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Forum: Pentax K-30 & K-50
11-04-2017, 02:38 AM
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Good job, very interesting post.
Somebody here in forum measured the internal resistance of the original 'green' solenoid and it has been about 31 ohms. I have also measured the resistance at solenoid from an old HP DVD drive and it was 14 ohms. This is vice versa to yours measurement. The DVD solenoid is with 'white' plastic body. Does that mean PENTAX used solenoids with different specs ? Can the solenoid with lower resistance damage the output transistor with higher current flowing trough ?
Maybe it would be enough to change the wires on the solenoid to change the direction of magnetic field.
I hope that when my K50 dies { I have sometimes first frame black} I can use a DVD solenoid for repair too.
Thanks
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Forum: Pentax K-30 & K-50
10-19-2017, 12:12 AM
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There are some strange points. Why the black frame problem is worse with higher voltage even when the OEM battery can deliver enough current ? - If the battery is overloaded, the result is complete shutdown of the camera.
Mechanical wear with 2k clicks ? Probably not.
It looks like a problem in the electronics. The camera internal electronics is powered with stabilized voltage from some switching stabilizer. In standby mode energy consumption is low, just for powering electronics parts. But when you press the release button, a lot of mechanical equipment is involved - mirror, aperture block and so on. This consumes a lot of power. The stabilizer has to deliver a lot of energy in couple of msecs. And this is the point - the reaction time of the stabilizer circuit, when powered from higher voltage is longer than with low voltage from eneloops. This corresponds with your experience with LiveView - mirror is already down, electronics is in full operation and stabiliser is settled under load. It has probably something to do with capacitors loosing their capacity especially when not used for longer period. With changed solenoid {white with smaller magnet} or with filed anchor the magnetic force is lower and camera needs less current to release it.
- Everything i wrote above are just speculations -
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Forum: Pentax K-30 & K-50
10-18-2017, 07:12 AM
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K50 black frames
Set of 4 eneloops has about 5.2 Volts new, Lion battery has 8.4 Volts with no load. I checked the voltage on OEM battery with 2 Amps load - it is still at 7.2 V, that is enough for powering the solenoid actuator. According my measurements, same solenoid from CD ROM needs about 320 mA to release at approx. 4 Volts. My K50 has black frames with OEM battery, but with eneloops only first frame is underexposed, after 28 months and 2400 clicks only.
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