K-50 / K-500 Aperture Solenoid fix (DIY with pics)

**photogem** · 03-18-2019, 03:28 AM

I have uploaded 2 photos to show why the flash-condenser by all means should be discharged

and
why the top-part of the K30 and all others should be lifted:
K-50 / K-500 Aperture Solenoid fix (DIY with pics) - Page 17 - PentaxForums.com

keos · 03-24-2019, 10:01 PM

followed the directions in the OP (also watched a few YouTube Videos). Had this happen to my K-50 and I left it alone for a few weeks. Finally gave in and bought the white solenoid on ebay for 35 bucks. Worked like a charm. I kind of half assed the solder of the wires to the new solenoid, but it seems to work, so let's see how long it holds. I mean I just applied some solder to the prong on the solenoid, then held the exposed wire up to the newly applied solder and melted them a little to attach the wire. Not exactly an A effort, but seems to be good enough.

**photogem** · 03-25-2019, 02:23 AM

Originally posted by keos

followed the directions in the OP (also watched a few YouTube Videos). Had this happen to my K-50 and I left it alone for a few weeks. Finally gave in and bought the white solenoid on ebay for 35 bucks. Worked like a charm. I kind of half assed the solder of the wires to the new solenoid, but it seems to work, so let's see how long it holds. I mean I just applied some solder to the prong on the solenoid, then held the exposed wire up to the newly applied solder and melted them a little to attach the wire. Not exactly an A effort, but seems to be good enough.

This could be a bit tricky because a bad soldering joint is more like glueing than soldering.
Solder only perfectly holds when both parts have solder on it and melt in the moment of touching.
Then one has to be absolutly still/quiet.... i.e. zero movement, once can see the solder getting hard.

Because the solenoid itself has a strong movement in its body, it then vibrates. A bad soldering-joint will then show.

Also: Each time you touch to be soldered parts with the tip of the soldering-iron, you first clean the tip!
You don't want residue dirt which collects due to heat on the tip "melting into the solder"! Usually this is carbon-residue.

Don't worry about what appears as red paint on the solenoid:

This is not protection on the solder with feltmarker paint as somebody once tried to convince others: It is red threadlock-paint . It gives some extra hold to glue the solenoid with the tiny plastic rod it sits on next to the screw. You can apply nailvarnish laquer instead if you feel the need to do so.

But anyway, good soldering is essential.

So if your K-50 strikes again, that's why.

But you have done it already, so a 2.nd time is that much easier.

keos · 03-25-2019, 05:29 PM

Originally posted by photogem

This could be a bit tricky because a bad soldering joint is more like glueing than soldering.
Solder only perfectly holds when both parts have solder on it and melt in the moment of touching.
Then one has to be absolutly still/quiet.... i.e. zero movement, once can see the solder getting hard.

Because the solenoid itself has a strong movement in its body, it then vibrates. A bad soldering-joint will then show.

Also: Each time you touch to be soldered parts with the tip of the soldering-iron, you first clean the tip!
You don't want residue dirt which collects due to heat on the tip "melting into the solder"! Usually this is carbon-residue.

Don't worry about what appears as red paint on the solenoid:

This is not protection on the solder with feltmarker paint as somebody once tried to convince others: It is red threadlock-paint . It gives some extra hold to glue the solenoid with the tiny plastic rod it sits on next to the screw. You can apply nailvarnish laquer instead if you feel the need to do so.

But anyway, good soldering is essential.

So if your K-50 strikes again, that's why.

But you have done it already, so a 2.nd time is that much easier.

it seems to hold for now, I took several shots. I'm more worried about cold solder joints since I didn't use any flux at all. not sure if I've ruined the low temperature operations, not that I can test easily as it's warming up now.

