Pentax k 500 aperture block failure resolved!

robtcorl · 03-26-2017, 09:39 AM

Originally posted by Kevin B123

I'd jump on this, for the cost of a of a third party higher capacity that might be a cheap fix.

Thanks for your suggestions.
Two things I've tried, one is the new battery that came with my KP, and the other is a 3rd party 1400mAh, 7.4v same as the original.
Neither worked, and my K-S2 doesn't want to clear at all, no matter what I try.
Like others, I wish Ricoh/Pentax would do something about this issue.

**Kevin B123** · 03-26-2017, 10:07 AM

Originally posted by robtcorl

Thanks for your suggestions.
Two things I've tried, one is the new battery that came with my KP, and the other is a 3rd party 1400mAh, 7.4v same as the original.
Neither worked, and my K-S2 doesn't want to clear at all, no matter what I try.
Like others, I wish Ricoh/Pentax would do something about this issue.

Thanks for replying on this, at least we know that avenue is closed

zburatoru · 03-26-2017, 12:27 PM

For robtcorl: I will give you a link with some body in states that are saying they've got the fix. You should try them: Pentax Camera Repair - Aperture Control Repair. Good luck!

robtcorl · 03-26-2017, 03:27 PM

Originally posted by zburatoru

For robtcorl: I will give you a link with some body in states that are saying they've got the fix. You should try them: Pentax Camera Repair - Aperture Control Repair. Good luck!

Thank you!
Yes, I may have to go that route.

ekip · 03-27-2017, 04:08 AM

Originally posted by Kevin B123

Did you have the aperture block failure before trying this, and did it work?

I'd jump on this, for the cost of a of a third party higher capacity that might be a cheap fix.

Oh right yeah I forgot to say. I have existing aperture block failure and doing what I said made no difference, all images still came out severely underexposed.

**UncleVanya** · 04-20-2017, 11:19 AM

Originally posted by ekip

Oh right yeah I forgot to say. I have existing aperture block failure and doing what I said made no difference, all images still came out severely underexposed.

When my k-50 failed, I was using both AA and lithium battery about equally. There was no difference for me. I'm glad this works for some people, but I wish we had clear data on why this works.

LensBeginner · 04-20-2017, 01:10 PM

Issue with the aperture block was an electromagnet and a magnet "sticking" together... various fixed included adding solder to increase the distance between the elements, or filing the magnet's tips to reduce its "catchyness".

Using Ni-Mh would probably result in a reduced overall tension, which would affect the electromagnet as well.
Remember remarks about AF motors being "snappier" with CR-V3s than Ni-Mh AAs?

D-LI109: 7.4V
CR-V3: 3.2V * 2 = 6.4V
AA pack: 1.4V * 4 = 5.6V

Ni-Mh are actually rated 1.2V and Alkalines 1.5V, but I've found ~1.4V to be a more typical tension for fully charged Ni-Mh.

Last edited by LensBeginner; 04-22-2017 at 11:59 PM.

mfd · 09-10-2017, 04:52 AM

Originally posted by zburatoru

Hello! I was inspired by this thread: K30 Images dark / underexposed: Pentax SLR Talk Forum: Digital Photography Review.
My story: I have bought a Pentax K 500 in very good condition. I first I didn't realize but after some days I have observed that my first shot was completely dark, and the rest of shots were exposed well. Same story after an hour, after two hours and so on. So I've started to search for solutions and I've came to this thread and I've bought an adapter to resolve the problem. With the adapter and four NIMH batteries of 2500 ma I have tried with quick or slow burst shots, with on and off power as described in that thread. Well, after the treatment my K 500 was not 100% healthy. The first shot was quite underexposed but totally usable. The good news was that after an hour or two or during the same day the underexposed shot was not visible... But in the next day, same story, first shot underexposed but still usable. I was thinking that I can live with that and I didn't care anymore. But, in some day I've needed to buy some spare, and I have tried four AA batteries. I didn't realized first but after some days I've noticed that the first shot was always properly exposed, after an hour, after two, after a day, after days... Evrika! Problem resolved!
My advice: If you have Pentax K-r, K-30, K-50 or K 500 don't use the original battery. Buy an adapter and use NiMH batteries or alkaline and If you have the dark first shot or dark first shots try the method described in this thread. Good luck!

