Grandmeister 40 Deluxe standby noise

Hey guys,
         There are many of you with much larger brains than I on this forum so I wanted to check this with you before I take my head to the shop. When I turn on my amp and it is on Standby it makes noise though my speaker, fizzes and pops and a couple other strange sounds, my first thought is that maybe I have a Capacitor going bad(which would suck as it is less than a year old!) Any ideas from the forum brain trust?

This shouldn't happen of course, on Standby it should be stone cold quiet. It could be down to a valve problem which is an easy fix or it could be the bias current control which is outside of anything we owners can fix no matter what our background. A couple of simple things to try first.

It would be useful to know, does it show the noise when you are not in Standby mode and are set to run normally with a playing level volume dialled in? If it is not noisy in normal use then it is most likely a problem with the standby system and not the valves themselves.

Have you checked the TSC status LEDs on the back? These should all be on in Standby and all off when running at 40W. Check the valves' bias conditions with your "pick" switch on the back. Put a pick in the switch slot and press, then see how the number of flashes matches up for the inner and outer pairs. This is all covered in the TSC section in the manual. In the GM40D manual it is section 7 on page 10.

If that doesn't show anything to worry about, try setting it to 20W on the power soak and put it onto Standby mode again. Does it fizz and pop then? If not try swapping the outer pair of EL84s for the inner pair and try it again. In half power mode one pair of the valves is off so it may be possible to isolate a single pair to test. It is entirely possible that, if it is a TSC problem, the noise would be there whether a valve pair is in circuit or out of course but it may be worth trying.

Finally, if you have them available, put in a replacement set of known good EL84s and simply rule out the valves the old fashioned way.

Thanks for the insight Bordonbert, I will check those things and post the results!

Well the tubes are fine....all within one flash from each other. After I did the tube test I played through it for a bit an out of no where it made a loud popping sound...just once and not again, played thru it for about a half hour and no other pops...so strange...Guess I have to take it in fro service...sadness. On the other hand still blown away by how good it sounds, much better than the Grandmeister 36 I had.

That sounds hopeful.  I know it is a bit traumatic to hear a pop like that but with all the valves spot on according to TSC it may have just been a valve with a long burning in period.  Let's hope so.

Interesting to hear you say the GM40D sounds much better than the GM36.  I still love my GM36 even though it has been superceded now by my Marshall JVM205H as the goto amp.  I love the MIDI capability of the GM and would dearly wish for an amp with that degree of control and with the Marshall's tone for the music I play.  Others have said the same thing as you about the two amps' comparative tones but, if I am honest, the YouTube reviews I listened to, a there were a lot of them, weren't at all convincing.  They are all only interested in thrashing high gain sounds with the obligatory super Clean twiddling which high gain players all have to do to show they have soul as well as head thrashing neck muscles.  And that plain 'aint for me!  Maybe it's time I went and tried one.

bordonbert,
I am a Marshall man from way back, have 3 in my studio now. I was attracted to the Grandmeister series because of the "all in one" format, now that I am off the road and play in a cover band I need to mock a ton of tones and not worry so much about "my own sound". I was never able to successfully get the Marshall "oomph & push" out of the 36 despite my best efforts and was always searching for tone on it. I use in-ears so it was painfully apparent at all times. The 40 came much closer and had a warmer clean tone to boot...really more body all around. I use an older Marshall 1936 cab(the little one) with it and it really sounds pretty stellar.....will it ever supplant my 70'S JMP 50 for pure rock tone....nope, no way...but that is a one trick pony, a beautiful soul wrenching pony...but still one trick. I have a LM6100 that has 3 channels and a plethora of tone shaping features but man I hate carrying that thing, it is a BEAST!!! All said, aside from the fact something is amiss in my standby channel I am more than happy with the 40 and get tons of compliments on the way it sounds. It may be worth taking a listen, and I agree on the Youtube stuff....either glassy clean or ultra channel....cracks me up.