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02-27-2017, 07:47 AM - 1 Like   #421
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QuoteOriginally posted by sys3175 Quote
It surely looks like it. To make sure, you should compare the coil's resistance after you removed the other part, they should be roughly the same.
You need to measure more than just that. Between both systems: You need to measure the force of the permanent magnet - a simple separation force measurement with a spring scale would suffice. You need to measure the voltage and current used to operated the coil. You need to measure the timings and force on the lever that pulls the plunger out of coil. You need to measure the voltage and current used by the motor or whatever that drives the rest of the mechanism.

02-27-2017, 08:33 AM   #422
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QuoteOriginally posted by altopiet Quote
Hi, I found this, in my MZ-50, which I've already stripped for other parts...The screwdriver points to where I removed it from.

I just want to make sure that it's the part that needs replacement, before starting to strip my K-30.

(Sorry about the cellphone quality)
Is there any resting tension on the pin that goes through the horseshoe piece? and in which direction?
02-27-2017, 08:45 AM   #423
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QuoteOriginally posted by ekip Quote
Is there any resting tension on the pin that goes through the horseshoe piece? and in which direction?
Sorry I'm not very technically inclined, if you mean some magnetism...I lifted it from position (in the MZ-50), with just minimal resistance when pulling it away from the point you mention...
02-27-2017, 09:39 AM   #424
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QuoteOriginally posted by altopiet Quote
Sorry I'm not very technically inclined, if you mean some magnetism...I lifted it from position (in the MZ-50), with just minimal resistance when pulling it away from the point you mention...
In the second pic there is a brass pin left behind in the camera. The horseshoe moves it up and down but it has a spring attached I think.

02-28-2017, 01:16 AM   #425
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QuoteOriginally posted by Not a Number Quote
You need to measure more than just that. Between both systems: You need to measure the force of the permanent magnet - a simple separation force measurement with a spring scale would suffice. You need to measure the voltage and current used to operated the coil. You need to measure the timings and force on the lever that pulls the plunger out of coil. You need to measure the voltage and current used by the motor or whatever that drives the rest of the mechanism.
What danger if one just takes the risk and uses the solenoid?

As I understand it, Pentax used those solenoids first in the late SLR film bodies for control of the flash compartment.
Then followed by *ist, K10D, K100D, K200D, K M, K X, K R which all use two of those solenoids.


QuoteOriginally posted by Not a Number Quote
Right. But if the coil is shorting or insufficient current is being sent to the coil then it could fail to disengage. The system failure can be a combination of stronger magnet, coil failure, insufficient power to coil, failure of the mechanism that pulls the plunger out. Replacing the solenoid with one with a weaker magnet may solve the problem only because less current or mechanical force is required to overcome the attraction of the magnet. If the rest of the system continues to deteriorate failure could re-occur due to once again not being able to overcome the attraction of the weaker magnet.
If it is insufficient current, than more so the chance that K30s with Li-Ion batteries might fail easier than those used with AA Eneloops (NiMH) (although we have a member proving the opposite) because AA NIMHs can provide more current.

Some data can be compared here:

http://batteryuniversity.com/learn/archive/whats_the_best_battery

NiMH batteries are known for their "high drain" performance:
Rechargeable Batteries explained in detail (NiMH, NiZn, NiCd, RAM)

What was said here
QuoteOriginally posted by victormeldrew Quote
Battery manufacturers rarely publish maximum current drain specs to end users...but lithium have by far and away the best (Li-Po being better than Li-Ion) and alkaline by far the worst. AA batteries on the whole have about half the available current and so, in use, will cause a greater drop from the nominal voltage. Lithium AAs should fare better, but are unusual items.
is misleading: AA batteries is a too vague: Alkaline, NiCd, NiMh, Eneloop (which are high quality NiHh)… all those have different characteristics but have less CAPACITY in mA/h, so they are drained empty quicker.


---------- Post added 02-28-17 at 01:52 AM ----------

QuoteOriginally posted by ERNR Quote
For the record, I usually use AA batteries and my K30 has experienced the aperture failure.
There are many different types of AA batteries but as far as I can remember Pentax recommended Energizer batteries but they were not up to it.

Eneloops worked much better (was also my experience).

As far as I understand some differences between NiMH AA and Li-Ion batteries:

The internal resistance of Li-Ion batteries is higher. Thus (good) AA batteries are better suited for higher current.

AAs have a very flat discharge curve (particular Eneloops) which makes it difficult to measure the state of charge.

As far as I studied posts relating to the difference between those two solenoids it seem so that the new (green) solenoid is out of voltage specs
and needs more power (current).

If I got this right this explains why in some cases the use of (good!) AA batteries might help (for some time at least), because of their lower internal resistance and thus are able to provide higher current?

