|
After replacing two resistors, the second being a 180 ohm at the 6LN8 hor-AFC triode grid drifted to 270 ohms, it was unlikely to fix the problem until this VDR is sorted out.
With the 27K plate resistor changes, plate voltage settled at 205 volts - right on. 280 volt supply measured 282 volts
Even better improvement the HOT grid drive to G1 pins 5/9 increased to 140 volt p-p and bias went from -30 to -55, this is progress for sure. I tried a new 6BL8, still no further improvement.
Now for the totally expected when swapping in sweep tubes; Both 6LR6 HO tubes that came with the set are shot, so I found my last new one, an RCA. I connected an ammeter to the cathode with a .33mf cap across the meter. Powered up and as current rose past 300 ma., I cut power. But HOT G2 voltage did settle at 160 vdc, right on spec.
Now for the interesting part - I swapped in another 6CG3 damper tube and HOT cathode current stopped rising after hitting about 270ma, still 30% too high.
My guess at this point is that the VDR is totally wrong and overloading the HOT and damper through the flyback.
__________________
"When resistors increase in value, they're worthless"
-Dave G
|