[Ron O]

I soldered the wires to the solenoid exactly as they came off the old solenoid. Because they are clamped together near the solenoid, one would have been too long and the other too short to solder the wrong way. After having read results of "black pictures on K50" on Google for hours, I was reluctant to try to use burst because of what the guy who offers to fix them warned not to do this. I put a manual lens on and enabled the shutter and changed the green button to Tav and the camera took nice pictures. Reading this thread I became convinced that the problem could only be the solenoid and I ordered the white one and installed it. The problem was not rectified in auto, scene, P, TV or AV. As it has always worked in auto ISO, that is where I left it. I don't think I have used live view 5 times in the years I have owned the camera until I saw here that it might help trouble shoot my problem. After the white solenoid did not fix the problem, I tried burst mode which did nothing except give me a bunch of black pictures. I tried all the different auto focus modes. I am curious as to why "hopefully not auto" ISO? I went to the Ricoh/Pentax website and was directed to Precision for repair. The sight said they could give an estimate on repairs, just tell the product and model. The estimate was $175 and I didn't even say what was wrong with it. I called and asked if there was a recall because others had the same problem. They said not recall, the solenoid wasn't the only thing that could cause black pictures and if I wanted it fixed send it in and then they would figure it out. I figured out that buying a used F7 and a 2.8 zoom lens for $200 was a much better deal but I would still love to have the K50 working right instead of a manual lens only camera. Thank you people for trying to help me out.

[reh321]

I am curious as to why "hopefully not auto" ISO?

Exposure problems are harder to trace down when auto ISO - because ISO can change from exposure to exposure, so it is harder to compare shots.


What I would do if I were you is to take one photo using viewfinder and Av mode.

Take a similar photo using LV and not changing anything else from previous one.

Without editing either photo, post both here so we can see what you are seeing.

[Ron O]

I forgot to say that I updated the firmware and tried what a user on another forum did that did not involve disassembly. It was to define the raw/fx button to optical preview, then in manual or av mode push the button 10 to 20 times. He said he did this and pictures usually were good but sometimes not so he repeated the process and after the third time, his pictures were all good. I did this and could hear something inside slamming back and forth with each push. However it did nothing to improve my pictures no matter how many times I pushed the button.

---------- Post added 04-10-19 at 02:18 PM ----------

I do not know how to post pictures but I set the camera on ISO 400. The Av picture of our flower garden in the sunlight was black, the picture in live view was slightly overexposed.

[photogem]

I am pretty sure you first had the typical fault of the jammed solenoid.
But then during the repair something possibly went wrong.


First try the reset!

Then 1.10 firmware

If nothing helps, then open it again and get the white solenoid out.

Test it with 2 x CR2 batteries or something like 5-6 Volts for a short moment (solder thin insulated wires on the solenoid)

Test it for correct polarity. Then you know at least it is working.

Then sand/grind the green solenoid and built it in. Test it! But don't leave it in, not a long-term solution (see my post/manual about solenoid change Pentax K30).

Then report.

Lots of work, I know, but alas... why not.
Good stuff to learn something

[Ron O]

I am pretty sure you first had the typical fault of the jammed solenoid.
But then during the repair something possibly went wrong.


First try the reset!

Then 1.10 firmware

If nothing helps, then open it again and get the white solenoid out.

Test it with 2 x CR2 batteries or something like 5-6 Volts for a short moment (solder thin insulated wires on the solenoid)

Test it for correct polarity. Then you know at least it is working.

Then sand/grind the green solenoid and built it in. Test it! But don't leave it in, not a long-term solution (see my post/manual about solenoid change Pentax K30).

Then report.

Lots of work, I know, but alas... why not.
Good stuff to learn something

I did the reset. I had already updated to the latest firmware. There is no short as indicated by the approximately 32 Ohm reading on the multimeter. As for testing for polarity, polarity is used on power supplies to determine positive and negative. There is no power on a solenoid by itself. The only way to make a solenoid work one way and not the other is for it to have a diode in line with it. There is no diode in either of my solenoids as indicated by having the same reading no matter which post had positive or negative leads on it. I have worked in automotive electrical systems and computers and have repaired circuit boards, etc for over 30 years. The process of replacing the solenoid went smoothly, nothing fell into the camera and everything that worked when I took it apart worked when I put it back together. I have opened up the camera twice more to make sure nothing had gone bad.

[slartibartfast01]

As for testing for polarity, polarity is used on power supplies to determine positive and negative. There is no power on a solenoid by itself. The only way to make a solenoid work one way and not the other is for it to have a diode in line with it. There is no diode in either of my solenoids as indicated by having the same reading no matter which post had positive or negative leads on it. I have worked in automotive electrical systems and computers and have repaired circuit boards, etc for over 30 years.

