#1
So I went ahead and bought myself a JCM 900MKIII and I finally got my combo's cab all wired up for the correct impedance, I went to start it up for the first time and no signs of life whatsoever, the tubes don't glow, don't heat, the switch doesn't light up, the speakers don't pop or make any sound, nothing. I checked the fuse next to the input and it appears to be blown so I'm going to replace it, but I was wondering if a fuse would be the source of my problem or if I should just go ahead and send it back for repairs?
Quote by R45VT
Bastards.
#2
Quote by Viban
So I went ahead and bought myself a JCM 900MKIII and I finally got my combo's cab all wired up for the correct impedance, I went to start it up for the first time and no signs of life whatsoever, the tubes don't glow, don't heat, the switch doesn't light up, the speakers don't pop or make any sound, nothing. I checked the fuse next to the input and it appears to be blown so I'm going to replace it, but I was wondering if a fuse would be the source of my problem or if I should just go ahead and send it back for repairs?


Put a fuse in it and retest. Are the tubes seated? Keep the blown fuse...
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#3
Sounds like you just bought it. Warranty?
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#4
Quote by R45VT
Put a fuse in it and retest. Are the tubes seated? Keep the blown fuse...

I have no spare fuses, I checked the tubes for seating the second it got in my door, then once more before I started it. They were indeed seated, I don't know if they can unseat actually, The pre-amp tubes have the guards over them that don't really let them move and the power tubes have some sort of cap on top with springs attached. I also plan on keeping the blown fuse.
I'm pretty sure it's blown but I can't really tell, There is no filament in the middle of it and there appear to be a couple of tiny burn spots on the glass, I'm assuming that means that it is blown correct?
Quote by R45VT
Bastards.
#5
It's toast.

Sounds like a bad tube or something more sinister. Call them and see what they will do for you. You don't want eat a set of tubes to have something else wrong with it.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#6
Quote by R45VT
It's toast.

Sounds like a bad tube or something more sinister. Call them and see what they will do for you. You don't want eat a set of tubes to have something else wrong with it.

That's what I'm afraid of, I think it's evident that this fuse is blown, but what I'm worried about is that there are more fuses on the board that are fried, or that there's something more than a stray power surge to blame for the fuse blowing. I'll try a fuse change upon the morrow, and if that fails then I'll call up GC. Luckily I had the right mind to drop the extra money on the repair plan.
Quote by R45VT
Bastards.
#7
Get a few fuses. If it blows again remove the power tubes and repeat.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#8
Yeah, there's a couple of fuses inside. They're 500mA slow blows. Grab some to have as spares while your buying a main fuse. You've blown the main fuse though so chances are they'll be ok but either way, you should have spares.
You haven't pulled the chassis out to have a look inside yet? I'm dissapointed in you. I thought that would be the first thing you'd do.
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#9
are you using the right key? some guy at work was trying to start a ford with a dodge key and he called a mechanic in before they figured out why the car wouldn't start.

i would say fuse, but that could indicate another problem.

i would say return the amp if you just bought it... but it does make me wonder if they'd take it back if you 'just wired up the combo properly'
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#10
Quote by Cathbard
Yeah, there's a couple of fuses inside. They're 500mA slow blows. Grab some to have as spares while your buying a main fuse. You've blown the main fuse though so chances are they'll be ok but either way, you should have spares.
You haven't pulled the chassis out to have a look inside yet? I'm dissapointed in you. I thought that would be the first thing you'd do.

I think I can actually change the 500mA slow blows from outside actually, I checked them and they look ok. And I know I know, I should have it all dissected and seen by now, but I'm still trying to figure out how a teardown would work on this thing.


Quote by gumbilicious
are you using the right key? some guy at work was trying to start a ford with a dodge key and he called a mechanic in before they figured out why the car wouldn't start.

i would say fuse, but that could indicate another problem.

i would say return the amp if you just bought it... but it does make me wonder if they'd take it back if you 'just wired up the combo properly'

I tried my chevy key a couple times, it opened the door but it wouldn't crank

I double checked with my multimeter, it read out at around 19 ohms when I wired the speakers in series. I am almost 100% sure that I wired it right, the speakers in the combo were wired in parallel to create the 4 ohm load that the combo works on, which would mean that they would have to both be 8 ohms, so it would make sense that in series they would be a 16 ohm load. I even made sure to set the amp to 16 ohms. I'm also rather proud of my solder work on this jack, I tightened up my iron and it let me get a really great solder join on this thing.
Quote by R45VT
Bastards.
#11
i never consider a fuse broken visually i also do that when i put in fuses. get a meter on the fuse and see if you have continuity.
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youre just being a jerk man.


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#12
Quote by trashedlostfdup
i never consider a fuse broken visually i also do that when i put in fuses. get a meter on the fuse and see if you have continuity.

no continuity, thanks for making me feel like a dunce though, why did I not think of that . Can you tell the finals are getting to me?
Quote by R45VT
Bastards.
#13
Quote by Viban
no continuity, thanks for making me feel like a dunce though, why did I not think of that . Can you tell the finals are getting to me?


lol. not a big deal. everybody forgets once in a while

i am sure you know more about amps than i do, but i could wire up a drag car with no harness in no time flat. i know that side of electronics better than electrical equipment (amps/pedals/etc.)
WTLT 2014 GG&A

Quote by andersondb7
alright "king of the guitar forum"


Quote by trashedlostfdup
nope i am "GOD of the guitar forum" i think that fits me better.