Ajax156 · 03-25-2019, 07:32 PM

Originally posted by keos

followed the directions in the OP (also watched a few YouTube Videos). Had this happen to my K-50 and I left it alone for a few weeks. Finally gave in and bought the white solenoid on ebay for 35 bucks. Worked like a charm. I kind of half assed the solder of the wires to the new solenoid, but it seems to work, so let's see how long it holds. I mean I just applied some solder to the prong on the solenoid, then held the exposed wire up to the newly applied solder and melted them a little to attach the wire. Not exactly an A effort, but seems to be good enough.

Well done.

It's a fairly simple operation but very satisfying when it all works as intended.

**photogem** · 03-26-2019, 01:32 AM

Originally posted by keos

it seems to hold for now, I took several shots. I'm more worried about cold solder joints since I didn't use any flux at all. not sure if I've ruined the low temperature operations, not that I can test easily as it's warming up now.

Depends on the solder you used.
Most modern solder has flux inside.

This was the name which evaded me: Cold solder joint!
That's what I meant with "glueing".

What do you mean with "warming up now?" What warms now up? I don't understand what you mean!

Ajax156 · 03-26-2019, 06:19 AM

He means spring/summer is approaching...

keos · 03-26-2019, 06:37 PM

Originally posted by Ajax156

He means spring/summer is approaching...

yes, it was tongue in cheek. not that funny I guess.

Ron O · 04-09-2019, 12:44 PM

I replaced my solenoid with the white version on eBay for $45 but the pictures were still very dark to black. I unsoldered one wire and checked continuity with my fluke multimeter and it was the correct approximately 30 ohms. I resoldered the wire back again thinking it might have been a cold solder joint but it still does not work. Any ideas? It does take brighter pictures in live view but they are not correctly exposed. I have multiple Pentax cameras and like them very much and would love to have my K50 work again. Thanks for your time.

reh321 · 04-09-2019, 01:06 PM

Originally posted by Ron O

I replaced my solenoid with the white version on eBay for $45 but the pictures were still very dark to black. I unsoldered one wire and checked continuity with my fluke multimeter and it was the correct approximately 30 ohms. I resoldered the wire back again thinking it might have been a cold solder joint but it still does not work. Any ideas? It does take brighter pictures in live view but they are not correctly exposed. I have multiple Pentax cameras and like them very much and would love to have my K50 work again. Thanks for your time.

There is some evidence of metering issues - which have been misdiagnosed as aperture control issues (*). If you get different results depending on whether you use viewfinder or LV, that would be something to investigate. Can you use Exposure Compensation { +/- button } to bring results to within reasonable?

(*) One guy apparently gave up when he didn't get any help here - or from Pentax Repair {they replaced the aperture control unit, and announced it "fixed" .... but it still didn't work right}

Ron O · 04-09-2019, 01:27 PM

If I go to plus 5, I can get a picture that is only moderately underexposed.

**photogem** · 04-09-2019, 11:50 PM

Originally posted by Ron O

I replaced my solenoid with the white version on eBay for $45 but the pictures were still very dark to black. I unsoldered one wire and checked continuity with my fluke multimeter and it was the correct approximately 30 ohms. I resoldered the wire back again thinking it might have been a cold solder joint but it still does not work. Any ideas? It does take brighter pictures in live view but they are not correctly exposed. I have multiple Pentax cameras and like them very much and would love to have my K50 work again. Thanks for your time.

This is why one should always prior assembling the body after having changed the solenoid do a check/test with an A or AF-lens.
You see the solenoid in action. With aperture wide open you should see the plunger moving when you take a photo. The photo is then shown for a short time on the LCD.

Did you check that the wires are on the correct side? If you look onto the solenoid with its plunger facing downwards: Pink left, lilac right! The solderjoints: Where did you solder, on the solenoid itself (the correct way) or on this flat-ribbon cable as shown HERE ?
The correct way is ONLY on the solenoid itself! The flat-ribbon cable (is that the correct English name for it?) is a very bad place to solder. To easy to damage it and difficult to repair then as you can't get underneath.

I admire all the work madphys has done here but this idea to unsolder the wires on this cable is just not at all a good idea!

But first let's see how you did it, nevertheless this needs to be mentioned again and again.