There is a permanent magnet in the solenoid which does give it polarity.

[photogem]

I did the reset. I had already updated to the latest firmware. There is no short as indicated by the approximately 32 Ohm reading on the multimeter. As for testing for polarity, polarity is used on power supplies to determine positive and negative. There is no power on a solenoid by itself. The only way to make a solenoid work one way and not the other is for it to have a diode in line with it.

I'm sorry but this is very wrong!

This type of solenoid has 2 windings. If DC-voltage is applied to the 2 poles, it either enhances the magnetic force of the permanent magnet or it goes opposite, it cancels the magnetic force!

There is no diode in either of my solenoids as indicated by having the same reading no matter which post had positive or negative leads on it.

Sorry but this is also very wrong. There is no need for a diode. The solenoid gets a short impuls of DC (direct current) voltage of 6V - 7,2 Volts and thats it!
DC Voltage has polarity: +/-


Also what you say about polarity being used on powersupplies to determine positive and negative is wrong!
Powersupplies "supply power", and that can be as much AC = alternating current.
Powersupplies convert power to a desired power. There are also "switching powersupplies".


If you measure impendance, you don't measure + (plus) or - (minus) but you measure impedance! There are no plus/minus readings!
Impedance is ohm-resistance, which works both ways. I diode has complete different functions.

It is very simple and straight forward:

The solenoid has 2 poles (plunger facing downwards):

for the correct way this solenoid is meant to function, i.e. to release the plunger, it is:

Left (pink wire): plus
Right (lilac wire): minus

If you apply lets say 6Volts DC to it (plus left, minus right), you will immediately notice the plunger will fall down, because the 2 coils induce (induction) a magnetic field, which works opposite to that one from the permanent magnet.


But if you apply the same voltage but Plus DC5Volts to the right and Minus DC 5Volts to the left, the plunger holds even stronger, you need much more force to pull it out.

That is how it works and not to any single 0,00001 percent different!

I have worked in automotive electrical systems and computers and have repaired circuit boards, etc for over 30 years.

Then I don't understand why you believe all this you tried to explain here about the solenoid, because it is totally wrong.

The process of replacing the solenoid went smoothly, nothing fell into the camera and everything that worked when I took it apart worked when I put it back together. I have opened up the camera twice more to make sure nothing had gone bad.

Something must have gone wrong.

---------- Post added 04-11-19 at 12:12 AM ----------

There is a permanent magnet in the solenoid which does give it polarity.

Not quite because what is meant here is intentionally applied electric polarity which one can measure in DC Volts (or alternating if it would be AC
but then polarity would switch/alternate lets say 60 times per second from plus to minus)

The permanent magnet has (magnetic) polarity (the magnetic equivalent of electric polarity) but you even can turn it around, it will still pull the plunger and not push it!

Attraction of repulsion would only work with 2 magnets because then their (magnetic) polarity will define this.

Here we have a desired pull towards the plunger and a desired cancelling of magnetic force but not polarity.
Polarity here defines if the force of this permanent magnet would be made stronger (not desired!) or is cancelled (desired).

---

Last edited by photogem; 04-11-2019 at 02:48 AM.

[slartibartfast01]

Not quite because what is meant here is intentionally applied electric polarity which one can measure in DC Volts (or alternating if it would be AC
but then polarity would switch/alternate lets say 60 times per second from plus to minus)

The permanent magnet has (magnetic) polarity (the magnetic equivalent of electric polarity) but you even can turn it around, it will still pull the plunger and not push it!

Attraction of repulsion would only work with 2 magnets because then their (magnetic) polarity will define this.

Here we have a desired pull towards the plunger and a desired cancelling of magnetic force but not polarity.
Polarity here defines if the force of this permanent magnet is made stronger or is cancelled

I just meant that if the solenoid contains a permanent magnet it will have an electric polarity. That is true isn't it?

[photogem]

I just meant that if the solenoid contains a permanent magnet it will have an electric polarity. That is true isn't it?

Just think (or google) about it:

- Electric polarity is measured how?
- Magnetic field and magnetic polarity is measured how?

[slartibartfast01]

Electric polarity is measured how?
Magnetic polarity is measured how?

Meaning it acts differently if the wires are reversed.

[Ajax156]

This is totally wrong!

