Announcement

Collapse
No announcement yet.

Magnatone Custom M10

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Originally posted by Rhodesplyr View Post
    FWIW, 1122 is Hammond Organ Co.'s EIA code. I've seen people on other sites confused by that number.
    Yes, and Hammond has the patents on the spring reverb. They used to make them in house and then started up the Gibbs company to make them.

    Comment


    • #32
      Originally posted by TelRay View Post
      So, I am going for the 4FB2A1C
      REVERB:
      Actually no, I have a Horizontal Mount and the open side needs to be facing down. So, the last alphanumeric code needs to be a "B".
      Need to respect the IMPEDANCE you guys have highlighted (1,475 - 2,250) and the INPUT and OUTPUT to be grounded.
      So it'll be finally be a: 4FB3A1B (3 is for long decay)

      Comment


      • #33
        Originally posted by Diablo View Post
        Yes, and Hammond has the patents on the spring reverb. They used to make them in house and then started up the Gibbs company to make them.
        Yes, I'm a Hammond tech, so I know the whole story going back to 1939 and the oil-tube (not oil can) spring reverb units with their crystal pickups. The necklace style spring reverb appeared in 1959 with the spring tank appearing in Hammond A-100s around 1960. The necklace reverbs are really nice, but very easy to crash, even playing the pedals on the organ. Hammond kept using the necklace types in their PR-40 tone cabinets. I've heard conflicting accounts about which guitar amp was the first to incorporate Hammond's reverb tank. The Ampeg Reverberocket is often cited as the first.

        Comment


        • #34
          I have one of those necklace reverbs from a PR-40 tone cab. Is there any reason to use the necklace reverb over the conventional stretched spring tank for a guitar amp? Like I need another project.

          Comment


          • #35
            Originally posted by Rhodesplyr View Post
            The Ampeg Reverberocket is often cited as the first.
            Imagine the furore that must have set off at Fender's engineering department. Beaten to the punch by some little upstart manufacturer in New Jersey. Oh, the ignominy!

            Didn't take long for Fender to dig their heels in, then dominate the market with their reverb amps. Meanwhile, score a point for Joisey!
            Enjoy. Every. Sandwich.

            Comment


            • #36
              ... and those are the battles that fast forward innovation

              Comment


              • #37
                Originally posted by TelRay View Post
                DIODES:
                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.
                That's the bias supply rectifier, not a zener so another UF4007 will be fine there.
                "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

                Comment


                • #38
                  Originally posted by Diablo View Post
                  I have one of those necklace reverbs from a PR-40 tone cab. Is there any reason to use the necklace reverb over the conventional stretched spring tank for a guitar amp? Like I need another project.
                  In the Hammond world, we tend to acknowledge the necklace reverb as the best-sounding spring reverb, but its drawback is that it's so sensitive to any motion around it like someone walking past the tone cabinet. I'm sure you could use it as a stand-alone studio reverb, but it was never suitable for something like a guitar amp that would be moved frequently. It actually has a locking mechanism you're supposed to engage if you move the tone cabinet.

                  Comment


                  • #39
                    I am thinking about ordering a replacement transistor for the REVERB RETURN, 2N2614. Just in case...
                    Anyone knows of a good modern equivalent?

                    Comment


                    • #40
                      hello all, after some days out traveling for work I'm back working on the amp.

                      After re-constructing the POWER SUPPLY section (all resistors, capacitors and diodes - marked in green in the image below) and receiving the REVERB TANK I decided to plug it in for the first time.

                      As I have recently gotten a VARIABLE ISOLATION TRANSFORMER I started at around 40 VAC... no smoke, no jump in current... and gradually increased until 120 VAC. Plugged in the guitar with the amp cranked and got a glorious distorted sound, I really liked it.

                      The REVERB worked.
                      The VIBRATO is there, a bit subtle maybe.
                      The thing is, there's no clean sound, turning down the volume there is a crackling distorted guitar sound that fades away.

                      Checking the voltages, the main thing seems to be that I am not able to get the 400 VDC shown in POINT A (I'm at half of that, 211 V) and higher than I should on the BIAS VOLTAGE, pin 8 of the 12 pin connector (-67 V instead of -50 V).

                      My first doubt: is the Hammond 369BX the right transformer for this amp? (this is the transformer I got with the amp and there were all the evidences of the original transformer to have blown)

                      Here are the voltages measured at the Transformer Secondary (green and red actual values added to the table "ELECTRICAL DATA")



                      The voltages are OK, with the exception of the one going to the HEATERS and LAMP, which is 6.3 VAC instead of 7.01 VAC. But actually the amp's schematic shows a requirement for 6.3 VAC. So, I think this is OK too.

                      Until now, the TRANSFORMER does the job according to its specification (the TRANSFORMER's spec, not the AMP's spec)

                      Here are the DC values measured:



                      I honestly tried to figure out the way to calculate the DC Voltage provided by the Half Wave rectifier (the one with the single diode) and the one provided by the 2 pair of diodes in series but I got a bit confused.

                      Is it possible to extract some conclusions from these values?
                      - transformer to small for the job?
                      - something wrong with the way I re-constructed the POWER SUPPLY SECTION?
                      - etc

                      thanks!

                      PS: tested all tubes (with a Precision Apparatus tube tester) and all seemed to be in good shape
                      Last edited by TelRay; 02-03-2020, 05:34 PM.

                      Comment


                      • #41
                        It's the transformer HV winding. Normally you would see something like 300-0-300 for that kind of rectifier arrangement (have a look at Fender Deluxe, etc.).
                        "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

                        Comment


                        • #42
                          Originally posted by g1 View Post
                          It's the transformer HV winding. Normally you would see something like 300-0-300 for that kind of rectifier arrangement (have a look at Fender Deluxe, etc.).
                          thx!!!

                          mmm... i see. can I re-engineer the rectifier to make this transformer work or do i need to go shopping for a new one?

                          the same reasoning works for both the 400 V and -50 V shown in the schematic?

                          Comment


                          • #43
                            You can use bridge rectifier with no center-tap for the HV. That will roughly double the voltage to where it should be.
                            But you will have to find a different method for the bias circuit as it will not work without the center-tap. Alternate methods would be a small separate transformer for bias, or the cap coupled type bias circuit.
                            Examples would be Ampeg V4 or Marshall JCM900 series, both using full-wave bridge and cap coupled type bias circuit.
                            "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

                            Comment


                            • #44
                              ..........or go for full cathode bias.
                              - Own Opinions Only -

                              Comment


                              • #45
                                uhhh... this is getting interesting
                                I will need to do a bit of research to get some clarity about what I should do if I want to avoid blowing up something
                                Last edited by TelRay; 02-04-2020, 03:30 AM.

                                Comment

                                Working...
                                X