Is just looking to find out the exact sequence of forces used to do the lens down to explain my solution and found this.

This matches my findings exactly. A weaker battery seems to be the solution, so that it doesn't over close the aperture. Eneloop s are good but they sometime need to be run down a bit. Probably why the quick burst solves the problem.
I also think there is a charge left in the camera. I put the original battery in to check my findings and usual problem. When I put the AAs back the first shot was underexposed, but not as hard as normal. Subsequent shots had the exposure correct. Maybe this is also why I need to fire off some shots when the AAs had just been put in.

Everybody should try this as it is far less destructive than surgery and the adapter is less than £2 on eBay.

**Kevin B123** · 09-10-2017, 11:52 AM

Sadly, I have to report that my K-50 has started to underexpose the first shot on startup after being idle for a while

. Standard battery. The second shot is always good. I have an AA adapter and so I will take that route if necessary. I have manual lens options too.

Shutter count 18,954 and date of manufacture 2013:09:21

mfd · 01-20-2018, 02:40 AM

Sad to report my camera is back to its old ways. At Christmas it needed a 5 shot burst and it was fine for a few days. Now it's taking up to 50 shots. Yesterday when I left home I'd got it working but by the time I took some shots, a couple of hours later, the first 20 were black.

I'm now waiting for some other suggestions. Hope others are faring better.

**Kevin B123** · 01-20-2018, 06:26 AM

Originally posted by mfd

Sad to report my camera is back to its old ways. At Christmas it needed a 5 shot burst and it was fine for a few days. Now it's taking up to 50 shots. Yesterday when I left home I'd got it working but by the time I took some shots, a couple of hours later, the first 20 were black.

I'm now waiting for some other suggestions. Hope others are faring better.

The answer lies here:
K-50 / K-500 Aperture Solenoid fix (DIY with pics) - PentaxForums.com

**Cerebum** · 01-20-2018, 04:38 PM

I split my time between eneloops and the proprietary battery. I suspect the higher voltage from the lithium causes the problem to occur more readily but it still happens with the AAs. Bottom line, I sent mine to Pentax UK. As my K30 came from eBay and internally was far from pristine I decided to get it serviced at the same time. The cost for the aperture block, a service and a new CMOS battery was £174 +£38 tax.

ekip · 02-01-2018, 08:00 AM

Originally posted by Cerebum

I split my time between eneloops and the proprietary battery. I suspect the higher voltage from the lithium causes the problem to occur more readily but it still happens with the AAs. Bottom line, I sent mine to Pentax UK. As my K30 came from eBay and internally was far from pristine I decided to get it serviced at the same time. The cost for the aperture block, a service and a new CMOS battery was £174 +£38 tax.

Did they give any info on the CMOS battery like a part number or specification?

**Cerebum** · 02-01-2018, 09:37 AM

Originally posted by ekip

Did they give any info on the CMOS battery like a part number or specification?

They didn’t in the quote. I know the parts have arrived from Japan which is good, because Japanese aperture block units are said to be better than Chinese

but I am still waiting for the return of my camera. If it mentions the part number I will let you know.

09-10-2017, 11:52 AM	#24
Kevin B123 Loyal Site Supporter Join Date: Jul 2016 Location: Hampshire Photos: Gallery \| Albums Posts: 3,190	Sadly, I have to report that my K-50 has started to underexpose the first shot on startup after being idle for a while. Standard battery. The second shot is always good. I have an AA adapter and so I will take that route if necessary. I have manual lens options too. Shutter count 18,954 and date of manufacture 2013:09:21 Last edited by Kevin B123; 09-10-2017 at 11:58 AM. Reason: Shutter count and date of manufacture added

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03-26-2017, 09:39 AM	#16
robtcorl Veteran Member Join Date: Feb 2011 Location: St Louis, MO Photos: Gallery Posts: 11,606	Originally posted by Kevin B123 I'd jump on this, for the cost of a of a third party higher capacity that might be a cheap fix. Thanks for your suggestions. Two things I've tried, one is the new battery that came with my KP, and the other is a 3rd party 1400mAh, 7.4v same as the original. Neither worked, and my K-S2 doesn't want to clear at all, no matter what I try. Like others, I wish Ricoh/Pentax would do something about this issue.

