I tryed to mod my valve jr with the billy gibbins mod by patfurfan on the internet.now no sound or noise just nothing after power up. is their a point to point voltage reading to see were i when wrong? iam an electrician but i just dont know how a guitar really works. i there any one that can help. i know enough not to get hirt by the amp.but not enough to know were i went wrong. patfurlan amp sounds great.

Sounds like it might not be cleaned enough. They may have done the pots but the internal circuit boards may not have been done enough.

You have several options:

1. Do nothing and live with the occasional problem.

2. Check your guitar cable and the battery connections for loose or intermittent connections/noise. Try to see if it's the amp responsible for the noise....ie, Is it caused by vibrations, or maybe static....especially in winter when it's dry. Your home power may have noise on the line, so borrow or rent a power conditioner which filters out noise. If that fails, go to 3.

3. Bite the bullet and pay a competent guitar tech/luthier to repair it. Most of these issues are due to loose/faulty connections. Should be less than an hour. Hey....It's a Martin.

3a. Pay a guitar tech to loosen the end pin connector so you can see if you can repair it yourself.

This is because your clean channel only runs through the pre-amp section, requiring an increased volume level to match that of the volume of the drive section which is overdriven by the pre-amp circuit. my suggestion is to use lower volume level on the clean channel of the amp. To get any volume boost you may need to match the two channels you could use a signal/volume booster or overdrive pedal between your guitar and amp input, switching it off and back on when you switch back and forth between channels.

How new is the amp?

A single faulty solder can do that...I'd try returning in to the seller.
Have you tried a different amp with the same equipment?

Sounds like a wiring issue.

Hope I've helped
PvT

Likely the filter capacitors have a problem. Best to take this in for repair... it is ODD that there is noise with the standby switch is in standby... That makes no sense... In standby it appears that power is removed from the power amp high voltage so nothing should come through the speaker... Unles maybe one off the power tubes had a total meltdown which should have blown the fuse.

Chances are there is nothing wrong with the mixer. IF you accidentally turned on Phantom power, that would cause the problem. Phantom is ONLY used with condenser mics and a few DI boxes. Turning it on can create noise unless balanced lines are used everywhere.

If more than one input is bad, then problem has NOTHING to do with the preamps. Check list:
1. Make sure you are using BALANCED lines everywhere... either XLR or TRS cables.

2. Make sure ALL interconnected equipment, mixers, amps, powered speakers, CD players, etc. are ALL powered from the SAME receptacle or power distribution unit.

3. Do proper setup. Select each channel PFL and set the trims so the indicator never goes into clipping, but is in the 70% range during max volume input to mics, etc..

4. During operation the sliders should be at least 50% up on used channels and the mains. Setting of levels throughout the system is important for noise free operation. Using EXCESS gain at some point results in distortion and noise. Using sliders near the bottom position results in poor signal to noise ratio.

Now re-read #2 above... and believe it. I have seen a lot of equipment blown due to ground bounce of building power. That is why the pro's run power back to their mixer from the area where the amps are powered.

The Tolex covering loves to stick... Take a dull blade and go all around the edges... then a bit of prying will likely be required.

Yes, the pickups can be changed.

However; In my opinion this is not worth it. Pick up a pair of aftermarket pickups for a better sound that will fit your playing style.

-Sheeves

okay so buzzing noise. i have seen this once before. the extension cord feeding a power strip with two amps plugged in and powered on off of a low amp electrical outlet with fluorescent lights overhead.......try running only one power unit off of the electrical outlet you are using, just one straight into the wall with the lights out. if you still hear it i wonder if the output transformer is starting to go south. if you listen close sometimes you can hear the buzz of a transformer powered on, example: you can hear the buzz of a power transformer on a power pole in peak hours. tubes usually make hisssing, crackling type noises. next would be to tap on the tubes while in play with an orange stick or pencil eraser to listen for microphics or the tapping itself thru the speakers. if you hear with out a doubt change them.