Announcement

Collapse
No announcement yet.

Weird reverb tank issue

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

  • Weird reverb tank issue

    Working on a '84 JCM800 with reverb not working. Turns out it was just a bad RCA jack connection, but I sure chased my tail for a while. Rather than taking the tank out of the head chassis, I grabbed a used one of the shelf and wired it up. The drive signal was there, and I got spring noise if I touched them, but it was along with a loud sputter that went away with the reverb control. I checked the parts around the recovery triode, everything looked good. I grounded the base of the mute transistor, nothing changed. All I had to do was touch or move the tank slightly and there was a loud sputter. Wasn't making sense.

    It was then I decided to check his tank, and found it did not cause this sputter sound. I cleaned and tightened up the jacks and it worked fine. I think my tank was actually producing reverb, but the sputter was so loud I couldn't turn up the control enough to really tell.

    So what was I experiencing? The original tank is a 4DB3C1B, and my test tank is a 9BB2C1C with one of the three springs missing.
    It's weird, because it WAS working fine.....

  • #2
    Well there's a small difference in the respective units input impedance. That might cause some sort of anomalous circuit behavior.
    "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

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

    Comment


    • #3
      Yes, that's as far as I got with it as well.
      It's weird, because it WAS working fine.....

      Comment


      • #4
        Without looking up the code numbers, it could be that the grounding scheme of the two tanks were different.

        When the original tank was in place, a bad connection could have ungrounded the shell, while the other tank wasn't grounded by design.

        Comment

        Working...
        X