1968 Deluxe Reverb refurb (pic heavy)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by infiniteposse, Apr 15, 2016.

  1. infiniteposse

    infiniteposse Member

    Messages:
    1,685
    Joined:
    Mar 2, 2006
    Location:
    PDX
    Hi all-

    This is a new-to-me 68 Deluxe Reverb that I'm going to go through and clean up for my own use. I'd like to do it right. I worked for a year under an extremely good amp tech and I'm good with the monkey side of things: I solder expertly when told where to do so:) My theory is very poor/non-existent, so I just write everything down, take pictures and go slowly and check my work.

    My hope is to get verification on the work I'm planning to do, the parts I'm planning on ordering and perhaps a good vendor to order from for a good price. My old boss is out on tour till the end of the month and I'd like to get the ball rolling, so I thought I'd get to it.

    The Deluxe came with a rather crappy set of tubes, so I'll likely retube after I'm done with the service.

    My old boss used to have me doing recaps, but my notes are all missing, so I'm going from reading I did last night, some memory of a few things and the layout drawings for the appropriate AB763 circuit. I'm planning on doing filter caps + accompanying resistors, screen grid resistors (2 resistors over each power tube?), all interior caps, bias cap, any interior resistors that tend to drift and/or be problematic. The amp does have the "brown turd" tone caps, but I'm thinking I'll take care of maintenance, make sure it's operating well and then move onto tone snobbery.

    Lastly, I'll mention that the speaker looks like a bit of an odd bird, but seems to be, based on it's codes (465-202), an Oxford of some flavor. It's a little fugly, but I'm down to try anything.

    I checked out the EL84 world page (Hoffman amps) and wrote down this parts list based on what I read. If I'm missing anything, I'd love to be schooled. In terms of specific brands, my old boss used to swear by F&T for the filter caps and then the smaller caps inside could be Sprauge (I think...Black with green writing).
    • Bias cap = 47uf/100v cap
    • Interior caps = 7 x 25uf/25volt
    • Interior resistors:
      • 100K plate load resistors x ?
      • Per Hoffman - "I only change these if the amp has an excessive amount of hiss when operating. These resistors are in a V shaped pattern usually but you may have to trace them from the tube socket to find them. Pins 1 and 6 are the plates on the pre amp tubes. You can follow those pins back to the board to find the 100K plate load resistors. On most Fender combo amps, the phase invertor tube has an 82K and a 100K plate load resistor. These resistors can be the source of bacon frying and hissing hissing noises."
    • Power tubes/Screen grids:
      • 2 x 470 ohm 3 watt metal film resistor
      • 2 x 1.5k resistor
    • Filter caps:
      • 5 x 20/500v - F&T
      • 1k/3-watt metal film resistor
      • 4.7k/3-watt metal film resistor
    Am I missing anything obvious or that you'd suggest? I'll also be re-tensioning the tube sockets, spraying out all sockets and pots, tightening all bolts/screws and re-biasing.

    Any help is greatly appreciated!

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  2. Jeff Gehring

    Jeff Gehring Silver Supporting Member

    Messages:
    4,576
    Joined:
    Jan 17, 2008
    Location:
    Kansas City area
    Got a Dremel? Get one of the circular steel brush attachments (#428). Then take the input jacks for both channels loose and push them inside the chassis -- no need to desolder. Put the nuts, washers, and star washers in a pretty small plastic cup and spray 'em with DeOxit and set aside. Chuck up the brush, and using the slowest speed setting on the Dremel, do the brass plate where the jacks make contact with it. Once that's done, swab that area with alcohol to clean it, then swab with DeOxit. You can also use the Dremel brush on the tip connector mating face of each jack, it will not mar the contact surface, but cleans and polishes it nicely. Again, clean with alcohol, then DeOxit. With a relay contact burnishing tool dipped in DeOxit, do the tip switches on the jacks. Lastly, swab out the sleeves with some DeOxit too. Once that's all done, reassemble, being sure to get the jack with the 1M on it in the #1 hole, and tighten it up.
    You can gain a few dB on the hum and noise floor of the amp this way, especially if it was pretty groaty to start with (which you would expect a 60's/70's amp to be).

