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 Post subject: BEWARE! the early Simpson 260
PostPosted: Nov Fri 08, 2019 11:16 pm 
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Location: Phoenix, AZ
Several weeks ago I was galumphing through a Goodwill and spied a Simpson 260 for $5.

"OH COOL!" thinks I. *oh my sweet summer child how wrong you are*

I get it home and test it out, and it is WILDLY off and the ohm meter no worky.

I open it up and holly jebus what a mess. ALL the batteries are horribly disintegrated, the metal battery holders someone installed are partially corroded and there are all sorts of "modifications" (that I find out about later).

I start by looking for a schematic. I find 2 and also figure out that this is possibly the second model made after the original (this is not good).

I start trying to trace out the schematic and it is done weird. the other one is slightly better but the resistor list is partially wrong (missing decimal points and other things).

None of the resistors match the schematic and some aren't even marked. after a while I figure out that they were making "precision" resistors by hand picking resistors to make the value they wanted. some are wire wound and not marked, I have to identify them by taking readings, which takes a while because I have to factor in my test leads on my Fluke 45 to get correct readings.

Someone else has been in here! there are resistors in parallel to some of the factory resistors, a 10 ohm precision pot, resistors added on to make up for what someone thought was an under value resistor but aren't. wire wound resistors that have broken loose from their solder joints. the meter has a problem where it does not always go back to exactly zero after a reading in AC, DC, or Ohms, adjusting the meter does not help. There is a resistor on one of the shunt resistors that I find out does not belong there and is not needed.

It takes me about 3 weeks to slog though this things and I take breaks ever day or so to keep from throwing it across the room. At one point I realize one of the wire wound resistors I removed was badly needed and I had tossed it. Since it was in the resistance part of the meter I replaced it with a resistor and a 1k precision pot.

I am not even going to try and mess with the 5000 volt portion of this thing as I won't be using that.

I replaced the AA battery holders with plastic ones. The C battery holder is fine.

Long story not even remotely short, It works, the ohm part is almost perfectly accurate, the DC and AC is good enough for quick not important measurements. So I stopped there, next time I find one of these if it is not a MUCH later version I am not going to buy it. what a pain.

This is what it looked like when I opened it and after I replaced the Capacitor.
Image

no after picture because it looks terrible.

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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sat 09, 2019 1:53 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5363
Location: Sunbury, Ohio 43074
I feel your pain. I've got one or two slightly newer ones that almost made the final trip into the wall across the shop..... but I put them away "for later" (hamfests or auction probably lol).

Sometimes if you wait long enough, a solution will appear. I bought a box of "junk" at an auction for $5 a while back that included a well hidden Simpson 270 in pristine condition. Full disclosure.... I knew it was there, but I did not hide it. I just put it back in the box exactly as I found it and waited for it to come across the block.

A touchup of calibration and it's a gem. It replaced my much beloved Triplett 310 because ..... it's got a scale I can read without my glasses. ;-). y'all understand......

Previously I had bought a few other 260s of various ages at various auctions, and each one had something wrong enough that I didn't feel like putting the time in. Mostly corrosion from batteries.

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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sat 09, 2019 2:09 am 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 3912
Location: Florida
Just for information, you can make an old meter as accurate as specified by using screened 5% resistors instead of trying to find precision ones of the correct values. Here's how I did it with a Triplett 630 that read low on all ranges except the lowest one (3V).

First, I set the 630 to 3 volts then fed a voltage corresponding to full scale on the next range (12V) through selected resistor combinations until I got a full-scale reading. This combination was then soldered in place and the meter set to 12 volts. Then a voltage corresponding to the net higher range (60) was fed through another set of resistors selected to give full scale. This set was then soldered in and the process repeated until all ranges had been covered. When finished all ranges were in spec. as compared to a DMM. This kind of process sort of uses the meter to calibrate itself and proved much more accurate that trying to select values using the resistance ranges of a DMM.

