EICO HF-12 pair total restoration...

Discussion in 'Eico Place' started by cajunpepe, Jan 8, 2017.

  1. cajunpepe

    cajunpepe New Member

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    ...so I happened to find an HF-12 buried in my dad's old "junk room". It was pretty dirty and needed some TLC...all tubes were original Mullard and tested "very good".

    ...but who listenes in mono, right? So off to eBay I went, and immediately found another--in really good shape (sans the tubes).

    Once it arrived, I made arrangements with a fellow in Canada to have these things fully restored--new caps, all wiring, tube sockets, fuse holder, IEC power outlet, and rear mounted on/off toggle. The brass cages will be send to a place here in New Orleans to get electrically dipped along with the faceplate.

    I should have the pair back in late January 2017 to run a pair of Caintuck Audio open baffle 8" full range speakers and a 15" open baffle sub, which is a second system that I built to play around with.

    I'll post some pics of before and after when they arrive...


    :beerchug:
     
  2. drtool

    drtool It might get loud In Houston Subscriber

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    You will be a happy camper. Waiting on pics. Funny, I was thinking open baffle before I finished reading your post.
     
  3. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Who needs mono? ME! <G>

    Sort of ... I was looking for something to drive a center channel on my classic quad system and found a 12a. Cosmetically perfect, but with a bad multi-cap. Fixed that, and a very sweet sounding amp, driving the Bose speaker just below it in the rack. I've also got the super tweeter hooked in via a switch, but seldom use it. Plan is to add a load balanced pot to that so I can tune it down some, as it tends to be a bit harsh.

    [​IMG]

    You want a decent pre out of the deal, have your guy "repurpose" the existing tape head input to take straight line level. That's certainly something most of us would never use otherwise.

    PS ... I was kinda bummed to find out the phono section applies RIAA equalization ... was hoping the amp was old enough to work well with my old 78rpm shellac. Been looking to mod that someday, but that's definitely back burner stuff.

    Oh. Tubes ... the shielded driver may be the most important ... the Eico prefers something with ultra low microphonics there. I used a Sovtek 12AX7LPS (spiral filament) there. Other drivers are TAD 7025WA's for a nice fat midrange. Finals are the TAD EL84STR's ... basically a military grade version similar to the old Russian EL85m. I've also got a matched pair of Westinghouse "star" EL84's, but prefer the sound of the TADs.

    (and I kept the "death cap" ... I like to live dangerously) <G>
     
    Last edited: Jan 8, 2017
  4. cajunpepe

    cajunpepe New Member

    Messages:
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    The tape head will be changed to a line level input as well...

    I told the fellow restoring them that I want them to look "museum quality", and I also am not cheating on any parts, resistors, or caps.

    I realize that I am putting way more money into them that they are worth, but it was my dad's old amp in college and I am doing it right.
     
  5. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Now I feel guilty ... I cheated on the caps. <G>

    Finding a multi-cap that fits is difficult due to the low profile. I ended up leaving the old one in place to preserve the "look" and snipping the terminals. Plenty of room underneath to go with separate JJ replacements soldered to the floating terminals for each stage. Had to get a bit creative with the grounds, but fortunately no hum as a result. Amp is dead quiet on idle.

    [​IMG]
    Check out the -10 to +30% tolerance. I metered mine and they came out to exactly 40uf ... perfect! The 20uf read a bit high, but I can live with that.

    Oh. Have your guy add a fuse if there isn't one. The HF12's didn't have them from the factory. Only other real problem is the ganged power/treble switch - those tend to go bad over time. Here's a good replacement ...

    https://www.tubesandmore.com/products/R-VS-500KA
     
    Last edited: Jan 8, 2017
  6. cajunpepe

    cajunpepe New Member

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    28
    Adding a fuse and also replacing the treble/volume pot...
     
  7. ferninando

    ferninando AK Subscriber Subscriber

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    I got 2 of em I refurbed, cleaned and painted. just painted the cage black and enclosure met red. looks great sounds great too. booff em.
    circuit is orig. sept new Rs/Cs/can cap
     
  8. cajunpepe

    cajunpepe New Member

    Messages:
    28
    All right...My guy doing the restoration is finished and going to run them for a week before shipping back to me, so I should have them in about 2 weeks!

    He says they look great!
     
  9. sKiZo

    sKiZo Hates received: 8641 Subscriber

    Make sure your guy does all the hum adjustments those old Williamson's require. Mine had a killer hum when I first got into it, but is now dead silent. Come to find out, most of the problem was with the hum pot itself.

    Enjoy ... you're gonna love them things!
     
  10. cajunpepe

    cajunpepe New Member

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    Buying the tubes today...gonna go with Gold Lion reissues for the 12ax7 and the EL84 and the Phillips miniwatt for the EZ81.

    I figured since it is the fourth system in the house and just a little temporary/play around thing, I really don't need to use BugleBoy or NOS Mullard at $170 a pop!

    I need (6) 12ax7, (2) EZ81, and (4) EL84 total for both amps.

    So with 12 new tubes and all new amp parts and resto labor and all tariffs and shipping to and from Canada, total restoration for both HF-12's is coming in around $1400...not too bad!

    I have some pics from the person that did the resto and they are truly beautiful!!...they look new!

    I will try to post those pics tomorrow...
     
  11. cajunpepe

    cajunpepe New Member

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    28
    Here ya go!!!...this is one of the 2 EICO HF12's that was restored. The secod amp (not pictured) got the same treatment.




    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
    drtool likes this.
  12. cajunpepe

    cajunpepe New Member

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    28
    more pics to come...
     
  13. x3workshop

    x3workshop AK Subscriber Subscriber

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    Harlem
    That looks amazing! I have a pair in the queue that I should get to in a couple months. Would love to know what mods were done.
     
  14. cajunpepe

    cajunpepe New Member

    Messages:
    28
    No "hot rod" mods were done to the circuit, but just about all caps, resistors, wiring, tube sockets, and solder joints are new. The transformers are original.

    The physical mods added were :
    (1) the addition of a fuse on the back panel
    (2) converting the old 120v aux power plug on rear to an IEC power socket
    (3) the addition of a rear mounted ON/OFF toggle switch
    (4) changing the speaker terminal barrier strip with screws to modern binding posts (5) the conversion of the old "tape head" input to an input that can be used to bypass the pre-amp stage, thus giving me the option to use them as mono block power amps I can use with another pre-amp of my choice.

    You can see the physical changes in the pics above...
     
  15. interalian

    interalian Super Member

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    1,110
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    Chestermere (Lake) AB
    Nice job. Bet they'll sound amazing.

    Something to remember about these old tanks though - the chassis is cadmium plated and that's something you don't want to be be sanding as the dust is hazardous. I'm not sure what I'll be doing with my HF-81 as regards this issue.
     
  16. drtool

    drtool It might get loud In Houston Subscriber

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    Location:
    Houston Texas
    ^ Wet sand with a water flush.
     
  17. cajunpepe

    cajunpepe New Member

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    I poked a hole through my Beryllium tweeter and live to tell about it...
     

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