03-26-2017, 10:07 AM	#17
Kevin B123 Loyal Site Supporter Join Date: Jul 2016 Location: Hampshire Photos: Gallery \| Albums Posts: 3,190	Originally posted by robtcorl Thanks for your suggestions. Two things I've tried, one is the new battery that came with my KP, and the other is a 3rd party 1400mAh, 7.4v same as the original. Neither worked, and my K-S2 doesn't want to clear at all, no matter what I try. Like others, I wish Ricoh/Pentax would do something about this issue. Thanks for replying on this, at least we know that avenue is closed

03-26-2017, 12:27 PM	#18
zburatoru Senior Member Join Date: Mar 2010 Location: Sfantu Gheorghe, Romania Photos: Gallery \| Albums Posts: 266 Original Poster	For robtcorl: I will give you a link with some body in states that are saying they've got the fix. You should try them: Pentax Camera Repair - Aperture Control Repair. Good luck!

03-26-2017, 03:27 PM	#19
robtcorl Veteran Member Join Date: Feb 2011 Location: St Louis, MO Photos: Gallery Posts: 11,606	Originally posted by zburatoru For robtcorl: I will give you a link with some body in states that are saying they've got the fix. You should try them: Pentax Camera Repair - Aperture Control Repair. Good luck! Thank you! Yes, I may have to go that route.

03-27-2017, 04:08 AM	#20
ekip Forum Member Join Date: Apr 2016 Posts: 68	Originally posted by Kevin B123 Did you have the aperture block failure before trying this, and did it work? I'd jump on this, for the cost of a of a third party higher capacity that might be a cheap fix. Oh right yeah I forgot to say. I have existing aperture block failure and doing what I said made no difference, all images still came out severely underexposed.

04-20-2017, 11:19 AM	#21
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,472	Originally posted by ekip Oh right yeah I forgot to say. I have existing aperture block failure and doing what I said made no difference, all images still came out severely underexposed. When my k-50 failed, I was using both AA and lithium battery about equally. There was no difference for me. I'm glad this works for some people, but I wish we had clear data on why this works.

04-20-2017, 01:10 PM	#22
LensBeginner Veteran Member Join Date: Sep 2014 Photos: Albums Posts: 4,696	Issue with the aperture block was an electromagnet and a magnet "sticking" together... various fixed included adding solder to increase the distance between the elements, or filing the magnet's tips to reduce its "catchyness". Using Ni-Mh would probably result in a reduced overall tension, which would affect the electromagnet as well. Remember remarks about AF motors being "snappier" with CR-V3s than Ni-Mh AAs? D-LI109: 7.4V CR-V3: 3.2V * 2 = 6.4V AA pack: 1.4V * 4 = 5.6V Ni-Mh are actually rated 1.2V and Alkalines 1.5V, but I've found ~1.4V to be a more typical tension for fully charged Ni-Mh. Last edited by LensBeginner; 04-22-2017 at 11:59 PM.

