SB 200

[rayfri]

youve also got to remember one thing that has been mentioned in the past
about
higher current and voltage levels....  the higher primary voltages that
exist today
that weren't around when the sb 200 was first marketed.
back then the house voltage was around 115 volts and thats what most of
our radio equipment worked with...  Measure the voltage at one of your house

sockets now and chances are you'll see around 125 volts...   True, its only
10
volts more, but that 10 volts is multiplied many times by the power
transformers..
and so is the current.  In the case of the 30L-1, there are now recommended
modifications to keep the 811A tubes from drawing too much while in
standby...
that extra current and voltage can shorten the life of tubes..... and in
some cases
destroy them rather quickly.....
ray  wa7itz


Mark Graalman WB8JKR wrote:

>   John,
>
>   I don't think the plate blocking cap or any other cap has
> anything to do with your plate current levels. Is the
> idle current about the same as it was before? (90ma or so)
>  There is a good chance that these newer tubes may have
> a bit more gain than the old Cetrons and in that case a simple
> reduction in drive may be order. As long as the amp is in cutoff
> during receive and idles around 50 to 100 ma or so when keyed
> with no drive, the cutoff and operating bias levels are probably
> ok. If your current still levels seem high, I would think there is a
> better chance of a resistor in the plate meter circuitry having
> a change in value. This is all assuming the amp can be properly
> tuned, you should be at about 500ma plate I, 2000 V plate E, and
> about 60 to 80 ma. grid I when properly tuned up.
>
> Mark  WB8JKR
>
> On Wed, 3 Apr 2002 16:37:08 EST John Barkow <KD6PT at AOL.COM> writes:
> > Hi Gang.  Well,I finally got around to installing the new finals in
> > my old SB
> > 200.  Now I am drawing too much plate current so I suppose some of
> > the HV
> > caps are leaking.  Mouser has the HV ceramics but no doorknobs.
> > Does anyone
> > know where I might obtain one of the !000 uuf. doorknobs?  Also,
> > what type of
> > capacitor is used nowadays to replace the old Mica caps  There are
> > so many
> > new types, I am confused.  Any help will be appreciated.
> > John kd6pt
> >
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