#1
I took this with my phone this morning. No, it's not a microphonic preamp tube. I've ruled that out completely to death.

http://www.youtube.com/watch?v=F90IwMpMdnM

It only happens when crunch mode is enabled, and it started recently for no apparent reason or cause. The squeal even bleeds over into the lead channel when the crunch mode is engaged.

Any ideas? I've checked every resistor on the board and they are all within spec. I've cleaned everything with contact cleaner, reseated every cable, patched the FX send and return loop, and even reversed the OT secondary wire harness. At this point I'm just dumbfounded. Adjusting any of the other pots makes no difference on the squeal. IT's only when I adjust the Pre on the rythym channel.
Tastes like chicken, if chicken was a candy.
Last edited by ConfederateAxe at Nov 23, 2009,
#3
Adapt it into your playing

Have you brought it to your local amp tech? have you asked him what he thinks?
Quote by patriotplayer90
Lolz that guy is a noob.

Egnater
Leave it on the press, Depress Depress Taboot Taboot.
#4
There are no local amp techs. The nearest one is an hour and a half away and he wants $90 an hour to work on my amp.

I can't adapt it to my playing. It's overpowering, and the second I stop playing, it resumes. It increases in volume with the volume of the amp itself.
Tastes like chicken, if chicken was a candy.
#5
Mind=blown
Quote by angusfan16
I got my sister pregnant once. Yeah, that was awkward, but mostly because she's 6 years younger than me.
#6
Quote by O.O Meow O.O
Mind=blown



I know, isn't that the weirdest shit? If crunch mode is off, the clean and lead sound normal...awesome even, especially after i did the bias mod. But have it on either channel and hit the crunch switch and weeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee....


Tastes like chicken, if chicken was a candy.
#7
Quote by ConfederateAxe
There are no local amp techs. The nearest one is an hour and a half away and he wants $90 an hour to work on my amp.

I can't adapt it to my playing. It's overpowering, and the second I stop playing, it resumes. It increases in volume with the volume of the amp itself.

I'm sorry, but that's a definite 'take it to a tech' issue if ever I saw one.
#8
Quote by ConfederateAxe
There are no local amp techs. The nearest one is an hour and a half away and he wants $90 an hour to work on my amp.

I can't adapt it to my playing. It's overpowering, and the second I stop playing, it resumes. It increases in volume with the volume of the amp itself.

have you tried using a noise gate? maybe you can borrow one from a friend and give it shot.
Quote by patriotplayer90
Lolz that guy is a noob.

Egnater
Leave it on the press, Depress Depress Taboot Taboot.
#9
keep it,thats make you unique
Quote by angusfan16
I got my sister pregnant once. Yeah, that was awkward, but mostly because she's 6 years younger than me.
#10
Interesting to say the least..
If you start a reply with: I have never played one but I have heard good things about it! Your opinion is invalid.
#11
Its the turbo model...duh. It's gotta have time to spool up!


Seriously though....get that thing to a tech
#12
to be honest, i kinda want it..
Fender 72' Deluxe Tele
Schecter Damian Elite 7
Fender '62 Reissue Jazz Bass (MIJ)
Peavey XXX 212 (back on the East Coast)

Macbook Pro 15" Retina
Logic Pro X 10.0.7
Revalver 4
LePou Amp Sims
Ignite Amp Sims
LeCab2
RedWirez Impulses
#13
I've clawed my way through dozens of threads on numerous boards about the 6505+ and I've yet to come across anything like what my amp is doing.
Tastes like chicken, if chicken was a candy.
#14


I LAUGHED SO FREAKING HARD!!!!! Sorry dude but that sound when you turned the pot sounded just like a slide whistle from some cartoon!!!