When you found out that your K50 did not work correctly anymore, how did you first try to solve it?
Right away change of solenoid or burst-mode first?

reh321 · 04-10-2019, 08:22 AM

Originally posted by photogem

This is why one should always prior assembling the body after having changed the solenoid do a check/test with an A or AF-lens.
You see the solenoid in action. With aperture wide open you should see the plunger moving when you take a photo. The photo is then shown for a short time on the LCD.

Did you check that the wires are on the correct side? If you look onto the solenoid with its plunger facing downwards: Pink left, lilac right! The solderjoints: Where did you solder, on the solenoid itself (the correct way) or on this flat-ribbon cable as shown HERE ?
The correct way is ONLY on the solenoid itself! The flat-ribbon cable (is that the correct English name for it?) is a very bad place to solder. To easy to damage it and difficult to repair then as you can't get underneath.

I admire all the work madphys has done here but this idea to unsolder the wires on this cable is just not at all a good idea!

But first let's see how you did it, nevertheless this needs to be mentioned again and again.

When you found out that your K50 did not work correctly anymore, how did you first try to solve it?
Right away change of solenoid or burst-mode first?

How would an aperture problem cause photo taken using OVF to be darker than photo taken using LV?

reh321 · 04-10-2019, 08:25 AM

Originally posted by Ron O

If I go to plus 5, I can get a picture that is only moderately underexposed.

Which mode are you using - 'P', 'Tv', 'Av', 'TAv', .....

What ISO setting are you using - hopefully not 'auto'?

**photogem** · 04-10-2019, 09:38 AM

Originally posted by reh321

How would an aperture problem cause photo taken using OVF to be darker than photo taken uYour Notifications:sing LV?

Often when the plunger of the solenoid is jammed, LV does still work (for a while). The solenoid is used twice during LV. I have not investigated this further, because I hardly use LV.

03-18-2019, 03:28 AM	#256
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Photos attached for solenoid change of K30 I have uploaded 2 photos to show why the flash-condenser by all means should be discharged and why the top-part of the K30 and all others should be lifted: K-50 / K-500 Aperture Solenoid fix (DIY with pics) - Page 17 - PentaxForums.com

04-09-2019, 01:06 PM	#265
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,177	Originally posted by Ron O I replaced my solenoid with the white version on eBay for $45 but the pictures were still very dark to black. I unsoldered one wire and checked continuity with my fluke multimeter and it was the correct approximately 30 ohms. I resoldered the wire back again thinking it might have been a cold solder joint but it still does not work. Any ideas? It does take brighter pictures in live view but they are not correctly exposed. I have multiple Pentax cameras and like them very much and would love to have my K50 work again. Thanks for your time. There is some evidence of metering issues - which have been misdiagnosed as aperture control issues (). If you get different results depending on whether you use viewfinder or LV, that would be something to investigate. Can you use Exposure Compensation { +/- button } to bring results to within reasonable? () One guy apparently gave up when he didn't get any help here - or from Pentax Repair {they replaced the aperture control unit, and announced it "fixed" .... but it still didn't work right} Last edited by reh321; 04-09-2019 at 01:09 PM. Reason: added ()*

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03-24-2019, 10:01 PM	#257
keos Senior Member Join Date: Jan 2018 Posts: 108	followed the directions in the OP (also watched a few YouTube Videos). Had this happen to my K-50 and I left it alone for a few weeks. Finally gave in and bought the white solenoid on ebay for 35 bucks. Worked like a charm. I kind of half assed the solder of the wires to the new solenoid, but it seems to work, so let's see how long it holds. I mean I just applied some solder to the prong on the solenoid, then held the exposed wire up to the newly applied solder and melted them a little to attach the wire. Not exactly an A effort, but seems to be good enough.

