Old test meter need repair and callibration?

[mso]

I've found a pair of Simpson VOMs that are in need of calibration I think, I tested them at 10 volts on the 10 volt range and while one did ok the other needle did not return all the way to the starting point. Also they seem to need a battery that is a half inch longer than a double A. Can anyone help on this?<p>Thanks<p>Mark

[toejam]

the first thing you need to do is make sure 0f how many cells the batt. is made up of it is probabally one cell and any c,or d cell will work just fine.As far as calibrating them they are probabally both close enough to use, the sticky one will require dissassembly and cleaning /adjustment a job that requires a steady hand and delicate work unless tickeling the zero adjust screw works.good luck.

[Chris Foley]

Hi, Mark. Specific information invites specific answers (or even possibly scanned copies of schematics). Is it a 260, 270, or what?<p>The one with the problem meter movement is probably your spare parts meter. Just for yuks, look closely at the needle, and see if it's possibly bent and rubbing against something. If so, you might try (very carefully) using two fine point needle noses to try to straighten it out. Try not to torque the movement itself.<p>Most Simpsons can be opened by the 4 screws in the back. Take a close look at the innards for obvious smoked componenets. Also, take a look at the batteries in the box -- they have a number on them. The batteries in old Simpson meters are higher voltage and somewhat rare -- but they're still made by Everready. You can get them through Newark, or you can special-order them through a camera store that stocks Everready batteries.<p>An old Simpson is a wonderful thing to have. Also, they go well over 1000VAC, which can occasionally be of use. By the way, you may be able to find someone who's interested in buying the Bakelite case, if it's in good condition, even if the meter doesn't work.<p>Good luck.
Chris

[mso]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> Hi, Mark. Specific information invites specific answers (or even possibly scanned copies of schematics). Is it a 260, 270, or what? <hr></blockquote><p> Sorry, I should have put that down. I did some more work on them this morning. The first is a simpson 260 series 3 and I managed to get the back off of it this morning. It had 1 D cell and 4 double A's. All corroded so I have some cleaning to do. It measured 7.5 on the ten volt scale when I put +10 dc volts on it. <p>The second one is a simpson 260 series 5, and this one is had no screws or anything holding it together, it takes the same types of batteries but the leads are gone, which is why I got confused over battery size (also you should never try to do this sort of thing when your tired). It read 7.9 on the ten volt scale when I put +10 dc volts on it.
The two meters have been beat up a lot, but I think they can still be worked with. Any advice on where I can get a skematic? <p>Mark

[Edd]

MSO:<p>This site has quite a bit of data on your unit …..but is from an older collegiate designated server and is CANTANKEROUS at times if under students high demand……or when the temperature is above 90deg and the wind is out of the SSE or an old ’48 Chevy pickup’s stray ignition wiring emissions swamp it, etc,etc,etc. (Early A.M. hrs.)
Simpsom 260 Datum:
http://bama.sbc.edu/simpson.htm <p>Still another viable alternative is:
http://www.nostalgiaair.org
In their manual files
I still am a definite user of those instruments in certain unique applications , however the Triplett is my favorite.
I haven’t looked at the schematic of your unit. But if it is like the Triplett the battery(ies) are only involved in bias for the operation of the OHMS function of the unit. <p>73's de Edd
[email protected] ........(Interstellar~~~~Warp~~~Speed)
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[Edd]

MSO:<p>This site has quite a bit of data on your unit …..but is from an older collegiate designated server and is CANTANKEROUS at times if under students high demand……or when the temperature is above 90deg and the wind is out of the SSE or an old ’48 Chevy pickup’s stray ignition wiring emissions swamp it, etc,etc,etc. (Early A.M. hrs.)
Simpsom 260 Datum:
http://bama.sbc.edu/simpson.htm <p>Still another viable alternative is:
http://www.nostalgiaair.org
In their manual files
I still am a definite user of those instruments in certain unique applications , however the Triplett is my favorite.
I haven’t looked at the schematic of your unit. But if it is like the Triplett the battery(ies) are only involved in bias for the operation of the OHMS function of the unit. <p>73's de Edd
[email protected] ........(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled-Spam*Cookies*Crumbs)

[mso]

Thanks, I will check out the sights. The best time I've found to do it is 4 am to 7 am sunday mornings, if you are on the east coast that is. Traffic seems to be minimal then.<p>Mark

[Chris Foley]

Thanks for the sites, Edd! It's good to know they're there.<p>As we were talking about before, the first thing you want to do is look at the meter movement. The schematic says the movement is 50uA, approx 1800 ohms. Your first step is to use the screwdriver adjustment to get the meter needle to rest at zero, then disconnect one end of the meter from the circuit, and put 10.00V with a 200K ohm 1% series resistance across the meter (that's 50E-6 Amps, I guess -- check my math). You should see pretty close to full scale deflection on the meter. When you disconnect, it should go back to zero. If it doesn't do that, I believe you can scrap it. If not, start working through the rest of the circuit after reconnecting the meter.<p>Note that 50 microamps is not a lot of current -- be careful with your ohmmeter, or you might damage the movement. Watch the diodes, too.<p>This voyage of discovery can lead somewhere -- it's worthwhile looking very carefully at the schematic, taking your time and learning exactly what's going on in the circuit.<p>By the way, what kind of calibration are you looking for? That word means several different things. At its simplest and least stringent real world meaning, you would just use variable DC and AC voltage/current power supplies and a resistance decade box, and compare readings between a calibrated meter and the Simpson on the different ranges. At its most stringent, you would be using sources and resistances traceable to NIST standards in Colorado, with printout of all values, non-conforming noted, and repair/replacement of individual resistors and components in the Simpson so all readings meet spec, along with another printout and traceability documents (along with a rather stringent bill). All depends on what you need, and what it's for.<p>Good luck.
Chris<p>[ September 27, 2003: Message edited by: Chris Foley ]</p>

[mso]

Thanks, I got the skematic for the series 3, but when I check on the five I got a file download that has as it's extension .djvu file. Does anyone know what sort of file that is? I have tried opening it with simple text, internet explorer but without sucess.<p>I guess given a choice I'll go as far as I can in the stringent category. I figure this is a good way to really get into the basics of measurement and measurement instrements. For starters though I'll simply check against a known meter and a decade box, and as I have time I'll do more stringent test. Sounds like fun actually. The trick will be finding the time.<p>Mark