F-50 constant Snap, Crackle, and Pop

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andyurban

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I have searched the web and forums and it appears that this is a common problem. (I google the hell out of everything I barely think anymore) I have an F-50 that has the constant snap crackle and pop problem. This occurs with the guitar plugged in or the cable disconnected from the amp. I also tried it with the speakers disconnected and headphones plugged in. So nothing connected, not using the speakers in the cabinet, I have narrowed the problem down to the amp itself. I replaced all the tubes; that is four preamp and two power tubes with: preamp 12AX7 from Groovetube and two 6l6's from groovetube. These were recommended by my local music shop who is a mesa dealer so I'm hoping that their recommendation was correct. I bought this amp second hand fairly inexpensively so I looked at it as getting a tune up for a used car. Even after the all around tube replacement I still get the crackle noise when the amp is off standby. Any forum I search says its the preamp tube and if it isnt that there is no resolution. I would like to start this thread to find what could possibly be doing this. If anyone has any recommendations I would appreciate it. This would be my first post for amp problems so if I didnt supply any required information just let me know and I'll have it for you. My plan is tonight I was going to spray some PB blaster on the old tubes and plug them in and remove them to clean out any corrosion. Do you think PB blaster is okay for these components? Thanks to whoever is listening!
 
I got an F-30 as a present a few years ago back when i wasn't playing guitar (long story) ONe of the first things I noticed was that it popped and crackled like a MF. As I lived out in the country I attributed this to poor line power. Now that I am divorced and living in a urban area, i found i now had plenty of time to play guitar again, and pulled the f_30 out of the closet. guess what, it still popped and crackled like a MF. of course by now the warranty had expired but i still took it into the shop where i purchased it. they retubed it and guess what..... it still popped and crackled like a MF.
I noticed on some other unrelated forum that someone else had the same problem with their f-30. I have never got to the bottom of it but if anyone can help us out, it will keep a bogus F-30 off kijiji or out of the dumpster. in the meantime, it has moved back to the closet collecting dust
 
Well I hosed down the old tube pins with electronics cleaner, non lubricating & quick drying, and did my best to clean each socket. Sprayed a tube, plugged it in, moved it around a little, unplugged it, repeat a few times. Each socket I resprayed the tube. I didnt blast any compressed air but I dont think thats gonna be the resolve. I feel like it is part of the input circuit. I am doubtful it has anything to do with the pots as it doesnt change as I adjust the volume what so ever. Maybe a bad solder join somewhere? I dont think its the transformer as it still occurs with no speaker hooked up but plugging in headphones, I would think that this would be a lesser load. I dunno Im no gear expert. Still here, still working on it. Oh andI checked for blown caps but they all look perfect.
 
I have an f-50 also. It did that at one time but tubes fixed the problem. Quiet as can be now. I also play thru a friends f-100 pretty often and it is very quiet also. I'd say bring it to a good repair shop unless you're good at that kinda thing. Dont know where you are but I know a good one in the Philly area.
 
Well I just took out the power toggle switch. Actually when removing it the switch fell into multiple pieces. Looks like somebody got to it first as the standby switch had a metal clip holding it together and the power did not. Contacts inside the switch were black and burnt. Guess I will replace this before moving on. I live in Florida and I am pretty handy with this kinda stuff. I feel confident I can fix this myself. Thinking after I repair the power switch I will purchase a line conditioner just to rule out that possibility. I have used this amp in multiple homes in different outlets and still always have this popping. It is fairly immediate in action and typically starts within the first 30-60 seconds of the amp being on if not immediately.
 
Just an update - still having issues with the noise. Tried running a new ground from the chassis but no dice no change. Running out of ideas here, I guess at this point it can be anything from a bad tube socket to a bad capacitor. I will upload a recording of the sound once I let the amp cool down for a little bit. I have seen this issue go unresolved in other posts on many boards and I feel like I just cant let the challenge beat me. Was gonna call Mesa Boogie tonight and didn't realize they are closed on Friday, Bummer.
 
Alright so if anybody wants to hear the issue I uploaded it to this link http://picosong.com/wi9s
I recorded this with a BR-800 Boss recorder hooked up to the headphone/record jack. All cables and instruments have been tested on a separate amp with no sound issues. I began this recording with nothing plugged into the amps input. All though this is coming from the headphone jack the sound is identical to what comes out of the speaker. The only difference is that when I go to standby the speaker will go silent but when hooked up to the headphones there is no change. I flip through all channels and make adjustments to all the volume and equalizer knobs. The Mid on channel 1 does on occasion make a slight noise when adjusted but it can be distinguished from the real problem. I plug my guitar too give a reference to what it sounds like with an instrument being played. There is one point where the recording peaks as I was adjusting the volume on the recorder. The reverb tank is not connected during this recording but it makes no difference. I have read that people remove preamp tubes to see which one could be causing the issue. I have tried removing one tube and receive no sound. I attempted this will all tubes to see what would happen and ultimately if one preamp tube is removed I have no sound. I would like to thank anybody who takes the time to read this long post and listen to my brief recording. Its roughly two minutes but really you get the picture after 20 seconds. Thanks a lot for any input!
 
Well I wanted to give it a few days before posting. Sunday evening I went through anything I could to find the solution. I bypassed both switches to take them out of the equation. I tested the two resistors on the power-tube PC board and both tested at their rating, I believe its 240 ohms or so. As I stated previously that I gave the amp a thorough cleaning to be certain a bad connection was not the case. Well I guess I did not clean up well enough the first time. I pulled out the Input jack but did not remove the wires. I inspected the inside with a flash light and observed some scratches, dirt, etc. Using electronics cleaner that I bought at Auto Zone designed for sensitive electronics equipment and a Q-tip I began to clean. I saturated the Q-tip, cleaned, got a new Q-tip, saturated and repeat. When I got it all back together the sound that I have recorded disappeared. I placed the amp on stand-by for twenty minutes and returned to play. Still the sound did not return. By this time it was late so I figured I would continue my testing the next day. The next morning I let it run for 30 minutes still no return. Well its Wednesday and I have used the amp every day and the sound has not returned so I feel I am essentially in the clear. I really hope that this helps somebody who finds themselves in this position. I would also like to include this link: [color=#0000BF]http://www.geofex.com/ampdbug/ampdebug.htm[/color]. Its a pretty good diagnostic site as it pointed me in the right direction. I don't plan on removing the recording as I figure hearing it may help someone compare to their amp. Thanks a bunch! This thread can be closed I suppose.
 

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