[volt-nuts] Fluke 720a self calibration repair

[Rob Klein]

Dave,

How many of those pots do you need? I've had the innards of an 88(something) lying around for ages and your welcome to a few, if you're willing to pay shipping from the Netherlands. With only the trimmers in a small box, that should not break the bank.


Met vriendelijke groet,
Rob Klein.

Verstuurd vanaf mijn tablet

Dave M <dgminala at mediacombb.net>schreef:

>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wirewound pots have all been replaced by Cermet.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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