[Heath] Results Of Tests On DX-60B - Whoa!! Back up a bit!!!!!

[Kenneth G. Gordon]

On 2 Apr 2018 at 16:39, Doug & Kathy Davies wrote:

> Measuring the B+     All tubes removed
> 
> Voltage measured at the + side of C39 = 700vdc
> Voltage measured at the + side of C40 = 348vdc

Those are OK.
 
> With radio unplugged and power supply isolated from rest of radio:
> 
> Resistance on lead going to the 6146 (V3) Final Amp

Am I correct in assuming you mean the 700 VDC lead going through C-20 (.001 mfd) 
through the plate .425 uH RF choke, to the 6146 parasitic choke, to the 6146 plate 
connection? You HAVE removed the 6146 from its socket, I presume for this test?

> - 32 ohms

This is NOT OK !!!!!! 

Resistance to ground at that HV lead SHOULD be well above 100,000 ohms. Infinity sounds 
about right, in fact. 32 ohms is NOT right.

I=E/R, 700/32 = 21.875 AMPS, or P=EI = 700 * 21.875 = 15,312 WATTS.

Assuming your power supply would handle that much current/wattage, which, of course it 
couldn't.

THIS is why your resistor(s) burnt up. As I said earlier, you have what amounts to a dead 
short to ground somewhere between the 700 VDC output of your power supply and the plate 
of the 6146. At 700 VDC 32 ohms to ground IS a "dead short".

Find it and clear it.

Ken W7EKB



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