Last edited by photogem; 03-03-2017 at 03:26 AM.
02-28-2017, 02:03 AM   #426
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QuoteQuote:

As far as I studied posts relating to the difference between those two solenoids it seem so that the new (green) solenoid is out of voltage specs
and needs more power (current).
I am not aware that anyone has said that the green solenoid has a lower resistance. Is this true?

02-28-2017, 10:48 AM   #427
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QuoteOriginally posted by ERNR Quote
For the record, I usually use AA batteries and my K30 has experienced the aperture failure.
Roughly what was the shutter count when your K-30 first experienced the aperture issue??

---------- Post added 02-28-17 at 01:14 PM ----------

QuoteOriginally posted by photogem Quote
What danger if one just takes the risk and uses the solenoid?

As I understand it, Pentax used those solenoids first in the late SLR film bodies for control of the flash compartment.
Then followed by *ist, K10D, K100D, K200D, K M, K X, K R which all use two of those solenoids.

---------- Post added 02-28-17 at 01:52 AM ----------



There are many different types of AA batteries but as far as I can remember Pentax recommended Energizer batteries but they were not up to it.

Eneloops worked much better (was also my experience).

As far as I understand some differences between NiMH AA and Li-Ion batteries:

The internal resistance of Li-Ion batteries is higher. Thus (good) AA batteries are better suited for higher current.

AAs have a very flat discharge curve (particular Eneloops) which makes it difficult to measure the state of charge.

As far as I studied posts relating to the difference between those two solenoids it seem so that the new (green) solenoid is out of voltage specs
and needs more power (current).

If I got this right this explains why in some cases the use of (good!) AA batteries might help (for some time at least), because of their lower internal resistance and thus are able to provide higher current?
I'm not aware of anyone's measuring current, but the D-Lion batteries provide much higher voltage
Tested: Battery voltage/type affects K-50 burst rate - PentaxForums.com
Unless battery resistance is a substantial portion of overall resistance, the resulting current when using D-Lion batteries would also be higher.

Last edited by reh321; 02-28-2017 at 11:35 AM.
02-28-2017, 12:03 PM - 1 Like   #428
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QuoteOriginally posted by photogem Quote
What danger if one just takes the risk and uses the solenoid?
Yeah, that's what I did, of course you could measurebate about all these things, but the only thing really relevant is the DC resistance of the coil. If this were much lower than the original, it might cause damage to the supply circuit by drawing to much current. So I checked it, and it was roughly in the same range for both parts. (I didn't write down the value, though, so don't ask ;-)).

The holding force of the permanent magnet btw was much stronger in my replacement part, at first this made me sceptical if it would work, but, when you think about it, this force by itself is irrelevant; the force of the electromagnet has to be able to counteract it, that's what counts.

So, of course it's a risk, you have to be careful not to damage something else when opening the camera (which seems to happen, if you read through this thread), but other than that, the replacement should either work, or, if it's in deep disharmony with some of the other parameters, it won't, then you'll have to find another one. But hey, I used a part from a CD drive lock, and it just worked.

02-28-2017, 12:26 PM   #429
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QuoteOriginally posted by sys3175 Quote
the force of the electromagnet has to be able to counteract it, that's what counts.
Right. But if the coil is shorting or insufficient current is being sent to the coil then it could fail to disengage. The system failure can be a combination of stronger magnet, coil failure, insufficient power to coil, failure of the mechanism that pulls the plunger out. Replacing the solenoid with one with a weaker magnet may solve the problem only because less current or mechanical force is required to overcome the attraction of the magnet. If the rest of the system continues to deteriorate failure could re-occur due to once again not being able to overcome the attraction of the weaker magnet.

Since @altopiet K-30 was "factory" repaired I'd be interested to see a "green" solenoid was used as a replacement. But then as I recall his K-30 failed early on so Ricoh/Hoya may not have had enough cases to isolate a faulty component.
02-28-2017, 02:13 PM - 1 Like   #430
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Replacement, manufactured 11/2016, is green.
Coil resistance is ~ 31 Ohm.
03-01-2017, 07:33 AM   #431
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QuoteOriginally posted by reh321 Quote
I'm not aware of anyone's measuring current, but the D-Lion batteries provide much higher voltage
Tested: Battery voltage/type affects K-50 burst rate - PentaxForums.com
Unless battery resistance is a substantial portion of overall resistance, the resulting current when using D-Lion batteries would also be higher.
Thank you for this very useful link!

Particular post #5 is interesting offering some useful explanation why the solenoid might receive non-regulated voltage (as for the motor) while other electronic parts receive regulated voltage.
The voltage of 4 x AA Eneloops is 4,8 Volts and of 4 x alkaline batteries 6 Volts.

