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Just picked up a 50's tweed pro and need some help!

Discussion in 'Amp Central Station' started by Twangbanger, Apr 22, 2004.

  1. Twangbanger

    Twangbanger Tele-Holic

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    Ok, amp tech I know, has had this early tweed pro. I picked it up for 250, due to the guy that ownes it has no time for it and owes the tech lots of money. The deal was legit on everyones behalf, but really good on mine. This one uses the 6sn7's. Model 5B5.

    My problem is that I need to re-tweed and replace the speaker(radio shack). It has the original tweed on the back covers.

    The covering is burlap with what appears to be shellac or epoxy. It has an orange faded tint, which makes me believe shellac. I think it is the original grill, but it looks similair to door screening.

    I know where to get tweed and I wonder if I should get a same era speaker, reissue Jensen, or Weber.

    I know that I have a gem on my hands, just got to polish it up a bit.

    Thanx before anyone ever posts.
     
  2. Twangbanger

    Twangbanger Tele-Holic

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    Oh, yeah, how do I remove light oxidation or rust off of the control panel. All of the screen printing is still there and I don't want to mess it up.

    Do I use vinegar
     
  3. Twangbanger

    Twangbanger Tele-Holic

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    Just to add this.
    There are 6v6's in it but the chart calls for 6l6's. Also the power tranny is original, but the output looks like it's from a 60's/70's fender
    code:
    95-1698-a
    172 6910
     
  4. dean

    dean Friend of Leo's

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    What do you want to do with it?

    When I stumble across a deal like that, I eventually have to decide what my ultimate goal is going to be. I almost always say I'm going to keep something, but usually, I realize that I'll be selling it.

    Regardless of whether you keep it or sell it, get it working as well as possible - caps, tubes, good speaker (Weber), 3-prong cord and plug, etc. At this point, if I wasn't going to keep it, I'd let it go and allow someone else to have all the rest of the fun.

    Then, think about the cosmetics. Maybe strip the burlap and sand the cabinet and leave it like that for a while - see how much you like it. The retweed would be the last thing I'd do. If the amp was going to be a keeper, I'd do a retweed and probably try to relic it a bit - get it looking as close to original as possible.

    The corrosion on the control panel can be a problem. I generally use a plastic spoon or something of the consistency of my thumbnail and scrape it off with that. The plastic won't scratch the chrome but will take off any of the surface corrosion. The deep corrosion may not come off. I'll also use a metal cleaner/polisher.

    Sounds like you got a great deal on a super-cool amp. What model number is on the tube chart?

    Have fun!

    Dean
     
  5. Twangbanger

    Twangbanger Tele-Holic

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    5B5

    I cleaned the control plate with vinegar and a tooth brush, looks great now.

    Now I'm in the amp.
    I just realized that it has 6V6's in it and the tube chart and schem calls for 6l6's, so I slapped some in and biased them about 45ma. I really need a good speaker and maybe a new output tranny. I took some pic of the chassis and trannies and I'll have those up tonight.

    This is a keeper for me. I have 3 amps of different outputs and styles, but all fender.
     
  6. Twangbanger

    Twangbanger Tele-Holic

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    just found out after lots of research:
    output tranny is a ensign coil brand, which was found in some late 60's fender amps

    Now I just need to get the right one or a replacement equivlent
     
  7. AtomicMassUnit

    AtomicMassUnit Tele-Meister

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    Hey, if you're going to do a replacement tranny, give Mercury Magnetics a shot. I've used theirs in a tweed Tremolux and a homebrew Deluxe, with superb results. I've also heard good things about David Allen's transformers, but have yet to use one. Be sure to get the electrolytics changed and a grounded cord installed. Did you say you were biasing each tube at 45ma? That seems a little on the high side. What's your plate voltage? Good luck and nice amp. It's great to see them getting repaired and played!

    Atomic
     
  8. Tremo

    Tremo Banned

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    If that amp is cathode biased, they do run at about 45 mA idle current.

    Wide panel?
     
  9. Twangbanger

    Twangbanger Tele-Holic

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    Yeah, it's a wide panel.

    I forgot to add that someone has put in a grounded cable.

    That ole' radio shack speaker rattles on "C" notes.
     
  10. Tremo

    Tremo Banned

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    I've worked on a bunch of those things. I know their innards very well. They actually sound pretty good with the proper P15N speaker installed.