#15
Yeah it was funny two weeks ago. Now It's just annoying.
Tastes like chicken, if chicken was a candy.
#16
i'd recommend taking it to a tech like the others have said here. i'm sure you have, but look around for more techs/electrical repair shops/audio equipment repair shops and what have you. you shouldn't have to pay $90/hr.

it sounds pretty sweet though!
main rig:
MIM Tele->VP Jr.->CryBaby->Fuzz Factory->TS808->Carbon Copy->Phase 90->TU-3->Vox AC30CCH+Avatar 212 and Peavey VTM60+Marshall 1960A


Quote by necrosis1193
Fuzz...It's wonderful and horrible and beautiful and repulsive and so many things all at once.
#17
I could imagine that getting a little hard to live with. You say it happened after you did a bias mod?
Quote by Marty Friedman
Because I bend in such an unorthodox fashion; the notes kinda slide up and slide down...
#18


I really would love to make that into a pedal somehow, instead of having to constantly run my wah backwards

If it happened after a bias mod.. hmm. Can you restore it to the original state, and see if it happens then? It could be something ****ed up with the mod.
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#19
No it did this before the bias mod. I thought it was a preamp tube issue and ordered a new preamp tube along with a matched quad of power tubes. I did the bias mod in preparation for the new tubes. I installed the tubes to find out that did not fix the problem.
Tastes like chicken, if chicken was a candy.
#20
Quote by ConfederateAxe
No it did this before the bias mod. I thought it was a preamp tube issue and ordered a new preamp tube along with a matched quad of power tubes. I did the bias mod in preparation for the new tubes. I installed the tubes to find out that did not fix the problem.

The only thing I can think of it being is (don't shoot me, I'm an idiot ) maybe something is looping the signal backwards. That sounds an awful lot like a wah when you run it backwards, and rock it back and forth.

That's really the best I got . Has it always done it? Or did it just randomly start one day?
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#21
Do you have any kind of electronic knowledge? Whatever the problem is, it is strictly contained in the crunch circuit. Theres is always an amount of feedback from amps no matter what and this is usually filtered out with a combination of resistors, filter caps, and diodes.

Resistor: if this went out then it could let too much current through other components and cause all sorts of havoc. but i thinks it unlikely since most of these in an amp have pretty high values and would mostly likely blow some tubes or something if it went out.

Capacitor: if its one of the smaller filter caps then i see it as a possibility.

Diode: i say the most likely. if it was wired in parallel with something then it could make a feedback loop.

So yea if you know this stuff and want to tackle it yourself then unplug the amp and turn it on while unplugged to discharge it. let it sit like this for about 5-10 mins then i would get a digital meter and measure the resistance of all the resistors. if all good then measure capacitance of all the caps. if thats good then check the diodes.

Current flows from negative to positive contrary to what most people think. so to measure a diode put the meter so that negative is on the side of the diode that lets current in and the positive on the side that lets it out.

Now tube amps are some really high voltage and current devices and can very easily kill you so some rules of thumb are to put the amp on a rubber mat, stand on a rubber mat, and whenever you're not using your other hand take it out of the amp this way you current doesn't have a way to cross your heart if something terrible happened.

On a final note, i would never suggest you do this unless you know what your doing. If it was a solid state amp it would be different but its not and its much more dangerous to work with tubes. If you don't understand everything i said then don't do it and take it to an amp tech. This stuff is not to be taken lightly

Also don't buy parts from. Search Allied Electronics in google and get the stuff there. i could probably get that same cap for 38 cents. The original cap should say what type it is and its values.
#22
Quote by CrysisFX
*super helpful post*

Just out of curiosity, for my education, are you saying it's basically creating a feedback loop by leaking too much current (as a possibility)?

I'm hoping to go into electrical engineering and this stuff fascinates me to no end.
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#23
Quote by stratman_13
Just out of curiosity, for my education, are you saying it's basically creating a feedback loop by leaking too much current (as a possibility)?

I'm hoping to go into electrical engineering and this stuff fascinates me to no end.


Ill describe it with a pic lol...




