Results 1 to 16 of 16

Thread: Redplating Fender Super Twin Reverb.

  1. #1
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0

    Redplating Fender Super Twin Reverb.

    Hi,

    New here, but have had success in the past with other forums!! I have a '78 Fender Super Twin Reverb (blackface) that has a power tube redplating. I know it's a beast, and some say to put it out on the curb. But it's loud if not heavy. The first tube from the power side is redplating. I pulled the chassis, and the 2 resistors on # 3 are burned to a crips. Everything I've read pertain to 4 power tube amps, this has 6. So I want to replace the resistors and see what happens, maybe still redplating. I quess my question is where can I find replacement resistors?. RadioShack? Thanks, Mark.

    0 Not allowed! Not allowed!

  2. #2
    Supporting Member Randall's Avatar
    Join Date
    Jan 2013
    Location
    Cape Coral, FL
    Posts
    1,781
    Thumbs Up/Down
    Received: 110/0
    Given: 16/0
    Antique Electronics Supply for all your amp needs https://www.tubesandmore.com/

    Or Mouser when you need to go a little deeper https://www.mouser.com/

    Consider replacing that tube.

    0 Not allowed! Not allowed!
    It's weird, because it WAS working fine.....

  3. #3
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks Randall, is it weird that the tube with the bad resistors isn't redplating? I've 2 new tubes!

    0 Not allowed! Not allowed!

  4. #4
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    2,717
    Thumbs Up/Down
    Received: 264/4
    Given: 558/11
    Just an FYI, don't let the cosmetics fool you: this thing is about as far from a BlackFace amp as you can get. It's not a Super "Twin Reverb." It's a "Super Twin" WITH Reverb. The first gain stage is different, the Tone Stacks are different, the output is different, etc. About the only thing it has in common with a Twin Reverb is the 2x12" speakers.

    This thing is more akin to the 400PS, 300PS, & PA160.

    Justin

    0 Not allowed! Not allowed!
    Last edited by tboy; 12-01-2017 at 08:25 AM. Reason: typo
    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  5. #5
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,452
    Thumbs Up/Down
    Received: 181/2
    Given: 84/0

    0 Not allowed! Not allowed!

  6. #6
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,452
    Thumbs Up/Down
    Received: 181/2
    Given: 84/0
    Quote Originally Posted by Mljbone View Post
    Thanks Randall, is it weird that the tube with the bad resistors isn't redplating? I've 2 new tubes!
    If the 470 ohm screen resistor is open, then the tube will not conduct.
    Hence, no red plating.

    0 Not allowed! Not allowed!

  7. #7
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Location
    Chicago, USA
    Posts
    4,908
    Thumbs Up/Down
    Received: 60/0
    Given: 0/0
    I never thought of the first gain stage cap making all that much difference; whenever i work on any of those amps I end up diode biasing that stage and making them all sound the same.

    I can't hang my hat on that treble cap in the tonestack making all that much difference either. Yeah, it's different, but not like it's night and day.

    I always thought that the additional gain stage is what made the preamp different, in a way that isn't particularly that appealing. What else is different? Perhaps most significant to me is that the STR is a single channel amp that lacks tremolo, while the TR is a conventional Fender dual channel tremolo amp. That tremolo difference is HUGE!

    The STR is an amp that appeals to an entirely different kind of player than a BFTR, IMO.

    0 Not allowed! Not allowed!
    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

  8. #8
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks for the input! I picked up 470 ohm and 1500 resistors to replace on that power tube socket. But they are 2 watt , I'm not sure if that makes a difference I think they need to be 1 Watt. Also is there a way to tighten up the power tube connections inside the socket, some of them look like they're open. I was told loose ones could cause my red plating problem. THANKS!

    0 Not allowed! Not allowed!

  9. #9
    Senior Member nevetslab's Avatar
    Join Date
    Apr 2010
    Location
    Burbank, CA
    Posts
    1,038
    Thumbs Up/Down
    Received: 219/1
    Given: 545/1
    When you look down the tube socket insets, are they wrap-around or fork-style terminals? The wrap-around type are easy to re-tension, using a very tiny bladed screwdriver to somewhat close down the opening without preventing pin insertion in the process. The forked terminals require a much smaller but stiff tool that can enter in the narrow slot that keeps them captive and aligned for mating with the tube pin. They're a bit tricky to bend in a bit in the attempt to make a tighter fit again.

    With regards to the wattage on the screen resistors, I normally use Metal Oxide power resistors. There are two sizes available for each wattage up to 5W. MO2 is the larger 2W body size, and MO2S is a smaller 2W body. A MO2S looks like a MO1 in size. The real difference is surface temperature under load. A MO2S will run hotter than a MO2

    0 Not allowed! Not allowed!
    Logic is an organized way of going wrong with confidence

  10. #10
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks nevetslab, they're wrap around.

    0 Not allowed! Not allowed!

  11. #11
    Supporting Member Randall's Avatar
    Join Date
    Jan 2013
    Location
    Cape Coral, FL
    Posts
    1,781
    Thumbs Up/Down
    Received: 110/0
    Given: 16/0
    With regards to your resistor wattage question, you can always go up in wattage with resistors. A 1 watt is built to withstand 1 watt of power, where a 2 watt will withstand 2 watts of power, so in your case, not a bad thing to go to 2 watts.

    0 Not allowed! Not allowed!
    It's weird, because it WAS working fine.....

  12. #12
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks Randall!

    0 Not allowed! Not allowed!

  13. #13
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    So I replaced the resistors on the 3rd power tube socket. Plugged the head in to check output on pin number 5 on all sockets. Started with the first 3 with -53.6v the others at -49.1v. Waited a minute or two and went back to check output. They climbed up to -59.1v and -53.4. Then the resistors on first socket zorched and the fuse burned out. This socket is the one with red plating issues. Any ideas?

    0 Not allowed! Not allowed!

  14. #14
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    30,941
    Thumbs Up/Down
    Received: 892/5
    Given: 0/0
    You have an obvious arc, if there were no tubes. The resistor has no circuit, it goes to a socket pin and stops. Even with a tube in the socket, it goes to a grid, which is a wire hanging in space. To get that resistor to burn up, it has to have current from somewher, and most likely is pin 4 next to is, several hundred volts different. I'd replace that socket.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  15. #15
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks for the information Enzo!

    0 Not allowed! Not allowed!

  16. #16
    Junior Member
    Join Date
    Nov 2017
    Posts
    8
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    I replace resistors, cleaned and tightened up terminals on sockets. No redplating, amp sounds "great". Thanks all for the help!

    0 Not allowed! Not allowed!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Fender red knob twin vs Fender twin reverb 65 reissue clean channel with Les Paul
    By jalexquijano in forum Maintenance, Troubleshooting & Repair
    Replies: 3
    Last Post: 11-20-2017, 03:34 AM
  2. Add Line In: Fender Super Twin Reverb?
    By tbryanh in forum Theory & Design
    Replies: 1
    Last Post: 01-06-2014, 05:27 PM
  3. Fender Super Twin Reverb with 6 6l6gc's
    By Jay D in forum Maintenance, Troubleshooting & Repair
    Replies: 15
    Last Post: 10-26-2011, 11:05 AM
  4. Super Twin Reverb
    By imaradiostar in forum Maintenance, Troubleshooting & Repair
    Replies: 4
    Last Post: 04-02-2010, 01:17 PM
  5. Super Twin Reverb Mods
    By joethefenderdude in forum Mods & Tweaks
    Replies: 4
    Last Post: 10-26-2006, 05:04 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •