>I thought I had the henry 2K up and running.Power out abt 1100 watts on
>all bands. Now another problem. It occasionally lets out a loud bang in
>the power supply. I found some slight evidence of arcing on the top of
>one of the oil filled capacitors (where the wire goes in on top, there
>is a band of ceramic insulating the connector from the metal body) that
>insulating material looks as though it arced. After these loud bangs
>occur the HI-Voltage is down abt 400 volts (2200 from 2600volts).
>However after things cool down voltage and all is back to nornal until
>the next BANG. Tonight I also heard a singing or some such sound from
>the RF deck. This usually happens after the amp has been powered up for
>at least 5 minutes. Is this a symtem of one of these oil filled caps
>failing?
No. When an oil filled capacitor fails, it usually shorts.
>The arcing mark I see is very faint and may be old but the wife
>saw a flash and is sure it came from that cap. suggestions? stan/kb8jlv
. HV+ to ground arcing in the 2K RF unit has been known to cause arcing
in the 2K's power supply unit. IMO, glitch R protection in the HV+
circuitry is needed to limit peak fault current.
If it were my amplifier, I would:
1. Add (2) 10 ohm 10w resistors in series with the HV positive lead.
(two glitch resistors needed due to the low ESR of the Henry 2K's filter
capacitor.)
2, Connect sturdy glitch protection diodes (3A) across the (no longer
being mfg.) meter movements.
3. Remove the 7.5 ohm 25w resistor (and the associated relay) from the
neg. HV return circuit and replace it with a wire.
4. Measure the resistance of the vhf suppressor resistors to determine
whether or not the arcing you heard was possibly vhf parasitic-related.
5. Another way to tell if you may have had a parasitic is to measure the
C between the grid and the filament in the 3-500Zs. The rated C is
8.3pF. If the measured C more than one pF higher than 8.3pF, you
probably have a bent filament helix - a problem which tends to occur
during 'big bangs'. . {see p.15 in 9/90 *QST*}
6. A high-pot. test would be useful to see whether or not the tubes have
a gas problem, and to measure the fil./grid breakdown voltage. {should
be 6kV or better}
... ... note: the above list is just for starters
cheers
Rich...
.
R. L. Measures, 805-386-3734, AG6K
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