Simpson 260 multimeter completely dead

[MissionTroll]

Hello,
I just open an account here to ask this question. I got my Simpson 260 multimeter from a landfill electronics shop for quite cheap. It wasn't working as I expected from the price and I was looking for a way to fix it. It was reading voltage but not resistance I think. The odd thing was when back side was removed and it was put on its back to ground it did work but when I put back the back cover it stopped. So I understood that something was not touching something it supposed to touch and figured out the issue being the broken standoffs of the PCB. After glueing those it worked perfectly. I was very happy with my new, almost free multimeter. It had some battle scars around the housing missing back screw and fuses and resistance zero knob. It was obvious that it had seen better days and it was dropped pretty hard at some point. I immediately bought probes, couldn't find originals so I made them myself. I installed correct fuses and this hopeless multimeter was working fine. You can see the places where it was broken:

I glues these broken parts as best as I can.




Unfortunately this perfect lucky find moment did not last long. Multimeter slowly started losing functionality. When I turn the mode dial it would sometimes work but it sometimes did not. When I put some pressure to the mode dial it did work sometimes. It was obvious. The middle dial was the main course of problem when I first got it since it was dislocated due to broken standoffs so I looked at it again. I cleaned it with ISO and rust removers multiple times. It did not work even a tiny bit and only got worse until at some point it completely stopped working. Now it doesn't even read voltage like it did when I first got it. Non of the functions work. I can't measure current, can't measure resistance, voltage, anything. Even the safety relay in there that would trigger when I touch the positive probe to 50u amp pin or whatever doesn't trigger anymore. The meter is completely dead. And there was no reason I can tell for this. I want to take a look at the other side of the PCB but I can not remove the knobs. Checked batteries, probes, fuses, voltage on the back side of the PCB where battery cables are ending. So PCB is getting power. I tried directly connecting croc cables to where ground and positive leads are and gave voltage from there but no it doesn't do anything.

I don't live in US and I don't know anyone who would be willing to repair this. I want to do what I can but it looks like it will require further disassembly. I am sure problem is something stupid like a broken wire or connection somewhere since it was always like that with this meter.

There is some corrosion on the contacts that I can not remove, but it was always like that and it did not stop it from working before:



I don't know what edition or the exact model this guy is so it will be awesome it someone can identify it. I have my suspicion that the power switch is not working since it is completely dead right now. But middle selector switch acting up is also very possible since it did before. Although I believe that something else occured and killed it off for good since now it doesn't respond to anything. I really want to use this meter since it is only good meter I have. Knowing I can't use it makes me really sad. I mean it should work without batteries at voltage range but it doesn't and I think it is concerning. Please show me the way because I can't find anyone with similar problem.
I soldered the new 9V battery contact since old one snapped off at some point. I did not modify the circuit board or did any other soldering except changing the battery contact. Possibility of cleaning agents and alcohol I used to clean the switches creating additional damage is slim since I did not bathe it in those stuff and just cleaned the back surface. Also the brass nuts were missing when I got it. It was already in this sad state when I got it.

 

[kellys_eye]

There are many different versions of the 260 - can you add more information or a picture of the front itself?

The schematics are available online https://www.simpson260.com/downloads/downloads.htm and the meter is a worthwhile tool if you can get it fixed.

Worst case is the meter movement is open-circuit. There are some adventurous DIYers that can repair them but for most, if this is the case, the meter is considered junk. You can test the meter movement itself using a battery and resistor.

The brass nuts would seem to be essential as they make the contact to the meter movement itself and their lack could be the reason for the intermittent operation.

Another good resource site is here: https://www.simpson260.com/

 

[MissionTroll]

There are many different versions of the 260 - can you add more information or a picture of the front itself?

The schematics are available online https://www.simpson260.com/downloads/downloads.htm and the meter is a worthwhile tool if you can get it fixed.

Worst case is the meter movement is open-circuit. There are some adventurous DIYers that can repair them but for most, if this is the case, the meter is considered junk. You can test the meter movement itself using a battery and resistor.

The brass nuts would seem to be essential as they make the contact to the meter movement itself and their lack could be the reason for the intermittent operation.

Another good resource site is here: https://www.simpson260.com/

I hope this helps. I noticed that those brass nuts were actually making some connections. I can probably find regular nuts that will fit there but I doubt I will be able to find brass ones. Pressing the PCB against the nuts doesn't help. Are those directly connected to the meter movement? I may try testing the movement as you said.

 

[MissionTroll]

Found something broken moving inside the movement. One of the screw post was broken off.
After getting those bits out I found one nut that fit the back. Unfortunately there were not a second one. But this looks like Metric 4 so I should be able to find another by taking the one I found to a hardware store. I actually noticed that meter actually moves now a tiny bit when I take it to 100 to 10000 resistor read area. And I got it to almost zero while I was messing with it and shorting the + - probe wires. As I guessed at first something is not touching somewhere it should.
There is a code inside the front panel maybe that will help identify its model:


You can see the crack that goes across the body from front and it looks like someone before me tried glueing it in the middle. It is not me since I never opened this area before. Meter seems super delicate so I put it back without messing with anything. I don't think the movement gone bad. I think It may work if I find a second nut.