When you get to the higher ranges you need to be aware of the voltage across each resistor in order not to exceed their ratings. A half-watt will typically be rated 350 volts.

My Simpson 260 was bought at a thrift shop for $3. I replaced one resistor and used epoxy to fill cracks and make a cover corner. A good deal.

RRM


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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sat 09, 2019 2:12 pm 
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Joined: Jun Wed 08, 2011 2:33 am
Posts: 9527
Location: Ohio 45177
IF you get ahold of one of the later series that has modern 1% metal film like Dale, etc. you should find it does not need much done to it.
I have an old VOM in a wood case stashed somewhere that I got in misc. and it is full of non-precision resistors, too. Have never attempted to correct it. I would think it very tiresome to try to rebuild a VOM with all new resistors, if you could find the values you need . Same deal I have a little Simpson baby meter called a 230 with limited capabilities, it is not filled with precision resistors either. I suppose I could spend alot of time overhauling it to be acceptable accuracy for general use but I got too many meters that are already OK.

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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sat 09, 2019 5:47 pm 
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Joined: Jan Tue 10, 2012 8:39 am
Posts: 793
I never could understand the popularity of the ubiquitous 260. There are so many things wrong with it that it's surprising how they seem to be the choice for casual measurements. I used to use mine all the time, while cursing at its deficiencies. And the Triplett 630-NA next to it, albeit far superior, didn't get used much. It has charm but I don't know why.

These days I use digital meters mostly, although I have a few tube meters like the HP 400D and 410B and 412A and 428B. Add to that mix a junk Micronta VOM that gets a lot of use.

Someone with a meter can make satisfactory measurements. Someone with several meters has no idea what he is measuring.


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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sat 09, 2019 11:36 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5363
Location: Sunbury, Ohio 43074
Well, for one thing you could drop a 260 off a ladder and it would still work. I know this for a fact. The case might crack a bit but.......

Also you can’t beat a vom for quick and dirty transistor checks or to watch a capacitor kick

As I mentioned earlier...... I can see the 260 without my glasses..... shhhhh

That and a DVM are mostly all I use besides a scope for most measurements. I’ve found the scopes DMM function to be only so- so on accuracy but it’s handy for quick approximations

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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sat 09, 2019 11:48 pm 
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Joined: Sep Mon 10, 2012 10:41 pm
Posts: 3966
Location: Phoenix, AZ
My go to DMM is a bench Fluke 45 I got from a Goodwill. For old tube gear I have 2 VTVM's. My Portable go to is my Fluke 27fm. This is going outside in my work shed as I can leave it there and it won't be damaged by the heat of summer and our slightly cold winters.

I have at least 12 volt/ohm meters digital or analog.

If you think that's weird, recently I decided to count the flashlights in my house, I was astonished to find 24 of them I told my wife this and not a day later she brought home another that someone gave her. so now we have 25. :shock:

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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Sun 10, 2019 1:50 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 9331
Location: Beaver Falls, PA. USA
I'm almost as bad... My bench DMM is a Sencore DVM38, and I also have a Heath 2372 multifunction tester.There is another Heathkit around that I built back in 1986. Analog meters include a Heathkit IM-1104, and a Triplett 630-APL. The VTVM is a HP 410B. I have an old 260 around, but the 630 is newer and nicer. I carry a Fluke 8060A in my tool kit.

I thought that my 260 was old, but that one is even older.

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 Post subject: Re: BEWARE! the early Simpson 260
PostPosted: Nov Wed 13, 2019 4:14 am 
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Joined: Oct Thu 04, 2018 2:11 pm
Posts: 188
Location: Suburban Chicago
I got a 260 a couple of months ago, a 6M, out of nostalgia mostly. Now that I have it I love it. I guess I subconsciously knew how much I missed the one I used to have at work many years ago. Mine didn't need any work, the seller even put new batteries in it and included some cheap but serviceable probes. I don't know what makes them so endearing, I guess I appreciate their simple elegance and there is just something in the way that taut band meter needle moves....


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