Quote by andersondb7
youre just being a jerk man.


***9V BATTERIES ARE FROM HELL!*** (updated 2016-11-27)
Resentments and Rambling from a Guitar Junkie
---> http://trashedengineering.blogspot.com/
#14
Quote by trashedlostfdup
lol. not a big deal. everybody forgets once in a while

i am sure you know more about amps than i do, but i could wire up a drag car with no harness in no time flat. i know that side of electronics better than electrical equipment (amps/pedals/etc.)

I know jack about amps actually, set me loose on an engine rebuild and I can do it pretty easily, set me on some CAD software and I could make the damned thing for you, but for some reason electrical things just elude me.
Quote by R45VT
Bastards.
#15
Running it with the wrong load (or even without a load) generally wouldn't blow a fuse, at least not right away so I would look at something else. Buy some fuses and use your multimeter. Could it have been blown when you bought it or are you sure "you" blew it? (did it work in the store?)

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#16
Those 500mA fuses are for the power tubes.

http://www.drtube.com/schematics/marshall/cd0192-100-iss1.pdf

FS1 and FS2. Notice how they go between the cathode of the power tubes and ground? When the tubes start to fail they draw more current and blow the fuse. Now see the resistor and LED across the fuse? When the fuse is sound it shorts that out and no voltage appears across the LED. When it blows there is voltage across it and the LED lights up. The resistor is just there to limit the current through the LED so it doesn't blow.
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#17
Quote by jthm_guitarist
Running it with the wrong load (or even without a load) generally wouldn't blow a fuse, at least not right away so I would look at something else. Buy some fuses and use your multimeter. Could it have been blown when you bought it or are you sure "you" blew it? (did it work in the store?)

I know I didn't blow it, it never started in the first place, I have a feeling that the standby would have at least worked on first startup if I had blown it. I ordered it to my front door from a GC in Oklahoma so I never got to check if it actually started or not, but now I have a feeling it's a matter of simple troubleshooting to get her screaming to my every touch.
Quote by R45VT
Bastards.
#18
Quote by Viban
I know I didn't blow it, it never started in the first place, I have a feeling that the standby would have at least worked on first startup if I had blown it. I ordered it to my front door from a GC in Oklahoma so I never got to check if it actually started or not, but now I have a feeling it's a matter of simple troubleshooting to get her screaming to my every touch.


You never know what happened in shipping. I would target the power tubes first.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#19
Quote by R45VT
You never know what happened in shipping. I would target the power tubes first.

Well there's absolutely non continuity in the main fuse, so that has to get changed before I can even start other troubleshooting procedures, I think I might grab a groovtube El34 from the local pawnshop just for troubleshooting purposes, then once I get a cab I'll get a nice set of JJ's.
Quote by R45VT
Bastards.
#20
Quote by Viban
Well there's absolutely non continuity in the main fuse, so that has to get changed before I can even start other troubleshooting procedures, I think I might grab a groovtube El34 from the local pawnshop just for troubleshooting purposes, then once I get a cab I'll get a nice set of JJ's.


I would buy 3 or 4 fuses:
Install new fuse and turn amp on. Check fuse,
If blown pull power tubes and install new fuse.
Recheck.

If you think the tubes are bad callGC and see what they will do for you.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#21
I am drunk sonindint know if it makes sense or not.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#22
Quote by R45VT
I would buy 3 or 4 fuses:
Install new fuse and turn amp on. Check fuse,
If blown pull power tubes and install new fuse.
Recheck.

If you think the tubes are bad callGC and see what they will do for you.

Pull the power tubes, replace FUSE, start it without the tubes in?

And I'd hope they'd at least find me a set of cheap tubes to put in so I can figure out if it works, that damned $60 repair plan has to be good for something.
Quote by R45VT
Bastards.
Last edited by Viban at Jan 12, 2013,
#23
Quote by Viban
Pull the power tubes, replace tubes, start it without the tubes in?

And I'd hope they'd at least find me a set of cheap tubes to put in so I can figure out if it works, that damned $60 repair plan has to be good for something.


Turn it on with the tubes out.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#24
Quote by R45VT
Turn it on with the tubes out.

Isn't that like, bad for it?
Quote by R45VT
Bastards.
#25
Quote by Viban
Isn't that like, bad for it?


Ask Cath. I don't think so but check with him p.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#26
Not bad for it in the slightest. When you're building an amp you check your voltages before you plug the tubes in.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#27
That's what I thought but I am drunk. I wouldn't trust me right now.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#28
Quote by Cathbard
Not bad for it in the slightest. When you're building an amp you check your voltages before you plug the tubes in.