    They do idle at real high current, like I said, 45 mA sounds about right for those amps. Just be sure the cathode bypass cap is fresh and not situated too close to the resistor. Heat from that resistor will shorten the life of the cap.

    You might also measure the actual values of the resistors and compare what they *are* to what they're *supposed* to be. I've seen a lot of those real old resistors drift **WAY** off value, and in that case need replacement. A friend of mine had a 53 Pro with grid leak bias 9-pin preamps and an octal base PI tube, transition model. Anyway, most of the resistors in that amp had to be replaced, they were so far off. All those old yellow and red Astron tubular caps were history as well. Once that amp was put back as it's supposed to be, it sounded great and was pretty loud, considering it's only 25 Watts.

    One other thing I saw a few times with those wide panel Pros, guys would bring them in for service (first ever), and they still had their original cone P15N installed. Once the amp was electrically healthy again and putting out full power, the P15N would blow at the next gig. The old voice coil and animal glue couldn't take the power any more. Since yours doesn't have the original speaker, this is a non-issue. To make that amp sound "correct", you will need a P15N. Not cheap, but worth it.
     
  11. Twangbanger

    Twangbanger Tele-Holic

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    so, is the Reissue Jensen worth all the money, or should I find an era correct speaker and have it reconed.
     
  12. Tremo

    Tremo Banned

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    The Jensen reissue, while not sounding exactly like an original, nonetheless sounds good. Pricey. A Weber 15A150 is a viable alternative, also not cheap. A period correct vintage Jensen P15N is also going to set you back some money, and will need a recone most likely, and probably a remag as well. You also need to find one for sale.

    None of the above P15N solutions will be cheap. Worth it, yes. You really need to decide what you want to do here, and what sounds good to your ears. Are you repairing the amp to use as a player? Are you trying to restore it as original as possible? Let your application, your ears, and your wallet decide your course of action. You might want to go to the Weber board and post some questions about these things and get some opinions over there, and on the Amp Workshop board as well. All the above solutions will sound good.
     
  13. Twangbanger

    Twangbanger Tele-Holic

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    I'm restoring as close as to original as possible, but I'm also going to be using it as much as possible.

    I need to get a aftermarket output tanny. Should I wait for Weber to get theirs in stock(may 15) or get one from that magnetics company?

    I need to rewire the power amp. Some guy modded it to have a bias control, but changed it too much.

    Ewww! This burlap and shellac is nasty. Almost got it stripped, then I'm going to sand anything else off. Play it with the bare wood till I can get it retweeded. The current setup doesn't sound that bad for bedroom play, but I need to get it back to specs.
     
  14. Tremo

    Tremo Banned

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    Well, if you want it as "original" as possible, start looking for a period correct P15N. Have it sent off to Ted for a recone and remag. The end result will be a relaible, giggable, good sounding and *real* vintage (reconed) Jensen.

    A bias control on a cathode biased amp? Bah. Just put it back to stock. Use like a 250 ohm 10 Watt wirewound sandbox resistor for the cathode bias, and a 25 uf 50 Volt bypass cap. Do NOT use a 25 volt rated bypass cap, as the voltage developed across the bias resistor greatly exceeds 25 volts!!!!

    For the OT, I'd go ahead and get the restoration rolling and get a Mercury Magnetics unit on order right away. Not to diss Ted, but MM is available NOW, and Ted's isn't.

    Burlap?? Ewww...is right.
     
  15. Twangbanger

    Twangbanger Tele-Holic

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    Last night I went on a shopping spree!!!!!!!!!

    I found a canadian company who sells antique radio schematics and new caps. I bought 8 16uf 450v caps for 8$ and a few others too. Paypal safe!!!

    Then I went to Partsexpress and ordered a bunch of resistors and some power resistors.

    This morning I thought I was dreaming!!!!!!!!!!!! Antique Electronic Supply is haveing a sale on their Jensen RI P15n's w/o bell covers! 139$.

    Now just got to get the cab covered and get me a replacement output tranny.

    This restore job is going fast!
     
  16. Tremo

    Tremo Banned

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    Uhhh, a Pro needs a P15N, not a P12N.
     
  17. Twangbanger

    Twangbanger Tele-Holic

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    oppps, I meant p15n
     
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