[Heathkit] HD-1410 Keyer Question

[Mark K3MSB]

I've got a strange problem with this keyer.

Without it being connected to anything, dit and dash operation is OK 
over the entire speed range.  A VTVM on the keyer output shows about 
1/2V when keyed.

I tried using it with my B&W 5100B transmitter.   The dashes perform as 
advertised throughout the entire speed range,  but the dits do not key 
the transmitter above about 7 to 10 WPM, but gradually do key the 
transmitter (increased power output.... that's not a typo....) as speed 
is reduced, until keying is normal at very low dit rates.    I've 
verified this via my monitor scope and also by receiving on the IC-746 
Pro.    Dot and dash operation within the keyer, at least evidenced by 
the side tone, is OK.

Also, with the keyer not connected to anything, or connected to the 
transmitter,  the output is keyed when the speed switch is pulled out as 
expected.  When the speed switch is pushed back in, the output stays 
keyed.   The exact same operation happens with a straight key connected 
to the EXT KEY jack.    Tapping either paddle ceases keying.    I tried 
following the discrete logic in the schematics and got lost as I thought 
this might be how the keyer should work,  but then I figured it can't be 
if closing the "EXT KEY" jack does this.

I replaced C1 and C2 and this had no impact.

Since the keyer works with the transmitter on dashes,  that indicates to 
me the output stage (Q4...Q7) is OK.   Ditto with the current sink max 
of 10 mA as mentioned in the manual.

Help!

73 Mark K3MSB