This type of solenoid has 2 windings. If DC-voltage is applied to the 2 poles, it either enhances the magnetic force of the permanent magnet or it goes opposite,
it cancels the magnetic force! No more, no less, ONLY THIS! Nothing else.


This is also totally wrong. There is no need for a diode. The solenoid gets a short impuls of DC (direct current) voltage of 6V - 7,2 Volts and thats it!
DC Voltage has polarity: +/-


Also you claim about polarity being used to determine positive and negative is totally wrong!
Powersupplies "supply power", and that can be as much AC = alternating current.
Powersupplies convert power to a desired power. There are also "switching powersupplies".


If you measure impendance, you don't measure + (plus) or - (minus) but you measure impedance! There are no plus/minus readings!
Impedance is ohm-resistance, which works both ways. I diode has complete different functions.

It is very simple and straight forward:

The solenoid has 2 poles (plunger facing downwards):

for the correct way this solenoid is meant to function, i.e. to release the plunger, it is:

Left (pink wire): plus
Right (lilac wire): minus

If you apply lets say 6Volts DC to it (plus left, minus right), you will immediately notice the plunger will fall down, because the 2 coils induce (induction) a magnetic field, which works opposite to that one from the permanent magnet.


But if you apply the same voltage but Plus DC5Volts to the right and Minus DC 5Volts to the left, the plunger holds even stronger, you need much more force to pull it out.

That is how it works and not to any single 0,00001 percent different!


Then I don't understand why you believe all this you tried to explain here about the solenoid, because it is totally wrong.



Something must have gone wrong.

---------- Post added 04-11-19 at 12:12 AM ----------



Not quite because what is meant here is intentionally applied electric polarity which one can measure in DC Volts (or alternating if it would be AC
but then polarity would switch/alternate lets say 60 times per second from plus to minus)

The permanent magnet has (magnetic) polarity (the magnetic equivalent of electric polarity) but you even can turn it around, it will still pull the plunger and not push it!

Attraction of repulsion would only work with 2 magnets because then their (magnetic) polarity will define this.

Here we have a desired pull towards the plunger and a desired cancelling of magnetic force but not polarity.
Polarity here defines if the force of this permanent magnet would be made stronger (not desired!) or is cancelled (desired).

Hi mate, I know you are trying to help and I appreciate your knowledge in this area but could we stick to helpful suggestions of things to try rather than telling people everything they know is wrong?

My question to the OP would be, as we don't know the "new" solenoid is actually good, does he have another he can test with?

Cheers

[photogem]

Meaning it acts differently if the wires are reversed.

The solenoid acts differently, yes. Not the permanent magnet, it still acts.

See it like this: If you pull against a lever you act (apply force).
If now the lever pulles back with the same force, you still act but your action is cancelled.
(like in arm-wrestling)


This is what happens. The action of the permanent magnet is cancelled.

If you reverse polarity (i.e. the wires), it is as if this lever pushes now instead of pulling (or vice versa, you push against the lever and double its action

---------- Post added 04-11-19 at 02:14 AM ----------

Hi mate, I know you are trying to help and I appreciate your knowledge in this area but could we stick to helpful suggestions of things to try rather than telling people everything they know is wrong?

My question to the OP would be, as we don't know the "new" solenoid is actually good, does he have another he can test with?

Cheers

First: I did give directions of how he can test it. It is very simple and straight forward.

Only if you understand that there can be opposite polarity you can test it.
And then you also know if it works.


Second: I am not telling people "everything they know is wrong" but if something is wrong it is just important to point at it because otherwise it can lead to confusion and in some cases even to damage. Some people suggested once to use a demagnetizer. Those who know and understand about it have to tell that it is wrong. This is not personal. It is to prevent confusion and damage. I really don't understand why this is so difficult to take or understand? Honestly!

People are trying to find out "how to DO things the correct way" and not "how to do things the wrong way".

If something is wrong it is wrong. When you measure the impedance of the solenoid you don't measure polarity. You can attach the probes of the multimeter as you wish. Has zero to do with polarity.

[Ajax156]

Sometimes the best way to learn is to do things 'wrong'...

[photogem]

Sometimes the best way to learn is to do things 'wrong'...

That is very true. But only if I am willing to learn and are open to learn. Because after all it is about how to do it right.

Here I find we try to tell people how to do it right and not let them make avoidable mistakes, or am I wrong with this?


The function of the solenoid is well known in this forum.

All has been written about it.

[Ron O]

Okay, I can see I was wrong about how this solenoid works. I hooked it up a 6V battery and one way was stronger and the other way was weaker, so I deduce that the solenoid is working correctly. What now? And why does the lens aperture work in live view?