Would this old Gibson scare you away?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by xilef_regnu, Apr 16, 2008.

  1. xilef_regnu

    xilef_regnu Member

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    Hi,
    I am checking this amp out for possible purchase and am still a neophyte when it comes to knowing what to look for.

    The amp seems to play fine(all features work) except for 2 things:

    1) When switched to standby, there is a big volume swell.

    2) It's not very loud. On 10 it's just loud-ish. If you run a pedal or preamp into it it does get much louder.

    Here's some pics.

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    She really sounds pretty sweet and the reverb/tremolo are nice.



    Any insight you all can offer would be greatly appreciated.
     
  2. vibroverbus

    vibroverbus Member

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    Two different questions... first one would be 'of course I wouldn't be scared off, but then again I'm stupid and have lots of doorstop boat anchors already'. But of course 'at what price' is the issue. Your second question is 'why too quiet'.

    To address the first more seriously, I don't know these amps at all but what the heck... Hopefully somebody who knows these in and out will comment. Your pics actually would be MUCH more helpful if you had a lot more looking straight down on the circuit board, but there's a few things right off the bat that jump out as being a bit of a mess. No idea what that wad of foam is (could it possibly be a factory Gibson thing!?), that hanging cap underneath is totally bogus and probably dangerous, and the other various wires coming out the bottom don't look right. What's the grey wire coming out of the chassis at the base of one of the pre-amp tubes? Trannies look clean and tight (and big) but of course appearance doesn't count for much. I assume the cardboard tube that almost looks from afar almost like an old cap is something weird like the LDR and lamp for the reverb or something, which would be fine. Looks to me that there are a few different kinds & gauges of wire - the thicker stuff that has nice 'lead dress' bends in them are clearly OEM, while some of the thinner stuff looks just tossed in. Maybe this is factory, but I doubt it, and some of the lead-dress string has been chopped up - some to be expected from servicing the caps but looks like more than just that from a quick glance. Somebody's replaced all the electrolytics (fine in and of itself), including the hanging weirdo, but it kind of looks to be short of enough filter caps unless there's something I'm not seeing from the pics... The cabinet is in reasonable shape, if the trannies test out OK it'd be worth at least good 'core' value for a rebuild.

    Regarding your second question about being too quiet, tubes are first question - new/used/unknown? I'd be wary of that sketchy cap hanging out in space, and a little afraid to toss any great tubes in there without a rundown on if all the wiring is OK... A little volume swell isn't a big deal, probably just caps discharging as you shut it off...

    What does it have for a speaker driver?
     
  3. xilef_regnu

    xilef_regnu Member

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    Thanks for your reply!

    I'll try to cover some of what you brought up. The gray wire goes to the reverb/tremolo footswitch. The cardboard tube IS some kind of cap. I'm not sure what lead-dress string is... The cap hanging next to the tubes seems very odd to me as well.

    The amp has been re-capped and re-tubed. Sprague caps and JJ and Sovtek tubes. The recap apparently was done in stages by two different people. Also, a 3-pronger was added. I don't know how to check the trannies for proper output or I would. CTS speakers date code to '64.

    I've recently played a very similar amp(the Crestline GA-77 RVT with 1-15" speaker) and it was considerably louder than this one (although I didn't A-B them). Considering the wattage the amp does not get very loud. It does, however, run quietly and sounds very musical. Only other thing I've noticed soundwise is the amp seems to overemphasize the sounds of the pick hitting the string(plastic on metal), it's very audible.

    Thanks again for your thoughts.

    Here are some more pics per your suggestion:

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  4. vibroverbus

    vibroverbus Member

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    'lead dress string' is that string that's tying the wires up in places.

    actually looks like some of the work was done quite nicely. some of it's still an atrocious mess.

    but the reason it's so quiet is there's only one speaker connected! can't drive a speaker with just one side connected! wire up the other side... :jo:jo:jo

    what is that crazy contraption in the bottom? at first I thought transformer for an old field-coil type speaker but that wouldn't make sense - this was too late for that and has a huge transformer anyway.

    speaker wires look a mess so I'd bet those speakers not original even if they are 'period'.
     
  5. Trout

    Trout Member

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    I may be mistaken, but isnt that the mechanical echo unit?

