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Thread: Voltage reading too high

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    Voltage reading too high

    Looking for some help with a new 5e3 build. The amp has almost 0 clean headroom. It starts distortion around 2 on the volume control. Also voltage readings are high throughout. It has a mojotone transformer for the deluxe reverb and was built with the weber schematics. Is there a way to lower voltages without having to switch out the transformer? It is quiet without any hum but only good for heavy distortion playing.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    A good place to start would be to measure the DC voltages throughout. There is a good chance that something is wired up wrong. It will be helpful if you could post the layout and schematic you followed.

    Report like this:

    Tube Pin Voltage
    V1 1 ??
    V1 2 ??
    and so on for all tubes. You can skip the heater pins for now.

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    Experience is something you get, just after you really needed it.

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    V1= 223/229
    v2 = 217/ 229
    b+ = 464

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    Supporting Member Jazz P Bass's Avatar
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    I believe that what was asked was to report all of the voltages/ pins. (sans heaters)
    The plate voltage and the cathode voltage will tell how well the tube is conducting.

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by Mark59 View Post
    V1= 223/229
    v2 = 217/ 229
    b+ = 464
    Well you have the right idea but we need ALL the pins of ALL the tubes less heaters. You do get a bonus point though for adding B+ which I forgot. But I have to subtract a point for not mentioning the pin number. The details are really important.


    The schematic you are using is going to be important so we know without guessing which tube is which.

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    Supporting Member mozz's Avatar
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    Also, are you using a 12ax7 or 12ay7 in V1?

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    Thank you for the warm welcome to this group. I appreciate the criticism and feedback. I apologize that I did not have the required information for my question. The voltage info that I provided were part of a text that I shared with an amp buddy and now I have left for the holiday so I will need to revisit this post. I am not a forum dweller so I will try to figure out how to attach the weber schematics that were used. For the person that asked about the pre amp tubes, they are 12ax7 in both v1 and v2 also the voltage was measured with a s/s rectifier. I have since ordered a nos 5y3 and when I get back will try some different pre amp tubes. This may be part of the issues. I thought by mistake that there might be a common answer to this issue.

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    Click image for larger version. 

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    Supporting Member eschertron's Avatar
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    On a new build there are simply too many variables to allow the common answer. But don't fear, the posters who have already responded are among the best on the forum, and you *will* get the help you seek. Just be patient and understand the troubleshooting process as it unfolds.

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    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
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