Pentax states in the manual of the K30 (page 3) as well as on their website, that alkaline batteries can be used:

K-30 Optional AA-Battery Holder
Q. Can the K-30 use AA-batteries instead of the rechargeable D-Li109 battery?
A. Yes, by use of the optional AA Battery Holder D-BH109, the K-30 can operate on 4 AA Batteries.
(K-30 Optional AA-Battery Holder | Ricoh Imaging Support)

But the manual of the K50 (page 48) as well as on their website they are suddenly precarious of alkaline batteries, in the manual not as firm as on their website:

Q: What type of batteries can be used with the K-50?
A: AA lithium batteries, AA Ni-MH rechargeable batteries, AA alkaline batteries, or the optional rechargeable Lithium-ion Battery D-LI109 can be used with the camera.
Note: due to the properties of AA alkaline batteries, we do not recommend their use in the K-50 except in emergencies or when checking the camera functionality.
(K-50 Useable Battery Types | Ricoh Imaging Support)

I wonder what made them change their mind?

It seems that this statement
QuoteOriginally posted by athlonus Quote
The culprit is the new CHINESE MADE plunger solenoid. It is out of voltage specs and it MUST be replaced with a quality Japanese product such as Panasonic, Alps or Mitsumi made.
is true.

That the green solenoid is out of voltage specs.

This does not mean that the resistance of the green solenoid has to differ from the early Japanese version, it doesn't:

As "marabella" stated, the green solenoid has about 30,1 ohms.

I measured today 2 solenoids taken out a K100D:

Both have exactly 30,5 ohms.

Hmmm.....those o,4 ohms difference should not make them green solenoids misfire.

As somebody stated already: The force of the permanent magnet seems to be different.

But all this doesn't explain why many K30s and K50s die when not in use for longer periods.
Attached Images
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PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 

Last edited by photogem; 03-01-2017 at 11:00 AM.
03-02-2017, 07:09 PM   #432
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I disassembled my K-30 today, I have yet to remove the solenoid from the body but I did attach it to my oscilloscope and my camera is pushing about 1 volt across the coil in a 12ms burst per shutter activation. Does anyone know the spec for what that should be or is this time to invest in the service manual? This was tested using a fully charged D-Li109.
03-02-2017, 08:22 PM   #433
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My K-30 started black pics last week. Have read most of posts in this thread. Tested with a Vivitar 28mm, f2.8 and problem left. It seems I have ap-block problem. My question is how likely are the K-70's to develop this problem? I have been wanting to up grade for some time and planned to purchase a K-70 but I don't want the hassle of this rather common problem.
Thanks. wdb
03-02-2017, 11:32 PM   #434
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QuoteOriginally posted by Purevulcan Quote
my camera is pushing about 1 volt across the coil in a 12ms burst per shutter activation.
Is this constant or does it vary with f-stop setting and/or shutter speed? What about current or amperage?

Unless someone has the service manual I'm afraid that spec is probably unknown. And it may not even be in the service manual.
03-03-2017, 02:45 AM - 1 Like   #435
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Pentax K-70 solenoid

QuoteOriginally posted by manmarco Quote
My K-30 started black pics last week. Have read most of posts in this thread. Tested with a Vivitar 28mm, f2.8 and problem left. It seems I have ap-block problem.

My question is how likely are the K-70's to develop this problem?
I have been wanting to up grade for some time and planned to purchase a K-70 but I don't want the hassle of this rather common problem.
Thanks. wdb
I have heard only that the K-70 has the same solenoid inside.
I know for sure that the K-S1 as well as the K-S2 have it as well.

I have disassembled a K50 yesterday and posted my results here:
K-50 / K-500 Aperture Solenoid fix (DIY with pics) - Page 2 - PentaxForums.com

I did not find it too difficult, it was the first time I've done it but I disassembled 3 damaged K100Ds before, using this as a kind
of training.

here a video I found of a nice gentle-man disassembling his K50:

What you need is:

- very fine soldering-iron (temperature controlled is best)
- excellent fine solder (low melting point)
- PH00 screwdriver for all screws disassembling the body
- PH000 for the screw which holds the solenoid (I managed to do it with my very good PH00 but I think it would work better with a PH000)
(buy good quality, I had some cheap ones as well which I used on the K100Ds and finally broke both when I disassembled a Z-20 which
does not have a solenoid inside!)

If confident it will take about 1 hour of work alltogether to repair a K50

I took extra time to check the K50 when open, the solenoid remained stuck.
After the exchange: Perfect functioning

If you are not scared to take on this work one day, then no problem purchasing the K70.
Or you take into account that one day you have to invest about $ 120 for repair.
This anyway might happen as well with cameras of other brands.

QuoteOriginally posted by Not a Number Quote
Since @altopiet K-30 was "factory" repaired I'd be interested to see a "green" solenoid was used as a replacement. But then as I recall his K-30 failed early on so Ricoh/Hoya may not have had enough cases to isolate a faulty component.
Attached a photo of the solenoid Ricoh used 1 year ago for repair of a Pentax K-30. As you can see, it is the chinese green devil
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PENTAX K-30  Photo 
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