#1
Hello all,

I have a Peavey 6505 head and, admittedly, I bought it when I knew very little about guitar (I still know very little) and had no idea what tubes were.

Roll on 3 years later and I'm curious, how do you tell if tubes have gone bad?

I've read up on the subject and have found some tell tale signs to watch out for and, as far as I can tell, my amp shows none of these. Of course, I'm no expert.

- I've noticed that when you crank it at high gains there's a constant hissing sound, kind of like static?
- When turned on and switched off the tubes will occasionally make clicking sounds (I'm assuming this is them heating up and cooling down).
- Inspecting the tubes shows that the top of them is silver rather than clear.

I have no idea whether these are bad signs or not but hopefully someone could shed some light for me?

I've also included a picture but, alas, this may be about as helpful as posting a picture of a sandwich...


Any help at all would be much appreciated
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#2
Your tubes look fine.

Power tubes will usually let you know they are done when the volume fluctuates or starts to fade. Or, the tube just up and dies.

The first 2 items I am not aware of as signs of age. The last one about the getter (silver top) is true. If it is clear it is borked.


Preamp tubes show different signs, one of which may be hissing.


I'm not an amp tech though so maybe someone else can confirm or elaborate.
Last edited by 311ZOSOVHJH at Jul 12, 2013,
#3
toby - we mussed have got our around the same time then. I am going on three years with mine too and just now getting to the point where I need to replace the tubes. The way I know my power tubes need replaced is just as 311 described, the output is just not as ballsy as it once was.

How often do you play it? I only play mine once a week up loud and the rest of the time I am playing my vypyr so it doesnt get a TON of play time.
#4
Hi, I also own a 6505 head.

Quote by tobysaurus

- I've noticed that when you crank it at high gains there's a constant hissing sound, kind of like static?


That's normal.

Quote by tobysaurus

- When turned on and switched off the tubes will occasionally make clicking sounds (I'm assuming this is them heating up and cooling down).


That's normal.

Quote by tobysaurus

- Inspecting the tubes shows that the top of them is silver rather than clear.


That's normal.


Hope that makes you feel better, and hopefully this thread reassures some other people too, tubes are not standard maintenance that has to be done every 6 months or every year or anything ridiculous like that. I mean tubes can easily last a decade, it just depends on how often you use them and how hard you run them. On average I'd say expect something to start to go bad in 3-5 years.

I'm sure this has been covered or will be covered by the time I post this, but these are the most common signs that a tube needs to be replaced:

1. If your gain drops suddenly, or your gain fades in and out, or your volume fades in and out, you most likely need to replace a preamp tube, almost always in V1 or V2.

2. If you're having problems with your FX loop, either signal not coming through or volume problems, you likely should replace the preamp tube that controls your FX loop.

3. If your amp shuts off, stops making sound completely, makes a whining or buzzing or otherwise "broken" sound, then you have a power tube problem. Always replace power tubes in pairs, most of the time the middle two are pairs and the outer two are pairs, but sometimes they are side by side pairs. Ask around for your partictular amp.

4. If "something" is wrong and you can't really identify it, 90% of the time replacing or just switching your preamp tubes around, or just cleaning the pins on your preamp tubes will solve your problems.


Most amp problems are the preamp tubes, and luckily they're only $10-15 a piece. When power tubes go, you'll know, without a doubt. Power tubes tend to die more suddenly, preamp tubes can slowly degrade, sometimes to the point that it takes you a long time to realize something is wrong. If you're unsure, just swap a few out and see what difference it makes. You should always have at least a handful of spare 12AX7s lying around as a tube amp owner.

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#5
I've had a Line 6/Bogner Combo, a Double Rectifier, and a Tiny Terror combo. i'm no expert, but as far as i can tell you all three "issues" you described sound normal. The hissing may actual be coming from somewhere else in your signal chain, if it's really that bad look into some kind of noise gate. i use an ISP Decimator but when i cranked the Rectifier waaayyy up i'd still get it. As far as clicking and popping, make sure you power on, let the tubes warm up a few minutes (2-5, the longer time if you're cranking it) and make sure you're always in stand-by when doing anything with switching the power.
#6
Here's the best way to tell. Have spares and try them. You can test preamp tubes one by one via substitution. power tubes you change as a set.. You should have spares anyway.
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