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 Post subject: Simpson 260 Help Needed
PostPosted: Apr Thu 02, 2020 4:26 pm 
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Location: Traverse City, Michigan
I just picked up a couple of crusty series 2 meters and am trying to troubleshoot the cleanest of the two. I can zero the meter with the screw in front but have no luck getting it to budge while trying to read the voltage of a good 9v battery. I've tried all the ranges. Leads are in common and plus. Any thoughts on where to look first? Thanks.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Thu 02, 2020 4:38 pm 
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If it were me, which is isn't, I'd get it cleaned up enough to stick some batteries in it and see if I could get some R readings on it. Look at anything that might be damaged from past leaky batteries left in in. It's not impossible that the meter is shot, but there is a fuse or two in there also. Not sure without looking if it has one or two in the series 2. Work some cleaner in the switch while in there. If there is corrosion evident on the board, it can be tough to impossible to clean if it's soaked in. You have to get radical and cut and jump traces and convert to a more P2P wiring method. Not very convenient. Not suggesting that at first though.

Get your schematic from the 260.com site.

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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Thu 02, 2020 4:48 pm 
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Tony Wells wrote:
If it were me, which is isn't, I'd get it cleaned up enough to stick some batteries in it and see if I could get some R readings on it. Look at anything that might be damaged from past leaky batteries left in in. It's not impossible that the meter is shot, but there is a fuse or two in there also. Not sure without looking if it has one or two in the series 2. Work some cleaner in the switch while in there. If there is corrosion evident on the board, it can be tough to impossible to clean if it's soaked in. You have to get radical and cut and jump traces and convert to a more P2P wiring method. Not very convenient. Not suggesting that at first though.

Get your schematic from the 260.com site.


The D cell holder looks good so I'll start there. I don't believe there's a fuse in this early model. I have the schematic but not in front of me right now.

UPDATE: No dice. When shorted and set to R1, the needle should have moved all the way to the right. Didn't budge.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Thu 02, 2020 8:27 pm 
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I'd be inclined to connect that 9V battery directly to the meter terminals through a 220k resistor. If the meter doesn't move then there is no point in going further.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Thu 02, 2020 9:50 pm 
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khutch wrote:
I'd be inclined to connect that 9V battery directly to the meter terminals through a 220k resistor. If the meter doesn't move then there is no point in going further.

No movement.
However, the meter on the other one bounces around so I'll do a swap.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Fri 03, 2020 7:53 pm 
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My recent experience.
Very good meter, and working very well for me at this point.

viewtopic.php?f=8&t=367768&hilit=Simpson


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Sun 05, 2020 4:17 am 
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cdoyal wrote:
khutch wrote:
I'd be inclined to connect that 9V battery directly to the meter terminals through a 220k resistor. If the meter doesn't move then there is no point in going further.

No movement.
However, the meter on the other one bounces around so I'll do a swap.


I'm glad that at least one of the meters is functional. I probably should not have said that there is no hope for the one that won't move. Someone may have some ideas on how to fix it. I don't think I could fix one. But now you have a start and hopefully the rest will be straightforward!


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Sun 05, 2020 4:12 pm 
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Sometimes there is a simple reason that the meter is dead that can be easily determined. If the meter case is carefully removed usually there is a wire-wound resistor going from one terminal to the meter movement. Sometimes the connection is not good at one end or the other which can be soldered to fix it. There should be a resistance across this resistor (usually less than 1 k-ohm). Theere should be continuity to the terminal to the resistor and from the resistor to the meter movement. There should be continuity from the other terminal to the meter.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Mon 06, 2020 3:16 am 
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You might want to test the bad meter again when it is completely disconnected from the rest of the circuitry. I suppose it is possible that the rest of the meter circuitry is shorted and that would keep the meter from deflecting.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Mon 06, 2020 2:29 pm 
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You could also try rotating the meter back and forth in your hand and see if the pointer moves; if not the pointer could be stuck. If there are protection diodes in parallel with the meter, they should be tested to verify that they were not shorted during an overload. If so, they could be removed and the meter retested with the 220k resistor and the 9 volt battery.


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 Post subject: Re: Simpson 260 Help Needed
PostPosted: Apr Mon 06, 2020 3:40 pm 
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One shortcut is to put the meter on its lowest mA (current range) and try a resistor and a battery in series to the probe jacks. The lowest current range is 100-uA full scale so a 9-volt new alkaline battery and 22,000 ohm resistor should deflect the meter about 50% of full scale. Using the current ranges eliminate a lot of "trouble spots" like the battery holders, resistors on the ohms ranges, voltage divider resistors, meter rectifier, etc. VOM current ranges tend to get used less often than the others so they're less likely to be damaged through accident or misuse.

On the Series 2 meters there are no protection diodes and little else that can go wrong on the current scales except the switches, R11 (left side) on the schematic, and the meter movement. R11 (left) is only used on the 100-uA range so if it was bad, the other ranges would not be affected. The meter is a 50-uA movement and shunted to give the 100-uA, 10-mA, 100-mA, 500-mA, and 10-amp ranges. The reason for using a battery and resistor combination that produces about 50-uA of current is in case one or more shunts are open. In that case the meter will deflect full scale but no harm will be done. Never trust an unknown ammeter to have its current shunt intact.

If the meter still won't deflect, the next thing to try is a DMM on the low DC voltage range. The schematic tells you that this is a 50-uA, 2000-ohm movement, which means there should be 100 millivolts across it at full scale. So see if the approximately 50-mV or 100-mV (with a 10-k resistor in place of the 22-k) appear at the meter terminals. If voltages are reaching the meter terminals but it won't budge, the movement is internally damaged. If the voltages aren't getting there, trace the circuit to find out where they are getting lost.

https://www.simpson260.com/downloads/simpson_260-2_schematic.pdf

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