Crackling Tube Amp

I just bought my first tube amp, used, its a fender hot rod deluxe. First day i had it, it sounded great. Next day while im playing i start to smell some BBQing coming from the amp, before i turned it off i check to look at the back but nothing looked abnormal. I let it sit for about 45 minutes and now when i turn it on it makes crackling noises whether im playing it or not. I dont know if i just need to change the tubes or if i need to take to a tech. Some advice would be great
Thanks

LOL@Something BBQing!!!

Take it to a tech, sounds like you've got some electrical problems somewhere.

Have them check out the solder joints on the pots and inputs.

The 2 most common causes of crackling noises are pre-amp tubes or old failing resistors, since you bought the amp used, theirs a pretty good chance the pre-amp tubes are the original factory tubes and are getting tired, if you know a good tech or shop it wouldn't be a bad idea to take it in and have all the tubes replaced and the bias checked on the power tubes, I didn't say it would be cheap but some new tubes would probably make it sound like a new amp and if you did happen to have a bad resistor the tech could take care of that too, now if that's not the way you to go, here's the alternate plan, go buy a couple of new pre-amp tubes, it's always a good idea to have a few spares anyhow if you own a tube amp, unplug the amp,let it cool down, in the back of the amp on the right hand side you'll see the pre-amp tubes, small tubes that will probably be marked 12ax7 or STR 7025, their will be several of these, starting with the one on the farthest right, grab the old tube and slowly work it out, pulling down and working it in a small circular motion, it's a good idea to use a cloth to grasp the tube with when you are doing this, take a new tube, look at the pins, should be 9 pins with a large gap, look at the socket you are going to put it in, make sure you line up the pins with the socket, make sure the tube is seated good, then turn on the amp and let it warm up, if it doesn't crackle then you found the bad tube, if it still crackles, turn it off and unplug the amp again, take the new tube out, and replace it with the old tube and repeat the process on down the line with all the pre-amp tubes, if it's a pre-amp tube making the noise you find it, the last tube before the power tubes will probably be a 12AT7, thats the phase inverter tube, that's where you stop the tube swapping, if it's still noisy, take it to a shop! Don't even think about taking the chassis out of the cabinet to have a look, tube amps store high voltage and can do you serious harm. Pre-amp tubes are the cause of alot of the noise in tube amps, new, quality tubes usally will clean up a noisy amp.... Keep us informed on how things turn out, if you have any questions, just ask...........Correction to the above, your amp does not use a 12AT7 for the phase inverter tube, it uses a 12AX7, so your first 2 tubes will be your pre-amp tubes..........

[Edited by pstring on 08-18-2003 at 10:14 AM]

thanks guys, I am going to get some new pre amp tubes today, Im posistive the stocks were still installed when i got it, hope that will fix my problem. I thaught it might have been dirty pots or something so i did take the back off and look at things, everything looked normal at an uneducated glance. I didnt see any burn marks....so i dont think or know if a resister is blown or what. Yeah my amp has 3 12ax7 preamp tubes, im not sure what a phase inverter tube is. If i do want to spend some more money to get some new power tubes, should i take it in to get those replaced or can i do those myself too. I very interested in all input and knowledge you guys have for me.
Thanks again

Tubes are supposed to alst a long time though, the Hot Rod deluxe has only been made since 1997, I have original tubes in mine and there is no noise.

My Hot Rod amp's speaker blew up on our first gig during sound check. What a pain in the arse to fit a new Celestion Vintage into it.
Good amp though and all is ok now.

A few words on tubes, 1. Tube Life Expectancy, could be ten seconds, could be ten years, no guarantee, new tubes can be bad right out of the box, and high dollar, NOS, US or Euro tubes can fail just as fast a cheap China tube, it's alot like buying light bulbs. 2. Power Tubes, when replaced need to have the bias checked/adjusted/set, the bias must be set because it controls the current thru the tube, it affects tube life and the way the amp sounds, brand new high quality tubes won't make an amp sound great if the bias is not correct. Buycomp4, if you do get new power tubes , you will need to take the amp to a good shop and make sure they check and adjust the bias, pre-amp tubes are self-biasing so no worries there, ........
To answer TeleMaster, yes tubes are supposed to last a long time, some are designed to last over 10,000 hours of continous use, but we are faced with 2 major problems, quality control in manufacturing and the worst one of all, putting them in guitar amps, component failure inside the amp, power surges, rough handling and the use and abuse that guitarists knowingly and unknowingly put them thru takes a toll, if your tubes still sound great thats good but not everybody will have that kind of luck.........

Thanks everyone. I got some new 12ax7 Electro-harmonix preamp tubes and the amp sounds better then ever. This has been a pain in the ass but a major learning experiance.

Great!...... Glad to hear things worked out for you.......