From: "Allen (Marty) Martin" 
Subject: Re: [drakelist] CM 12 Solution???


As Garey said replacing T-9 isn't the easiest repair on a Drake rig. I have
had the pleasure myself a couple of times. I have decided to do my best to
find the correct replacement as there is not a lot of room to work with for
a haywire job in most cases and because I also like originality. ( I also
like a stock R-4C).

Marty

----- Original Message ----- 
From: "Garey Barrell" 
To: 
Sent: Friday, April 30, 2004 6:01 AM
Subject: Re: [drakelist] CM 12 Solution???


>
>
> > On Thu, 29 Apr 2004 20:51:16 EDT, OTAKEBI{at}aol.com wrote:
> >
> >
> >>Could Marty find out the resistance of the bulb he is looking for and
use the
> >>bulb base to wire in a resistor and then place the unit back in the rig?
> >>Seems that this would solve the problem of a hard to find or obsolete
bulb.
> >
>
> Jim Shorney wrote:
>
>  >
>  > It would seem that there is more to it than just having a resistor
>  > there.  The temperature characteristics of the lamp filament would
>  > cause it to act as a sort of a surge limiter as well as a fuse.
>  > Similar to the way Bose used a Chevy dome light lamp as a tweeter
>  > protector in thier 301 bookshelf speakers.  Call it a
> primitive version
>  > of the PTC "thermal fuses" used in modern electronics.  It
> should be a
>  > simple matter to look at the specs on the lamp and find a more
> "modern"
>  > equivalent.  What say the gurus?
>  >
>
> The #47  bulb is also 6.3V at 0.15A, so is probably close enough.
>
> The object in the TR-4 is to protect the input winding of T9, a
> worthy goal which you can only appreciate after you've had to
> replace one!  The bulb won't do much for lightning induced
> transients or other HV spikes, but it should "fuse" before that
> coil fries.
>
> So either solder a couple of pieces of wire to the bottom of a
> 47, or even put in a "bare" bayonet type socket.
>
> 73, Garey - K4OAH
> Atlanta
>
>
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