03-25-2019, 02:23 AM	#258
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by keos followed the directions in the OP (also watched a few YouTube Videos). Had this happen to my K-50 and I left it alone for a few weeks. Finally gave in and bought the white solenoid on ebay for 35 bucks. Worked like a charm. I kind of half assed the solder of the wires to the new solenoid, but it seems to work, so let's see how long it holds. I mean I just applied some solder to the prong on the solenoid, then held the exposed wire up to the newly applied solder and melted them a little to attach the wire. Not exactly an A effort, but seems to be good enough. This could be a bit tricky because a bad soldering joint is more like glueing than soldering. Solder only perfectly holds when both parts have solder on it and melt in the moment of touching. Then one has to be absolutly still/quiet.... i.e. zero movement, once can see the solder getting hard. Because the solenoid itself has a strong movement in its body, it then vibrates. A bad soldering-joint will then show. Also: Each time you touch to be soldered parts with the tip of the soldering-iron, you first clean the tip! You don't want residue dirt which collects due to heat on the tip "melting into the solder"! Usually this is carbon-residue. Don't worry about what appears as red paint on the solenoid: This is not protection on the solder with feltmarker paint as somebody once tried to convince others: It is red threadlock-paint . It gives some extra hold to glue the solenoid with the tiny plastic rod it sits on next to the screw. You can apply nailvarnish laquer instead if you feel the need to do so. But anyway, good soldering is essential. So if your K-50 strikes again, that's why. But you have done it already, so a 2.nd time is that much easier.

03-25-2019, 05:29 PM	#259
keos Senior Member Join Date: Jan 2018 Posts: 108	Originally posted by photogem This could be a bit tricky because a bad soldering joint is more like glueing than soldering. Solder only perfectly holds when both parts have solder on it and melt in the moment of touching. Then one has to be absolutly still/quiet.... i.e. zero movement, once can see the solder getting hard. Because the solenoid itself has a strong movement in its body, it then vibrates. A bad soldering-joint will then show. Also: Each time you touch to be soldered parts with the tip of the soldering-iron, you first clean the tip! You don't want residue dirt which collects due to heat on the tip "melting into the solder"! Usually this is carbon-residue. Don't worry about what appears as red paint on the solenoid: This is not protection on the solder with feltmarker paint as somebody once tried to convince others: It is red threadlock-paint . It gives some extra hold to glue the solenoid with the tiny plastic rod it sits on next to the screw. You can apply nailvarnish laquer instead if you feel the need to do so. But anyway, good soldering is essential. So if your K-50 strikes again, that's why. But you have done it already, so a 2.nd time is that much easier. it seems to hold for now, I took several shots. I'm more worried about cold solder joints since I didn't use any flux at all. not sure if I've ruined the low temperature operations, not that I can test easily as it's warming up now.

03-25-2019, 07:32 PM	#260
Ajax156 Junior Member Join Date: Jan 2019 Posts: 45	Originally posted by keos followed the directions in the OP (also watched a few YouTube Videos). Had this happen to my K-50 and I left it alone for a few weeks. Finally gave in and bought the white solenoid on ebay for 35 bucks. Worked like a charm. I kind of half assed the solder of the wires to the new solenoid, but it seems to work, so let's see how long it holds. I mean I just applied some solder to the prong on the solenoid, then held the exposed wire up to the newly applied solder and melted them a little to attach the wire. Not exactly an A effort, but seems to be good enough. Well done. It's a fairly simple operation but very satisfying when it all works as intended.

03-26-2019, 01:32 AM	#261
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by keos it seems to hold for now, I took several shots. I'm more worried about cold solder joints since I didn't use any flux at all. not sure if I've ruined the low temperature operations, not that I can test easily as it's warming up now. Depends on the solder you used. Most modern solder has flux inside. This was the name which evaded me: Cold solder joint! That's what I meant with "glueing". What do you mean with "warming up now?" What warms now up? I don't understand what you mean!

03-26-2019, 06:19 AM	#262
Ajax156 Junior Member Join Date: Jan 2019 Posts: 45	He means spring/summer is approaching...

03-26-2019, 06:37 PM	#263
keos Senior Member Join Date: Jan 2018 Posts: 108	Originally posted by Ajax156 He means spring/summer is approaching... yes, it was tongue in cheek. not that funny I guess.

