HELP! Tube question for '69 Deluxe Reverb

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Mark Ray, Apr 21, 2003.

  1. Mark Ray

    Mark Ray We're Jammin' Gold Supporting Member

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    Hey everyone, as a long time Marshall/EL34 user, I have no experience with anything like an amp I have here at the house right now. It's a '69 Fender Deluxe Reverb, in very good shape for it's age. However, it's missing one of the power tubes. The one that's left is a 6L6. The chart on the inside of the amp lists the two power tubes as 6V6. What's the deal? Are those two tubes interchangeable? I'm checking it out for someone who is looking for a platform for a Fuchs mod, and need to know. A buddy is coming over tonight with a set of tubes that came out of his 60's Band Master. They still work, so I can at least check out the operation of the amp. Just need to know for sure about which tubes to use.

    Thanks, Mark
     
  2. forestryguy

    forestryguy Member

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    I owned a Deluxe Reverb back in the sixties. I am sure that we used two 6V6. I do not know if they are interchangeable with other types. The Fender website list the following for the Vintage re-issue:3 X 12AX7, 2 X 12AT7, 2 X 6V6, 1 X 5AR4 RectifierTube.
     
  3. FlyingVBlues

    FlyingVBlues Gold Supporting Member

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    The blackface Deluxe Reverbs made from 1963-1968 and the silverface Deluxe Reverbs made from 1968-1979 used 2 6V6's. However, you can use a matched pair of 5881's,6L6GA's,6L6GB's,6L6WGB's or Visseaux 6L6G's in silver and blackface Deluxe Reverbs. Make sure you re-bias the amp when you replace the tubes.
     
  4. John Phillips

    John Phillips Member

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    They are not directly interchangeable. Unless it's been modded, it will not have enough bias voltage to run 6L6s safely - the change is beyond the range of the bias trimmer.

    It can be modded though - it's quite a popular thing to do as it increases the clean headroom and bottom-end of the amp quite a bit. You need to change one resistor to do this.

    In theory, you should need to halve the speaker impedance load because 6L6s have roughly half the impedance of 6V6s, but in practice it appears that the amp was not designed 'ideally' for 6V6s anyway, and 6L6s are no worse a mismatch, or may even be closer, for the stock 8-ohm speaker.

    There is some debate as to whether the PT can handle the extra filament current draw reliably too.

    If you are in any doubt at all, fit 6V6s.

    If you do, and you can't get a clear clean sound (you hear 'nasty' sounding distortion which is probably crossover distortion) the amp probably has been rebiased for 6L6s. In this case, I would get it checked over by a tech before going any further.

    If you do want to test it with the 6L6s, watch the tubes VERY carefully when you flip the standby to 'play' - and for several minutes afterwards. Any sign of overheating at all and the amp is probably still biased for 6V6s.

    If you have a voltmeter, you could also try measuring the voltage on pin 5 of the tube sockets - you can do this with the standby to 'mute' and no tubes in. You should get about -35V for 6V6s and -50V for 6L6s.
     
  5. Mark Ray

    Mark Ray We're Jammin' Gold Supporting Member

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    Thanks for the info guys!

    Mark
     
  6. jayn

    jayn Member

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    Check out the rectifier tube. A Deluxe with 6L6's should have a solid state rectifier (either none in the tube slot or a non-tube plug in).

    Ideally, it should have some changes in the filter caps too (parallel...) and probably a few other changes too...

    Don't mod that thing! A few changes and they are just the sweetest amps. I just bought a '69 and freshened it up with some NOS tubes and new caps and it sounds fantastic.
     
  7. kevmin

    kevmin Member

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    Even a late 60's Deluxe Reverb is a valuable vintage amplifier that is sought after. It will continue to increase in value if well cared for. Your friend would be better off having a reissue DR modded by Fuchs. IMHO
     
  8. Fuchsaudio

    Fuchsaudio Member

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    I agree with the concept of not hacking anything "really vintage". Anytime I've done anything remotely vintage, it was a basketcase or previously hacked.

