[que es tu]

OK, now to show my inexperience!! I am finally considering repairing the aperture solenoid on my KS-2. I just want to know what kind of solder to use and what is the best type of soldering iron to use. I know this is a simple question with a simple answer, but it is new to me. I figure if the camera doesn't work correctly anyway, I might as well try to fix it. Thank you!

[photogem]

A 15W to 20W soldering iron with a pencil-tip and thin solder which flows at lower temperatures.
I gave a hint here:
Manual: Solenoid replacement: Pentax K-S2 (and K-70) - PentaxForums.com
Another possibility is a USB soldering-needle... just check for the thin pencil-type tip!

I use leaded solder also it is not officially allowed anymore.
Open window can help, I have a special fan to keep the "smoke" away from me.

Leaded solder is bad when used often, of course, but for such a tiny job, no danger at all imo.

[AstroDave]

Try to find your local ham radio club, and then the oldest guy(s) therein (preferably 50+ or even 60+). They will

a) know how to solder

b) have some solder and an iron around

and

c) probably be overjoyed to help you out!! Show you how, or even just do it.

Soldering is conceptually quite simple. You want to find some rosin core solder (NOT ACID CORE, as you might find in a plumbing store) and a rather low wattage soldering iron - maybe 25 watts or so (not a 100 W "gun" unless you know what you are doing - that can make toooooo much heat!).

Actually, if you can find the iron, I'd be glad to send you a few feet of solder.

Do some practice first & look for some youtube videos. You need to heat the wiring hot enough to melt the solder, not just heat the solder itself and let it drip onto your connection!

[photogem]

Soldering is conceptually quite simple. You want to find some rosin core solder (NOT ACID CORE, as you might find in a plumbing store) and a rather low wattage soldering iron - maybe 25 watts or so (not a 100 W "gun" unless you know what you are doing - that can make toooooo much heat!).

Indeed, but even if you know very well what you are doing:
Solenoid problem return plus sound - Page 3 - PentaxForums.com

The heat of a 100W gun will kill parts there if you solder with it.
Those tiny contacts want that very fine pencil tip even most guys who solder a lot don't have.
And there is a need for special solder with a low melting temperature:
https://www.digikey.com/en/product-highlight/c/chip-quik/low-temperature-indium-solder-wire

I would be very wary letting anybody on my Pentax because a DSLR ain't no vintage radio or radio-transmitter.

One has to prepare in a very different way and have a dustfree place.
Sorry, but I have met hundreds of those very nice and helpful guys, but no way shall they touch my Pentax.

[jlstrawman]

Use rosin core solder, not the type used in plumbing.

Is there no way to use a heat sink on the leads while soldering, as you would for a diode or transistor? (I'm not familiar with the part, so I have no idea how much room you've got to attach the heat sink.)

[nicolpa47]

My K50 has started to show the first signs of the aperture solenoid fault and I am preparing to do a self repair. This thread has been useful in that it has confirmed a few thoughts I've had. I have followed this subject on previous threads and it seems to me that preparation, care, and soldering capability are the important factors.

I have experience of soldering, sometimes with small and heat sensitive components. My interest in model railways means I have 12v soldering irons with alternative bits and controllers to alter the bit temperature. I also have available low melting point solders and thought to use the 145 degree version.

I am waiting to receive a non-working camera purchase from which to harvest at least one solenoid. Some time ago I did strip a solenoid from an MZ50 but I think Photogem prefers to use solenoids from later dslr cameras which I hope to obtain. It is clear that space to solder will be limited, but I could practice on the non- working camera.

I won't be rushing to do the repair as the K50 is only a back up, but I would like to keep it working.

Thanks to all, but particularly Photogem, for the guidance on how to repair this fault.

[photogem]

My K50 has started to show the first signs of the aperture solenoid fault and I am preparing to do a self repair. This thread has been useful in that it has confirmed a few thoughts I've had. I have followed this subject on previous threads and it seems to me that preparation, care, and soldering capability are the important factors.

Yes, soldering is very important.

I have experience of soldering, sometimes with small and heat sensitive components. My interest in model railways means I have 12v soldering irons with alternative bits and controllers to alter the bit temperature. I also have available low melting point solders and thought to use the 145 degree version.

That is perfect of course. I never heard of 145 degree solder nor other degrees.

I am waiting to receive a non-working camera purchase from which to harvest at least one solenoid. Some time ago I did strip a solenoid from an MZ50 but I think Photogem prefers to use solenoids from later dslr cameras which I hope to obtain. It is clear that space to solder will be limited, but I could practice on the non- working camera.

Good not to use the MZ50 solenoid. There are tiny differences but if you buy a K100D or any of those with 2 solenoids, you can insert it into the flash-circuit, there it will work. Also if opposite polarisation (as many SLR Pentax solenoids in Europe are) there changing wires is very easy. Not so for the aperture-solenoid.
So buying a working *ist-D Series (I still like the D and DS due to TTL) or a K100D/K200D is maybe even more sensible. They are not expensive.

