#1
Just a few questions if anyone has any knowledge of this subject. I'n my XXX super 40 I changed to el34's and a resistor kept blowing, so I was told it's because the screen grid resistors can't handle the voltage of them so I had to change the screen grid resistors to 1k 5w. Is there one screen grid resistor per power tube? A tech is changing them for me but I wondering If I could have done this myself. I can solder just fine, is changing any type of resistor in an amp just as simple as desoldering then soldering in a new one?
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#2
If you've not done this sort of thing before, leave it to the professionals i reckon, there are a lot of dangerous voltages in amps and capacitors that will hold their charge for months after it's unplugged.
EH


"Show me war; show me pestilence; show me the blood-red hands of retribution..."
#3
I realize that, but I just want to know how many screen grid resistors there are, where are they and is it as simple and just unsoldering and desoldering.
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#4
Quote by JoePerry4life
I realize that, but I just want to know how many screen grid resistors there are, where are they and is it as simple and just unsoldering and desoldering.


well i dunno, consult a wiring diagram or something?
EH


"Show me war; show me pestilence; show me the blood-red hands of retribution..."
#5
Quote by JoePerry4life
I realize that,
good.

Quote by JoePerry4life
but I just want to know how many screen grid resistors there are,
There are 5 resistors involved. 1 for each tube and 1 that drops the voltage from the B+ to the where all the screen resistors are connected.

Quote by JoePerry4life
where are they
R64 is on the preamp board.

R104, R105, R114, and R115 are on the power amp board near the output tubes.

Quote by JoePerry4life
and is it as simple and just unsoldering and desoldering.
Pretty much that.
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#6
Quote by SomeoneYouKnew
good.

There are 5 resistors involved. 1 for each tube and 1 that drops the voltage from the B+ to the where all the screen resistors are connected.

R64 is on the preamp board.

R104, R105, R114, and R115 are on the power amp board near the output tubes.

Pretty much that.


Thank you very very much SomeoneYouKnew.

Edit: There are only 2 power tubes in the super 40 so wouldn't that mean there are only 3? If so does it have the same code IE R104?
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Last edited by JoePerry4life at Aug 29, 2009,
#7
Quote by JoePerry4life
Thank you very very much SomeoneYouKnew.

Edit: There are only 2 power tubes in the super 40 so wouldn't that mean there are only 3?
Probably.

Quote by JoePerry4life
If so does it have the same code IE R104?
Probably not. Can't say for sure. I don't have a schematic for a Super 40, just the 120w version.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#8
I could be wrong but isn't one of the pins of the power tubes connected to a resistor? If so is there any other resistors attached to the pins? Also, do I use a carbon film or metal film resistor?
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#9
Quote by JoePerry4life
I could be wrong but isn't one of the pins of the power tubes connected to a resistor? If so is there any other resistors attached to the pins? Also, do I use a carbon film or metal film resistor?
You don't do anything. You have a qualified amp tech do it, so you stay alive and your amp works properly after he's finished.

Gear:

G-400 w/MRG Rocker
Agile Al-3000
Partscaster w/GFS Alnico Texas Wound
Peavey XXX Super 40
Dano Cool Cat Drive
That was fast.
When you started this thread you had a Peavey ValveKing 100.
Now you have a Peavey XXX Super 40.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#10
No, I didn't change anything in my sig. You must be thinking of someone elses sig

I gave the tech 3 weeks and I'm just sick and tired of waiting lol. I emailed peavey and asked for a schematic but I don't know if they'll give me one. Why should I pay someone to replace a few resistors, should I be fine if I wear goggles and rubber gloves?
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Last edited by JoePerry4life at Aug 29, 2009,
#11
Quote by JoePerry4life
No, I didn't change anything in my sig. You must be thinking of someone elses sig

I gave the tech 3 weeks and I'm just sick and tired of waiting lol. I emailed peavey and asked for a schematic but I don't know if they'll give me one. Why should I pay someone to replace a few resistors, should I be fine if I wear goggles and rubber gloves?


You have to discharge the capacitors, they're essentially like batteries and they can hold their charge for a long time, i wouldn't reccomend doing anything to your amp if you don't know about any of this because if you slipped it could be curtains. I can solder too, i've done several guitar wiring jobs. I still wouldn't touch an amp with a bargepole though because i am underqualified to deal with such things. Most (sane) people who do guitar amp electronics will have started out with those really simple amps you see that you can buy in kits and stuff which is literally just one tube or something and a few resistors and capacitors here and there, not a multi channel high gain monster like a peavey XXX.
EH


"Show me war; show me pestilence; show me the blood-red hands of retribution..."
#12
Quote by JoePerry4life
No, I didn't change anything in my sig. You must be thinking of someone elses sig
lol, you're right! I was replying to a guy on a thread about heaters on his VK right about the same time as this one.

