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CM-28 bulbs for Yaks

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jill(at)m-14p.com
Guest

Posted: Tue Jul 22, 2014 4:57 am Post subject: CM-28 bulbs for Yaks

Group,



I have the original Russian bulbs - both types:  Warning and Fuel.  $4.25

each.  FYI - I bought the retrofit bulbs recommended on the Yaklist a couple

of years ago and they were the wrong wattage.  I had a customer call and

tell me their GIB burned their hand on one.  I also had to modify them when

they arrived.....so all is not always as it seems. Do your homework.



RPA members:  I will be talking about magneto care and maintenance at the

meeting on Weds. at Oshkosh.  See you there!

Jill

M-14P, Inc.

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mark.bitterlich(at)navy.m
Guest

Posted: Tue Jul 22, 2014 6:58 am Post subject: CM-28 bulbs for Yaks

To Jill,



What exact light bulbs were recommended that were too much wattage Jill?   And ..... What is the wattage of the Russian bulbs?   Exactly.   If you do not know, have you ever measured current flow at a known voltage in the standard bulb to determine it by P=E/I ??  "Burning your finger on the lightbulb" is a difficult datum point if you know what I mean.



To "Group",



I've kind of lost track of this thread.  I know lots of postings came out for LED replacements for the CJ-6A, but did anyone ever come up with a source for LED replacements for the YAK standard bulbs used in the landing gear warning indicators?   I know I saw it for the CJ, just not sure I saw it for the Yak model.  Sorry to ask for a repeat of this information, but it became hard to know who was talking about exactly what and which.  



Thanks,



Mark Bitterlich





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wlannon(at)shaw.ca
Guest

Posted: Tue Jul 22, 2014 7:57 am Post subject: CM-28 bulbs for Yaks

The CJ 6 indicator lamps have a 9 mm base,  the Yak lamps are apparently 7 

mm.

The "standard" lamp used in the CJ (or the Harvard) is the #313,  It's 

rating is 27VDC, 0.17A.   In the Harvard it is used in series with a 

resistor (can't remember value). Not so in the CJ.



Walt



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Rob Rowe

Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

Posted: Wed Jul 23, 2014 2:29 am Post subject: Re: CM-28 bulbs for Yaks

 	  mark.bitterlich(at)navy.m wrote: 	
		  To "Group",



I've kind of lost track of this thread.  I know lots of postings came out for LED replacements for the CJ-6A, but did anyone ever come up with a source for LED replacements for the YAK standard bulbs used in the landing gear warning indicators?   I know I saw it for the CJ, just not sure I saw it for the Yak model.  Sorry to ask for a repeat of this information, but it became hard to know who was talking about exactly what and which.  :-)



-- 	




Hi Mark,



I've been using Marl International type 253 replacement LEDs for the last 7 years. They're a T2 BA7s fitting (Yak gear/flap indicators) and rated 8-48V AC/DC, although not cheap (c.10USD each) especially for the 16 needed in a -52. At least your -50 only needs 4!



http://ds.leds.co.uk/ds/253series.pdf



Experience as follows;



- white LEDs tend to wash out the dome lens colour, so use green/red/yellow LEDs to improve colour rendition



- initially tried the "DC" version (type 213, no longer available) but had a couple of failures after a few years, whereas the rectified (AC/DC) version (type 253) have never failed. Not too surprising given Yak bus negative transients are not LED friendly without rectifier protection.



- LED sits well forward in Yak bulb holder and needs c. 0.5mm chamfer (scalpel works well) on plastic leading edge to ease it past the collar found in the lens cap assembly.



Also good to be aware of following UK CAA advisory letter (2006) on cleaning lamp holders ...



http://www.caa.co.uk/docs/1594/LTO2918.pdf



CAA reference to "Corrosion inhibitor" (sic) in this case probably means residual air/oil/carbon particles from air compressor rather than the alcohol/glycerin used for maintenance (albeit it was never intended for that purpose, but that's another story!).



FWIW - interested if  your experience is  similar to mine in that it's mainly the bulbs in the vicinity of the cockpit gear vent that fail. IMHO due to contamination from air system gunk, as lots of carbon particles in this from compressor pump lubrication carbonising on the hot outlet valve. Having examined many bulbs I've never found one with a broken filament (suggesting shock/vibration failure) they've all been blackened by the filament burning out. Believe this is caused by the bulb holders heating up (as per CAA advisory) through carbon particle contamination, in turn the metal part of the bulb then heats up and expands. Cycle this lots of times and eventually the metal/glass bond fails and the inert gas seeps, with the filament burning out as a consequence. So keeping the bulb holders clean might also help reduce incandescent bulb failure, as well as avoiding a cabin smoke/fire risk. Maybe this was a contributory factor in Jill's hot bulb issue too? 



As always YMMV!



Hope this helps, Rob R

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mark.bitterlich(at)navy.m
Guest

Posted: Wed Jul 23, 2014 10:24 am Post subject: CM-28 bulbs for Yaks

THANKS ROB!  GOOD INFO AS ALWAYS!



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