09-10-2017, 04:52 AM	#23
mfd New Member Join Date: Aug 2017 Posts: 8	Originally posted by zburatoru Hello! I was inspired by this thread: K30 Images dark / underexposed: Pentax SLR Talk Forum: Digital Photography Review. My story: I have bought a Pentax K 500 in very good condition. I first I didn't realize but after some days I have observed that my first shot was completely dark, and the rest of shots were exposed well. Same story after an hour, after two hours and so on. So I've started to search for solutions and I've came to this thread and I've bought an adapter to resolve the problem. With the adapter and four NIMH batteries of 2500 ma I have tried with quick or slow burst shots, with on and off power as described in that thread. Well, after the treatment my K 500 was not 100% healthy. The first shot was quite underexposed but totally usable. The good news was that after an hour or two or during the same day the underexposed shot was not visible... But in the next day, same story, first shot underexposed but still usable. I was thinking that I can live with that and I didn't care anymore. But, in some day I've needed to buy some spare, and I have tried four AA batteries. I didn't realized first but after some days I've noticed that the first shot was always properly exposed, after an hour, after two, after a day, after days... Evrika! Problem resolved! My advice: If you have Pentax K-r, K-30, K-50 or K 500 don't use the original battery. Buy an adapter and use NiMH batteries or alkaline and If you have the dark first shot or dark first shots try the method described in this thread. Good luck! Is just looking to find out the exact sequence of forces used to do the lens down to explain my solution and found this. This matches my findings exactly. A weaker battery seems to be the solution, so that it doesn't over close the aperture. Eneloop s are good but they sometime need to be run down a bit. Probably why the quick burst solves the problem. I also think there is a charge left in the camera. I put the original battery in to check my findings and usual problem. When I put the AAs back the first shot was underexposed, but not as hard as normal. Subsequent shots had the exposure correct. Maybe this is also why I need to fire off some shots when the AAs had just been put in. Everybody should try this as it is far less destructive than surgery and the adapter is less than £2 on eBay.

01-20-2018, 02:40 AM	#25
mfd New Member Join Date: Aug 2017 Posts: 8	Sad to report my camera is back to its old ways. At Christmas it needed a 5 shot burst and it was fine for a few days. Now it's taking up to 50 shots. Yesterday when I left home I'd got it working but by the time I took some shots, a couple of hours later, the first 20 were black. I'm now waiting for some other suggestions. Hope others are faring better.

01-20-2018, 06:26 AM	#26
Kevin B123 Loyal Site Supporter Join Date: Jul 2016 Location: Hampshire Photos: Gallery \| Albums Posts: 3,190	Originally posted by mfd Sad to report my camera is back to its old ways. At Christmas it needed a 5 shot burst and it was fine for a few days. Now it's taking up to 50 shots. Yesterday when I left home I'd got it working but by the time I took some shots, a couple of hours later, the first 20 were black. I'm now waiting for some other suggestions. Hope others are faring better. The answer lies here: K-50 / K-500 Aperture Solenoid fix (DIY with pics) - PentaxForums.com

01-20-2018, 04:38 PM	#27
Cerebum Site Supporter Join Date: Oct 2017 Location: Lancaster Photos: Gallery Posts: 3,829	I split my time between eneloops and the proprietary battery. I suspect the higher voltage from the lithium causes the problem to occur more readily but it still happens with the AAs. Bottom line, I sent mine to Pentax UK. As my K30 came from eBay and internally was far from pristine I decided to get it serviced at the same time. The cost for the aperture block, a service and a new CMOS battery was £174 +£38 tax.

02-01-2018, 08:00 AM	#28
ekip Forum Member Join Date: Apr 2016 Posts: 68	Originally posted by Cerebum I split my time between eneloops and the proprietary battery. I suspect the higher voltage from the lithium causes the problem to occur more readily but it still happens with the AAs. Bottom line, I sent mine to Pentax UK. As my K30 came from eBay and internally was far from pristine I decided to get it serviced at the same time. The cost for the aperture block, a service and a new CMOS battery was £174 +£38 tax. Did they give any info on the CMOS battery like a part number or specification?

02-01-2018, 09:37 AM	#29
Cerebum Site Supporter Join Date: Oct 2017 Location: Lancaster Photos: Gallery Posts: 3,829	Originally posted by ekip Did they give any info on the CMOS battery like a part number or specification? They didn’t in the quote. I know the parts have arrived from Japan which is good, because Japanese aperture block units are said to be better than Chinese but I am still waiting for the return of my camera. If it mentions the part number I will let you know.