Oooff... main board needs replacing...

Drew_TNBD

So I wasn't entirely sure what was up, but I just got back from Marshall after hulking my JVM into them on the train today.

Bad news: Main board needing replacing as there was a critical IC that malfunctioned.
Good news: They had one in stock and are replacing it free of charge (warranty repair) and are shipping the amp back to me tomorrow, also free of charge!

So I should have a working JVM for my gigs on Friday+Saturday!

frankus

yay

digitalscream

One big reason I like my amps as simple as possible - there's already enough to go wrong in a basic valve amp as it is. Keep all the complimacated stuff on the outside, thanks

ddlooping

That's good news.

ICBM

Seems surprising they replaced the entire board just for one IC, but it may have been cheaper for them in labour given that they have an essentially free stock of them.

It's more normal that they have to replace the board because it's caught fire due to arcing from poorly-designed trace separation . (DSL/TSL series.)

Marshall's customer service is at least pretty faultless though!

Roaster

Just on the TSL/DSL series and amp repairer in Manchester , called Roland Lumby always carries out a mod on these, ( now bear with me, no expert) on lifting the power rail above the board?? which is prone to failure?

ICBM

There are several points which are prone to failure. The two most common are between the support legs of the screen resistors and the filament trace - easy to fix if you catch it before it arcs by bending the legs away from the traces, and Marshall did redesign the trace shape slightly after the first version (although they missed one, unbelievably!), and between the HT and the bias supply through the thickness of the board, which is much harder. You probably could lift all the HT stuff away from the board if you were determined enough... although there are still other issues like the band-aid arc suppression cap on the last power valve which is prone to failure as well. It's just a poor design really, you would think a company with the history and experience of Marshall would know better.

Van_Hayden

The big problem with companies like Marshall is despite a long history and much experience, the guy doing the layout is under pressure to get it done on budget and at a price. And that guy doesn't automatically get all of the past knowledge just because he works there. Roland is a pretty respected tech up here- but I suspect it's cheaper to get a new board, they're not that expensive if I remember. Black star managed to do a similar error in. One of the little amps...

martinw

 

ICBM said:

 You probably could lift all the HT stuff away from the board if you were determined enough...

Indeed it can be done, but I would usually just fit a new board as it works out cheaper and you get all the mods and a latest spec, brand new, board.. Of which Marshall have good stocks! They're not as cheap as they used to be though.

 

The only problems I've seen with JVMs have been switching ones.

ICBM

martinw said:

Indeed it can be done, but I would usually just fit a new board as it works out cheaper and you get all the mods and a latest spec, brand new, board.. Of which Marshall have good stocks! They're not as cheap as they used to be though.

I think it still works out cheaper than the labour cost of fixing the old one usually. To be fair, they have updated the boards several times, and they've probably cured most of the faults now... I haven't seen one of the recent ones burned. (Yet!)

martinw said: 

The only problems I've seen with JVMs have been switching ones.

Same here, although what Drew_FX has reported sounds like a partially shorted noise gate buffer IC. (Amp appears to have very low input impedance, works fine with a buffer in front but dull and quiet without.)

Drew_TNBD

Back in the world of Marshall, and boy does it feel good!

Comment on the repair slip says there was a faulty IC on the input line repaired. Doesn't mention a new main board, but that is what they told me when I took it over, so I guess that is what they did. Either way, happy to have it back and fully working!

ddlooping

Cool, enjoy.