Faulty Marshall JVM advice

Bod

RiftAmps;1110951" said:

I see you're in Leicester...



Milton Keynes (Bletchley) is only an hour down the M1 from you and Marshall's service dept. offer while-you-wait appointments so might be worth giving them a call on 01908 375411.

I contacted them via the website support and was told to return it via the retailer. I'll give them a call on that number (thanks) if I have further problems.

@ICBM I bought them from Hotrox as they're reasonably local. Never used them before so we'll see.

@peteri the noise wasn't random but the start of it was. Once it kicked in, it was metronomic and would continue until power off if I didn't hammer the strings a bit, almost like it was a capacitor charging and discharging.

Anyway, thanks all for your input folks. I'm keeping everything crossed that it's fixed now but will do more testing tonight.

Jalapeno

If it's only 6mths old, send it back via the dealer to Marshall.

It's what warranties are for (unless it WAS the delay pedal )

DJH83004

HotRox are pretty good, I use them all the time, but they will test them and unfortunately spurious faults like yours exhibited don't always show up under test. Similarly the fault may not appear exactly the same when plugged into another amp. But anyway definitely contact them and explain the circumstances.

jpfamps

The JVM series from my recollection employ quite high HT voltages in excess of 500V.

Most valve vendours don't use as high a voltage to test there valves, and it's possible that the valve could test fine at lower voltage but fail at the higher voltages found in the JVM.

My Maximatcher tests valves at 400 VDC, which is relatively high for a valve tester, but even so I've had valves test fine on it but fail in an amp where the voltages are higher.

Bod

@jpfamps Thanks for the info.  That could help me with my return.

I've been trying to join the jvmforum.com for months to get access to specific JVM-related info, but it seems to be pretty difficult to join - accounts created but the admin team never approve my request.  Very frustrating.

jpfamps

Bod said:

@jpfamps Thanks for the info.  That could help me with my return.

I've been trying to join the jvmforum.com for months to get access to specific JVM-related info, but it seems to be pretty difficult to join - accounts created but the admin team never approve my request.  Very frustrating.

What criterion do you need to fulfil to join the JVM forum?

You would have thought that owning a JVM might be enough.............

Bod

You would have thought that, yes.  I'm not entirely sure, but it seems they've implemented policies to combat spammers that's made it difficult to actually register as a genuine participant.

ICBM

Maybe you need to own a working one.

To be fair I've seen a lot fewer of them than the DSL/TSL series - in fact apart from a couple of early ones with switching-control problems which I sent back to Marshall, none.

Bod

ICBM said:

Maybe you need to own a working one.

Mine does now, thanks to you!  It's knocked my confidence in it though.

So, the valves in there are not a matched pair (though both JJ, one branded Marshall) is that a big deal?

ICBM

If they both bias correctly it will be fine - it would be best if they're properly matched but in practice it doesn't make that much difference.