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Thread: Modding a Bassman

  1. #1

    Modding a Bassman

    [IMG]/Users/s/Desktop/Bassman pic.jpg[/IMG]Hello all,

    My nephew has asked me to look at his 67 Bassman head. He would like to sound better and also check the regular things like caps, tubes, etc. My question is on the mods. It needs a new power cord for sure. Will changing that affect the value of the amp? I have read that it is an acceptable upgrade that doesn't affect value at all and should be done. However, if any of these things are adversely affecting future value, I want to be able to let him make that decision. I will, of course keep any parts so they can go back if desired. Apologies if its already been asked and answered. I did not see anything specific.

    Anyway, that's it, just looking for things to do or avoid doing and why. Experienced replies appreciated.

    Steve.[IMG]Bassman pic[/IMG]

  2. #2
    Forum Member phantomman's Avatar
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    Re: Modding a Bassman

    Your photo(s) are not visible but it's of no consequence at the moment.

    Safety upgrades are mandatory if the amp is to be used for its intended purpose. These would include a fully-grounded 3-conductor main power cable, disabling or removing the "death cap", and a comprehensive visual inspection of the chassis. If not already done, all of the electrolytic caps should be replaced -- the filter array beneath the "dog house", the cathode-bypass types on the main board, and the bias supply cap adjacent to the rectifier diodes. Any carbon-comp resistors which look crispy should be ditched in favor of metal-oxide types. Cleanse all jacks, pots, and switches with spray contact cleaner (use crocus or emery cloth on the jacks). Finally, check all the tubes and pay special attention to the output bottles. The latter may require an idle-bias adjustment. The AB165 circuit is equipped with a balance control which is somewhat of a compromise over a traditional bias adjust pot. If you can achieve a reading that's within ten percent between the tubes that's considered to be adequate.
    "When injustice becomes law then rebellion becomes duty."

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