This is something you see in a lot of amps. signal will come in the resistor will filter out most of the non-audio from the signal. Guitars and amps pick up all sorts of things like cb radios and radio stations so there are usually 4 or five of these setups in an amp to filter it out. The diode is there to ensure that the resistor does its job. But if the diode shorted then current could bypass the resistor and go straight to ground. In amps the positive side of the signal goes to ground while the negative is amplified. Ground also goes straight to the speakers so it creates a massive feedback loop.

So think of ground as your positive for the most part and it goes straight from guitar to speaker and it will create a loop if its not correctly filtered. If you've ever play an electric guitar with an amp plugged into a non grounded wall, you will be able to shock people because any current not used by the amp will go back through the guitar and build as static electricity.

In reality there are a lot more factors to it but thats the major parts of it. And thats if the diode is out not anything else. But its most likely the diode because its made of silicon which is a semi conductor. Semi conductors have properties of both a conductor (allows current through) and an insulator (does not let current through) and semi conductors do not play if they were ever overload by lets say a power surge or something along those lines. Thats also why computers are so sensitive to power surges and static because they are just one big semi conductor.
Last edited by CrysisFX at Nov 23, 2009,
#24
Yeah, I know exactly what you're talking about. Your last little scenario happened to me once. That was better than coffee .

And I see. So the resistor's job is to almost act as a "shielding" of sorts to filter out radio waves/shortwave signals, etc.

But I had the feedback loop part right. Just not the reasoning

Cheers mate. Fascinating, fascinating stuff.
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#25
Crysis, thanks a ton. You've gotten me closest to what the problem might be. I may very well have to check diodes and caps, because I checked all the resistors and they all read within tolerance. I've even pulled the main circuit board out and flipped it over to examine the solder points.

I'm trying everything in my power to further educate myself on this issue and solve the problem myself to keep from having to take it to a tech, because I am technically inclined, and I just don't have the $$$ to be throwing at repair labor.
Tastes like chicken, if chicken was a candy.
#27
QUICKLY! GO TO CARTOON NETWORK FOR JOBS!!

Or take it to another tech...
"RAWR WIRES >:O"
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#28
Quote by stykerwolf
Some Post Rock guitarists actually pay a shitload of money for that sound :P



Yeah I bet the cat from Death By Audio would love my amp. Probably not hipster-vintage enough for him, though.
Tastes like chicken, if chicken was a candy.
#29
Quote by stykerwolf
Some Post Rock guitarists actually pay a shitload of money for that sound :P




I do agree that it's probably a messed up diode. It might even be backwards.

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Solder fume huffer σƒ τλε τρπ βπστλεπλσσδ

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Electronic Audio Experiments
#30
BTW,if you found the problem,tell us so we can reverse engineer it
Quote by angusfan16
I got my sister pregnant once. Yeah, that was awkward, but mostly because she's 6 years younger than me.
#31
After careful study of the schematic, as well as probing with a multimeter, I'm thinking it's either the K4 relay, or one or more of the 470k resistors connected to it.

Replacing the K4 is gonna be a bitch, because I dunno if it's SPST, SPDT, DPDT or what. All I know is that it's 12 volts. It doesn't even mention amperage.

Amperage and pole/throw is what I need to know in order to replace it. Unfortunately Peavey corporate is closed until Nov 30.

I can email someone the schematic if they think they can tell me what type of relay and what amperage it is. Just PM me your addy.
Tastes like chicken, if chicken was a candy.
#32
It took a while, but I'm almost certain at this point that the issue is a bad Pre potentiometer. It's not reading like it's supposed to on my DMM, so I've got a replacement coming in the mail from Peavey. I took the reading on the pot quite some time ago, but I wasn't looking for a problem in that area, so for whatever reason, I conveniently ignored what is a blaring red flag now.

Will let you know how it goes with the replacement.
Tastes like chicken, if chicken was a candy.