Marshall JCM2000 DSL Popping on powering down

[selloutrr]

I've got an amp that's been troubling me and i'd like some other opinions. The amp sounds tonally amazing! for that marshall hi gain new modern rock tone. but when you go to power it off you get a loud pop. I've openned it up several times and it's just a cluster of poor quality PCB's and corner cutting with very little quality or attention to detail. the marshall magic has def been whored out for mass production. I've also had it brown out on me once. I powered it off and it came right back on. the tubes test great but I have replaced them with know good ones and still have the pop. I'm wondering if it's the OT? or just poor quality PCB and the traces are just close enough to arch? and I should video the amps death and post it on youtube? I've gone threw the caps already and they tested good both in and out of circuit. It's built in such a way that i have to remove all the cards to work on it so it's hard to get motivated. I know these amps are nothing but problems and if it was marshalls first amp they would have gone under on warranty repairs alone. they were natorious for shipping them out with under spec'd parts, oops!

thanks for your help!

[benoit]

Does it pop if you switch it to standby and wait a bit before you kill power?

[selloutrr]

yes, always powered off with standby first let the tubes calm down for a 12 count and then shut off the main power. With the amp opened up i can only see about 40% of the amp but in the dark i can't see a spark. and i cant recreate the problem poking with a stick. it's sure a piece of shit compared to my 60's and 70's marshalls.

[Jana]

I had a JCM 900 that did the same thing. It seemed to help to turn the master all the way down before turning off the power. I know, not a solution, but it leads me to believe that there is a spike related to the preamp. I always suspected that it had to do with the op-amps and that part of the circuitry, maybe its power supply. I never explored it though, I sold the amp.

Yeah, it's a pitiful sight to look inside one of these and see how much marshalls have devolved.

[selloutrr]

I find some comfort in knowing i'm not the only one, lol

it raises a good point.. is it even worth the time to fix it?

[selloutrr]

Funny thing I did a show a couple nights ago with two JCM2000's (Marshall Endorsements) and they both had the same issue. Flipped the standby during soundcheck and about wripped my face off threw the IEM and wedges. I've decided to give the amp a new home and not bother with wasting anymore time or $ on it. I have a feeling it's probably always going to have an issue in some way or another it's just got a tempermental vibe.

thanks for listening

[Jana]

I've decided to give the amp a new home and not bother with wasting anymore time or $ on it.

I think that is a smart move. I loved the sound of my 900 too, but after having a look inside and seeing what a cheap mess it was, I sold it. I had contemplated going through it and upgrading parts but decided against it. To do it right would involve totally gutting it and starting from scratch with new boards. It's easier just to build an amp from scratch.

[Wayne]

I've got a 900 as well - I think it would make a perfect platform for a turret board 800

Mine doesn't pop that bad, but there is a little something there. I have noticed, however, that it doesn't pop if you power down with the standby switch still on. I got in that habit during a period of repeated tweaking. There are no bleeder resistors, so I powered down hot to drain the caps. Maybe that would provide a work-around for you, as long as you remember to move the standby switch after powering down - since developing this habit, I've powered back up "hot" more times than a few

W

[RHGraham]

The two 800s I had did the same thing, kind of a pop with a weird little squeek, that happens just a tiny bit after the switches clicked.
Annoyed the crap out of me.

[Andy Le Blanc]

friends dont let friends buy marshalls....

all the current models are built like that... nothing like a super lead
even the pots and jacks are crap ...and hard to source

[selloutrr]

the jacks are Cliff jacks you can find them at tubesandmore.com the korg jacks also work TRS PCB mount. they are about $3.00 each.

[April]

yeah.... current marsh's are not so good as they could be...

i modded tsl60, change caps to paper/oil, metallized paper and silver mica - and it sounded much more musically.

my recomendation: change schematic to realy marsh, 800 or hotrodded 800 (like Bogner Extasy or Shiva)

[selloutrr]

better idea just don't buy one to begin with why go threw the dissapointment and frustration if you can avoid it?

[billyz]

I just worked on a TSL 100, similar amp. Anyway, I found several shorted small bypass caps/ I don't know why Marshall did this but they bypass several of the Power supply caps with little disc caps of like 10pf or 22pf. They are of poor quality and short out. Odd thing is some of them are not even close to the Large high voltage cap they are bypassing.

What a piece of Crap.

[selloutrr]

it's really sad the qualilty of the work they are putting out. I'll admit since it's a PCB and wave solder I automatically lower my hopes 30% but there lastest work really is the pits. the circuit sounds fine, when it works but the build quality leaves crate and peavey looking like a boutique hi fi. At least they can put the proper component in the right slot. if they keep this up it might be the end of marshall as we know it. guess we better stock up on the golden years they just might be going up in value!!!