[Heath] DX 100 B

[RAY FRIESS]

First thin is to check the tubes associated with the vid.  Could be weak and not giving enough drive.  Then check the VFO alignment.

Sent from my Verizon LG Smartphone

------ Original message------
From: John King via Heath
Date: Sun, Jul 30, 2017 3:58 PM
To: Heathkit List;
Cc:
Subject:[Heath] DX 100 B

If there are DX 100 experts out there, I can use some guidance. I have a very nice DX 100 B that has been recapped and is working "somewhat".

I have it on a dummy load and can easily  get the 5 ma. of drive and the hear the VFO or Crystal in an adjacent Hammarlund Sp 600. The plate meter reads 800 vdc. I have it connected to a dummy load.

When being driven with crystal excitation the two 6146 tubes are more responsive. At one point on crystal   I got the final  amplifier section to load and dip at 200ma, not the current that the manual indicates the tubes can be loaded to 250 ma.. Rocking the amplifier tuning cap causes a change in plate current from resonance but not a runaway type of change.

The transmitter produces needed grid drive and current with the VFO but the amplifier does not load up as it does when switched to the crystal.

Using crystal excitation on 3.885 with output through a Bird 43 to a 50 ohm dummy load the DX100 B the transmitter is putting out 50 watts in CW mode with approximately 180 ma of plate current, 800 vdc on plates and 5ma of grid current.

Using internal VFO excitation the transmitter does not load up to more than 100 ma, and is only putting about 20 watts through the Bird to the dummy load.

I have substituted other 6146 pairs with almost identical performance. It looks to have been use with an SB 10 sideband adapter, Pin 3
(grids) of the 6146 tubes measure  -70 vdc bias and the schematic shows -75 vdc which should not be the problem.

I  plan to use this DX 100B in my AM station as soon a I get to produce more  power than "somewhat". I would like your thoughts, but please don't ask me if it is plugged in. Thanks and 73, John, K5PGW
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