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Thread: Sano excelsior no reverb

  1. #1
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    Sano excelsior no reverb

    This reverb is not doing anything. Not even the expected crash when hitting the tank. Of course I think I've tried everything I know to get some reaction out of it so that brings me here for help.
    This is what I've done so far. change cables, tried different tanks, measure the original and it appears to be OK, that is I'm getting readings on the ohm meter for the both transducers. There is a driver transformer so I'm thinking that an AB... style tank would work here.. Tried an AB.. tanks and an FB.... tanks with the same results.
    I have only one 6AN8 that I just got for this repair(probably should have gotten a couple, in case this one is not working).
    Trying a couple of el84s. Also swapped in a new reverb transformer with no luck there.
    Changed out the cathode bypass caps on the el84 and the 6AN8(pentode) as well.
    There's high voltage on the el84 screen and plate. I can see a signal with the scope on this tube but there's nothing on the 6AN8.
    Does anyone have an idea where to go with this?

    thanks
    pete
    Attached Files Attached Files

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    Supporting Member Jazz P Bass's Avatar
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    Is this the Sano amp that the reverb recovery goes to a separate 5" or 6" speaker?

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    Supporting Member Jazz P Bass's Avatar
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    The schematic copy with better resolution:

    Excelsior Pwr Amp 30WR-50WR.pdf

    Excelsior Preamp.pdf

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    I believe it the one you are talking about. The owner said that the 2 rectangular speaker on either side of the cab were dedicated to the reverb.Click image for larger version. 

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    Someone previous to me had wired all the speakers together parallel/series/parallel (15", 8", rectangular) in that order. How should they be wired?

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    Lifetime Member Enzo's Avatar
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    No, your guy already told you, the reverb has its own little speakers. If you wire all the speakers up to the main, then there is nothing to produce reverb sound. Look at the schematic, the reverb drive is taken off the main speaker, and the return goes to its own EL84 stage. See where it says reverb speakers?

    Wire teh small speakers to the reverb speaker output, then see what might be wrong - if anything - with the amp circuit.

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    Not sure I'm connecting this up correctly, but what I did was splice into an RCA cable and connected the shield to the negative terminal on speaker and the tip to the positive and ran the other end to the return.
    When I turn the reverb volume up it oscillates.

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    Still banging my head against the wall with this one. Anyone know what this means, where it says input on the left of the tank circled? Where does that go?


    Click image for larger version. 

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    here are some more pictures


    Click image for larger version. 

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    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Quote Originally Posted by pontiacpete View Post
    Still banging my head against the wall with this one. Anyone know what this means, where it says input on the left of the tank circled? Where does that go?


    Click image for larger version. 

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    It's not clear from the schematic, but I think it should go to main speaker output. Just wondering why there is no attenuation except for the 4 causing a high pass. I would wire something like a 100 Ohm/5W resistor in series with the 4 cap to protect the reverb transducer from excessive high frequency power and test it.

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    Thanks Helmholtz! that helped a lot. Reverb is working. Had to change the old cap on the speaker frame which was 25uf . With a new 4uf cap there's plenty of reverb. I added the in series the 100R resistor also.

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    Senior Member nevetslab's Avatar
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    Quote Originally Posted by pontiacpete View Post
    I believe it the one you are talking about. The owner said that the 2 rectangular speaker on either side of the cab were dedicated to the reverb.Click image for larger version. 

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    This is what I love about this forum. There's ALWAYS something new to discover in how stuff was built over the ages. Never until now have I seen a pair of dedicated speakers used for the Reverb, instead of the traditional re-mixing of the reverb signal in with the main audio feed. When was this built? OH, I see a date code on the Reverb Tank...6736.....1967, 36th week. So probably built late '67 or '68. Never seen one of these..........very interesting!

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    Quote Originally Posted by nevetslab View Post
    This is what I love about this forum. There's ALWAYS something new to discover in how stuff was built over the ages. Never until now have I seen a pair of dedicated speakers used for the Reverb, instead of the traditional re-mixing of the reverb signal in with the main audio feed. When was this built? OH, I see a date code on the Reverb Tank...6736.....1967, 36th week. So probably built late '67 or '68. Never seen one of these..........very interesting!
    I've seen a similar Sano, where one of the 8" speakers carried reverb only, and the 15" and other 8" handled the dry signal, with a resistor - 10 ohms IIRC - in series with the dry 8. Seems they were trying anything & everything in Irvington... My theory on weird reverb & vibrato setups, some companies were doing their best to not set off a patent infringement suit, leading to some very unusual circuits.

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    Quote Originally Posted by pontiacpete View Post
    Still banging my head against the wall with this one. Anyone know what this means, where it says input on the left of the tank circled? Where does that go?


    Click image for larger version. 

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    I just worked on an old amp with separate reverb speaker recently - can't remember the make/model at the moment, anyway the reverb spring was driven from the main amp output along with the main speaker.

    edit: It was a Guild Thunder T1.

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    Last edited by dmeek; 06-13-2019 at 08:17 PM.

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    I think that deriving the reverb drive from the speaker out is actually a superior concept regarding natural reverb sound. This way the reverb drive receives the sound information of the complete amp sound chain and undesirable reverb distortion by output stage clipping is avoided. Processing of the reverb recovery signal requires a separate power amp and speaker and preferably some filtering. Both could be achieved e.g. by an active monitor with Baxandall E.Q.

    IIRC, Chuck H reported to occasionally having employed a similar concept.

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