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Do some quick tests to locate the fault area....
i) With all gain controls at minimum & amp warmed up, turn on the standby switch & observe the large output valves for sparking or flashing (could be breakdown in one of them).
ii) Remove V6 (12AT7). Is the crackling still there? If so, the fault is in the final output stage (four 6L6GT's).
iii) To test the output stage, keep V6 removed & remove V7 & V9. If the fault clears then one of those 6L6's is likely to be faulty.
iv) If the fault persists, reinsert V7,V9 & remove V8,V10. If fault clears, then V8 or V10 is the culprit.
v) If the fault still doesn't clear, then desolder coupling capacitors C22,C23 - which may be leaky.
I suspect the fault is the output stage valves, in which case it's best to buy a matched set of 4 & re-bias.
Hi J Wade. I'm Dave P. I'm not a guitar amp expert or technician but I've been using amps and effects for 35 years and there are a couple things I can suggest.
That kind of periodic noise/switch noise can be a symptom of having the polarity of the amp reversed. If your amp has a 3-position OFF/ground switch, try reversing the ground. If it doesn't, take the plug and turn it around. Just don't get near a microphone unless you're sure your amp is grounded the same as the P.A. It could fry your lips off.
Dirty switches to that too. You said the noise is in time with the delay's tap time which is set by a foot switch. If tapping that switch the first time generates a pop, the delay may have catch it and is repeating it. Turn off the amp, remove the delay foot switch and turn it back on. Still noisy? If not, give the foot switch a good cleaning.
When you turn the EFFECTS knob up, is it scratchy? Might need the potentiometer cleaned. What happens when you specifically turn the DELAY level down all the way while using the other effects? Noise still there?
That's all I've got. Hopefully, it was helpful. Don't wrack your brain over this too much. There could very well be an internal problem with your amp that will require a trip to the shop. You don't want to open it up yourself. Rock on but be safe.
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.
If you are using headphones, then I'm guessing you are practicing and running the amp as quietly as possible while still able to hear it. Unfortunately, most channel switching guitar amps will have a tiny bit of bleed-through from the other channel when turned all the way down and listened to at close distance from the speaker. And yes, using a mechanical switch or relay to switch the connection from one channel to the other would mostly eliminate this, but due to the high amount of signal gain in guitar amp preamp sections, this type of switching causes very loud pops and other unwanted noise when switched. The amps are made with either photocell (optical) resistors or reverse biased transistors or op amp chips to switch channels. These are 'softer', partially because they don't fully turn off when in the off state(or fully on either). This creates bleed through, but it is better and easier than a CRACK THUMP POP!! every time you stomp the channel switch pedal. Amps are designed to be used at output levels generally much louder than a dorm room at 11:30 pm, and at stage volume in a club, the channel bleed is so far below audible, it is never heard by anyone. That's just the way it is.
That supposedly is the correct footswitch for the amp... there may be a defect in the amp. Contact the factory support about this problem. Make sure you are FULLY plugging in the plug as SOMETIMES they feel like they are clear in but they are not.
Not uncommon for a switch to fail... especially the weak types they use on these strips. The inrush current when turning on the amps makes quick work of these switches. Replace the switch and get spares for the next time it fails.
Hi there. Check the foot switch. Plugged in all the way? Still not working? Use an ohm meter to check the foot switch. (unplug from amp and check for continuity across the plug. click switch on and off.) If alway open (no continuity) bad switch. Thanks Paul
Replace the switch. You gave no make/model number for your amp but if it has a jack for foot pedal operation of clean/dist function then try that. (on most amps) it will switch in spite of a bad front panel switch.
You suspect the power switch when you should have immediately dismissed it because the ON light is on, as it should be. The fact that it does in fact produce sound at all indicated that the amp is being powered on. There is a malfunction somewhere else in the amp, most likely a bad tube. If you have access to a tube tester, then by all means, have the tubes checked. You could check your guitar and cord with another amp to make sure that they are working OK. Beyond those simple things, it's my opinion that for you to open this amp and attempt repair, you would risk further damage.
it would be much cheaper and quicker for you to take the amp to a
qualified repair shop and pay the price for a competent repair.
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