    Plus, the bonus comedy reel:

     
    pdf64 and infiniteposse like this.
  3. swiveltung

    swiveltung Member

    Messages:
    14,550
    Joined:
    Feb 5, 2011
    Location:
    PNW
    Nice amp! That's a black face amp from the factory (inside) Yes do as Jeff says! those jacks often need this cleaning for sure.
    I would go with the 25uf/50v spragues now days.
    That is an oddball old Oxford alnico speaker for sure. Probably '52. I have a couple old Utahs in a 54 amp that look nearly the same as that.
    I'm a bit surprised that amp has the brown turds in it, with a Blue Ajax also. Seems like most 68 and older I've seen were all blues...? Maybe me memory is failing. Just sold a Vibrolux 68 this year with all blues though.
    The other thing is, no black vertical lines on the faceplate at the name? Was that only '67 SF? I thought it went into early '69?
    example: https://gbmedia.azureedge.net/usercontent/gear/3442763/p2_ujfax1gwl_ss.jpg
     
    Last edited: Apr 15, 2016
  4. xtian

    xtian Member

    Messages:
    1,790
    Joined:
    Dec 15, 2010
    Location:
    NorCal
    Your approach sounds good. Don't forget to check the death cap!
     
    pdf64 likes this.
  5. zenas

    zenas Member

    Messages:
    6,656
    Joined:
    Jul 1, 2011
    Wierd it's got the bigger toilet paper roll bypass and bias caps inside. Don't even see those on the late blackface amps. No big deal they're junk any way now.

    Should be five 16uf 450 volt caps under the dog house. You can replace those with 16uf 475 or rewire the first two like the bigger amps with two 80uf caps in series for 40uf where there's two 16uf in parallel now at 32uf.
    I just use all 16s.

    Oh you did have 5 20uf caps. Thought it said 2.
    Those'll work too.
     
  6. Blue Strat

    Blue Strat Member

    Messages:
    30,068
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    I assume you've played through the amp? If not, definitely do that before doing any work. You want to be sure you haven't created any new problems with the work you do.

    For the same reason I recommend checking the amp after you do small stages of work. This makes it much easier to find newly created problems (trust me, even the most experienced people make mistakes!). You can go in any direction you like, but I'd probably start with the power supply caps and test, then the internal caps, and test, etc.

    Enjoy the process!
     
    Aaron Mayo, zenas and TheWayfarer84 like this.
  7. infiniteposse

    infiniteposse Member

    Messages:
    1,685
    Joined:
    Mar 2, 2006
    Location:
    PDX
    Thanks for all the feedback.

    I demo'd the amp at the sellers house for a second but that was it. Once I got home I cracked open the doghouse and found this:

    [​IMG]

    I haven't powered it up again since:)
     
    zenas, TheWayfarer84 and Jeff Gehring like this.
  8. zenas

    zenas Member

    Messages:
    6,656
    Joined:
    Jul 1, 2011
    No point in testing those filter caps before you replace them. :)
     
    infiniteposse likes this.
  9. Jeff Gehring

    Jeff Gehring Silver Supporting Member

    Messages:
    4,576
    Joined:
    Jan 17, 2008
    Location:
    Kansas City area
    Aw c'mon, man. I think that 2nd one in the pic is just bursting with enthusiasm! Kind of funny it's splitting the end cap rather than the usual pooching out of the pressure relief vent.
     
  10. Ringo

    Ringo Supporting Member

    Messages:
    776
    Joined:
    Mar 24, 2004
    Location:
    midsouth
    Congrats , that will make a great amp after you or someone qualified goes through it. As mentioned you might want to get the mods / repairs done in stages so you can really tell the tonal differences.
    I don't know about that speaker though, if you want more clean headroom I'd suggest a more efficient newer speaker, some of the Eminence speakers are great, I've used the Red White and Blues, Cannabis Rex and GB128 in Deluxe Reverb amps, they all sound great.
    I got a beat 68 DR years ago, it was in much worse shape than yours, I restored it and played it for years.
     
    GuitarsFromMars likes this.
  11. ardpan

    ardpan Member

    Messages:
    15
    Joined:
    Jul 13, 2009
    No matter what you read on the internets don't go swapping or worse shotgunning the brown turds until after you have the amp re e-capped, strong tubes, biased, symbiotic speaker, Bf'ed any post CBSness, cleaned up wiring etc - though that amp looks very very fine. All those old coupling caps, ajax, astrons, blue drops, brown drops tempered the Fender brightness. If you still don't like the sound after you got it working right then play with cap swapping but save the turds, and note, they are fragile, the leads pull out easily on them.
     
    pdf64 likes this.
  12. infiniteposse

    infiniteposse Member

    Messages:
    1,685
    Joined:
    Mar 2, 2006
    Location:
    PDX
    Quick question: What values should I use for the 2 resistors beneath the filter caps? Existing values seem to indicate 2 x 10kOhm 2-watt resistors. Is this correct? I'll be using F&T 20/500v caps.

