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  1. I'm using a digital multimeter and I'm sure it...

    I'm using a digital multimeter and I'm sure it works fine.

    The hum sounds more like 100Hz (I'm in Europe) and it comes from the output section.
    The preamp is absolutely quiet.
    If were the filter...
  2. Thank you for your reply. Now I now that the...

    Thank you for your reply.

    Now I now that the amp is correctly working, but what about 0V across R213 and R214?
    I'm asking even just for educational purposes.

    I've already cleaned the headphone...
  3. Ampeg BA-110 Trouble shooting - help needed

    Hello

    My Ampeg BA-110 started to produce a low pitched hum, not very loud, but annoying.
    I've measured 450mV DC at the output without load and the input grounded through the return jack socket....
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    Switching the ultra high switch doesn't change...

    Switching the ultra high switch doesn't change the cathode voltage.
    I've swapped the the tubes obtaining the same results.
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    293

    Thank you for your reply. I've checked all the...

    Thank you for your reply.

    I've checked all the connections between the tube board and the main pcb and they're all ok.
    Now I'm focusing on the first issue in the chain, V2a.
    As you can see from...
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    Ampeg SVP-Pro troubleshooting Need Help

    Hello

    My Ampeg Preamp SVP-Pro started to distort heavily, so I opened it up I take some voltage measurement.
    They are out especially on V2a and V4(12AU7), but I can't understand why.
    I've...
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    Thank you for your reply. Here is a more clear...

    Thank you for your reply.
    Here is a more clear schematic with original voltages added.

    I haven't measured the ripple at voltage nodes yet.
    Do you suspect a bad filter capacitor?
    I had the same...
  8. Replies
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    509

    Ampeg SVP-Pro troubleshooting Need Help

    Hello

    My Ampeg Preamp SVP-Pro started to distort heavily, so I opened it up I take some voltage measurement.
    They are out especially on V2a and V4(12AU7), but I can't understand why.
    I've...
  9. Replies
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    1,266

    Bill, C212 is ok, but you're right, the problem...

    Bill, C212 is ok, but you're right, the problem is Q205 since it doesn't amplify the signal, modulated or not.
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    Thank You for your replies. Yes, I've changed...

    Thank You for your replies.
    Yes, I've changed all the electrolytics, from the power supply to the last coupling cap.
    However I've re-checked them but hey tested good, even C224.

    The volume drop...
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    Vox Buckingham Tremolo Problem

    Hello!

    Months ago I've totally rebuilt a Buckingham for one of my customer.
    Following R.G.'s suggestions (thank you once again Mr.Keen!) We ended up with a great sounding and more reliable amp. ...
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    1,373

    Eheh...I'm lost too! I'll try to make it more...

    Eheh...I'm lost too!
    I'll try to make it more clear.

    Monitoring TP33 from the turn up in “Drive Mode”


    Drive -13,5 after about one minute and a half the voltage suddenly rise to -12V...
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    1,373

    ...another mistake. The actual voltages at TP...

    ...another mistake.

    The actual voltages at TP 36 are:

    Normal Mode - 16

    Drive - 16

    More Drive + 16
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    I've made a mistake... At TP33 the voltage go...

    I've made a mistake...

    At TP33 the voltage go more positive, while at TP34the voltage go more negative.

    At TP36 I have -16 volts in all positions.
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    Thank you for your replies. The Led tested...

    Thank you for your replies.

    The Led tested good outside the board on a Atlas Peak DCA75.
    Once resoldered, all the connections tested good as the components, but the problem still remains.

    When...
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    Hot Rod DeLuxe I switching problem

    Hello.

    I'm troubleshooting the switching circuit of a Fender Hot Rod Deluxe.
    The problem is that after a while it's not possible to switch from drive to more drive, the led stay yellow and...
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    Fender Concert pot bracket resistor

    Hello

    I'm troubleshooting a Fender Concert Reverb reissue for a bad and noticeable hiss.
    I was looking at the schematic (see pics) when I noticed that there are some 10 ohm resistor from the pots...
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