#1
Hey guys I've had a 6505 head for about a year and a half, and today I was playing by myself and the volume just dropped out of nowhere. So I turned it off, checked my cables, then when I powered it up again it started making this static noise. That's all it does.

has this happened to anyone? The 4 big tubes are glowing normally (none of them out).

This sucks so bad

jd
Last edited by jorgeD at Oct 4, 2008,
#4
Tubes?
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#5
I'm scared to open it up and get electrocuted or something, but I still have to check the 12AX7 tubes and the fuse.

Thanks for the quick input, I'll be back in a few with more data.

you guys rock.
jd.
#6
Quote by jorgeD
I'm scared to open it up and get electrocuted or something, but I still have to check the 12AX7 tubes and the fuse.

Thanks for the quick input, I'll be back in a few with more data.

you guys rock.
jd.

Unplug it first.
#7
A volume drop sounds like a possible power tube problem, but who knows. It wouldn't power up if the main fuse had blown, unless there's some other fuse out.
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#8
Quote by Ekofu
Unplug it first.

Theirs still electricity stored. I know from exp
#9
Don't go poking around at caps, and you'll be okay, as far as stored electricity goes.
Feel free to call me Kyle.

Quote by ibz_bucket
Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

Quote by tubetime86
I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...
#10
it sounds like the first or 2nd 12ax7s is gone becaus it can run without those there the first in the cycle
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#11
Quote by False_God
Theirs still electricity stored. I know from exp

yeah, this is true... (i've learned before-hand, and pre-caution myself, now. Lol... )
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#12
I think it's best if i take it to an authorized center to have it looked at.

I couldn't even check out the 12ax7 because the screws were so tight.

This sucks.
#13
Well yes there is stored electricity, but you won't get blown away changing tubes and fuses (note fuses aren't the case). What screws? If there is a shroud on the back, unscrew it. They are likely just tamper evident ones, but it won't hurt anything. Just don't take out the chassis.
#15
You can't really get shocked changing the tubes on that amp, especially the power tubes (which sound like the problem) because all that is exposed is the tube sockets which won't do shit. As the other guy said, you won't run any capacitors unless you open the amp up.
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#16
Input Jack. My Marshall does the static thing all the time, I hit it and it goes back. Maybe I should tighten it up a bit though so I don't punch a hole through it.

Or maybe powertubes, or were your tubes not biased?
#17
^Yes, but can he bias them. Any time a new power tube touches my amp it will have the bias matched by a tech. Do what you like, but different brands of tubes have different outputs and qualities. So it's really best to have it biased whenever you change the power tubes, even when using the same brand.

That being said you can put any preamp tube that'll fit in your amp and it'll be okay, but the power section is a different animal.

Edit: to Kaymen
apparently UG's only type O-


Quote by Strike9

Thanks jb_designs.
#18
Quote by jb_designs
^Yes, but can he bias them. Any time a new power tube touches my amp it will have the bias matched by a tech. Do what you like, but different brands of tubes have different outputs and qualities. So it's really best to have it biased whenever you change the power tubes, even when using the same brand.

That being said you can put any preamp tube that'll fit in your amp and it'll be okay, but the power section is a different animal.

Edit: to Kaymen



He COULD specify the same dissipation rating when he's ordering if he so chooses.
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#19
Guys I just got back home and I was able to unscrew the back section. The first 2 tubes are dead dead (only the last 3 are glowing). Here are the pics, and also a video of the noise it makes when it's turned on.

Should I just replace the first 2 tubes or the whole set? Is it ok to buy them online or is it best to go to a local store (for tubes to arrive safely)?

Here is the link to the video

http://www.youtube.com/watch?v=I4MPJ4QshSM

Thanks for all your input!
jd.
Attachments:
6505-Problem.jpg
#21
I had the same problem with 2 of my heads. Had to take em both back to Peavey to get repaired coz no matter what I did I couldnt fix it.

When I went and picked the 2nd one up the artist relation guy asked if I'd had it hotrodded coz the tech guy said it was an absolute mess inside, he said none of it matched the schematics they had and was like nothing they'd ever seen! It was the best sounding 5150 I'd ever heard and when I got it back after it had been done to the original spec it sounded like the other ones. Wierd.
#22
Those caps store charge and are grounded to the chassis. Don't go poking around in there because even if you're not interacting with the caps directly, you could still get a nice (potentially lethal) shock.

But volume dropping, sounds like a power tube issue?
#24
Remove the preamp tubes and inspect them. Glowing means nothing. Some glow a lot, some barely and still work fine.

Also, are you running a Marshall 1960 cab with your amp set to 8 ohms???
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Last edited by Van Noord at Oct 4, 2008,
#25
No, it's a 1936 (8ohms mono)

So is it safe to just pull the pre amp tubes and replace them without touching anything else? I keep hearing it's safe, but then I hear a comment saying you could still get shocked, etc. My amp hasn't had any mods, i bought it new almost 2 years ago and still has stock tubes.

jd.
#26
Quote by jorgeD
No, it's a 1936 (8ohms mono)

So is it safe to just pull the pre amp tubes and replace them without touching anything else? I keep hearing it's safe, but then I hear a comment saying you could still get shocked, etc. My amp hasn't had any mods, i bought it new almost 2 years ago and still has stock tubes.

jd.


Nothing'll happen
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#27
You'll be just fine replacing tubes if you don't touch anything else.
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I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...
#29
quick update. When I checked the pre amp tubes, I saw the first two were not glowing at all, so I switched them with the last 2 pre amp tubes, and now the amp doesn't make that static sound when it's powered up. I've decided to replace all the pre amp tubes since it only costs like 50 bucks. I wish I could re tube the whole thing (aprox 120) but I can't afford it right now.

I want to thank everyone's input on my problem.

jd.
#30
Hopefully that settles things.
Feel free to call me Kyle.

Quote by ibz_bucket
Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

Quote by tubetime86
I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...