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Gibson GA45RVT reverb died.

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  • Gibson GA45RVT reverb died.

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    I get a healthy signal into V2A, a strong signal into the transformer primary, and a strong signal out of the transformer into the reverb tank. Then the fun begins. The output of the tank is simply a shielded RCA male to RCA male cable. If I scope the bare plug I get a signal from the tank. If I ground the plug shield, the signal dies. I've never seen this type of problem with a reverb tank. The input to the tank is spade lug connectors to the transformer and RCA male to the tank input. All the connections look good according to an ohmmeter check. I've tried reversing the connections of the spade lug connectors. The transformer doesn't read shorted by an ohmmeter check. Any ideas?

  • #2
    Isolate the problem. You have working drive? OK, check the return. power on, reverb pan not connected. touch something metal to the center pin on the return jack, where the reverb cable would go. You should get loud hum, do you? If not, check for shorted shielded wire from jack to tube. Or C45 could be shorted. The tube is a 6EU7. SWap places with another 6EU7 on the amp. ANy difference?

    You have the RCA cable. Is it shorted shield to center? Is it wired correct? SHield to shield and center to center?

    Plug some other RCA cable into the pan output jack, and run it to the input of some other amp. get reverb sound over there?

    Make sure you don't have pan IN and OUT reversed.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Re-flowed the amplifier / reverb trans. connections and replaced C47. Also re-cleaned the reverb tank connectors. Now I'm getting a hot signal on the reverb side of C47, but the signal goes way down on the other side. Maybe the tremolo bug is eating the signal. Thanks for your ideas Enzo. I'll pick this back up in a couple of days

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      • #4
        Trem bug has a 270k resistor between it and the C47. Is your foot switch plugged in? Try unplugging it if so. Measure resistance to ground from the right hand end of C47. SHorted or low resistance? If the trem bug were shorted, it would ground off the grid of V4a and kill that entire channel. I doubt it is the bug. If R72 is not open, then explore the wires to the FS jack.
        Education is what you're left with after you have forgotten what you have learned.

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