K70 and a 20-40 limited

onatur · 02-23-2023, 06:47 PM

Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

Hello all,

I have an issue with the aperture control on my k70 with the 20-40 limited lens. I don't have an issue with the k70 and a 55-300 lens.

Have exchanged the 20-40 for a new one, still have the same issue, pictures are far too dark. If I switch to the 55-300, all good.

What am I not doing properly?

Thanks in advance for the help.

jgnfld · 02-23-2023, 07:38 PM

Is there any chance of you testing on a 2nd body?

Weird.

**allanmh** · 02-23-2023, 07:49 PM

If your 55-300mm is the PLM version, that might be your answer.
Your K70 might have the dreaded aperture block failure. This would affect the 20-40 Ltd, but not the 55-300 PLM.
If your 55-300mm is not the PLM version, I have no idea what the problem might be.
Hope this helps.

**photogem** · 02-23-2023, 10:02 PM

I already guess with 99% certainty that your K-70 has aperture-block-failure (ABF)!

With your DA20-40 (at 18mm wide open do this check:
How to detect aperture-block failure/stuck solenoid on Pentax K-70 - PentaxForums.com
Then you know for sure.

I guess your telezoom is the latest HD DA55-300PLM. WIth this one you don't have that problem because it is KAF4, i.e. electronic aperture control.

If your K70 has the stuck solenoid, then read this:
Tutorial/Repair Pentax K-70 with aperture-problem: Exchange solenoid - PentaxForums.com
and see if you feel up to apply DIY.

More details why this happens here:
A LITTLE BIT OF HISTORY: Development of the solenoid in Pentax cameras - Page 9 - PentaxForums.com
On this last page I also explain which K-70's can be hit by ABF.

You find out which date your K-70 was manufactured here:
Check Camera Shutter Count and Manufacture Date
but most certainly before 2021!

onatur · 02-27-2023, 12:54 PM

Thanks for all the info.
Would it be better to exchange the 20-40 limited for a HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR
Or fix the k70

**mikesbike** · 02-27-2023, 03:50 PM

Originally posted by onatur

Or fix the k70

Definitely this! If wanting to continue with your K-70 as is, you could spend some big $$$$ for a Pentax DA* 16-50mm f/2.8 PLM lens, but less money is better spent putting the camera in shape to handle any lens. Your DA 20-40mm Limited is already a very fine lens, and capable of f/2.8 at the short end, while at the long end is only one stop off that aperture. Just make sure if you have the repair done professionally, they make sure they will only order the current part solenoid, not old stock solenoid. Read what photogem says, let this be your guide for action.

que es tu · 02-27-2023, 03:54 PM

++1 Repair the K70!! It is a fine advanced camera with features no other brand has at this level. Paired with the 20-40 it will make a wicked pair!

**photogem** · 02-28-2023, 01:09 AM

Originally posted by onatur

Thanks for all the info.
Would it be better to exchange the 20-40 limited for a HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR
Or fix the k70

no matter which lens you plan to buy, fix your Pentax K-70!

**JensE** · 02-28-2023, 03:11 AM

Originally posted by mikesbike

Definitely this! If wanting to continue with your K-70 as is, you could spend some big $$$$ for a Pentax DA* 16-50mm f/2.8 PLM lens, but less money is better spent putting the camera in shape to handle any lens. Your DA 20-40mm Limited is already a very fine lens, and capable of f/2.8 at the short end, while at the long end is only one stop off that aperture. Just make sure if you have the repair done professionally, they make sure they will only order the current part solenoid, not old stock solenoid. Read what photogem says, let this be your guide for action.

Just to make it explicit: Even if you choose to not follow this excellent advice, the HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database is a KAF3 lens, so it would not work any better than the DA 20-40mm, only the above mentioned DA* uses KAF4 in this focal length range.

onatur · 02-28-2023, 05:09 PM

Got it. So, where do I purchase a replacement solenoid?

**photogem** · 02-28-2023, 07:40 PM

Originally posted by onatur

Got it. So, where do I purchase a replacement solenoid?

Pentax K-30 K-50 K-70 K-S1/S2 K-500 Genuine White Solenoid Part - Japan - | eBay

02-23-2023, 06:47 PM	#1
onatur New Member Join Date: Feb 2023 Posts: 7	K70 and a 20-40 limited Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. Hello all, I have an issue with the aperture control on my k70 with the 20-40 limited lens. I don't have an issue with the k70 and a 55-300 lens. Have exchanged the 20-40 for a new one, still have the same issue, pictures are far too dark. If I switch to the 55-300, all good. What am I not doing properly? Thanks in advance for the help.

