[Hallicrafters] HA-1 keyer

[Roy Morgan]

At 09:30 PM 11/22/2005, jim wrote:
>Hi . I just put a HA1 back into service but am having some problems. 
>erratic cw when first starting up. also the OB2 tube looks like it goes 
>into self oscillation ... any pointers???

Jim,

1) Get a new 0B2.  If there are 12AU7's at V1, V2, and V3, replace them. 
Use 5963's if you have them.

2) Replace all, repeat all paper caps (I don't remember which are paper and 
which might be ceramic..):
   C12, 13 across the VR tubes 0.02uF
   C1, 2 mulitvibrator  0.02
   C3, 4, 5 0.001

3) Replace all high value resistors - these are almost certainly drifted 
high or open.
  R1, 6, 17, 19  - 2.2 meg
  R2, 7 - 5.6 meg

Measure the 470K and 680K resistors to check for excessive drift, replace 
as needed.

4) Replace the filter caps: 20uF 250 volt

5) Make sure R 32, 10 ohms and R30 2200 ohms, 5W are not changed in value

6) Replace the two rectifiers with 29 cent 1N4007's

7) I suggest a three wire grounded line cord for safety, and add a fuse 
under the chassis - half amp should be fine, or quarter amp if it does not 
blow.

Notes:

1) The mercury relay will/may not operate correctly if on it's side..it 
must be more or less upright to avoid the mercury shorting things 
inside.  An octal extender cable will do for testing if you need to put the 
keyer upside down.  The T/O keyer uses the Potter and Brumfield HG 1002 
mercury relay or equivalent. This has a coil resistance of about 4000 ohms 
and operates on about 10 ma in the plate of a 12AU7 in this keyer.  Other 
relays of similar coil resistance will work fine.

2) The manual is on BAMA:
  <ftp://bama.sbc.edu/downloads//hallicra/ha1>

3) The 5963's specified are "computer rated" tubes comparable to the 
12AU7.  The 12AU7's will work fine buy may not have full life. The 
"computer rated" business means in part that they were made for long on/off 
times without developing cathode interface - a degradation in the cathode 
material that appears as if a resistance is in series with the cathode.

4) If there's no sound from the speaker and there's no "control plug" 
present, jumper pins 6 and 7 on the rear apron socket.  These pins feed 
audio to the speaker from the normally closed contacts on the earphone 
jack. The "Control Outlet" is normally used to hook to the keyed 
transmitter, so a plug with audio jumper is normally present.  Some 
plumbers soldered wires into the circuit at the relay socket.

5) The manual tells of using a snubber circuit at the relay socket to 
prevent harm to the relay, but this is not needed with transmitters that 
have low power in the keyed line. Most Johnson transmitters and rice boxes 
do not need any snubber circuit.

6) The Origin of the "Model HA-1 T.O. Keyer" was an article by W9TO with 
following updates in ham magazine.

Roy



- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
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