    Thanks!
     
  13. pdf64

    pdf64 Member

    Messages:
    5,486
    Joined:
    Aug 9, 2008
    Location:
    Staffordshire, UK.
    I suggest metal oxide type power resistors with a flame proff / retardent coating.
    But 1 watt for the 470 ohm screen grids, unless you're also adding HT fusing, but even then I think it's a good thing for those resistors to fuse if a tube shorts, especially as much of the amp's vintage premium is tied up in its iron, so it makes sense to minimise the potential duration of the transformer's exposure to fault current.
     
  14. infiniteposse

    infiniteposse Member

    Messages:
    1,685
    Joined:
    Mar 2, 2006
    Location:
    PDX
    Thanks so much for all of the feedback. Things are coming along slowly but surely.

    Today I got all of the interior caps replaced, Bias cap and resistor replaced, screen grid and snubbers replaced (@ power tubes) and the filter caps and 2 resistors all done. I'm holding off on the 100k plate resistors until after I've powered it up for the first time, but I'll likely do those as well. Disclaimer: It's not my prettiest work, but the soldering is solid and everything's clean.

    Question about the power cable upgrade. The way I did the power cable upgrade (per instructions from my boss) was to pull the death cap, put in a grounding tab onto one of the Power transformers screws and then solder the black and white cable connections onto the same place that the former power cable went. I would ground green to the newly installed tab and that was that. After reading up on the subject today, it seems like a lot of people get the accessory outlet out of the equation all together. Is this a concern if you don't. My old 79 Vibrolux is wired this way and I've never had an issue with it. I just want to work with best practices here.

    Here some shots of the progress. If anyone sees anything of concern, please don't hesitate to let me know.

    Thanks!

    Lee

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  15. Jeff Gehring

    Jeff Gehring Silver Supporting Member

    Messages:
    4,576
    Joined:
    Jan 17, 2008
    Location:
    Kansas City area
    I usually include the accessory outlet in the new wiring. I completely remove it for cleanup, then put it back in. I use new, teflon jacketed wire for the AC input wiring, and move the fuse to the hot side with the switch. The "bright" lug (as opposed to the brass lug) on the accessory outlet is where I usually land the neutral and make the join to the PT primary low side.
     
    zenas likes this.
  16. TimmyP

    TimmyP Member

    Messages:
    2,473
    Joined:
    Nov 1, 2007
    Location:
    Indianapolis
    Make sure it's wired AC cord live (black or brown) to fuse post, fuse post to switch, switch to Xformer. Then of course AC cord neutral (white or blue) to the other side of the transformer.
     
  17. infiniteposse

    infiniteposse Member

    Messages:
    1,685
    Joined:
    Mar 2, 2006
    Location:
    PDX
    I'm a very visual thinker, so I looked up a diagram that I think described what you're explaining, with the exception of leaving the extra outlet and switch left in the chain. I just wired things up like this and double-checked against the descriptions above and I think it's good. If you wouldn't mind just eyeballing it, I'd appreciate it. I'm going to wait to test until I can go to my old shop and use a variac to bring things up slowly.

    [​IMG]
     
  18. Jeff Gehring

    Jeff Gehring Silver Supporting Member

    Messages:
    4,576
    Joined:
    Jan 17, 2008
    Location:
    Kansas City area
    Looks good to me! Do you have a ground lug to solder the green wire to that slips over the PT bolt, then?
     
  19. infiniteposse

    infiniteposse Member

    Messages:
    1,685
    Joined:
    Mar 2, 2006
    Location:
    PDX
    I do. I'm going to build a bias tester tomorrow that I've had laying around for ages and then I'll drag it into the shop and bring it up slowly on the variac.

    Thanks for the eyes!
     
  20. TimmyP

    TimmyP Member

    Messages:
    2,473
    Joined:
    Nov 1, 2007
    Location:
    Indianapolis
    NO! The way you have the ground switch wired would throw a short across the mains with the switch in one of the positions. There is no reason for the ground switch to be connected at all. It is just there to fill the hole in the chassis.

    You can take a chance on the courtesy outlet being un-fused, but everything else should be. In that case the black wire of the AC cord would go to the courtesy outlet hot terminal, from the same terminal on to the fuse post in (rear), from the fuse post out to the power switch in (either), and power switch out to transformer.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice