2204 Hum/Buzz/Noise

Discussion in 'The Workbench' started by CKCinMass, Dec 10, 2009.

  1. CKCinMass

    CKCinMass Active Member

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    I have a 1980 2204 that I had bought 20 years ago and at the time it was a basket case (and sat in the basement until a few weeks ago). After aquiring a good scematic for this amp I was able to revive it back to life. It was a bit noisy (pots were nasty) and it was making a buzz type noise which would be minimized if I turned down the tone knob on my guitar. I verified that it was not my guitar by using another one and had the same results. I have replaced all of the pots and and the filter caps figuring that I may eliminate most if not all of the noise. The buzz type noise is still there. The new pots & caps have improved the overall sound bit did not eliminate the noise. Where is a good place to start? I have not biased the amp as of yet. If the bias were to be out of whack could that cause the noise? Any and all help would be appreciated.
     
  2. Iron Mang

    Iron Mang New Member

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    An Amp seriously biased incorrectly could produce a pronounced buzz and making sure the amp is biased correctly should be your first step. Then does the amp buzz as well with nothing plugged in? And how loud is the buzz? Knowing this can help diagnose your issue.
     
  3. MajorNut1967

    MajorNut1967 New Member

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    It sounds like you may have some bad grounds somewhere, since you said that when you turn down the tone pots it cuts some of the buzz...

    You said you have basically started a restore on the amp right and replaced all the filter caps, so that’s ok? Now what Schematic are you going by, can you post it? Any way if you don’t know the ground points by heart, use your schematic to reference the ground points and make sure they are solid. Also replace the input jacks with real Cliff Jack sockets. Clear all these possibles first and see if you win.
     
  4. rockinr0ll

    rockinr0ll New Member

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    Is the amp grounded aka have a 3 prong...?

    Before you do anything else you really should replace all the tubes with fresh ones just to make sure that isn't the issue.

    Check other outlets in you house and try to turn off TV, Internet, and light dimmers. Getting some anti-static can also help.

    Everyone one I have played has had some TBH... Kinda sucks :(
     
  5. CKCinMass

    CKCinMass Active Member

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    Ok....now I have to rethink a few things here.........I also have a 2204S limited edition classic reissue that has also sat for some time and it also is encountering the same buzz. I replaced caps in this amp tonight expecting it to be buzz free. The buzz is greatly minimized when nothing is plugged into any of the inputs and if the master volume is turned up it can be heard quite well. Both heads utilize the three prong cord so that shouldn't be the issue. I know most of you are thinking that I should take it to a tech but, unfortunately thats not within the budget right now. Pardon me while I go beat my head against the wall............
     
  6. Iron Mang

    Iron Mang New Member

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    Why don't you just check to see if your residential "House" ground is actually connected properly first be for you run off to the Tech. Even though you are using a 3-Prong plug is the ground in the AC socket in the wall isn't connected properly. The have those little $5 yellow testers you can get at the hardware store, it will tell you if all is well.
     
  7. rockinr0ll

    rockinr0ll New Member

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    Again, every amp I have played has had some hiss.

    I also second the outlet tester. I got one for 6 bucks. I found some outlets that were bad but I still get hiss with good outlets.
     
  8. CKCinMass

    CKCinMass Active Member

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    Update: The house wiring checked out ok with the Radio Shack tester. With nothing plugged into either the Hi or lo input, the amp is relativley quiet with what I would consider a "hiss" sound with a tad of hum when all of the pots are maxed out. I have not biased the amp as of yet as I am waiting on the components to build my bias probes. (If it isn't painfully obvious, I am a novice at tube amp repair so please bear with me). When I do plug my guitar in I am getting noise. I originally thought my guitar was ok but I am having second thoughts. The guitar is a 2007 Gibson SG Special and all of the internal wiring looks unmolested. My guitar cable is a new Grover. One thing I had also noted that while the guitar was plugged and with one hand touching the strings, if I touched the chassis with the other the noise got slightly quieter (not much, but enough to hear). I also performed the chopstick test and got a fair amount of noise from some of the caps and resistors. I am going to pull the pcb and remelt all of the solder joints and see if I get any improvement (at least try to pass the chopstick test).

    Any other thoughts, opinions, Ideas?
     
  9. Iron Mang

    Iron Mang New Member

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    Ok so we know the house wiring is good. Now on a properly bias well running tube amp you should hear a sound similar to the ocean at a distance, a quiet whoosh sound. A tad of hum is ok. So now we will have to wait for you to build your own bias probe to check bias, nice project by the way.

    Don’t worry about the novice thing as long as you use common sense & safety, I’m no expert my self. Plus there are a couple of guys here that really know their stuff and they are usually willing to help, according to my Brother.

    You maybe you are going down a right path about the guitar. Can you do this? Take your meter put it on ohms or continuity touch one end to your jack sleeve (Ground) and the other to the tailpiece or the bridge, what does it read?

    If you want to do touch-up on the solder joints that could be of help.
     
  10. CKCinMass

    CKCinMass Active Member

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    I'm going to check out the guitar later today (probably tomorrow). I have another post regarding this am titled Bias Probes. I rambled on there about what has bee done so far to this chassis. I will post later what I get for readings from the guitar.

    Thanks for the help!
     
  11. CKCinMass

    CKCinMass Active Member

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    I do have good continuity from the jack sleeve to the bridge. Anything else I should check with the guitar?
     
  12. Iron Mang

    Iron Mang New Member

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    And have you tried different guitar cables?
     
  13. jcmjmp

    jcmjmp Well-Known Member

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    This is a long shot but... are all the input jacks on the amp isolated from the chassis? Grounding points can make a huge difference.
     
  14. CKCinMass

    CKCinMass Active Member

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    Well I guess I have to admit missing something obvious! I found an "old" cable and tried it and wouldn't ya know........ So much for my "new" cable......


    A sincere thanks to all of those who offered help. This amp project is far from over so I'm sure I'll be back needing more advice at some point.
     
  15. Iron Mang

    Iron Mang New Member

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    There you go! Some of the cables out on the maket now days leave a bit to be desired.
     
  16. MartyStrat54

    MartyStrat54 Well-Known Member

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    It seems like any support items for a Marshall you can't ever trust even the new one's. Tubes, cables, etc. At least my guitar pick still works.
     
  17. jcmjmp

    jcmjmp Well-Known Member

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    Are those NOS guitar picks?
     
  18. MartyStrat54

    MartyStrat54 Well-Known Member

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    Why yes they are. They say, "Ritchie" on them.
     
  19. rockinr0ll

    rockinr0ll New Member

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    I just bought NOS guitar strap.
     
  20. MajorNut1967

    MajorNut1967 New Member

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    I'm sorry they say Ritchie on what?
     

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