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- เผยแพร่เมื่อ 30 ก.ค. 2024
- **** See addendum video:
• Vintage VOM Rectifier ...
In this video, I describe a piece of classic electrical test equipment, the original version of the venerable Simpson 260 VOM (multimeter) which dates from the early 1900's. Then I demonstrate it, give an overview of the original users manual and schematic, then describe the circuit theory using my CAD re-drawn schematic.
I also present my efforts to replicate some original battery labels, and others who have needed to replace the original cells & batteries on these, using modern equivalents, might wish to apply these so their meters look more period-authentic internally.
The new schematic and label PDF files may be downloaded here:
www.serpentwebsite.com/filesh...
Here is a timeline table of contents for this video:
00:00 History & Overview
05:30 Making new batteries
08:18 Internal views
17:54 Retro battery labels
26:08 Demonstration
39:28 Beauty shot
39:44 Comparison with a more recent Simpson 260 Series 8 meter
44:00 Overview of the Simpson manual
52:55 Schematic diagram & circuit theory - แนวปฏิบัติและการใช้ชีวิต
The Symbol for the 1 1/2 volt battery is drawn correctly as a "Cell" which would be 1.5 v in a carbon cell while the other battery shows oty of"4" 1.5 volt cells in series which as you know would equal a 6 volt carbon battery....Love your Video!
Timothyhall, glad you like the video, but I don't understand the purpose of the rest of your comment. Are you responding to something in my video that you disagree with? You mention a schematic; WHICH schematic? The Simpson original, my version, or what?
Depends a lot on what you want to do you can't go wrong with 260-8P or 260-8XPi, and the newer series 260-9P that is available. There is a smaller meter, model 160 as an alternative to the 260.
thank you, well done
I will really appreciate if you could post a tutorial on how to use Simson 262.
It seems like the readout of this meter is different from Simpson 260.
I haven't seen any tutorials in regards with Simpson 262 and 269.
Thanks for your hard work and more power to you posting.
herosipet, what's to explain? Three DC Volt scales, use whichever corresponds to the selected range, two AC Volt scales according to range, and one Ohms scale. This is very conventional.
Is your schematic available for download or purchase? Also, mine is dead on AC, I suppose some high PIV diodes would be required? Thanks, nicely done…
The link to the schematic and other 260-1 resources is given in the description to this video.
There are only two diodes in the meter, and they are indeed needed for the AC Volts function to work. But they are located in the circuit after the resistor attenuation, and as such as not particularly high voltage. But given this meter's age, I think that they are Selenium diodes, not Germanium or Silicon. Selenium diodes are typically about 30V per layer, and are typically comprised of several layers stacked to achieve the desired rectifier voltage. They can be replaced using Silicon diodes, with one Silicon diode replacing the entire stack of a Selenium rectifier. HOWEVER, each Selenium layer has a forward voltage drop of several volts, whereas a Silicon diode only drops 0.6 or 0.7 Volts.
In the 260-1, the post-attentuator voltage applied to the two Selenium diodes is quite low, so I think only one layer is used on each diode, so they can't be seeing more than a small number of Volts. But this has the disadvantage of skewing all the precision resistors in the meter circuit, because they were selected by Simpson to result in the correct current through the meter movement when quite a few Volts are being dropped by the rectifier. If you put in Silicon diodes to replace blown Seleniums, the meter will probably read very high in the AC Volts function, because too much voltage is present after rectification, since not enough voltage is being lost in the rectifier diodes. You might find that you need to replace at least a few resistors with ones of different values in order to get the meter working properly for AC Volt measurements.
Study the circuit in DC Volts, AC Volts, etc; to see if there are any resistors unique to the AC Volts circuit, and that resistor(s) would be a good place to start tweaking once you have replaced the diodes.
Hello ! the best meter of simpson is series ?
Why are resistors for these VOM's are so expensive?
Anyone know?
SDsailor, "for these VOM's" seems to mean this particular VOM. In which case, the manufacturer is long out of business, the resistors are high power precision types with custom values
Why would anyone expect them to NOT be expensive?
@@youtuuba So to repair one of these is going to be expensive then. I have a 260 series 5 that is not accurate in some of the ranges. Ohms is good but AC and DC are of on a couple of the ranges.
@@SDsailor7 , while the "Simpson" that made the very early model I show no longer exists, another version of the company still exists in northern Wisconsin. They still survive some versions of the 260 series. You might find that they will still work on yours. You can Google them.......
@@youtuuba Yes I have read that they still make the and they still service them.
Thank you
@@youtuuba I also have a bench model vtvm by Simpson it is the model 312, but I think it also needs some work. I downloaded the operator manual to see if I can make it work.