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Help with date code on field coil speaker in early 50's Fender Pro

Discussion in 'Amp Central Station' started by William Perry, Mar 6, 2021.

  1. William Perry

    William Perry TDPRI Member

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    Hello all,

    First post. I have a very odd early 50's Fender Pro Amp that has a (stock) field coil speaker. See pics for the speaker magnet label and date code (F15 N C5563).

    Much appreciation for any assistance/input. I was not able to find much on the interwebs regarding Jensen Feild Coil date codes, so hopefully, someone here can shed some light.
     

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  2. Telekarster

    Telekarster Tele-Afflicted

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    F15N = Field 15" N magnet I believe... C5563 = June 3, 1955? Kinda guessing here but makes sense to me if your amp is from the early 50's. Neat old speaker! Hopefully someone will be able to confirm/correct my guess
     
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  3. William Perry

    William Perry TDPRI Member

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    That's what I was thinking as well, however that seems too late for the amp, which is a "TV" front. Though I am not sure when the last TV fronts were made. It does have a diagonal striped tweed. I had been assuming it was the earlier 50's. However I could be completely wrong
     
  4. Telekarster

    Telekarster Tele-Afflicted

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    If you're talking Fender, I think they stopped making the TV fronts about 1955 so, but I don't understand the field coil speaker in it, but then again I'm no expert on these. Just sayin' that all the early Fender amps I've ever seen had alnico 5 Jensens etc. in them
     
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  5. BobbyZ

    BobbyZ Doctor of Teleocity

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    Should be some more numbers on there the one you want looks like this 220xxx. 220 is Jensen's EIA code and the next three numbers are the date code.
    @Wally had or has an early field coil speaker Pro. Hopefully he'll chime in.
     
  6. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    This^^
    There should be another number inked on.
    I didn't think Pros had field coil speakers...I've seen plenty of early ones with the OT mounted right on the speaker frame, but I'll be danged if that one doesn't say "Field Coil" on it.
    Maybe its a bell cover from another speaker.
    A regular OT has 2 or 3 wires in and 2 out for the speaker.
    A field coil has more wires going in.
     
    Last edited: Mar 7, 2021
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  7. Wally

    Wally Telefied Ad Free Member

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    As BobbyZ notes, we are not seeing the EIA manufacturer’s code which contains the date code...220 for Jensen, x for the last digit of the year, and yy for the week of the year. I owned a 1952 Pro with an OEM Jensen F15N. The EIA date code was 220 2yy. I forget the week.
     
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  8. schmee

    schmee Doctor of Teleocity

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    Here's a 59 Jensen 15" Alnico I have for sale, code showing the date code, contract code, original cone number, speaker model etc:
    [​IMG]
     
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  9. Wally

    Wally Telefied Ad Free Member

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    In addition to the Jensen codes and for those who are not acquainted with Hammond organs, the “AO 22749 0” number is a Hammond stamp. There is a Hammond code on the cone as well.
     
  10. William Perry

    William Perry TDPRI Member

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    Hello all,

    Thank you for all the info. Few answers:

    Yes this a stock field coil speaker. I suspect it was an experiment or trial as, no I have never encountered another (in 40 years of using these), nor has anyone else I’ve talked to. In fact often arguments are started that fender never used a field coil, doesnt exist, I’m mistaken etc, until I show pics. See pics for confirmation of transformer wiring.

    Secondly, I feel a bit foolish about the code, in taking back plate off, there is the 220 code (duh). As you can see, in this case its 220134... so 34th week of 51 by my reading.

    I had it rebuilt after I acquired it a decade ago or so. Sound wise, it definitely has that “raw” early 50’s tweed sound, is very slightly darker and ‘thicker’ than a perm mag speaker, however not mushy in the least. Think zztop ‘brown sugar’ tone.

    To those interested. I have also included a pic of the label/tube chart. Hopefully it’s legible.
     

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  11. BobbyZ

    BobbyZ Doctor of Teleocity

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    They must have made a few with field coil speakers, two of them accounted for here.
    Could be Jensen was just slower to make permanent magnet 15s?
    Or maybe it was just the "N" magnet speakers that lagged behind?
    Just pure speculation on my part, all of this took place before my time. :)
     
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  12. Telekarster

    Telekarster Tele-Afflicted

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    Ah... the 220 code! Now we're on with that at least ;) 220 = Jensen 01= 1951 34= 34th week of that year. As to the rest, you got me! LOL!!! :lol:

    What about this - Did Fender make special order amps back then whereas someone want a field coil speaker in the amp for some specific purpose? Just throwing that out there...
     
