I tried to find this style trimmer pot with a wirewound resistance element,
but found that all I could find was the Cermet type. It appears that
wirewound pots have all been replaced by Cermet. the wirewound pots had a 1W
power rating, whereas the Cermet pots arte only rated at 3/4W. In the 720A,
the reduced power rating won't be an issue, but in some vintage equipment,
it might be.
I've also tried, to no avail, to find a source for the metal-cased wirewound
trimmer pots used on the K-V divider in some older Fluke differential
voltmeters, such as the models 883A, 885A and 887A. Does anyone know of a
source for replacements for those pots? I have an 887A on the shelf that
I'd like to get back to original condition if I could find a couple of that
style trimmer pot. They're only 2 ohms, making the search even more
difficult. At this point, my only recourse is to find a defunct donor unit
at reasonable cost, and salvage the parts. Does anyone have a hangar queen
that I could get for shipping charges? I'd be really happy to get mine back
on the road to health.
Cheers,
Dave M
Tony wrote:
Apologies - my mistake - I wasn't paying sufficient attention when
Google decided that this was a perfect match when searching for
300SP-1-502:
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?st=3400s&catalogId=15001&categoryId=700000005471&langId=44&storeId=10151
But £180.27 each whereas Newark, the US arm of Farnell only want $120
or approx £80 for the same part! Are there really that many Brits who
put up with being ripped-off to these levels?
Tony H
On 26/09/2015 01:27, Charles Steinmetz wrote:
Charles wrote:
I had to look it up. The company was Arrow (800 833 3557). The pots
were manufactured by Bournes with a manufacturer part number of
300SP-1-502. Unit cost $7.73 in 2011. I bought 26 so my cost was
about $200. I wanted a "Manufactured in America" part but can't
remember if that was too pricey or not.
Tony wrote:
They are now $92.55 from Arrow now and Farnell want over $200 each
if you buy 25 or more!!!! There don't seem to be any obvious cheap
alternatives for 10 turn 20ppm/C 5W pots.
The original pots were Bunker Ramo-Eltra (later, Bunker
Ramo-Amphenol) P/N 3800P-502. These were 20-turn, 5k, 10%, 1W,
+/-50 ppm/C wirewound parts in the 34b rectangular package. The
Bourns 3005P-1-502 matches these specifications (I suspect "300SP"
in Charles's message was a typo). I do not know if the pin layout
is the same as the 3800P-502. Verical has the lowest price on the
3005P-1-502 that I could find in a quick search, $7.68 each. Others
charge from $9 to $14. Tony -- what part number were you quoting specs
and prices for? I
found nothing searching for "300SP-1-502."
Best regards,
Charles
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