[Amps] [BULK] - Drake L-4B PSU burned resistor

[Will Matney]

Hal,

I fixed the rings arcing on a big open frame, 500 HP synchroness motor in ACF that way once. When you would apply the 4160 Vac on the stator, it acted like a big transformer and caused an arc on the DC slip rings, before the DC was applied when it go up to speed. I put a shunt with one of those resistor across the rings (in a cage) so when the contactor closed, it threw out the resistor, and applied the 250 Vdc to the rings. Worked like a charm, and saved me from having to crawl down in that pit to change brushes, and fix the slip rings every week. That had been going on since the big air compressor it ran had been installed in the late 40's! I never could understand why nobody had ever thought to do that before?

Best,

Will

*********** REPLY SEPARATOR  ***********

On 11/1/05 at 10:54 AM HAROLD B MANDEL wrote:

>Gents,
>
>HV safety resistors absorb glitches of the amplifier tubes,
>such as internal arcs. In such a situation the resistor may
>be absorbing the entire stored energy of the power supply
>filter and attempting to dissipate it as heat, which is
>the cause for many explosions.
>
>After reading AG6K's articles about this device, and by
>observing the quality of devices employed in commercial
>amplifiers it was decided to use a 225 Watt, 25-Ohm
>wire wound that resembled a cookie-cutter with wavy
>windings in my latest project. The power supply uses
>50uF at 5KV capacitance  and is rated at 3.0A CCS. 
>The resistor is located in the power supply cabinet
>and away from any delicate stuff, so if it did explode
>little else would be damaged by grenading porcelain.
>
>If you choose to use a vitreous enamel wire wound
>resistor of whatever value, please make sure it's
>mounted in such a way that if it did explode it will not
>destroy tubes, vacuum caps, vacuum relays, etc.
>
>Some folks surround this resistor with a cane metal
>(perforated) enclosure.
>
>Hal
>W4HBM
>
>
>
>
>> 
>>   Hv safety resistors are in place to protect the tube or tubes not 
>> the
>> diodes, who cares if a diode block goes compared to the price of a 
>> tube. I
>> have a 25W resistor in series with the B+ explode, wonderful fuse 
>> the tubes
>> survived, and so did the diodes. 73 Sam KF4YOX
>> 
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