[Heath] The DX-60B Issue

[Kenneth G. Gordon]

On 31 Mar 2018 at 16:09, Doug & Kathy Davies wrote:

> testing.  When I plugged it in, all seemed ok i.e all the tube filaments lit up and nothing smoked.  
> Then, I put the Function Switch in TUNE and got a loud hum from the transformer and I let the 
> smoke out of resistor R35.  I re-checked everything and found that resistor R34 was open.

The loud hum from the power transformer indicates that your +HV is dead-shorted 
somewhere. Either there was a wiring error or a component had failed or was installed 
incorrectly.

For instance, if you had inadvertently connected C-39 and C-43 in revese, they would show 
a dead short to ground.
 
> Now I don't know if R34 was open prior to R35 burning up.  I didn't check component values prior 
> to testing.  The question then is, did R34 open as a result of R35 smoking or was it open prior to 
> that event?

>From the sound of things, both burnt up at the same time. If R-34 was open, all that would 
do is prevent the plate-voltage (~ 700 VDC) from reaching the final amp plate.

>  I would think that if R34 was open prior to testing, it would certainly put a huge strain 
> on R35 causing it to burn out.  Am I correct here?

No. The two resistors are in separate parts of the circuit: if one failed, that would have zero 
bearing on the other one.

>  Going over the circuit, I can't see anything 
> else that would have caused R35 to smoke.  Any ideas?

You have a dead-short to ground at the 700 VDC output lead of your power supply.

Is C-19 shorted?

As another fellow mentioned, be EXTREMELY CAREFUL HERE: THAT VOLTAGE IS 
LETHAL!!!!!

Ken W7EKB

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