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 Post subject: Just scored a few estate sale goodies!
PostPosted: Jun Mon 10, 2019 12:56 am 
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Joined: Jan Thu 20, 2011 5:18 am
Posts: 1308
Location: Cottage Grove Oregon; 97424
Well at an estate sale I acquired a HP 400D in very nice condition for $20 I opened it up and it is full of all original looking parts. If I am having problems with a "simple" Emerson 261 radio what was I thinking? It will need test leads but I think those can be found.

I also got an old Triplett 630 meter that is in very nice condition but in shipping one of the resistor "legs" broke off right at the end of it, the 24 meg a ohm. So any leads on where I can get a precision 24 meg resistor? How does one find the date of manufacture on the model 630? in the serial number by chance? mine has 1949 in the sn. I know I will have to make a 30 volt battery for this thing. Oh well, more fun.


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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Mon 10, 2019 1:59 am 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
is 1% good enough? If not get a bag full and hand select one. They are cheap. Or do some series/parallel combo of other values. Still cheap.

Mouser Part #: 603-HHV-50FR-52-24M

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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Mon 10, 2019 11:24 pm 
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The 24 meg resistor is part of the divider for the 6000 volt range on the Triplett. How often do you use that? I Guess it would be nice to have it complete for the instance you might figure out some use for that range but I hope the test leads are up to the task. I thought the higher end leads for like Fluke were maybe rated to 1000 safely, and I might hook up the meter before I turned on the power so I am not holding them!

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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Mon 10, 2019 11:28 pm 
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wazz wrote:
I might hook up the meter before I turned on the power so I am not holding them!


+1

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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Tue 11, 2019 1:10 am 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
glue_ru wrote:
wazz wrote:
I might hook up the meter before I turned on the power so I am not holding them!


+1


......y'all have absolutely no spirit of adventure. :shock: :shock: :shock:

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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Tue 11, 2019 6:17 pm 
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Joined: Jan Thu 20, 2011 5:18 am
Posts: 1308
Location: Cottage Grove Oregon; 97424
Thanks Gents, I had no idea as of yet what part that that resistor played. I contacted Triplett and they no longer have it. Part number to Mauser was for some skinny half watt one and the original looks to be about 3 inches long and maybe at least 2 watts? I'm amazed by the condition of this old meter I have some test leads that came with it but I'm not sure they are the proper ones as they don't quite seem to fit tightly in the holes.

Any Idea how to find a date of manufacture?

And thank you for all the help and clues!
God bless.


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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Tue 11, 2019 6:39 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5023
Location: Sunbury, Ohio 43074
heh... well, you didn't specify wattage :-D. If you really need one it's likely you'll have to make one up out of a few others to meet your wattage and precision. Not difficult, but fussy. IF you actually need that scale for anything. Chances are it's close enough for anything likely to come along.

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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Tue 11, 2019 7:22 pm 
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Joined: May Thu 14, 2015 4:15 pm
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Location: Dallas, TX
It probably needs to be a high voltage resistor.
Normal half watt resistors and such cannot withstand the high voltage, that explains why the original is several inches long. Still, 6KV across 24 Megohm is 1.5 watts so something near a 3 watt rating might be best. You could probably use a string of lower voltage, lower wattage resistors on a separate piece of board to replace the original.

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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Tue 11, 2019 10:30 pm 
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Joined: May Wed 06, 2009 7:01 pm
Posts: 837
Congrats on scoring a Triplett 630. Yes, that 24 megohm is the high voltage resistor between the 1200 V point and the Triplett 6000 volt jack. Triplett's manual warns "For maximum safety, do not handle tester or leads when connected to high voltage". I would underscore that for all measurement of lethal voltages.

The power dissipated in the resistor is only about a quarter watt but the size is there for the 4800 volts possible between the ends. Small resistors cannot handle that level of voltage safely. Your best bet is to query someone on the list for a 24 meg replacement from a dead 630. That resistor is seldom used as has already been noted so other than it aging in place, a swap from a dead 630 should be fine.

Not long ago I purchased a 630 with broken glass and corroded batteries for a whole dollar at a swap fest. The movement was good. I replaced the broken glass with acrylic from a CD case cut to pattern with my oscillating tool. Wired up three nine volt snap in batteries in series and stuck a parallel pair of "AA" cells in a medicine bottle in the "D" cell compartment. A bit of DeoxIt on the switches and variable resistors and it was back in business!

Want to check the multiplier resistors in your 630? That's easy. Use a 10 megohm input digital meter such as a Fluke and directly read the resistance at the 630 prods with the meter on its selected DC ranges. The meter is 50 microamps and 20,000 ohms per volt so the math is quite easy. The 630 uses excellent resistors and should be very close to specs.

Best wishes
-- Rich


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 Post subject: Re: Just scored a few estate sale goodies!
PostPosted: Jun Thu 13, 2019 1:27 pm 
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Joined: Aug Sat 02, 2014 3:59 am
Posts: 1164
Location: Brooklyn, NY 11217
Post a WTB in the sale forum here. Someone has a triplett 630 parts unit I am sure.


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