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I love the 5e3. Just not mine! Please help.

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  • #76
    Originally posted by g-one View Post
    Yes, pin1 of 12AX7 is high, pin3 is low. Check there are good connections from pin1 to the 100K, from pin3 to the 1.5K, and from the 1.5K to ground. Also check that the resistor measures 1.5K.
    Also check the connection to pin 4. (Pin 4 should be connected to pin 5). The voltage on pin 1 shouldn't be higher than on the filter cap F3 so that doesn't make any sense unless there is some bizaar mis-wire on the back of the board.
    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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    • #77
      Pins one and three look good, so do their solders and resistors. Pin 4 and 5 is hooked up right. Slightly sloppy but no concern. The back of the board may be flawed. Easy to get turned around with it being mirrored from the schematic. I'll check now.

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      • #78
        The back of the board is wired correctly.

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        • #79
          What resistance do you measure with one probe on pin3 and one probe to chassis?
          "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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          • #80
            On the 12ax7, I read zero. I set the multimeter to the ohm logo and put the black to the chassis and the red on pin 3. Read zero. I put it on the cap that the white wire goes to and it tired zero. The resistor that is attached to that cap is verified. It works.

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            • #81
              Do you mean you measure 0 ohms across that cap (one probe at each end of cap)?
              "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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              • #82
                When I touched pin 3 I got 0. I didn't try each end of the cap.

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                • #83
                  Try it. Meter set to ohms, one probe at each end of the cap. (the cap that goes to pin3 of the 12AX7)
                  "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                  • #84
                    Put the speaker in. Now it reads 155.

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                    • #85
                      Well that's it for me. I'm freakin stumped. Clean build. Good solders. Can't find anything wrong visually. Still pretty much no volume and it's slightly distorted. Checked grounding points. They're good. Speaker maybe? It should be good. Tested it and know what the positive and negative leads are on it. So it's hooked up right. Jack inputs look good for the speaker also. Guitar inputs and pots are nice. All wires are to their correct post. All caps are correct. All pos and neg sides of caps in the right direction. Back of board is wired right. Fuse wires seem right. Same for on/off and light. Tubes light up. All voltage readings are ok except pin 3 on the 12ax7 or whatever was on the readings.

                      About to take this to a tech but damn! That will piss me off. I wanted to build this and really learn.

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                      • #86
                        You can still learn if you take it to a tech. They will usually talk shop with you about what happened and what they fixed. I sure would. Especially with an enthusiastic builder. You're bound to learn. This sort of thing can be very hard to troubleshoot as a novice, or in our case from a remote perspective, but a tech with the amp on a bench should be able to do it pretty easily. It'll cost a little but the learning experience will be invaluable. It's not at all uncommon for a novice to build an amp and then require a tech to troubleshoot it. It happens all the time. It does suck out a little of the savings, but that's not the point. The overall experience will get you closer to being able to build, tweak and maintain/repair your own amps. PERSONAL CONTROL OVER YOUR TONE!!! Nothing like it. If you're actually interested in becoming THAT guy it won't seem like wasted money. More like a first person lesson. I did it with Dan Torres when he was still working out of his home!!! He gets a little rough press here and there but he was one of the first players in the game and VERY enthusiastic. Combined with his experience that counts for a lot. It was a good place to start. I hope you can find a tech that actually knows vintage guitar amp circuits and wants to share. It'll be great.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                        • #87
                          Go over the voltages one more time. If pin 1 of the 12AX7 is higher than F3, that means current is flowing the wrong way (or there is a measurement or wiring error). Set your meter to AC volts. Measure from pin 9 to pin 4 of the 12AX7. Make sure you are touching the probe to the socket pin, not the wire soldered to it. Remove the tube from the socket and inspect the socket. Do the contacts look bent or discolored?

                          You should be able to see two glowing filaments inside the 12AX7. Do they look equal in brightness?

                          The voltages on both power tubes should be the same. Check again, no typos.

                          Unplug the speaker. Measure the resistance across the speaker terminals. It should be about 6 ohms. Now plug the speaker in. The resistance across the speaker should now measure very low, one ohm or so depending on you meter. Now unsolder one of the wires from the speaker jack that go to the output transformer. The resistance measured across the terminals of the speaker should go back up to 6 ohms. Now measure the resistance from the unsoldered output transformer wire to the terminal where you undoldered the wire, it should be 6 ohms. This checks that there is no short at the speaker jacks.
                          WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                          REMEMBER: Everybody knows that smokin' ain't allowed in school !

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                          • #88
                            How would I measure from pin 9-4? Am I measuring AC or DC? How would I measure the resistance across the speaker terminals?

                            I will do this as soon as I get home.

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                            • #89
                              Originally posted by g-one View Post
                              Try it. Meter set to ohms, one probe at each end of the cap. (the cap that goes to pin3 of the 12AX7)
                              Originally posted by JohnRose81 View Post
                              Put the speaker in. Now it reads 155.
                              So you got a reading of 155 ohms across the cap? It should be 1500 or 1.5K ohms. Recheck it and recheck ohms from 12AX7 pin 3 to chassis ground.
                              "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                              • #90
                                How would I measure from pin 9-4? Am I measuring AC or DC?
                                Originally posted by loudthud View Post
                                Set your meter to AC volts. Measure from pin 9 to pin 4 of the 12AX7. Make sure you are touching the probe to the socket pin, not the wire soldered to it.
                                Connect one probe to pin 9 and the other probe to pin 4. You can do this when the amp is in standby mode, it will be safer because the high voltage will be off. You still need to be careful, don't let the probes slip and short things out. Don't touch any part of the amp, hold the probes a safe distance from the tip. If you have any kind of clip that allows you to attach one of the probe wires to the circuit, use it as long as there is no possibility it will short to the chassis.

                                How would I measure the resistance across the speaker terminals?
                                The amp should be turned off for this test, or just about any time you are measuring ohms. Connecting voltage to the meter when it is set to measure ohms may damage the meter or give an inaccurate reading.

                                Set the meter to measure Ohms. If the meter has more than one range, use the lowest range, usually 2K. As a test, touch the probes together to verify you get a low reading below 1 ohm. The way your meter works, the resistance of the probes and interconnecting wires are added to any reading you take. The speaker has two terminals. Touch one probe to one of the terminals and the other probe to the other terminal.
                                WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                                REMEMBER: Everybody knows that smokin' ain't allowed in school !

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