stepping on the chord, something inside the amp was broken, which caused a shortcut, which killed one or two poweramp burns.. plus, I believe the tube sockets. I had to pay... I dunno, about 90 bucks... 2 new tubes plus the repair.
And after that, there still were occasional problems... the poweramp tubes didn´t last very long. I think the part that was broken was beyond repair.
Anyway, I can´t tell ya what´s wrong with your amp now, it just reminds me of what happened to me back then
Eric

[EricV]

These days, I put that cord behind the stack and run it between amp and cabinet, so if I step on it, nothing will happen... kinda like the same thing you do when you run the cord between guitar and strap before plugging it in... it´s safer
Eric

[DanF]

Hey Eric,

Although I know very little about tube amps I had a bad feeling that I may have blown a tube, I just wanted to see if that was a rediculous idea or not. Hearing that you'd done it was enough for me to get over my embarassment and take the damn thing back to the shop. Hopefully I'll have it back in a day or two. I'll let ya know how it turns out.

-Dan

[EricV]

Well, accidents like that just happen. And... seriously, I love tube amps, and I had some of my amps modded, changed tubes etc., and I know a few things about them, but really, I don´t know how tube-technique really works. Never got too much into the math / engineering part of it.
I just want my stuff to work, so even though it´s not always cheap, I have a technician fix my amps for me once they break down.
By the way, better don´t switch it on anymore till ya bring it to the store. One thing I know is "If ya know something´s wrong with yer amp, have it fixed immediately, or at least don´t use it till you get it fixed, cuz it´ll only get worse"

If you i.e. notice that you need new tubes, better change them right away. Otherwise, you´d risk that they burn out, and if they do that, they might harm the sockets or the poweramp, which makes it even worse
Good luck, let us know how it went
Eric

[Bongo Boy]

DanF if you do get a diagnostic on it I'd really like to hear the explanation. First off (and this question is for you and Eric)--did your instrument cable plug simple get jerked out of the input jack--that's it?

Eric said he had a 'short', and I wonder if--as the plug was jerked out of the jack it was jerked sideways (rather than straight out) and perhaps shorted the two sides of the input together. I don't know why this would be a problem--but I'm curious about it.

I've yanked my cable out of the guitar about 5 times now (too lazy to pull the cable thru the neck strap). Guess I should not be so lazy.

[Bizarro]

It's a bit late for this tip, but it's something to think about in the future...
Always wrap the guitar cord once around the handle of amp before plugging it into the input jack.

If you step on the cord, it'll put against the handle which is really strong and has nothing to do with electricity;). This removes any strain from being applied to the input jack. It's the same principle as wrapping your cord around the strap button before plugging into your guitar.

I do this with all cables that run into my amp(s). The footswitch cable, guitar cable, and the effects loop (if I use it).

It's the little things that can really save your butt! I also duct tape my cables to the floor during gigs so people can't trip over them, especially me!

I hope the amp repair is simple, robust, and inexpensive.;)

[EricV]

Bizarro, that´s what I do THESE days... :)

Bongo... no, the cord wasn´t ripped out of the jack, it stayed in there. It pulled the jack downwards, and that board the jack was mounted on inside got cracked... that´s what caused the short. At least that is what the tech explained to me.
A bit hard to believe, but then again, the amp was broken, the tubes were gone ( I looked at them )...
Eric

[metaljustice83]

I'm always afraid to wrap my chord through the amp handle for fear if yanked hard enough thenthe amp head could come off my halfstack, should I be scared of this??

[EricV]

Well, if you don´t put the cord between amp and cab or warp it around the handle, you might still cause the top to fall from the stack if you step on the cord... ?
Èric

[Bongo Boy]

Originally posted by EricV
... no, the cord wasn´t ripped out of the jack, it stayed in there. It pulled the jack downwards, and that board the jack was mounted on inside got cracked... that´s what caused the short.Ouch! Yup, that makes perfect sense. That would suggest an amp design tip--mount all external jacks on one or more separate panels, then connect them to the board with short leads (copper, copper ribbon, fiber optic, etc). Of course then you have to shield 'em and spend more time on assembly, etc., so the cost goes up.

[EricV]

Actually, I do believe that many vintage amps were wired that way.
I also remember Petersburg amps... those were pretty cheap tube amps built by hand in russia... very very basic amp, and if you looked inside of it, you could see it actually was hand-built =)
But with the pots and jacks mounted onto the front-plate and connected to the other components ( as you suggested )... I guess that´s the safer way...
I guess a lot of vintage-style "boutique amps" yoiu get these days are wired like that, too.
Eric

[Theoden]

Hi people. Just thought I'd throw my penny worth in here. When I used to play pro many years ago, I always used to put my input lead through the CABinet handles. The reason I did this is because twice I had amp heads pulled off the top of the stack by over excited stage diving types. and its a long way to the floor for a heavy item like a Marshall head, made worse, ( and easier !) , if you liked to stack two amp heads on the top of the cabs.

Just a thought.........


Rock onwards............

Nig, aka Theoden

[metalprep6969]

Nowadays, I leave the cab behind me but I keep my head beside me. It makes fine tuning during the show easier, puts the standby switch closer to reach, and prevents it from falling off of the cab (though arguably it could fall off of whatever else on which it is sitting).

\m/

BTW, good job resurrecting an old post Theoden.

[Bongo Boy]

Yeah this an old thread for sure. But it may be an opportunity to ask about wireless setups--seems like this would be the way to go. Other than cost, are the issues that make 'em unattractive?

[metalprep6969]

I definetly am going with a wireless, but they are so damn expensive. I'm going going to get a low quality one and have to deal with bad reception, I'd rather just stick with a cable. When I get around a grand to spend after I get a good cab and another guitar or two, then I think that'll be the next thing on my list.

\m/

[Bizarro]

FYI: The Sennheiser G2 EV172 series wireless are very good and only about $450. They are UHF and frequency agile.

[metalprep6969]

Cool man. Yeah, I haven't done a ton of research on all the available models because Sennheiser and Shure make SO MANY MODELS! I'll do more looking around when I'm really in the market for one. Anyways, the stages I play generally aren't big enough for me to do a ton of moving, especially with 4 other guys onstage and all of our gear.

\m/

[Bongo Boy]

You know, I haven't been able to find out if the receivers have their own internal power supply (and run off 115VAC) or if these units come with wall warts. What's the deal?

[Bizarro]

They all have wall warts, in my experience. My Nady has a wart, so do the Audio Technica, Shure, and Sennheiser's that I've seen.

The one exception is the AKG Bug system with the mini receiver. It runs off AAA batteries and it mounts on a pedal board like the rest of your pedals. It is very cool, but it is not frequency agile so I'm not really interested. I play too many venues in too many cities for single frequency systems... :(