[K4RY] Alinco DR-110 panel bulbs redux [even more; last tonight]

[John Klingelhoeffer]

A final evening update:  The DR-110 is on the bench.  All internal regulated supplies look nominal.  I have the front panel board off after seeing that I *could* see plenty of LCD digit activity when I changed switch settings.  With the case off, I was able to inject light behind the display to see this.  That is generally good news, meaning that the main microcontroller is probably not fried.


4 of the 5 incandescent bulbs are out.  I *may* be able to try putting some white LED's in the two positions behind the display.  I seem to remember the last time I tried this I had 'hot spotting' on the display, since most LED light goes out the end versus bulbs going out the sides.  I have some flat-topped LED's and I am going to try silver or thin white paint over the flat ends to see if that helps reduce the intensity and make more of the light go out the sides.  These are very bright LED's, about 10,000 mcd, and they have a 100,000 hour lifetime. We'll see how that works.  I do also have 6-8, 18 volt incandescent bulbs that *can* be put back in there, but we really don't want to do this again in 2 years (at least I don't!).  


The lithium memory backup battery is still much over 3 volts, so that should not be a problem.  


That is all for tonight, and I think it will be a couple of days until I get to work on it again.  


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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