I'm sure you're just laughing at my ignorance right now aren't you? its ok if you are, so am I
Quote by R45VT
Bastards.
#29
Well, thank you gentlemen, it was in fact the tubes, However my dad wants to make this difficult and he's making me take it to GC and won't let me say that it needs new tubes so they can monkey around inside the damned thing for a week to do a 5 minute test. The warranty doesn't even cover tubes but he insists that we take it in anyway even though I know the problem is now the power tubes. What's worse is they keep trying to get me to sell it or get rid of it. .
Quote by R45VT
Bastards.
Last edited by Viban at Jan 12, 2013,
#30
That's parents. They trying to look out for your best interests.

The tubes probably got fubar'd during shipping.

I would call GC at a minimum. You shouldn't have to buy tubes yourself right off the bay. Maybe they will split 50/50 with you.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#31
Quote by R45VT
That's parents. They trying to look out for your best interests.

The tubes probably got fubar'd during shipping.

I would call GC at a minimum. You shouldn't have to buy tubes yourself right off the bay. Maybe they will split 50/50 with you.

He doesn't even want me to mention tubes, I'm just afraid that they're going to claim that it was DOA and they're gonna try to give me an "equal value" trade and I'm gonna end up with $750 of some crap that I'll end up hating or something asenine like that, I simply don't trust them to maintenance my amp.
To top it off I went to hooters with my girlfriend and the wings gave me one hell of an upset stomach, that shit still hurts. The only upside to my day is that my truck finally started, I'll make sure to get a video of it up in the GB&C chat tomorrow, she sounds mean as hell.
Quote by R45VT
Bastards.
#32
Nice on the truck.

You will get the amp deal all sorted out. Hopefully sooner than later. Keep us posted.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#33
Well we realized that GC's warranty doesn't cover tubes so, after payday I'm gonna go ahead and order myself a set of jj's and see if she still blows fuses, if so I'll use the repair plan, if not then I'll enjoy my new amp finally.
Go figure I finally get my dad to see the light on this one and the starter motor burns out on my truck, the housing is cracked so it's not even like the thing is worth rebuilding in the first place, so I'm out an amp and my truck won't start again until friday. once I get both going reliably, I'll be happy.

Is there a way I can test the tubes and see which is bad? maybe until friday I can try to run only two of them? If possible is it the inside, the outside, the left, or the right that I can run?
Quote by R45VT
Bastards.
Last edited by Viban at Jan 13, 2013,
#34
Quote by Viban
Well we realized that GC's warranty doesn't cover tubes so, after payday I'm gonna go ahead and order myself a set of jj's and see if she still blows fuses, if so I'll use the repair plan, if not then I'll enjoy my new amp finally.
Go figure I finally get my dad to see the light on this one and the starter motor burns out on my truck, the housing is cracked so it's not even like the thing is worth rebuilding in the first place, so I'm out an amp and my truck won't start again until friday. once I get both going reliably, I'll be happy.

Is there a way I can test the tubes and see which is bad? maybe until friday I can try to run only two of them? If possible is it the inside, the outside, the left, or the right that I can run?

Are you sure there isnot something else wrong with the amp?
I really sugest you go to your GC with the amp, also take your recpt. Tell tem when you tried it it did not work. They will probably put new tubes in it if it arrived dead to your house. Actually call the GC that you bought the amp from talk to the MGR and explain your situation. I bet he makes it right. even though the amp was used, it is soposed to arrive in working order unless it is stated in the item discription.

My truck is in the shop since Fri. Damn clutch.....
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Last edited by Robbgnarly at Jan 13, 2013,
#35
Quote by Robbgnarly
Are you sure there isnot something else wrong with the amp?
I really sugest you go to your GC with the amp, also take your recpt. Tell tem when you tried it it did not work. They will probably put new tubes in it if it arrived dead to your house. Actually call the GC that you bought the amp from talk to the MGR and explain your situation. I bet he makes it right. even though the amp was used, it is soposed to arrive in working order unless it is stated in the item discription.

My truck is in the shop since Fri. Damn clutch.....

If it weren't the tubes, then it would have blown the fuse with the tubes out aswell, correct?

I feel your pain man, the worst thing about mine is that it started strong and roared hard and loud yesterday, that cam had that baby rocking so hard you could feel it throughout the car, inside and out. You could hear the compression in the exhaust tubes, I'm thinking a set of 3" H pipes and some headers eventually, I'm just not looking forward to having to re-torque my exhaust manifold bolts after every heat cycle for a while.
Quote by R45VT
Bastards.
#36
Call the GC in which it came from. Explain what has happened. They don't try to shit on their customers.

See what they can do for you.

Ask them what your next step should be.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
#37
Well we're gonna call them up and see if we can get them to go halves or at least discount us on some tubes.
Quote by R45VT
Bastards.
#38
Quote by Viban
Well we're gonna call them up and see if we can get them to go halves or at least discount us on some tubes.

No go for new tubes they cover first then, jew them accordingly if that does not work.

good luck.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
#39
Quote by Robbgnarly
No go for new tubes they cover first then, jew them accordingly if that does not work.

good luck.

I shall jew, repeatedly and strenuously until I get what I want, thanks.
Quote by R45VT
Bastards.