[Johnson] Slightly off topic question concerning mercury vapor rectifiers

[Roy Morgan]

At 08:29 PM 10/24/2002 -0700, Joe Yamond wrote:
>   I am having toruble with the power supply and am
>wondering if I may have done some thing wrong,

Joe,

Yes, unfortunately you may have.

>the
>supply uses 2 816 MVR tubes and I had heard that these
>tube filiments need to warm up completely before the
>high voltage is turned on. Is there any truth to this?

Yes absolutely.. "completely" may mean a couple of hours in the case of 
mercury tubes that have not been used for a long time.

>Before found that out I was testing the power supply
>and was turning on both the filiment power and HV
>power and noticed the tubes would glow very brightly
>and make some noise and then settle down to a lighter
>blue glow.

They were most likely arcing over inside.

>Voltage output was good but then the supply
>started blowng fuses on the HV side.

The tubes may be ruined.  But, they could be tested after a thorough warm 
up period.

>With the tubes
>removed the fuse doesnt blow. Also during testing the
>tubes were horizontal could this have caused them to
>fail?

Yes absolutely.

>And lastly is there a good source for
>replacements of the 816s

You may get some at AES  (http://www.tubesandmore.com/ ... they list them 
for $24.40 each.) or possibly at hamfests.. or try any of the many tube 
suppliers.

>  or are those solid state
>replacements better.

Yes, most likely the solid state diodes would serve you much better.  For 
circuits such as use the 816, they have many many advantages.  They just do 
not glow.

Roy



Roy Morgan
K1LKY since 1959
7130 Panorama Drive, Derwood MD 20855
301-330-8828 home .... 301-975-3254 work
roy.morgan@nist.gov