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Heathkit HA-14 Restoration thread

Discussion in '"Boat Anchor" & Classic Equipment' started by WA6MHZ, May 23, 2014.

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  1. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

  2. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    That resistor is mounted inside the HA-14 on a terminal strip near the Tube sockets.
    U can see the blue resistor in this pic
    [​IMG]
    The problem is that only 1 wire comes from the amp, which is the orange wire U see. That goes to
    the I/O socket and is routed over to the Power supply HP-240 through the cable. so it is a long ways to get to the meter
     
  3. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    OK, that's exciting! I guess that depending on where the low side of the meter is fed, there is a voltage drop that is throwing off things... If you have a dedicated meter for grid juice, definitely run a twisted pair right to that resistor and you will be stylin'!
     
  4. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    While Sue was working feverishly on her Swan Three Drifty, I resumed toil on the HA-14. Todays task inncluded a trip to Murphys, the last junk store in the San Diego area, where I scored a 12V fan. This one draws 380mA on so I will run it off of the 12Vregulator I installed for the relays. It is good for an amp but I better put a heatsink on it now!

    Back at the Radio hospital, I went crazy with my metal cutoff saw and built this contraption
    [​IMG]

    This required many MANY precise cuts, drilling and tapping of holes and designing.. This holds the 12V fan nicely and it will blow the 572Bs cold!
    The tray nicely holds the HA-14 with plenty of room for air being picked up from below and all around.
    [​IMG]

    so this is a great improvement!!!!
     
  5. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Powered it up and feel alotta air coming out the top above the 572Bs! I removed the grating on the top side, that is flush up against the cabinet bottom. I left the finger guard on the bottom of the fan.
     
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    That looks good pat all you need now is some perferated metal in the back or the front or both and some regular metal on the sides.

    Cool...
     
  7. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Hi HZ,
    That looks really nice. Wow, did Heath really make that radio without any kind of fan or was it supposed to mate with a similar base? Without any air moving, that sucker would FRY! My goodness...
     
  8. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    OK, just took a peek at the scheme about the grid current measuring and it looks to me like that without a separate return for the metering, the relay current will get added to the grid measurement (or something like that...)
     
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    opps, wrong button...
    Basically, this amp is an SB-200 sideways. The -120 volt supply holds the tubes off in receive (of course I know you know that...)
    When keyed, pin 12 goes to ground and the relay current plus the 10K resistor's current through R9 sets the idling current of the tubes in transmit (about 90ma) via the voltage drop at R9. The grids want to be at about -2 volts or so for 90ma quiescent current. R8 sets this.

    To measure grid current, the 1.5 ohm shunt can be in line between R9 and R2/RFC3. You could run the meter feed across that resistor and it will only develop voltage for the current in the grids ignoring all else, but it does take 2 wires to the meter for this to work.

    Hope this helps and I hope to hear you on the air with it sometime!
    cm
     
  10. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Thanks to KD2ACO for that tip!! I Axed the ALC line which I don't plan to use anyway and used that run of wire back to the HP-240 for measuring across the 1.5 Ohm resistor for Grid CURRENT
    SURE ENOUGH that worked great! NOW the grid current is properly displayed when the meter switch is selected for that position.
    To modify the HA-14 even further (this will be the most HIGHLY MODIFIED HA-14 In the world!!!)
    I cut the green wire that was ALC and soldered it to the other side of the 1.5 Ohm
    [​IMG]

    (I SHOULD BE HOME PACKING FOR THE TRIP TOMMORROW!!!)

    Anyway here is the System in actual use hooked up to the test Icom IC-737A

    I am whistling up the HA-14 on SSB, with 500W out (grid current not accurately calibrated but good enough for use) Plate Current is calibrated!

    [​IMG]

    Now it was time to label things. I decided not PAINT the unit as it would be difficult to label it after painting unless it was painted either BLACK or WHITE! So the HP-240 will remain aluminum color!

    here is the front labeled up
    [​IMG]

    and the back (Note the HV labeling for shock hazard!)
    [​IMG]

    and the HA-14 is labeled as well. If someone bought this at a Hamfest and plugged it into a normal HP-24 it would catch fire!!! Especially with the AC switch rewiring!!!!
    [​IMG]

    So other than adding the bottom feet (coming from Ebay, the seller is really LOLLY GAGGING on this one!!! It should have been here early this week!!!!!) (And it DARN WELL BETTER be here when I get back from HARTFORD or that seller is getting a NEGATIVE REVIEW!!!!)The GREAT MODIFICATION has been more or less completed and it ready for service!!!!
     
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