[Johnson] Viking II Problems

[Brian Carling]

It sounds like your electrolytic capacitors could have some 
bad leakage. You can disconnect things one at a time from the 
high voltage and see when the current drops.

Then troubleshoot on that branch. If you get all the way back to 
the filter circuit then you will know it is probably either 
the electrolytics or the rectifier.

> I have been trying to debug a Viking II, the saga so far:
> 
> re-capped
> 
> All low-voltage operations ok/normal.
> When HV was initially applied there were fireworks and a blown fuse.
> One wire under the HV rectifiers was melted and shorted to ground.
> Several of the .01 and .001 ceramic caps shorted and burned.
> 
> I have tested and replaced tubes as necessary.
> 
> Initial setup on low voltage is normal.
> 
> Switching on the HV results in high plate current, 200-300 mA.
> This current increases until the fuse blows.
> 
> Coupling is set to one and the final to zero.  I tried quickly tuning
> the final but the plate current just shoots up anyway.
> 
> The drive is set to zero and I measure zero volts at the potentiometer wiper.
> 
> HV = 750V
> LV= 350V
> Negative Supply = -75V
> 
> I believe this high plate current has caused the overheated wires on
> the HV side.  I am not sure what killed the ceramic caps, it is my
> understanding the these are very robust, oscillations perhaps?
> 
> I am a novice and so I appreciate any direction from you all.
> 
> 73
> 
> Rich
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