Fender BXR300 Amp Head

Discussion in 'Amps [BG]' started by repoman, Dec 25, 2013.


  1. repoman

    repoman

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    It's pretty rough but sounds decent though my GB4x10 focus cab.
    The on/off switch is all mucked up. I would like to get some kind of replacement part for that...and the plug needs replacing, seems the ground prong hasn't been in place for over ten years (according to the previous owner).
    Questions:
    Can I simply replace the plug with your run of the mill grounded plugs you get at the local hardware store? I've replaced plenty of extension cord plugs this way, would this be the same? I looked inside and it's wired green to the chassis, white and black insulated connectors to the on/off switch.
    Second question: Is there some type generic on/off switch that I can replace that busted one with?
    [​IMG]
    [​IMG]
     
  2. Bill Hughes

    Bill Hughes

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    The power switch is generic, and should be available from FENDER.

    The power plug can also be replaced easily. That missing ground pin is an issue. Somebody was lazy and cut it off probably for ground hum issues.

    When done make sure that the green wire is connected to to the ground pin of the new plug. You should see zero ohms from the ground pin to thr chassis housing.

    That amp is quite SVT like in tone with the sweepable mid.

    It is rated 300W / 4Ohm, but will do 520W / 2 Ohm, however, at 2 Ohm itm MIGHT themal out.

    The amp has a pre-clipper that is non symetrical on purpose. It sounds better that way.

    Bill
     
  3. negativefx

    negativefx complete hack Gold Supporting Member

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    You can replace it with a off the shelf plug but make sure you use one that's at least 14 gauge or 12 if possible. I recommend installing an IEC jack in place of the cord. I did that on my BXR 400 head. The power switch is replaceable as well... RadioShack will carry the necessary part.
     
  4. Bill Hughes

    Bill Hughes

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    What guage is the line cord? I can't remember. It is stamped into the black jacket.
     
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  6. repoman

    repoman

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    thanks guys, great info...
    I picked this thing up for $60 without knowing much about...I just figured I'd let you guys tell me what I got. :)

    The amp has two inputs. Input one appears to be stripped, the cable doesn't "click" into place, it just slides in and out. The second input works fine.
    Is the input casing(?) easily replaced?
     
  7. repoman

    repoman

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    18/3 SJT
     
  8. Bill Hughes

    Bill Hughes

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    There you have it! 18 ga as a minimum, with lower numbers acceptable
     
  9. Bill Hughes

    Bill Hughes

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    only Fender has that part. Other jacks can be made to work by so called "jury-rigging"
     
  10. beans-on-toast

    beans-on-toast Supporting Member

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    If you are lucky, you might be able to repair the broken jack. Fortunately, you can buy some parts. Here is one source, they have some hard to find Fender parts. Check out the jacks and switches.
     
  11. Bill Hughes

    Bill Hughes

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    Very cool site! They must have bought Fender obsolete inventory!

    They (Fender) dont do that service parts all that well.

    Bill
     
  12. repoman

    repoman

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    thanks man, I think I'll replace the whole cord, all crimped and ready to go ...[​IMG]
    ...seems like the easiest way to repair the plug.
    The input jacks they have look like they could work if I can figure out which one I need, I'm going to have to pull the broken one out to get a good look at it...
     
  13. beans-on-toast

    beans-on-toast Supporting Member

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    That's what I was thinking Bill. It is really nice to be able to find obsolete parts at a reasonable price. On the Ampeg side there is www.fliptops.net, mostly repro for the older amps but very handy to have around.
     
  14. Bill Hughes

    Bill Hughes

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    yea, but Fender should do better on their own. I always tried to use existing parts when ever possible.

    Thats more economical for Fender. The less part numbers in the system, the better.

    That BXR300 has some special parts that were designed for that application, like the dual pot for the midrange frequency, the power transformer, and various others.

    That amp I believe was a 1990 design. It should say the release date on the schematic.
     
  15. beans-on-toast

    beans-on-toast Supporting Member

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    I've found that getting parts from Fender can have its hurdles. Ordering through a dealer takes too long.

    It is true that a smaller parts inventory is easier to manage and larger quantity pricing can bring costs down.

    The other side of the coin is that constraints to use certain parts can lead to a compromise in the design. For example, I recall that Ampeg used a 70uF/40uF/40uF @450V cap can in a number of amps including the SVT. The 70uF was paralleled to a 40uF and they were in series with a 100uF (total 52uF @900V) in the first power supply node. I like a little more capacitance here. I've wondered if this cap was selected by the designers or imposed from above to keep inventory down.

    BTW, the date on the BXR-300 schematic is 8-28-89.
     
  16. Bill Hughes

    Bill Hughes

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    For every part in the system, there needs to be a "buy card" linked to the part number assigned by the customer (Ampeg, Fender, or who ever).

    For each of these numbers, a receiving / inspection procedure needs maintenance.

    Customer service is also another issue.

    A cad file also has to exist for both schematic entry and PCB layout.

    Many venders will let you group parts of different spec for a quantity buy.

    That 70/40/40 at Ampeg was a designer’s choice; it was there when I arrived. It was a standard part within the system. You design around it.

    In the SVT, it was stacked because 450 to 500 V was the limit back then, and still is. I seem to remember 600V parts in the Ampeg system, but they were really 350V cans in series in a cardboard tube.

    Those 32 Ohm speakers in the SVT were done specifically for SVT. Could have been eight ohms, but it was done with 32 for the most convenient failure mode.

    As a designer you need to look out for your customer as well as your employer. The customer “validates” your performance, and your employer makes it all happen.

    Running a design / manufacturing / sales / marketing / service operation is no simple task set.

    At Ampeg, there was not much of an "above", engineering was 5 people, purchasing was 2, service was 3. There was a sheetmetal shop. Cabinets were an outside wood shop (clark Lumber) and inside Case covering.
     
  17. beans-on-toast

    beans-on-toast Supporting Member

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    It seemed to be a favorite as it was used in a number of amps.



    True, it still is done today. Years ago caps were larger in size so stacking them in the design not only allowed you to raise the voltage spec but allowed you to take up less overall real estate on the chassis. Plus large valued capacitors costed more back then than they do today.

    That's an understatement! It takes a lot of resources to do it right.
     
  18. repoman

    repoman

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    So I took the easy way out and simply replaced the plug. Now I need to figure out a way to repair the on/off switch.
    The switch itself works fine, it is the casing around the switch that has been broken off. The previous owner simply cobbed a metal holder around the switch to keep it from falling into the amp.
    The replacement switches that I am finding from Fender are all toggle type switches that really won't fix this particular problem. I need a casing to hold the switch in place. Short of taking one off another amp I'm not sure what to do here.
    Any suggestions on a better way to fix this then what I have here?
    [​IMG]
     
  19. repoman

    repoman

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    BTW, nice discussion gents, I'm glad my question/thread led to some good info... :)
     
  20. Bill Hughes

    Bill Hughes

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    Beans on toast had a source for that switch and jack. I cant remember what thread it was in.


    Here it is!

    http://www.darrenriley.com/FenderAmpParts.htm

    That doesn't look like the stock switch, the site above has it. It is all plastic made by Marquart. There are two versions, that work with different thickness panels, although look the same.

    Fender Switch DPST .205 tabs global $7.95

    Fender part # 0040582000



    I believe it is the global version.
     
  21. repoman

    repoman

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