Quote by JoePerry4life
I gave the tech 3 weeks and I'm just sick and tired of waiting lol.
Find another tech who doesn't suck?

Quote by JoePerry4life
I emailed peavey and asked for a schematic but I don't know if they'll give me one.
without a schematic, you'd need to be familiar with the way Peavey does their layouts and use some care in tracing from the correct pins of the tubes back.

Quote by JoePerry4life
Why should I pay someone to replace a few resistors, should I be fine if I wear goggles and rubber gloves?
hopefully you won't need googles. it's not like you're welding or something. and rubber gloves don't have the kind of insulation you'll need for such high voltages.

Maybe your amp has bleeder resistors that will discharge the caps, but there's no way to know for sure without seeing a schematic.

Since these resistors are almost certainly on a printed board (Peavey builds that way) you'll have to be very "clean" about your soldering technique, or you could have arcing occur when you power this up again. How much experience do you have?

srsly, this kind of thing is best done by a pro. it's not like modding a pedal or smth.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#13
Quote by SomeoneYouKnew

hopefully you won't need googles. it's not like you're welding or something. and rubber gloves don't have the kind of insulation you'll need for such high voltages.


soldering can require goggles, i started using them since a bit of solder flew off and very nearly hit me in the eye.
EH


"Show me war; show me pestilence; show me the blood-red hands of retribution..."
#14
Quote by eddiehimself
soldering can require goggles, i started using them since a bit of solder flew off and very nearly hit me in the eye.
what on earth were you doing to cause flying solder?
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#15
Quote by SomeoneYouKnew
what on earth were you doing to cause flying solder?


It can happen when you're melting it that a bit comes flying off the end. Ahh well maybe i just didn't use it properly, i'm not the best solderer or anything.
EH


"Show me war; show me pestilence; show me the blood-red hands of retribution..."
#16
Quote by SomeoneYouKnew
lol, you're right! I was replying to a guy on a thread about heaters on his VK right about the same time as this one.

Find another tech who doesn't suck?

without a schematic, you'd need to be familiar with the way Peavey does their layouts and use some care in tracing from the correct pins of the tubes back.

hopefully you won't need googles. it's not like you're welding or something. and rubber gloves don't have the kind of insulation you'll need for such high voltages.

Maybe your amp has bleeder resistors that will discharge the caps, but there's no way to know for sure without seeing a schematic.

Since these resistors are almost certainly on a printed board (Peavey builds that way) you'll have to be very "clean" about your soldering technique, or you could have arcing occur when you power this up again. How much experience do you have?

srsly, this kind of thing is best done by a pro. it's not like modding a pedal or smth.


I can solder fine, no experience with amps or building a pedal though. But I guess its probably better to let the tech do it, but I figured I gotta start somewhere. The resistor that kepts blowing in my amp, I'm assuming this is one of the screen grid resistors? The one in the preamp I assume.
Agile AL3000
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#17
Quote by JoePerry4life
I can solder fine, no experience with amps or building a pedal though. But I guess its probably better to let the tech do it, but I figured I gotta start somewhere. The resistor that kepts blowing in my amp, I'm assuming this is one of the screen grid resistors? The one in the preamp I assume.


as i said, most people start on much simpler amps. Or even pedals.
EH


"Show me war; show me pestilence; show me the blood-red hands of retribution..."
#18
Quote by JoePerry4life
I can solder fine, no experience with amps or building a pedal though. But I guess its probably better to let the tech do it, but I figured I gotta start somewhere. The resistor that kepts blowing in my amp, I'm assuming this is one of the screen grid resistors? The one in the preamp I assume.
None of the resistors for the screen circuit are in the preamp, per se. One of them is in the power supply circuit on the preamp board.

It should be pretty obvious which one is the problem. Resistors look physically burnt when they fail that way.

If you're bound and determined to do this yourself, you really must get a schematic, though. Without that, there are too many questions you won't be able to answer.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#19
Alright thanks guys, I'm just gonna get the tech to replace the resistor and change the tubes to 6l6 so there won't be any problems anymore.
Agile AL3000
Douglas WRL90
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J&D Strat
Squier Tele
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Peavey JSX
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