#1
 Sorry for my english, it`s not my mother tongue ) But i hope you can  understand me. So, I have Marshall JCM 900 MKIII (2100), and when i  playing through, the sound level is randomly disappear. Sometimes sound  disappears totally for approximately 1 minute, sometimes i can hear  something but very quiet. Then sound could appears instantly or slowly.
I diassembled the amplifier and checked PCB (by eyes), also i checked  cables, and didnt found any suspicious things. Help me please, i dont  know what to do with that trouble.  
#2
change your tubes
Jumping on dat gear sig train.
PRS Hollowbody II / BKP Warpigs
Strandberg OS6T / BKP Aftermath
Strandberg OS7 / Lace Poopsticks
Skervesen Raptor 7FF / BKP Warpigs
Skervesen Raptor 6 NTB / BKP Juggernauts
Hapas Sludge 7 FF / Hapas Leviathan
Anderson Baritom / Motorcity Nuke BKP Sinner Anderson H2+
Warmoth Baritone / BKP Piledriver
Ibanez Rg2120x / BKP Nailbomb

Blackstar ID:Core Beam
#5
Quote by darkwolf291
Just because the tubes are new, doesn't mean they aren't bad now
Tubes are like light bulbs
You can get 5 years out of one
Or 5 days
It's really a crapshoot
Buy new ones and it should fix the problem


Ok, thanks for advice. ))  Also i have another question ) Recently i found alternate way for using this amp. I turn on Power, but not the Standby (it turned off), when i connect cable from Direct out to my sound card. So, question is: can i use this method with disconnected cabinet? I want to avoid amp damage because of using it without load. May i use few resistors (same impedance) instead cab?
#6
If you run without a cabinet connected, you will fry your output transformer.
WTLT 2014 GG&A

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alright "king of the guitar forum"


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


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youre just being a jerk man.



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#8
double post
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.



****** NEW NEW NEW!
2017-07-07 2017-07-07 Update and a Chat On Noise Constraints *** NEW FRIDAY 7/7
2017-04-13 RUN AWAY from COMPUTERS!!! TCE? RANT ALERT!!!
2017-03-02 - Guitar Philosophy 1001- Be Prepared For the Situation (Thursday 2017-03-02)
2017-02-21 How to Hot-Rod the Hell of your Stratocaster for $50! (Tuesday 2017-2-21)
Resentments and Rambling from a Guitar Junkie
---> http://trashedengineering.blogspot.com/
#9
Quote by trashedlostfdup
If you run without a cabinet connected, you will  fry your output transformer.

But as i read, if standby is off, the amp works as preamplifier, the power amplifier shouldnt work (no sound from loudspeakers, only direct out). When i turn on standby, power amplifier starts work and i hear loudspeakers. Am i right?
#10
Quote by darsteinov
But as i read, if standby is off, the amp works as preamplifier, the power amplifier shouldnt work (no sound from loudspeakers, only direct out). When i turn on standby, power amplifier starts work and i hear loudspeakers. Am i right?



i am 99% sure that is not the case. but i am un-famailer with your amp
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.



****** NEW NEW NEW!
2017-07-07 2017-07-07 Update and a Chat On Noise Constraints *** NEW FRIDAY 7/7
2017-04-13 RUN AWAY from COMPUTERS!!! TCE? RANT ALERT!!!
2017-03-02 - Guitar Philosophy 1001- Be Prepared For the Situation (Thursday 2017-03-02)
2017-02-21 How to Hot-Rod the Hell of your Stratocaster for $50! (Tuesday 2017-2-21)
Resentments and Rambling from a Guitar Junkie
---> http://trashedengineering.blogspot.com/
#12
darsteinov try to plugin your guitar to "Return" jack on the back of amp And try to play from there if it ok that not big problem, maybe your JCM900 preamp sections got problem you can get cheap 12ax7 10 buck each of it... But if you already play from "Return" jack-in on the back of the head but the problem still same, that would be big buck problem... Maybe your power tube or the worst is your output transformer...
Last edited by datresults at Mar 26, 2017,