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Magnatone Custom M10

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  • #16
    Agree. Old style "F" would be like modern AB impedance code. Old style "C" would be like modern FB or EB if FB not available.
    Fliptops has a MOD brand sub for the type "C" which has been altered for use open side up. Most of the MOD tanks that I know of can have the ground scheme easily altered by solder bridge jumper at jack board.
    https://www.fliptops.net/catalog/p-1...vintage-ampegs
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


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    • #17
      great explanation and suggestion!
      thank you guys!

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      • #18
        I don’t have an M10, but I do have an M13a. The M13a also uses a 12AU7 to drive the reverb tank. I’ll measure the impedance of my tank and post the findings.

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        • #19
          I’ll measure the impedance of my tank and post the findings.
          How are you going to measure impedance? Do you mean DCR?
          - Own Opinions Only -

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          • #20
            Originally posted by Helmholtz View Post
            How are you going to measure impedance? Do you mean DCR?
            DCR measurements are 177 ohm output, and 173 ohm input.
            It’s a 17 inch long Gibbs 2-spring tank.
            No model# on my tank, but I believe the modern equivalent is 4FB2A1C, both input and output jacks are grounded.

            The reverb circuit on the M13 is really nice.

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            • #21
              I believe the modern equivalent is 4FB2A1C
              Looks correct for the connectors up vertical mount version. Input and output impedance around 2k.
              - Own Opinions Only -

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              • #22
                Originally posted by Helmholtz View Post
                Looks correct for the connectors up vertical mount version. Input and output impedance around 2k.
                Yes, my tank is mounted vertically on the rear cabinet wall in a 3-sided aluminum box with foam.

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                • #23
                  Originally posted by Diablo View Post
                  Yes, my tank is mounted vertically on the rear cabinet wall in a 3-sided aluminum box with foam.
                  Interesting. In the M15A I'm working on, the tank was simply banging around under the amp in the cabinet. You can see where it had very old (now extremely deteriorated) adhesive foam applied to the outside of the tank.

                  Might an M15A also have had a box holding the tank in place?

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                  • #24
                    Originally posted by Rhodesplyr View Post
                    Interesting. In the M15A I'm working on, the tank was simply banging around under the amp in the cabinet. You can see where it had very old (now extremely deteriorated) adhesive foam applied to the outside of the tank.

                    Might an M15A also have had a box holding the tank in place?
                    I just found a picture online at Chicago Music Exchange. The M15 has the same style of aluminum box to mount the reverb pan.

                    https://www.chicagomusicexchange.com...1960s/26324141

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                    • #25
                      I saw that picture of the M15. The M15A cabinet is different, having an angled piece of wood between the amp and the speakers. Looks like whatever held the reverb tank was mounted vertically to the side of the cabinet.

                      How does the aluminum box hold the reverb tank? Seems like it would slide from side to side.

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                      • #26
                        Originally posted by Rhodesplyr View Post
                        I saw that picture of the M15. The M15A cabinet is different, having an angled piece of wood between the amp and the speakers. Looks like whatever held the reverb tank was mounted vertically to the side of the cabinet.

                        How does the aluminum box hold the reverb tank? Seems like it would slide from side to side.
                        My M13a cabinet also has the angled piece of wood between the amp and the speaker.

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                        • #27
                          Great discussion on the REVERB TANK guys, thank you for the exchange.

                          So, I am going for the 4FB2A1C. I've found it available in Europe but more difficult to find in the US, unless is the Chinese version (Revisit, with which I've had no good results with when looking for a replacement for the Fender Twin's push pull master volume potentiometer)
                          The Accutronics page re-directs to two distributors in the US (CE Distribution and New Sensor) that according to their websites do not seem to carry this specific model.
                          I think I 'll go with the one proposed by G1 HERE
                          thx,

                          PS: my amp did not have any reverb tank. however the 4 remaining holes in the horizontal wood division between the amp and the speaker side of the enclosure show that the tank was mounted horizontally and on the amp side (probably as shown in the M15 photos)
                          Last edited by TelRay; 01-18-2020, 09:40 PM.

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                          • #28
                            This one appears to be exactly like what’s in my M13A.

                            https://www.ebay.com/itm/GIBBS-sprin...IAAOSwf1leEj6H

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                            • #29
                              Originally posted by Diablo View Post
                              This one appears to be exactly like what’s in my M13A.

                              https://www.ebay.com/itm/GIBBS-sprin...IAAOSwf1leEj6H
                              FWIW, 1122 is Hammond Organ Co.'s EIA code. I've seen people on other sites confused by that number.

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                              • #30
                                Originally posted by 52 Bill View Post
                                The diodes listed in the schematic are too old and underrated for modern specs, just go with 1N4007s as replacements for all of them.
                                DIODES:
                                I wanted to double check before ordering them.
                                For me it is clear that I'll go for the UF4007s to replace the IN697s (4 of them in the SCHEMATIC)
                                However I am not so sure (because of being different, probably for a good reason, form the other ones) about the 5th diode: CODI-575, the one connected to the 50V t/f secondary, 100 uF 50V cap and to pin 8 of the connector.
                                Could you guys please take a look? (i've been told it might be a zener diode or maybe responsible for the bias)
                                thx!
                                Last edited by TelRay; 01-19-2020, 12:51 AM.

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