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02-22-2018, 08:09 AM   #676
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QuoteOriginally posted by bigyinn Quote
I've just purchased an MZ7 from e-bay for £9.99, so I hope it has the correct white solenoid!
Since performing the sanding on the horseshoe on my K50 it hasn't had any issues, although its had very limited use since. Im hoping to use it this weekend, as I'm dying to try out my new DA 55-300 PLM WR lens.
Assuming the MZ7 works ok, I may well use it for a bit first, as I have some film in my Super A that I'd like to finish off before I carve up the MZ7!
As long as you have the most latest V1.10 firmware for your K-50, the DA 55-300mm PLM will work perfectly fine even if the aperture motor is busted. The aperture motor is inside the lens (KAF4) & doesn't use the body's aperture motor at all. So you can use it right now before even fixing your camera.

You will need to fix it to use the older non-aperture ring lenses (KAF3) that you have.

02-26-2018, 02:51 AM - 1 Like   #677
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Firmware was updated when first released, I know the 55-300 has no aperture lever, so is unaffected by the aperture block issue. I meant that I just hadn't had a chance to play with it yet.

Annnywaaay, the MZ7 body turned up, but after having spent £8 on batteries for it, it wouldn't set the shutter, so I assume its got the usual MZ stripped plastic cog issue. Not to worry, as I'd bought it for spares anyway.

The good news is, that the MZ7 has TWO of the white solenoids. I suspect that the majority of MZ series have the same configuration. One for the aperture block and one for the flash raising. I chose to remove the flash one as its easier to get at. The one for the aperture block is soldered onto a ribbon cable, rather than 2 wires like on the K50, so a little harder to get to.

To get at the flash solenoid, remove the bottom plate, remove the lens mount surround, remove the film back (press the upper sprung loaded pin down to release the hinge pin and swing away from the body), remove the two side panels and then remove the top plate (carefully, as there are quite a few wires and ribbon cables in there). All the screws are visible and fairly obvious.The solenoid is located in the top plate and is held in place with one screw. Once released there is enough slack in the wires to withdraw the solenoid and de-solder the wires. I've put the MZ7 back together for now, the only difference is the flash doesnt stay down.
I'm hanging fire on fitting the replacement solenoid to my K50, as its been fine since I sanded off the horseshoe on the original green solenoid.
02-26-2018, 06:29 AM   #678
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The MZ50 appears to have only one solenoid. The flash raising is a simple spring loaded affair. Having a solenoid seems to be like using a sledge-hammer to crack a walnut.
03-07-2018, 06:55 AM   #679
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Solenoids found in MZ7, K200D and others

I came across 2 solenoids in an almost new MZ7 (only used for 1 wedding, stored away since).

Both solenoids have a stronger holding force even compared to the green made in China version:

see here: K-50 / K-500 Aperture Solenoid fix (DIY with pics) - Page 8 - PentaxForums.com

As I needed a good white solenoid and was not happy with those, I opened a K200D (very low shutter count) and surprise suprise:
green solenoid in the flash compartment! Too bad. The aperture-solenoid is white, but I wouldn't touch it because this K200D is absolutly alright,
I felt alright exchanging the flash solenoid but of course not the other one.

Not really a big surprise: I found green (useless) solenoids in the flashcompartment of:

K100D, K200D (one silver version had both in white!), K-m (K2000), K-x, K-r!

03-08-2018, 12:35 PM   #680
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QuoteOriginally posted by photogem Quote
I gave some white, green and blue solenoids to a student of electrical engineering to measure them.
All white and green solenoids have similar impedances of 30ohms (+/-3%), the blue solenoid are 15ohms)

The white solenoids measure a holding force of 3,2N - 3.3N at 0Volts (i.e. not in action).
3.7Volts applied to the coils result in a lowering of this force down to 0,7N - 0.9N, which releases the horseshoe.

The green solenoids have a holding force of 3.8N- 3.9N at 0Volts, which is about 25% more.
3.7 Volts applied result in 1,1N - 1.2N. Now those 1.2N are about 70% higher than the 0.7N of the white solenoid!

The green solenoids that you measured -- were they new ones, or ones that were exhibiting the problem? It might be helpful to measure one that works properly and one that doesn't to help determine what is wrong with the solenoid and potentially devise additional repair methods besides replacement.
03-09-2018, 12:54 AM   #681
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QuoteOriginally posted by leekil Quote
The green solenoids that you measured -- were they new ones, or ones that were exhibiting the problem? It might be helpful to measure one that works properly and one that doesn't to help determine what is wrong with the solenoid and potentially devise additional repair methods besides replacement.
We measured both, new and bad ones.
Both had the same measurements, i.e. the same holding force.
03-09-2018, 07:16 AM   #682
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Hi

Today I have pull apart my old Pentax K-x so I'm able to repair my bellowed Pentax K-50 if the solenoids get stuck. In the automatic pop up flash there was a green solenoid, and for the aperture control it was the white one.
There is a huge different in how mush force to pull the horseshoe out. The green one have nearly twice the holding force compared to the white solenoid.

Looking closely to them you can see there are a significant bigger Neodyn magnet on the green one.
I’m sure by cutting a bit of that magnet, or sandpaper it down to nearly half size, will solve the problem.

Best regards,

Torben Pedersen

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03-10-2018, 01:27 AM   #683
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QuoteOriginally posted by solvin_dk Quote
Today I have pull apart my old Pentax K-x so I'm able to repair my bellowed Pentax K-50 if the solenoids get stuck. In the automatic pop up flash there was a green solenoid, and for the aperture control it was the white one.
There is a huge different in how mush force to pull the horseshoe out. The green one have nearly twice the holding force compared to the white solenoid.
Yes, this is so. I gave the exact measurements of this holding force.

