1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

Just bought a Eico HF 65 pre nos kit

Discussion in 'Eico Place' started by drtool, Aug 18, 2015.

  1. drtool

    drtool It might get loud In Houston Subscriber

    Messages:
    2,194
    Location:
    Houston Texas
    Anything I should double check before I break out my soldering iron? No tubes :no:, rats. My first stand a lone tube pre. Can not wait to compare it to my APT/Holman.
     

     

    Please register to disable this ad.

  2. Lavane

    Lavane AK Subscriber Subscriber

    Messages:
    7,354
    Location:
    northern cal.
    New electrolytic caps just to be safe?
     
  3. s-petersen

    s-petersen Scott Subscriber

    Messages:
    4,572
    Location:
    Middletown,New York
  4. ferninando

    ferninando Lunatic Member

    Messages:
    12,462
    Location:
    San Jose Ca.
    If its anything like the HF85 you'll be delighted.
     
  5. Tubologic

    Tubologic Well-Known Member

    Messages:
    642
    I have some experience building N.O.S electronic kits and can give you some basic advices:

    1) Electrolytic caps have a finite shelf life and deteriorates if not used. They need to be checked for leakage, capacitance, and slowly reformed. If you don't know what this means and how to proceed better to buy new caps.

    2) Resistors and other parts are more stable but should be checked before starting the assembly. Remember these parts are 50+ years old now and way beyond their expected life.

    3) As the parts were not hermetically sealed they will be all affected by some corrosion depending on the storage conditions. This will highly compromise the soldering process, and a good quality soldering is essential for a reliable finished product. Before starting the assembly you MUST carefully clean and desoxidize ALL contacts which will be soldered later, this includes: tags, lug terminal strips, tube sockets , pots, selectors and switches, solder terminals and lugs, etc... dry cleaning is the best and I use Fiberpens and Eraser pencils (less agressive) which are very convenient and easy to use (see pictures). All parts must be bright and shiny before you install them in the chassis for soldering. Pre-tinning some parts like terminal lugs could also help. This might sound excessively laborious but will greatly facilitate the soldering process and contributes to the quality of the finished product.

    4) Beware of chassis mounted ground contacts and returns: once again surface oxidation is your worst ennemy and could induce all kind of strange and hard to locate faults, mainly hum and noise. Allways clean, scrape and desoxidise the chassis where it support a grounded component or lug and use new penetrating washers and tight screws. Perfect ground-to-chassis contacts should not be underestimated.

    5) Use a well tinned good quality soldering iron of about 30-50W, do not overheat. A controlled t° soldering station is recommended but not essential. NEVER use a soldering gun, whatever the manual says.

    6) Take your time and scrupulously follow the steps in the assembly manual, don't skip or improvise even if you consider yourself as an experienced electronic builder. Check and re-check your work.

    7) Parts upgrading is a very controversial topic but remember that low noise film resistors , rare and expensive 50 years ago, are dirt cheap today. Using them in the first stages of a preamp could dramatically reduce noise and hiss. Keep in mind It is allways easier and faster to fit a new part at the assembly stage than later.

    Building a N.O.S electronic kit is fun and a wonderful thrilling experience, bringing you back to the good old days, feeling the time-capsule effect. If you follow the few advices above you will be rewarded with a perfectly working 50 years old NEW preamp, and the unique satisfaction of having built it yourself.
     

    Attached Files:

    Last edited: Aug 19, 2015
  6. mhardy6647

    mhardy6647 AK Subscriber Subscriber

    Messages:
    52,739
    1) It is mono, you know.
    2) There were two versions of that preamp: one had an on-board HV power supply; the other took its power from an umbilicus connecting to a socket on an EICO power amp (most of them had the corresponding socket). I don't, offhand, remember which one was designated HF-65.

    EDIT: a quick google suggests it was the HF-61 had the p/s built in.
    EDIT^2: ... and... a little more thorough check, at Yahoo's EICO group, reveals that the HF-65 is indeed self-powered! :) It was the HF-65A that had no on-board P/S.
     
    Last edited: Aug 19, 2015

     

    Please register to disable this ad.

  7. drtool

    drtool It might get loud In Houston Subscriber

    Messages:
    2,194
    Location:
    Houston Texas
    Thanks Tubologic super info.Yes mono mhardy6647. stereo is just a passing fad.:D. I do plan to put low noise resistors in. We shall see. It WILL be checked before power and at any stages I am not 100% happy with.

    My first car to rebuild was a 1947 Dodge at the age 14 by my self. I feel like I am 14 again,in a very good way.

    Wayne.
     
  8. drtool

    drtool It might get loud In Houston Subscriber

    Messages:
    2,194
    Location:
    Houston Texas
    No manual for assembly. Any member have one for loan? I do check ebay for a repop or old one every day. To nube to just use a schematic. I will post in the Eico owner group. I just never post on that forum,so nobody knows me.
     
  9. Kegger

    Kegger R.I.P. 1/12/1966 - 6/1/2017 Super Mod

    Messages:
    11,600
    Location:
    Michigan,warren
    I'll be curius to see this when you get, plenty of photos please.. :)
     
  10. mhardy6647

    mhardy6647 AK Subscriber Subscriber

    Messages:
    52,739
    ... and I see that you have :)

    You might want to PM AK's Gary Kaufman; he might have a scanned copy.
     
  11. drtool

    drtool It might get loud In Houston Subscriber

    Messages:
    2,194
    Location:
    Houston Texas
    Kegger Pic's a plenty :yes:

    mhardy6647 Thanks for the tip. :thmbsp:
     

     

    Please register to disable this ad.

  12. canton

    canton Active Member

    Messages:
    467
    Thanks for the info on the HF 65 I have a pair that I am going to have looked over but another site was trying to say only use with Eico amp but as you posted that is the HF 65A not the HF 65 it can mate with any amp (all things considered) Dynaco MK's > Pilot SA 260 like that. Correct me if I am wrong in my take on these older but very clean pr. of mono pre amps.
     
  13. tubeactive

    tubeactive AK Subscriber Subscriber

    Messages:
    205
    Location:
    NJ
    So, Dr. Tool had one, hopefully singing well these days. I almost had one, but I stalled/balked. You canton, must be one of the luckiest to have an actual pair of these mono HF-65 preamps. The HF-65 shares some features of the earlier HF-61 plus some of the HF-85 ingredients !

    Power supply needs for each of these mono preamps can be pulled from any amp that can spare 6.3V AC@1A plus about 6-10mA DC of High Voltage(250-300V). Being dual mono, why not keep them dual mono and build two small, matching power supplies, or two supplies on one chassis ? There is no better way to obtain the ultimate in soundstage separation, bass definition and effortless dynamic range, than using independent power supplies for each channel.

    If you were to build a single stereo power supply with separate power supply reservoir capacitor banks for each preamp channel's high voltage, dual mono power trannies will sound better. There is no replacement for having two separate power transformers; even at such low current drain. Proof is in the listening and I can tell you that we will hear better soundstage and dynamics even if listening with a stereo power amp !

    While a common power supply can be made to work, easily, you will prefer the sound of separate cap banks for each channel. You can step it up a "large notch" by implementing fully dual mono supplies.
     

Share This Page