 

[kellys_eye]

The model number is shown on the scale - a 7P. The meter movement is very delicate and the case damage is indicative of it being dropped which may not be good news.

The dial movement is 50uA FSD (i.e. very sensitive) so use caution when testing using a resistor/battery a 1.5V battery and a 47k resistor will be enough to show the needle moving. Don't let the meter needle 'bang' against the end stop. A quick 'on-off' test will show movement (or not). As long as it actually moves you have a chance of fixing the rest of it.

The nuts may be 'BA' (British Association)??? Could be what's known as a 2A or 4A size - dunno - too long ago for even MY memory! The nut you used seems a perfect fit though.... Does't have to be brass but bear in mind that the different metals 'could' introduce an error reading.

 

[MissionTroll]

The model number is shown on the scale - a 7P. The meter movement is very delicate and the case damage is indicative of it being dropped which may not be good news.

The dial movement is 50uA FSD (i.e. very sensitive) so use caution when testing using a resistor/battery a 1.5V battery and a 47k resistor will be enough to show the needle moving. Don't let the meter needle 'bang' against the end stop. A quick 'on-off' test will show movement (or not). As long as it actually moves you have a chance of fixing the rest of it.

The nuts may be 'BA' (British Association)??? Could be what's known as a 2A or 4A size - dunno - too long ago for even MY memory! The nut you used seems a perfect fit though.... Does't have to be brass but bear in mind that the different metals 'could' introduce an error reading.

Drop damage was always there and it was working fine before so maybe I can get it working again. Do I just touch the 47k resistor to brass and ground to another. How do I tell the polarity. Do I need to remove the board first.

 

[MissionTroll]

It does work and responds well. Tried 100K first to see polarity then switched to 50K. Movement itself is fine. Lemme find another nut from store and report back if that fixes it.

There it is indeed 7P: https://www.simpson260.com/260-7/simpson_260-7p.htm

 

[MissionTroll]

I glued back the broken screw hole and used epoxy to fill the crack. Found another nut and secured the meter to PCB. It still doesn't do anything. Any ideas where to start trouble shooting now.

 

[kellys_eye]

Good! We can 'forget' about the meter itself. Now we need to see the reverse of the circuit board where there might be some broken tracks. Using the schematic of the meter we should also be able to trace a signal path from the input connectors to the meter itself, through the relevant rotary switch and other scaling components.

I'm assuming you know how to set the meter to the relevant range and which probe sockets the range relates to? The websites shown above have all the operator manuals too.

 

[MissionTroll]

Good! We can 'forget' about the meter itself. Now we need to see the reverse of the circuit board where there might be some broken tracks. Using the schematic of the meter we should also be able to trace a signal path from the input connectors to the meter itself, through the relevant rotary switch and other scaling components.

I'm assuming you know how to set the meter to the relevant range and which probe sockets the range relates to? The websites shown above have all the operator manuals too.

Yes I can operate it. Should I remove the PCB. I need to de-solder few wires to do so.

 

[MissionTroll]

I can see battery voltages across two black wires and red wires but there is no voltage across the red wires and that right ground wire. Is that normal.

 

[MissionTroll]

I followed that wire and it took me to the small fuse. Fuse was open. I can swear to god that I checked continuity of all fuses and they were fine. Anyway I put the spare in and now it all works. Only thing that is not working is the 1X resistor dial. 100X and 10000X sometimes doesn't work but they work when I flick the middle switch from left to right, bottom to up location. Contacts are failing at resistance range.

 

[MissionTroll]

After turning the mode dial few times around it seems that 1X is also working:

It seems like it is fully functional now. I am not sure how the fuse blow up and slipped from my checkups on this thing but that + switch corrosion seems to be the thing that caused the issue. It is nice that I put those nuts in place, maybe that will fix its being unreliable issue. I think it is still accurate enough checking with few resistors but I probably should tune it at some point with lab equipment.

 

[kellys_eye]

I doubt a device like that would be required to be 'lab' quality (tolerance) as digital meters offer a far better solution these days. As a general purpose meter, used appropriately (i.e. with due regard to its limitations due to internal resistance) it will serve as a decent test meter.

I have three 'ancient' analogue test meters Eagle EP20K, Honor TP12 and a Taylor 127A.

 

[MissionTroll]

I doubt a device like that would be required to be 'lab' quality (tolerance) as digital meters offer a far better solution these days. As a general purpose meter, used appropriately (i.e. with due regard to its limitations due to internal resistance) it will serve as a decent test meter.

I have three 'ancient' analogue test meters Eagle EP20K, Honor TP12 and a Taylor 127A.

Just for calibration I would use one of the sensitive HP meters in school I guess but that may be not necessary as you said since I use this meter to just get a relative idea of what is the voltage, resistance etc. Lovely that it is in working order now sine it wasn't working was bothering me greatly.

 

[kellys_eye]

It's always gives satisfaction to restore older equipment to working order. It's a useful tool and will remain so for many decades after the electronic stuff has failed - which is either not cost-effective to repair or spares would be impossible to source. Nice job, good outcome!