QuoteOriginally posted by solvin_dk Quote
Looking closely to them you can see there are a significant bigger Neodyn magnet on the green one.
Iím sure by cutting a bit of that magnet, or sandpaper it down to nearly half size, will solve the problem.
I don't think that this is at all the proper solution!

Magnets can loose their magnetism through vibrations such as sawing/filing/sanding

But even if this works out, we have by now found out, that other factors play a role as well witht he green solenoid,
i.e.:

- material of the metal body (horseshoe as well)
- material of the plastic parts which work like a bearing in which the horseshoe moves

The sanding of the horseshoe and thus it having less contact to the magnetic part and therefore being released easier when the voltage is applied to the coils inducing the opposite magnetic field leads pretty much to a similar reaction as if one would shorten the permanent magnet itself.

But many green solenoids having been modified led to further damage in the aperture mechanism.

A received a repaired Pentax K30 (with green solenoid filed via the Russian method). It has failed again after about 9 month regular use.
I tried to repair it by exchanging the solenoid with the white version but I could not get it back to working order anymore.

So if you repair one day your K50, use the white solenoid and don't exchange the magnet of the solenoids.
Not a good idea.

03-10-2018, 08:07 AM   #684
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Ref: a K-30 which hasn't YET suffered the problem - and I want to make sure it doesn't !

So, just ordered one of the ex K-r/K-X white solenoids from the link provided many pages ago in this thread, and going to get it fitted (I'm just not dexterous enough to do it myself) by a reputable local camera repairer (Asahi Photo in W.London) . I know they have fixed the problem before because I asked them this week and it costs around £100 - but they use the "filing" method which seems "dubious" at best, and so I'm going to supply them with a white one to fit!
03-11-2018, 01:40 AM   #685
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QuoteOriginally posted by jeallen01 Quote
Ref: a K-30 which hasn't YET suffered the problem - and I want to make sure it doesn't !

So, just ordered one of the ex K-r/K-X white solenoids from the link provided many pages ago in this thread, and going to get it fitted (I'm just not dexterous enough to do it myself) by a reputable local camera repairer (Asahi Photo in W.London) . I know they have fixed the problem before because I asked them this week and it costs around £100 - but they use the "filing" method which seems "dubious" at best, and so I'm going to supply them with a white one to fit!
Logical/sensible solution to chose .... doing it before more damage can happen.
03-11-2018, 06:03 PM   #686
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Just a quick question, does the failure effect ALL K-50s or just a certain production range or from a particular location? I have a K-50 and so far, never had an issue.
03-12-2018, 03:32 AM   #687
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QuoteOriginally posted by jimboombapete Quote
Just a quick question, does the failure effect ALL K-50s or just a certain production range or from a particular location? I have a K-50 and so far, never had an issue.
The potential failure can affect any K-50 - and K-30, KS1, KS2 - regardless of production range etc., as it is related to the "green" aperture block solenoid that was fitted by Pentax assembly plants in a number of locations. Seems heavily related to how regularly the camera is used, and the less that is then the higher chance there seems to be that the failure will occur.

Please read the rest of this, and related, thread for more details as the issue and the various solutions have been widely explained and discussed in detail.
03-24-2018, 04:18 AM   #688
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QuoteOriginally posted by jeallen01 Quote
Ref: a K-30 which hasn't YET suffered the problem - and I want to make sure it doesn't !

So, just ordered one of the ex K-r/K-X white solenoids from the link provided many pages ago in this thread, and going to get it fitted (I'm just not dexterous enough to do it myself) by a reputable local camera repairer (Asahi Photo in W.London) . I know they have fixed the problem before because I asked them this week and it costs around £100 - but they use the "filing" method which seems "dubious" at best, and so I'm going to supply them with a white one to fit!
A "white" solenoid has arrived in the UK from the US seller of ex K-X /K-M camera solenoids, and that cost $53 inc delivery - but now it has cost me a further £13.57/around $18 in Customs Duty, and won't arrive with me for a couple more days!
04-03-2018, 06:49 AM   #689
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Update on Asahi Photo in West London:

Just dropped my K-30 over there (only 10 miles away) for the aperture block solenoid to be replaced by the white one I had sourced from the US.

It should be done in around a week or so as I provided that solenoid because, when on the phone to them a few weeks ago, I was told that they used the "filing" method on the green solenoids. That said, I was also told today that they could actually get white solenoids if the customer is (obviously) prepared to pay extra for that and wait somewhat longer (but it would still have cost less and taken less time if I had known that 4 weeks or so ago - I think that will now be mentioned to anyone who enquires about similar repairs!)

Finally, for anyone with an old MZ-5 or similar film body, I found out that they can repair both the pop-up flash spring and the faulty internal film drive motors!

Last edited by jeallen01; 04-03-2018 at 07:15 AM.
04-03-2018, 07:33 AM   #690
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QuoteOriginally posted by jeallen01 Quote
A "white" solenoid has arrived in the UK from the US seller of ex K-X /K-M camera solenoids, and that cost $53 inc delivery - but now it has cost me a further £13.57/around $18 in Customs Duty, and won't arrive with me for a couple more days!
Do you know the exact breakdown? I thought you are only meant to get hit with VAT and possible Royal Mail charges. Customs Duty is not supposed to be charged on items under £135

Last edited by ekip; 04-10-2018 at 03:48 AM.
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