    The Deluxes (even trashed up or the reissues) are decent mod platforms, as are Bassmans. As long as the iron is good, everything is gutted anyway, so beat-up stuff is even more a bargain. Theres a few sources of combo cabinets for Bassman sized chassis on the market too. I have also done some Music Man HD-65 combos that came out pretty nice as well. Another sleeper-cell is: the Bassman-70, and the Rivera Era Concert and Fender 75's. In the lower end of the spectrum these things just really kick booty when redone. They just seem to be really good iron buried by less than optimal circuitry.

    I do think a 12" is the best driver. I've heard the modded amps with 2X10's and although "fast and detailed" seem to lack the ummmmpf a 12 brings to the party.

    The benefits of switching to 6L6's are negligible. The filament current is one issue. Going to solid state rectifiers is cool, as is a fan (which holds down chassis and power transformer temps), but there's little if any increase in power anyway. Juicing up the supply caps is a good idea as well. The first two banks should be 100uf or better. Fast switching rectifier diodes on main B+ and bias supply too. For fun, you can use the old 5-V supply to make a shweeet DC supply for the low level tubes, which can make things nice and quiet.
     
  9. gitarzilla

    gitarzilla Member

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    A 69 Deluxe, in decent shape, is a nice find. Should still be pretty much blackface on the inside. THat amp should use 6V6s and a 5AR4/GZ34 tube rectifier. Because of the dearth of decent current production 6V6s, a lot of people either convert their Deluxes to 6L6s or just shove a pair of 6L6s in there and hope for the best. THis all brings up an interesting and much debated topic re: NOS vs current production tubes. While there are some really good sounding and fairly rugged and long lasting 6L6s, EL34s, EL84s, KT66s, preamp tubes, etc. There aren't really any good current production 6V6s. THe ElectroHarmonix (branded -- actually made by Sovtek) aren't bad in Princetons, but do not tolerate Deluxe plate voltages regardless of what their ads say, and if they do, it won't be for long. And when they go, they usually take some resistors withh them. So... the choices seem to be:

    convert to 6L6s -- forfeit originality and the sweetness of 6V6s

    run the EH 6V6s if you don't regularly depend on the amp at gigs, recording sessions, etc. and won't be too bothered when it dies unexpectedly

    pony up for decent NOS 6V6s -- getting scarce, but they're out there. The thing is, once you spring for some nice NOS RCAs or Brimars, their longevity (provided all else is well in the amp) will be measured in years as opposed to months with the EHs.
     
  10. Mark Ray

    Mark Ray We're Jammin' Gold Supporting Member

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    I owned a Carr Slant6V for a while, and the EH 6V6's in it seemed to be pretty decent. Of course that's a totally different amp. Unfortunately Knoxville isn't known as a great tube source, and I'm doing the owner of the amp a favor by trying to find some tubes for it. The problem is that the deceased family member who left this amp to him didn't leave any info or tell anyone about any particulars of the amp. He may have converted it to 6L6's, but I sure wouldn't know how to check for that. There is one amp tech guy here in town that I would trust to go through it, but it's not my amp, and I don't think Eddie (owner) wants to put any money into it. (He's a drummer, and strapped for cash big time).

    The mystery continues.

    Mark
     
  11. kevmin

    kevmin Member

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    The bias pot is mounted in the bottom of the chassis between the power transformer and the circuitboard. (It is made to be adjusted with a screwdriver.) If the resistor that is on it is a 10K, then it is still set up for 6V6's. If it has been changed to a 27K, then it has been modded to accept 6L6's.

    A word of caution, don't use a solid state rectifier in that amp unless it is set up for 6L6's.
     
  12. Mark Ray

    Mark Ray We're Jammin' Gold Supporting Member

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    kevmin, thanks for the tip. I'll check that out. The rectifier tube is in the amp, and works.

    Mark
     

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