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  13. William Perry

    William Perry TDPRI Member

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    ahhh that’s one scenario I had never considered.
     
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  14. Telekarster

    Telekarster Tele-Afflicted

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    I think I read somewhere once that back in those early days, Fender would take special orders on guitars like colors etc. if someone wanted something other than the "white", and I think I remember that they did this practice for quite a while. Not sure how far in breadth that "special order" stuff went with them, but maybe they did this with amps as well. Or... another "maybe" is that Jensen was backordered on the normal N's etc. so Fender took what they could get at that particular moment in time when this amp was built? I suppose it's all speculation but one things for sure - I like this thread! :)
     
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  15. Wally

    Wally Telefied Ad Free Member

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    My ‘52 Pro, which lives in Oklahoma now, was a 5B5....very similar to your late 1951. It was a wreck when I got it....the cab had to e recovered, the speaker was reconed by Weber, and I did the electronics. I replaced all of the tone and coupling caps since those old paper in oils do not stand up over time. When I got it running, it was a dull and dark sounding amp....not correct at all. So, I went back into the circuit and started testing resistors. ALL of the resistors on the board had drifted significantly. I left the input grid resistors since they don’t carry much current and were dead on correct. When I fired the amp back up, glorious sounds emanated. I suppose I was listening to a brand new 1952 Pro....firm low end, brilliant high end, wonderful harmonics, great amp! If your Pro is dark sounding with little harmonic content and no dimension to its soundstage, you might look at the circuit again.
     
    Last edited: Mar 8, 2021
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  16. William Perry

    William Perry TDPRI Member

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    Wally, thanks fir this! I did not do the rebuild so not sure what all he did. I do know the coupling caps were replaced with something bonkers boutique (one of the fancy makes) and the filter caps, but nit sure about the rest. I’ll definitely have to check all that you suggest.

    it does have a “metal” tube (vs glass) for the input stage (or farthest right if looking at the back). Not sure if that is/would effect “flavor”.
     
  17. Wally

    Wally Telefied Ad Free Member

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    Your amp is running 6SL7s while the ‘52 ran 6SC7s. These are the same tubes but with different pinouts. If your amp was used much in it’s lifetime, the resistors likely will have drifted. The 250k plate load resistors all tested around 470kohms in my 5B5!! Yes, someone might take exception to all of those components being replaced, but I consider these things to be musical instruments as opposed to pieces of visual art. They need to be made correct, ime. PIO caps of that age were gone long ago....they just don’t last.
     
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  18. William Perry

    William Perry TDPRI Member

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    Awesome, thanks for the specifics on the plate load resistors. I suspect mine was used a-lot as it came to me pretty beat with clearly old wear and “stories” as I call them.

    I think it’s amazing to look at something like like an early 50’s amp. Especially one that would have been “upper end” and expensive in its time. Therefore probably owned by a “pro” and played 6 days a week on ancient stages/barns/studios/who knows.
    You just wonder, if it could talk, what music did it play, where, and by who? So many stories in those nicks, tears, stains, and scratches.

    Also, COMPLETELY agree with you on them being instruments first vs ‘collectables’! Very refreshing to hear. Imho what ‘makes’ them so cool is what they do when you do stuff with them... not when you point at them! We are definitely on the same page there. What’s the point if they can’t do their cool thing?!

    Anyway, alot of blather but great to hear a like minded attitude about these glorious old instruments/tools.
     
    Last edited: Mar 9, 2021
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  19. Wally

    Wally Telefied Ad Free Member

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    Note that the problem resistors in my 1952 5B5 included ALL resistors except for the input grid leak resistors. If your tech left the tone caps in, those need to come out as well. They are paper in oil, which have a shorter lifetime compared to more modern sealed film caps. got pics??
     
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  20. William Perry

    William Perry TDPRI Member

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    @Wally Apologies for the late reply, would DEFINITELY like to get mine to what you described after redoing your) here are the pics (from right to left and tubes, obviously right to left):
     

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    Last edited: Mar 15, 2021
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