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Heathkit HA 2500 tuner Perplexion

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Author Topic: Heathkit HA 2500 tuner Perplexion  (Read 479 times)
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« on: May 24, 2018, 06:18:56 PM »

Hi all - I am repairing a long failed HA 2500 tuner that I used in the late 1980s-early 1990s which failed sometime prior to 2003.  The immediate failure was in the roller inductor motor not operating in one position of the manual switch.  Years later now I am retired and have time to play with it, the motor direction likely has been cured  by detecting a failed transistor in the motor circuit.  In going through the initial checkout, the factory aligned "sensor circuit" for forward and reverse power measurement has a wildly different set of power off measurements (resistance to ground ohms) than called for in the manual.  In reviewing the schematic, my measurements are consistent with the circuit parameters, but not the manual.  Any Heath historians out there to reveal a secret?

I am waiting on components for the manual adjust circuit repair.  I have a MFJ 998 that has worked very well for several years, but I am working classic AM %100 duty cycle and prefer the Heath tuner, though may not in the automatic mode.  I would like the power and SWR features to operate, but stymied until the next "hot test" of the difference in readings (ie - resistance to ground of Brown wire at C8 is 365K, manual calls for 200 - 2000 ohms.  Open circuit and wire to wire measurements are consistent with the circuit schematic but no mechanism for the 200 to 2000 ohms in a passive circuit - power off.

I don't know how many of these are being used but it is a heavy duty tuner with a power rating for our old stuff...

Any help is appreciated and I will feedback on the progress - waiting on Mouser...

Thanks, Bob NS7H
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