[K4RY] Alinco DR-110 panel bulbs redux [a bit more]

[John Klingelhoeffer]

It is interesting when I look back at my email from 2 October 2010 about replacing these DR-110 panel bulbs, I see that I used 18 VDC bulbs rather than 14 (so I would 'never have to change them again'!).  Those should have really lasted 'forever', and much, much more than the 15000 hours or so they have on them.  Reducing the voltage to them from 18 to ~13.8 volts should have lengthened their lifetime by a factor of 16.  Something else may be wrong in there, or they really got a jolt of a lot more than 13 volts from the power supply.  This will be an interesting examination.  


73


John...
WB4LNM




-----Original Message-----
From: John Klingelhoeffer <wb4lnm at aol.com>
To: K4RY <K4RY at eng.auburn.edu>
Sent: Tue, Sep 11, 2012 5:17 pm
Subject: [K4RY] Alinco DR-110 panel bulbs redux


To AUARC:


Re:  Alinco DR-110 repair


Looking back at my email, I indeed did install new incandescent pilot light bulbs in this iGate Alinco DR-110 around October or November of 2010.  I would guess that they have been on pretty much continuously since then, or about ~15,000 hours of time.  This is a continuing problem with all amateur equipment from the 70's, 80's and 90's at least.  Only very recently has backlighting gone over to LED's.  


I am sure that I replaced the illumination behind the power button with an LED, which is probably why it is still functioning.  I remember that it was nearly impossible get in 5 individual dropping resistors to replace the 5 display back-light bulbs with LED's.  The bulbs are also in parallel, so trying to put them in series to run from 13.8 VDC would have required a lot of PCB surgery.  A single dropping resistor would have dissipated too much heat inside the radio, about 1.2 watts or so, so that was not practical.  Perhaps I'll decide differently this time, and we will just have a warm radio.  


I can remember how difficult this one was to disassemble and put new bulbs in, but figured I would never have to do it again!  Famous last words.  The heat from some of the original bulbs had melted the plastic frame around them.   



I think I will check the rest of the transceiver first.  If it seems to be working in the RF sense, then I will tackle the front panel backlighting.  If the rest does not work, then we can just consider it toast and move on.



73


John...
WB4LNM




 
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