I won't be rushing to do the repair as the K50 is only a back up, but I would like to keep it working.
Thanks to all, but particularly Photogem, for the guidance on how to repair this fault.

You are welcome, and yes, don't rush, good preparation is half of the work!

Is there no way to use a heat sink on the leads while soldering, as you would for a diode or transistor? (I'm not familiar with the part, so I have no idea how much room you've got to attach the heat sink.)

There is no need for heat-sink here at all, it would disturb! The wires have tiny contact area directly to the pins.

Also one hardly uses heat-sing on diodes or transistors. More for longer connections which could cause shortage if bare, such as capacitors or resistors and wires/cables which had been extended and the soldered parts need to be protected.

The wires to the solenoid must be flexible as they are:

[nicolpa47]

Yes, soldering is very important.

That is perfect of course. I never heard of 145 degree solder nor other degrees.

I have built a number of model railway kits. There are basically two types of metal kit. The first is cast whitemetal and these are best assembled using 70 degree melting point solder. The second is etched metal kits - brass, nickel-silver, etc. These are often assembled using high melting point solders for the main structure, and then lower melting point solders at around 243/188/145 degrees to attach further parts without "unsoldering" the larger parts. Sometimes cast whitemetal parts may need to be attached to brass/nickel-silver components which need "tinning" with a high/medium melting point solder to which the cast parts are attached using low melt 70 degree solder. 70 degree solder is not really intended for electrical work as it is quite soft and can be bulky, so I wouldn't attempt to use it in a camera.

Good not to use the MZ50 solenoid. There are tiny differences but if you buy a K100D or any of those with 2 solenoids, you can insert it into the flash-circuit, there it will work. Also if opposite polarisation (as many SLR Pentax solenoids in Europe are) there changing wires is very easy. Not so for the aperture-solenoid.
So buying a working *ist-D Series (I still like the D and DS due to TTL) or a K100D/K200D is maybe even more sensible. They are not expensive.

I did test the MZ50 solenoid for polarity, and it seems to be correct. I have bought(not yet received) a non-working Kx on Ebay, so hope to get 2 solenoids off that, one for the K50, and one in case my K30 succumbs to the aperture solenoid failure.

[Bob 256]

An alternative to solder is conductive epoxy (silver filled). It can be applied to the solenoid terminals and the connecting wire embedded in it and held in place until the epoxy sets. There is no heat involved nor risk to the plastic insulator which holds the solenoid terminals.

The downside is that conductive epoxy might be a bit hard to find and it is somewhat expensive if you get quality grade.

[Not a Number]

On the white solenoids the plastic is supposed to be PTFE which has a melting point of 327°C (620.6°F). The melting point for most commonly used solders for electronics is 183-304°C (361.4-579.2°F). A 25W soldering iron is usually 315.6-337.8°C (600-640°F).

[photogem]

An alternative to solder is conductive epoxy (silver filled). It can be applied to the solenoid terminals and the connecting wire embedded in it and held in place until the epoxy sets. There is no heat involved nor risk to the plastic insulator which holds the solenoid terminals.

The downside is that conductive epoxy might be a bit hard to find and it is somewhat expensive if you get quality grade.

There is another downside:
Conductive epoxy does need time until hardened. With bare multistrand copper wrapped around the pin of the solenoid this would work (allthough I always prefer a good
soldered joint and I do prefer leaded solder, it makes the best contacts)

Because one has to unsolder the wires from the bad solenoid, those thin wires have their copper already with solder and are stiff.

So they won't hold as well as if one would have bare copper of a multistrand wire which one could wrap round the pin.

One cannot cut off the soldered part to have bare copper, they are too short and working with a any tool there to get the insulation off is very critical.

As one has to solder anyway to get the wires off the bad solenoid, half of the job was done anyway.

Cutting the wires is not possible because of the shortness of the wires.

[nicolpa47]

On the white solenoids the plastic is supposed to be PTFE which has a melting point of 327°C (620.6°F). The melting point for most commonly used solders for electronics is 183-304°C (361.4-579.2°F). A 25W soldering iron is usually 315.6-337.8°C (600-640°F).

Thanks for that useful info. As I will be using a 12v iron and have a 12v model railway controller to reduce that voltage, I'll probably use the 145° solder and reduce the tip temperature. The wires/contacts will already be effectively "tinned".

[que es tu]

Thanks everyone for the tips!! I printed out the "repair manual". It doesn't look too hard?? I haven't really done any soldering since I raced slot cars back in the early 1990s, and that was just quick and dirty as things would just break again during the race!! We'll see how it goes on something important like a DSLR!!

[photogem]

Good luck and let us know. Take photos of the process!