Repair/refurbishing: AVT20

Discussion in 'The Workbench' started by slowcorrado, Mar 19, 2015.

  1. slowcorrado

    slowcorrado New Member

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    Hi all, this is my 1st post here after a long time lurking in the background, so please go easy on me. I've been interested in amps and electronics for over 20 years and recently decided to pickup a Marshall from a local classifieds that was not working.

    After researching many things here (tube selection, amp testing methodology, how to clean tolex, failure points for AVT amps, etc...) I got this guy in GREAT physical condition!

    It had cold solder joints on multiple pot and internal pin connections (speaker pins, transformer pins) and completely broken connections on the input jack. Quick solder job and everything was good as new.

    Assembled it tonight and was happy to see no flames! Of course, there's an issue though.

    ** Problem **

    No real volume, no bass, super thin sounding.

    ** Checked **

    Headphones sound great
    LS output connected to another cab sounds awesome (surprised the crap out of me!)
    Speaker output pulled from the internal speaker and jumped to the other cab ALSO sounds awesome.

    ** My diagnosis **

    Speaker bad? It is the stock Celestion G10-30 AVT. I am a noob at this and have never really known speakers to blow and continue to work? It still plays, just quiet and terrible. LOL.

    Does anyone have another suggestion for me?
    Does anyone have a replacement speaker sitting around I could buy? (I'll post this in classifieds as well)
    Does anyone have a suggestion on a cheap replacement speaker or vendor?

    Thanks for reading, pic below of the speaker in question.
     

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  2. JohnH

    JohnH Well-Known Member

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    Welcome to the forum!

    Seems like you have isolated the problem. Its not just a poor connection or jack is it?

    WGS do some good value guitar speakers, with 10" ones too. Haven't tried them though.
     
  3. JohnH

    JohnH Well-Known Member

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  4. slowcorrado

    slowcorrado New Member

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    Thanks for the welcome!

    I don't think so since I directly drove the external cab from the actual wires connecting to the original speaker. Perhaps something on the speaker's internal leads. I may pull it and have a look. I'll probably search for "how to test a speaker" here in a minute. :)

    Checked them out, look nice and are reasonably priced. Alternatively, I found this:

    Celestion Ten 30 10" 30W Guitar Speaker 8 Ohm | Musician's Friend

    [​IMG]

    There haven't been too many bad reviews and it should be a match for ohms and wattage? Thanks for your help!
     
  5. slowcorrado

    slowcorrado New Member

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    Well, it's been 2 weeks of backorder waiting and I finally got the replacement speaker. Looks good in the cab, but looks aren't everything. :) There's an issue!

    [​IMG]

    While testing it out I noticed a faint fast "ticking" coming through the speaker. The speed is consistent, but it gets drastically louder with gain. All functions of the amp seem to work well, but I never noticed it before. (Perhaps because the old speaker sounded so bad) It DOES come through the headphone out as well. I'm really at a loss for what could be causing it. I tried a different cable and source with no change. I could certainly use any hints to forward me along. I'm off to search like crazy now. Thanks!
     
  6. slowcorrado

    slowcorrado New Member

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    I'm in here talking to myself... :)

    The "Ticking" must be some type of environmental thing. I tried the amp later and it was quiet? Took it to another room, quiet.... there is some hum when the reverb is turned up, but others have said the same thing. There's a great write-up on how to move the reverb tank and quiet this, but I'd rather keep the amp as original as possible and let others modify it if they wish.

    So, I finished the cleaning/detailing of the amp and am going to post it up for sale in the classifieds. A little more testing tonight and its playing great. Lets see if it sells as fast as the last one I posted. LOL!
     
    Last edited: Apr 2, 2015

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