    Mode 1 simulates a room reverberation with soft a echo
    Mode 2 simulates a reverberation with a BOLD echo
    Mode 3 is same as above with a faster echo rate.

    Those are not especially common amps, Schematic Vangard GA77-RET. I have only seen 2 others in 30 years and they were on display in a music store at least 25 years ago. I never even gave them a glance back then.

    It does look like it has seen several trips to various levels of techs, but IMO it would be a great amp at the right price. Then carefully restore it to its former glory(or at least a good wiring touch up)

    Trout
     
  6. PRNDL

    PRNDL Member

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    Most likely there's an issue with an electrolytic in the power supply.
    Check them by measuring their resistance, which should be K or M ohms, or the value of the resistor in parallel.

    This is common in older amps like this.
    Is the instrument channel louder?


    Most likely there was a cap can attached to the piece of metal riveted to the chassis.

    That's how these old Gibsons sound ... very unique and more like a HiFi amp.

    It's my belief that many of the songs from that era were written and played that way because the guitars and amps had a completely different feel and tone than modern gear.

    I saw two similar Gibson amps recently at Rodgers shop (fixed one myself), and had some fun jumping the two channels together, which gave some interesting overtones (from the tremolo) to the crunch from the instrument channel.

    Yours looks like it's been completely rebuilt using carbon comps and orange drops.
     
  7. xilef_regnu

    xilef_regnu Member

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    Thanks for all replies!

    To remove the head from the amp I had to unsolder the speaker connections, I think that is what you're seeing.

    Here's a pic of a similar amp showing the original cap at the speaker wires.

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    As Trout has accurately identified, the 'contraption' is a Tel-Ray Adineko oil can reverb/delay unit which is a fun thing about this amp.

    http://www.geocities.com/tel_ray/

    What kind of price for this would be appropriate considering the work that should be done on it?
     
  8. brad347

    brad347 Member

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    To answer an earlier question, the piece of foam in the amp looks to be in place to shield light from the LDR/opto unit in the trem, thereby making the trem effect more pronounced.
     
  9. vibroverbus

    vibroverbus Member

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    OK, yours still has a big mess of wire, not sure how exactly the leads are supposed to come in there... are those speakers in series so a lead goes to each speaker? then why would it have all the rest of that wire mess going to the bottom? Maybe I'm just not getting it...
     
  10. xilef_regnu

    xilef_regnu Member

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    What you're seeing is a disconnected power connection to the reverb/delay mounted at the bottom of the cab(red plug) and 3 audio connectors from the same unit to cover it's 3 settings(gray triple RCA plugs). In the picture below the gray cable that emerges from the amp head near the transformer on the right is for the reverb/tremolo footswitch.

    Yes, the speakers are wired in series.

    Here's a pic with everything hooked up:

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  11. vibroverbus

    vibroverbus Member

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    Ahhh... I get it! The other pic made the power connection look like it connected to the left speakers terminals. Now I see it was just draped over that... Man that disconnected speaker wire seemed like such an easy answer too!
    :eek:

    Re: how much worth... always a complicated question... value predicated by 'to who' of course. especially with the crazy ripoff prices you see on junk stuff since the eBay era... but typically with any collectible item you start with an estimated market value for a mint restored one. Do two calculations:
    1. Deduct accepted rule-of-thumb amounts for various flaws like "less 10% for general wear-and-tear, %10-20 for non-original speaker, less another %10-20 for general molestation and non-original caps/resistors mess, less %10-20 for unknown volume problem"
    2. Then starting again with 'restored value', deduct quick estimate of restoration "$100 for general parts, 4 hours at $50-100/hr, $300 for correct original speaker and baffle... etc."
    Ruling out the "get an unsuspecting eBay chump to pay too much", value will be the higher of the two - flawed items (example: worn out collectible sports cars) are often worth much more than their full repair/restoration cost, but can't be worth any less (or else its a good profit opportunity to restore it).
     
  12. alltone

    alltone Member

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    I had & sold one of these guys a couple of years ago in good /original condition for $350.00. I think to the right person, one of these ,functioning should probably top out at $450.00 today.:argue
     
  13. Swarty

    Swarty Member

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    FWIW, I don't know if it's because I'm in Michigan, but I see lots of Gibson amps and have repaired scores for Elderly. This is IMO the worst era for Gibson amps, but the squirrel can echo is pretty cool, especially if it is still functional (the fluid often drys out). I might add $100 to the above price estimate if it works perfectly.
     
