Re: {Collins} Fwd: Re: 75S-3C Meter Lamp Replacement



Ahhhh, A very interesting question.  Since the bulbs are fed from the same
winding as the filaments, lowering the dial light and meter lighting current
by using an LED bulb will lower the total current in the winding which will
lower the IR losses in the transformer. This in turn will raise the filament
voltage. The increased filament voltage will in turn lead to more stress on
the unit since line voltage changes over the life of the unit have generally
taken the filament voltage to an undesirable level to start with. I think
that there is a good chance that this could be the "Proverbial Straw that
Broke the Camel's Back" and that the entire unit, including your desk could
go up in flames. This in turn could result in the loss of one's entire
Collins collection. Now this is serious business and, being a professional
electrical engineer, I really do not want this opinion questioned or any
more thoughts about this put out on the reflector since that may lead to
more experimentation - And therefore more losses of collections. I am going
through the calculations now on my slide rule. 

As they say, Caveat Emptor.....I guess that applies to this advice too.

I like my #47s.


Bill Carns, N7OTQ
K0CXX, Trustee MRCCC
President Collins Collectors Association
Editor, Signal Magazine
Founding Member # AC94-0009
512 618 2762 (Cell + VM)
512 847 7010 (Home + Fax)




-----Original Message-----
From: Dave Risik [mailto:wa3hsc@xxxxxxxx] 
Sent: Thursday, July 14, 2011 7:59 PM
To: rbt@xxxxxxxxxxxxxxx
Cc: collins@xxxxxxxxxxxxx
Subject: Re: {Collins} Fwd: Re: 75S-3C Meter Lamp Replacement

This one's for Bill...

How does changing the type of bulb affect the filament string?????

Dave WA3HSC

 "A simple way to take measure of a country is to look at how many want
in... And how many want out." Only two defining forces have ever offered  to
die for you:
 1. Jesus Christ
 2. The American G. I.
 One died for your soul, the other for your freedom.



---------- Original Message ----------
From: Bob Tufts <rbt@xxxxxxxxxxxxxxx>
To: Undisclosed-recipients:;
Cc: collins@xxxxxxxxxxxxx
Subject: {Collins} Fwd: Re:  75S-3C Meter Lamp Replacement
Date: Thu, 14 Jul 2011 17:23:36 -0400

Bill , while I agree that it's trapping too much heat with a krypton bulb
and an LED solution is preferred, the meter rising was with the lower watt
type 44 bulb (which I've been using to get a tiny bit more illumination than
a type 47 ). It was only when the reflector was put over the type 44 bulb
that the meter rose and the effect was instantaneous and disappeared as the
bulb was removed so I don' think that was heat but magnetic field of some
sort. There was no rising of the meter when the higher watt krypton bulb was
inserted and removed, but I did not leave it there as the watts are probably
too much in time. 
I just thought the reflector shield was something to also try on the small
watt bulb as it is used on the tuning dial lamp per OEM Collins. 
-Bob WA1KPA On 7/14/2011 4:10 PM, Bill Carns wrote: > I agree with
Robert...Too much heat and what I think you were seeing when > the meter
rose up to full scale was the coefficient of expansion on the > meter
spring...real bad and you don't want to go there. > > > Bill Carns, N7OTQ >
K0CXX, Trustee MRCCC > President Collins Collectors Association  > Editor,
Signal Magazine > Founding Member # AC94-0009 > 512 618 2762 (Cell + VM) >
512 847 7010 (Home + Fax) > > > >
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_______________________________________________
SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
http://www.collinsradio.org/membership/

 NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
  1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)

The Collins Reflector reserves the right to refuse access to anyone.

LIST HELP?  ADMIN EMAIL:  collins-owner@xxxxxxxxxxxxx This ONLY goes to the
list admins and does not post to the group!


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