Nikon Lens M/A switch - Page 1
Forum section: electronics / repair

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 01, 2020, 09:38:49 am
content: I tried to replace the lens motor but I accidentally cut the cables of the M/A switch.The cables were originally connected (if I remember well) on the pins 1 and 2 like the 1st photo I found googling it. Ok, I soldered them in this way, but I had always autofocus A/M (no manual mode, even I've switched to M mode).I got some quick connectivity switch position meters and it seems that the switch between pins 1 and 2 is always open circuit as well in all other combinations except only pins 1-3 when it is switched to M/A mode, otherwise is open circuit.So, to summarise, all pins are open circuit EXCEPT pins 1-3 when only M/A mode is selected.I tried to solder pins 1-3 like the captured photos and now I get a reverse effect where when the switch is in M/A I have no autofocus (manual mode) and when the switch is in M mode I have autofocus.I am pretty sure that the correct connection is pins 1 & 2 but this does not seem to work since I have always autofocus.I am confused about how this switch actually works. In my option, it should work like when A/M mode, pins 1 & 2 should have a short circuit and when the switch is moved to M mode pins 1 & 2 should have an open circuit as a state change or in a reverse way. What do you suggest? How this switch work?

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 01, 2020, 12:50:33 pm
content: Taking closer pictures of the 3-pin switch.I think that is internally broken, I can not give any other explanation for an SPDT switch.

author: Twoflower
author_rank: Frequent Contributor
timestamp: July 01, 2020, 01:26:33 pm
content: Not sure but I think you connected the switch wrong. Try 2-3. Usually the center one is the one that connects to the ones on the outside.Edit: Re-Read your text. It seems you measured that with the result it's open in both positions...

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 01, 2020, 02:38:14 pm
content: Quote from: Twoflower on July 01, 2020, 01:26:33 pmHi,In this way, ie. pin 2-3 connected, I get always Open-Circuit despite the location of the switch lever. Take a look in the diagram below.PINS1 2 3---------|| ----> Switch lever position (all pins are open circuit)PINS1 2 3---------|| ----> Switch lever position (1-3 pins are close circuit)

author: Twoflower
author_rank: Frequent Contributor
timestamp: July 01, 2020, 03:20:12 pm
content: The 1-3 connection is a bit unusual as I've seen in the past 1-2 and 2-3 connections. I can't remember seen a 1-2 and 1-3 switch. That led me to my post. But one learns everyday something new.With your observations I agree with your assumption that the switch is broken. I see 3 options: 1. buy a replacement switch, 2 see if you can repair (if you fail, use option 1) or 3. try to fit the switch up side down in there.

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 01, 2020, 04:01:36 pm
content: [ Specified attachment is not available ]Quote from: Twoflower on July 01, 2020, 03:20:12 pmOk, I didn't have any replacement switch right now, so I tried to upside down the original one. It worked flawlessly. I was very chary to accept that the switch was broken but indeed that was the problem, very curious......For the record, if someone will need the following information:A/M = needs open circuit ( switch OFF)M = needs short circuit ( switch ON)

author: Twoflower
author_rank: Frequent Contributor
timestamp: July 01, 2020, 04:14:50 pm
content: Nice that you got it working!Eventually the heat from desoldering the wires sightly deformed the plastic of the switch.Happy shooting!

author: tkamiya
author_rank: Super Contributor
timestamp: July 06, 2020, 08:37:03 pm
content: You are a very brave person! It looks like a higher end Nikon lens. 24-70 f/2.8???

author: sdancer75
author_rank: Frequent Contributor
timestamp: July 07, 2020, 01:01:31 pm
content: Quote from: tkamiya on July 06, 2020, 08:37:03 pmHi,They are pretty cheap lens but insanely good for that level of price.The lens is the primary Nikkor 35mm f/1.8G