  14. donnyjaguar

    donnyjaguar Member

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    This is an interesting amplifier. I'd go as high as 200$ myself in its current condition. Twice that if it were bone stock.
     
  15. lastwinj

    lastwinj Member

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    I too have noticed vintage 2x12 combos being not too loud. and were in perfect working condition. nature of the beast.
     
  16. capnjuan

    capnjuan Member

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    Hi xilef: The 'Echo' unit was designed by Ray Lebow in the early 60s and licensed it to Fender, Gibson, and others. I have a GA4RE which has the same mechanism installed in a cabinet that looks like an outboard reverb unit. This is the URL to the Oil Can Addicts BB http://p200.ezboard.com/btelrayoilcanaddicts The BB's software, like the 'Echo' mechanism, can be a little cranky. At 40+ years old;these units come in two types; working and dead and their physics is poorly understood by most people. If you're interested, browse the Oil Can BB; you'll find people screaming about how to resurrect dead cans.

    If your's is working correctly, you should get something close to a conventional reverb sound at one end of the pot and a very interesting warbly, wailing, piercing tone at the other; if the latter isn't present, then your Echo machine isn't working correctly. The oil can be bought from an eBay vendor; if you can't find it, PM/email me here or over on the LTG BB - I have some you can have.

    The two critical aspects of these are the physical condition of the rotating aluminum disc in the can and the drive belt. If the disc is corroded or damaged, except for replacing it with another known good, there is no bringing it back. The motor turns a flywheel with a belt that really is an O-ring; if you have an O-ring on it and the unit doesn't 'warble', you need to find the right size. The one on it will have stretched so you can't rely just on its diameter; gotta buy several somewhat smaller ones.

    Finally, I agree w/ the other posters re/ the chaotic wire dress. I also am not sure that the Orange Drops are original; the filter caps aren't but the reason for mentioning is that the smaller cathode caps are original. Without arguing 'authenticity', IMO it's good practice to change these caps at least when the filter caps are changed if not more frequently; others may feel differently but I think of this as maintenance, not modification and somebody, tech or owner, has overlooked them.

    Good luck w/ your decision and your amp. Regards, capnjuan
     
  17. Swarty

    Swarty Member

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    The orange drops are original.
     
  18. xilef_regnu

    xilef_regnu Member

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    Hey Cap'n,
    The 'squirrel can' seems to be working fine and is neat sounding. Like an echo in a well. An oil well that is.:)

    Thanks for the info!
     
  19. mopro

    mopro Member

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    WOW, after 37 years, I finally found my GA77's twin brother! You're right about it not being a loud amp. Mine can perform on a par with a Fender Deluxe Reverb when both of them are set from 8 to 10, but at 3, the Fender will blow it away.

    It's not a rocker's amp, unless you load it up with stomp boxes, and not at all a good sounding box. It was meant to be played clean and was aimed at jazz players. In the late 50s and early 60s, a lot of jazz guitarists were complaining about the very same distortion we now prize, and I guess this was Gibson's answer.

    I wish mine still had the oilcan, which was stolen from me years ago by a St. Louis amp repairman named Paul Bowen. I hope you know not to open it or mess with it unless you really know what you're doing. The capacitor fluid inside is dangerously carcinogenic (I take a little comfort in the thought that Mr. Bowen may have messed with it enough to get a killer dose).

    Yours does not have the original Gibson-branded speakers, which I very foolishly had replaced when I was 17 years old, and was too stupid to know that I was supposed to ask for the old ones back. I have no idea who manufactured them.

    I have a schematic for this amp if you want.
     
  20. phsyconoodler

    phsyconoodler Member

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    I don't know if anyone mentioned it,but both the power and output transformers have been changed.Gibson's units were smaller and the OT was open with no bell covers.Those are both new units.
    Those speakers are likely why the amp is not loud.They are probably pretty low SPL.
    It also may have an impedance mismatch,judging by the sloppy work done with the filter caps.That might be the reason for low volume too.Lots of 'if's' with that amp.Who knows what all has been done?

    Edit: I may be wrong,as the other amp with the 15" speaker has the same tranny's???
     

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