02-27-2023, 03:50 PM	#6
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,562	Originally posted by onatur Or fix the k70 Definitely this! If wanting to continue with your K-70 as is, you could spend some big $$$$ for a Pentax DA* 16-50mm f/2.8 PLM lens, but less money is better spent putting the camera in shape to handle any lens. Your DA 20-40mm Limited is already a very fine lens, and capable of f/2.8 at the short end, while at the long end is only one stop off that aperture. Just make sure if you have the repair done professionally, they make sure they will only order the current part solenoid, not old stock solenoid. Read what photogem says, let this be your guide for action. Last edited by mikesbike; 02-27-2023 at 04:03 PM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Debate and decide- FA 31 Limited or DA 20-40 Limited?	Wheatridger	Pentax SLR Lens Discussion	42	04-27-2022 01:25 PM
Limited kits: 15 - 20-40 - 70 or 15 - 21 - 40 - 70?	Cambo	Pentax SLR Lens Discussion	48	06-28-2021 10:45 AM
For Sale - Sold: KP, DA 20-40 f/2.8-4 LIMITED DA 35 f/2.8 Macro Limited	TerryL	Sold Items	2	08-05-2019 03:03 PM
For Sale - Sold: Pentax Cameras and Lenses (K-01, K-5, K-3, 18-135, 20-40, 50-135, 15, 30, 40, 50)	jazz_711	Sold Items	18	05-27-2019 11:00 PM
For Sale - Sold: PRICES REDUCED. DA 20-40 limited, DA 18-135, Sigma 10-20 f3.5	mills	Sold Items	3	03-27-2019 07:41 AM

02-23-2023, 07:38 PM	#2
jgnfld Moderator Loyal Site Supporter Join Date: Feb 2015 Location: Avalon Peninsula, Newfoundland Photos: Gallery \| Albums Posts: 1,799	Is there any chance of you testing on a 2nd body? Weird.

02-23-2023, 07:49 PM	#3
allanmh Loyal Site Supporter Join Date: Jan 2013 Location: København, Danmark Posts: 157	If your 55-300mm is the PLM version, that might be your answer. Your K70 might have the dreaded aperture block failure. This would affect the 20-40 Ltd, but not the 55-300 PLM. If your 55-300mm is not the PLM version, I have no idea what the problem might be. Hope this helps.

02-23-2023, 10:02 PM	#4
photogem Site Supporter Join Date: Apr 2015 Posts: 3,524	I already guess with 99% certainty that your K-70 has aperture-block-failure (ABF)! With your DA20-40 (at 18mm wide open do this check: How to detect aperture-block failure/stuck solenoid on Pentax K-70 - PentaxForums.com Then you know for sure. I guess your telezoom is the latest HD DA55-300PLM. WIth this one you don't have that problem because it is KAF4, i.e. electronic aperture control. If your K70 has the stuck solenoid, then read this: Tutorial/Repair Pentax K-70 with aperture-problem: Exchange solenoid - PentaxForums.com and see if you feel up to apply DIY. More details why this happens here: A LITTLE BIT OF HISTORY: Development of the solenoid in Pentax cameras - Page 9 - PentaxForums.com On this last page I also explain which K-70's can be hit by ABF. You find out which date your K-70 was manufactured here: Check Camera Shutter Count and Manufacture Date but most certainly before 2021!

02-27-2023, 12:54 PM	#5
onatur New Member Join Date: Feb 2023 Posts: 7 Original Poster	Thanks for all the info. Would it be better to exchange the 20-40 limited for a HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Or fix the k70

02-27-2023, 03:54 PM	#7
que es tu Pentaxian Join Date: Feb 2020 Location: Smoky Mountains, NC Photos: Gallery \| Albums Posts: 1,605	++1 Repair the K70!! It is a fine advanced camera with features no other brand has at this level. Paired with the 20-40 it will make a wicked pair!

02-28-2023, 01:09 AM	#8
photogem Site Supporter Join Date: Apr 2015 Posts: 3,524	Originally posted by onatur Thanks for all the info. Would it be better to exchange the 20-40 limited for a HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Or fix the k70 no matter which lens you plan to buy, fix your Pentax K-70!

02-28-2023, 03:11 AM	#9
JensE Site Supporter Join Date: Dec 2015 Location: Leipzig Photos: Gallery \| Albums Posts: 1,975	Originally posted by mikesbike Definitely this! If wanting to continue with your K-70 as is, you could spend some big $$$$ for a Pentax DA* 16-50mm f/2.8 PLM lens, but less money is better spent putting the camera in shape to handle any lens. Your DA 20-40mm Limited is already a very fine lens, and capable of f/2.8 at the short end, while at the long end is only one stop off that aperture. Just make sure if you have the repair done professionally, they make sure they will only order the current part solenoid, not old stock solenoid. Read what photogem says, let this be your guide for action. Just to make it explicit: Even if you choose to not follow this excellent advice, the HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database is a KAF3 lens, so it would not work any better than the DA 20-40mm, only the above mentioned DA* uses KAF4 in this focal length range.

02-28-2023, 05:09 PM	#10
onatur New Member Join Date: Feb 2023 Posts: 7 Original Poster	Got it. So, where do I purchase a replacement solenoid?

02-28-2023, 07:40 PM	#11
photogem Site Supporter Join Date: Apr 2015 Posts: 3,524	Originally posted by onatur Got it. So, where do I purchase a replacement solenoid? Pentax K-30 K-50 K-70 K-S1/S2 K-500 Genuine White Solenoid Part - Japan - \| eBay