04-09-2019, 12:44 PM	#264
Ron O New Member Join Date: Apr 2019 Location: southeast Colorado Posts: 14	I replaced my solenoid with the white version on eBay for $45 but the pictures were still very dark to black. I unsoldered one wire and checked continuity with my fluke multimeter and it was the correct approximately 30 ohms. I resoldered the wire back again thinking it might have been a cold solder joint but it still does not work. Any ideas? It does take brighter pictures in live view but they are not correctly exposed. I have multiple Pentax cameras and like them very much and would love to have my K50 work again. Thanks for your time.

04-09-2019, 01:27 PM	#266
Ron O New Member Join Date: Apr 2019 Location: southeast Colorado Posts: 14	If I go to plus 5, I can get a picture that is only moderately underexposed.

04-09-2019, 11:50 PM	#267
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by Ron O I replaced my solenoid with the white version on eBay for $45 but the pictures were still very dark to black. I unsoldered one wire and checked continuity with my fluke multimeter and it was the correct approximately 30 ohms. I resoldered the wire back again thinking it might have been a cold solder joint but it still does not work. Any ideas? It does take brighter pictures in live view but they are not correctly exposed. I have multiple Pentax cameras and like them very much and would love to have my K50 work again. Thanks for your time. This is why one should always prior assembling the body after having changed the solenoid do a check/test with an A or AF-lens. You see the solenoid in action. With aperture wide open you should see the plunger moving when you take a photo. The photo is then shown for a short time on the LCD. Did you check that the wires are on the correct side? If you look onto the solenoid with its plunger facing downwards: Pink left, lilac right! The solderjoints: Where did you solder, on the solenoid itself (the correct way) or on this flat-ribbon cable as shown HERE ? The correct way is ONLY on the solenoid itself! The flat-ribbon cable (is that the correct English name for it?) is a very bad place to solder. To easy to damage it and difficult to repair then as you can't get underneath. I admire all the work madphys has done here but this idea to unsolder the wires on this cable is just not at all a good idea! But first let's see how you did it, nevertheless this needs to be mentioned again and again. When you found out that your K50 did not work correctly anymore, how did you first try to solve it? Right away change of solenoid or burst-mode first?

04-10-2019, 08:22 AM	#268
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,177	Originally posted by photogem This is why one should always prior assembling the body after having changed the solenoid do a check/test with an A or AF-lens. You see the solenoid in action. With aperture wide open you should see the plunger moving when you take a photo. The photo is then shown for a short time on the LCD. Did you check that the wires are on the correct side? If you look onto the solenoid with its plunger facing downwards: Pink left, lilac right! The solderjoints: Where did you solder, on the solenoid itself (the correct way) or on this flat-ribbon cable as shown HERE ? The correct way is ONLY on the solenoid itself! The flat-ribbon cable (is that the correct English name for it?) is a very bad place to solder. To easy to damage it and difficult to repair then as you can't get underneath. I admire all the work madphys has done here but this idea to unsolder the wires on this cable is just not at all a good idea! But first let's see how you did it, nevertheless this needs to be mentioned again and again. When you found out that your K50 did not work correctly anymore, how did you first try to solve it? Right away change of solenoid or burst-mode first? How would an aperture problem cause photo taken using OVF to be darker than photo taken using LV?

04-10-2019, 08:25 AM	#269
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,177	Originally posted by Ron O If I go to plus 5, I can get a picture that is only moderately underexposed. Which mode are you using - 'P', 'Tv', 'Av', 'TAv', ..... What ISO setting are you using - hopefully not 'auto'?

04-10-2019, 09:38 AM	#270
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	Originally posted by reh321 How would an aperture problem cause photo taken using OVF to be darker than photo taken uYour Notifications:sing LV? Often when the plunger of the solenoid is jammed, LV does still work (for a while). The solenoid is used twice during LV. I have not investigated this further, because I hardly use LV.