Zinky Blue Velvet- reverb not working

Discussion in 'Amp Tech Center' started by soul-o, Jun 19, 2015.

  1. soul-o

    soul-o Friend of Leo's

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    LOVE this amp and it has never let me down. Honestly, I haven't had the need for the reverb on this much, but was dismayed to find that it doesn't work now. How does that circuit work on an amp like this, anyway? The tube is good. The RCAs going into the reverb pan seem solid. I don't have an official Zinky foot switch, but I have tried it with a variety of other switches and cables (both mono and TRS) and all I get is buzz when I turn the reverb knob up.

    It's the one area of an amp circuit that I'm not so sure about. I assume the RCAs send signal through the reverb spring and then return it back into the circuit.
     
  2. syrynx

    syrynx Tele-Afflicted

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    They do, and that's the first place to check. Disconnect and reinsert each of the RCA plugs several times and rotate them, to try to make sure the connections are good. If that doesn't work, pull the RCA plugs and sqeeze the sleeve connectors gently with pliers, to make sure they make good contact with the sleeves of the jacks. If you have an ohmmeter available, you might also measure the resistances through the tank. Sleeve to sleeve should be very low, only slightly above 0 ohms. The tip to tip reading through the springs should be higher, but still low. If no joy, you might have to get at the tip connector sleeves of the RCA jacks to squeeze them gently, insuring good contact with the tips of the RCA plugs.

    If the connections are good and you measure continuity through the tank, maybe the reverb driver stage has a problem. We don't think there's a problem with the reverb recovery stage, since you hear a buzz when you turn the reverb knob up. (Mostly we hates buzzes in amps, we does, but in this instance I take it as a good sign, indicating that the reverb recovery amp is working properly and is merely being deprived of its appropriate input signal.) Swapping tubes around to different sockets might reveal whether this is the problem.
     
  3. Wally

    Wally Telefied Ad Free Member

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    Zinky amp...one would suppose that the reverb is in the tube domain. Soul O, you say
    "the tube is good". Do you have a schematic for this amp? IT is likely that the reverb uses perhaps 1 1/2 12A_7 tubes. There are reverb circuits that use only one 12A_7, though. IT would be handy to know which tube or tubes are involved in the circuit. Good advice from syrynx on troubleshooting this.
    Most reverbs work without a switch. PUll the switch out of the amp...what happens to the rever? Fwiw, these days I am cautious about what pedal I plug into what amp because sometimes the circuit does some things that necessitate a special switch.
    Does the reverb still buzz? IF not, can you get any reverb action by shaking/slapping the amp? IF so, the reverb return signal is good. IF not, that part of the circuit is dead...for whatever treason.
    Fwiw, the ohmmeter readings on the tank's transducers....at the end of the cable or at the jacks on the tank or at the connections at the transducers inside the tank....will vary depending on what type of circuit is there and the parameters of the components in that circuit. IF you don't get good readings at the plugs on the cables, go to the tank and check out the transducers directly. Sometimes cables are bad, sometimes transducers are bad...and sometimes there will be a little wire that has a broken connection. Fix that and sometimes the reverb comes back online.
     
  4. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    IME, this is the cause of 90% of reverb troubles.
    Especially if your amp spends a lot of time riding to and from gigs.
     
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