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

[john]

The really GOOD news is

a) It should be an easy fix
b) You've been lucky in not roasting the transformer

Let us know what you find!

John K5MO



On 4/2/2018 8:18 PM, Kenneth G. Gordon wrote:
> 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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III