J-Mod 100 main power blue globe


New Member
Mar 30, 2024
Greeting all,
I might a technical issue, but i am not 100% certain.
I powered up my J-Mod 100 yesterday during the day and notice the main power blue light wasnt eliminating. I initially couldn't get any tone after a 20-minute warm up after i engaged the standby switch. :eek:

So, i power down and use another amp that day. (Marshall)
Having this issue running around in my head all day, that night i decide to repower up the J-Mod and was able to play with no noticeable tone deficiencies, but i did notice the main power light globe had a very faint glow that wasn't noticeable during the day light. (It wasnt a constant faint glow more like a content faint flicking glow that you had to stick your face wright up to the globe to see)
I purchase the amp new with only around 50 hrs use till now. (The rear has never been open, all tubes glow orange from what i can see)
I powered up and used the amp this morning for around 2-3 hours with no tone issues that i could pick up, but the globe issue is still there. Normally you can see the blue globe from the around side of the street lol.
I've tried to seek information on the web, regarding this issue, but that's near imposable.

My question:
I this a frequent problem with others or is this isolated issue.
What would course this to occur. I really don't want to open the back of the amp to explore as i haven't got the expertise nor the tools.
Please help Thank you :)
Of course I don’t own a JMod, I‘m not John Mayer after all.

But with Fender/Mesa Boogie this applies: Try unscrewing the jewel light, it might be a defective pilot lamp (get the lamp out by pushing and turning it about 90 degrees). When a lamp breaks the tube heater line fails, because it‘s powered via this transformer tap.