Hello,
I have measured the HT on a 300B amplifier power supply and there's a small voltage variation occurring. The voltage reads in average 542.0V on the multimeter, but it drifts +/- 1V over a minute. I made a small 1 min video of the measurement, would really appreciate some feedback. The PS has LC filtering and uses two 5R4WGY tubes for full rectification. Is this normal? if not, what can be causing it? Rectifier tubes?
Can't see any cap leaking... there are a lot of them, it would be a nightmare to test them all.
The measurement was done without any signal (inputs shorted)
Thanks in advance
I have measured the HT on a 300B amplifier power supply and there's a small voltage variation occurring. The voltage reads in average 542.0V on the multimeter, but it drifts +/- 1V over a minute. I made a small 1 min video of the measurement, would really appreciate some feedback. The PS has LC filtering and uses two 5R4WGY tubes for full rectification. Is this normal? if not, what can be causing it? Rectifier tubes?
Can't see any cap leaking... there are a lot of them, it would be a nightmare to test them all.
The measurement was done without any signal (inputs shorted)
Thanks in advance
but perhaps that small variation on the main explains the one on the VDC. I'll measure the mains again and compare. I guess if on average I have 1/2 of the DC variation then case is closed...
Multiply the change in Line voltage by the ratio of your (HT/Line)*.707 and see if this is close to your HT variation. If it is, then the variation in HT is due to variation in line voltage.
540V as 300B B+?
Loftin-White?
The capacitors in the PSU are stacked 400-550V electrolyte ones (with equalizer resistors) or 1kV MP?
This is probably the cause. There's indeed a 300-400mV variation on the mains (over a minute), which following that multiplication seems to explain the dc variation.
The PSU capacitor requirements are the same.
If it has stacked caps, and equalizer resistors not, it's a problem.
Before the power tubes begin to conduct, the voltage would rising even over 600-650V, so in the previous post capacitor voltages are not excessive.
If it has stacked caps, and equalizer resistors not, it's a problem.
Before the power tubes begin to conduct, the voltage would rising even over 600-650V, so in the previous post capacitor voltages are not excessive.
Yes, 2x stacked 400v caps and bleeding resistors (if that's what you mean by equalizers, forgive my ignorance).
If the secondary AC voltage alteration ratio not similar than DC variation ratio, the fluctuation due to the PSU (mainly the rectifier, or one of the stacked capacitor).
