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11-23-2017, 12:12 PM - 2 Likes   #1
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FA*85 1.4 - abnormal AF sound: Repaired

8 months ago pentaxforums.com member started the thread about Pentax FA*85 1.4 with abnormal AF sound. The link below:

Read more at: FA*85 1.4 Auto Focus Sound on K-1: Is this normal? - PentaxForums.com

I would like to share my joy about successful replacement of cracked spur gear with the dimensions 13T Spur Gear (Brass), 0.3 MOD, 2mm bore, 2mm thickness from:
https://shop.kkpmo.com/index.php


BIG THANK YOU to HarisF1 for providing very good source to buy the gear. The shippment was done in 1 week from Poland to Lithuania.
I bought metal (brass) and plastic gear. The procedure of the replacement was not difficult, but tricky. In fact the new spur gear is about 0,2 mm toller/higher than original and I shaved it with sandpaper.
You do not have to disassemble the entire focusing gear mechanism. Instead, you should first climb a pinch to the gear's hole and roll it off at least twice so that the axis then enters the same pockets under the strong pressure with fingers or some kind of hard flat tool.
Now the AF sound is normal.
Yahoo!

11-23-2017, 12:25 PM   #2
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Excellent news, I was supposed to receive mine on Tuesday but I missed the delivery! I didn't find the source directly but someone on the older thread mentioned it - I just decided to go ahead with the order

I will be getting them tomorrow so I should have mine repaired soon enough too.

@DCShooter - This should be an excellent source of parts if it works out for me too. It seems like a fairly common issue and a total price per part of around $6 isn't that bad.
11-23-2017, 12:48 PM   #3
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QuoteOriginally posted by HarisF1 Quote
Excellent news, I was supposed to receive mine on Tuesday but I missed the delivery! I didn't find the source directly but someone on the older thread mentioned it - I just decided to go ahead with the order

I will be getting them tomorrow so I should have mine repaired soon enough too.

@DCShooter - This should be an excellent source of parts if it works out for me too. It seems like a fairly common issue and a total price per part of around $6 isn't that bad.
BTW, if you will do repairment by yourself, be careful when you unmount lens bayonet ring (6 small springs under the ring!) and aperture ring (small metal ball, it may fall out due to the pressure of the spring!).
11-23-2017, 02:56 PM   #4
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QuoteOriginally posted by Medex Quote
BTW, if you will do repairment by yourself, be careful when you unmount lens bayonet ring (6 small springs under the ring!) and aperture ring (small metal ball, it may fall out due to the pressure of the spring!).
I disassembled mine two weeks ago for a temporary fix (to tighten the existing cracked gear, as mine was not rotating at all) so I have some idea

My solution for the bayonet springs is to place sellotape over the gold contacts and press down. The tape prevents the contacts from falling out, and the springs generally come up with the contacts. The aperture ring ball was extremely fiddly, if you have any solutions or tips then I would greatly appreciate it. I used a lot of trial and error and think I may even damage the aperture ring if I don't do it correctly again!

04-06-2018, 03:12 PM   #5
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I am about to order....

Would you have gone with the 1.5mm thickness instead of the 2mm since it had to be grinded down?


QuoteOriginally posted by Medex Quote
8 months ago pentaxforums.com member started the thread about Pentax FA*85 1.4 with abnormal AF sound. The link below:

Read more at: FA*85 1.4 Auto Focus Sound on K-1: Is this normal? - PentaxForums.com

I would like to share my joy about successful replacement of cracked spur gear with the dimensions 13T Spur Gear (Brass), 0.3 MOD, 2mm bore, 2mm thickness from:
kkpmo - KK Produktcja Mikroantriebe Zahnrad, Schnecken, Mikro Getriebe und Car System Hersteller


BIG THANK YOU to HarisF1 for providing very good source to buy the gear. The shippment was done in 1 week from Poland to Lithuania.
I bought metal (brass) and plastic gear. The procedure of the replacement was not difficult, but tricky. In fact the new spur gear is about 0,2 mm toller/higher than original and I shaved it with sandpaper.
You do not have to disassemble the entire focusing gear mechanism. Instead, you should first climb a pinch to the gear's hole and roll it off at least twice so that the axis then enters the same pockets under the strong pressure with fingers or some kind of hard flat tool.
Now the AF sound is normal.
Yahoo!

Last edited by dcpropilot; 04-06-2018 at 05:35 PM.
04-06-2018, 04:34 PM   #6
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It doesn't necessarily need to be ground down but I thought it was worth it to keep it in line with the original. You might want to order both the 1.5mm and the 2mm since the postage cost is significant and the parts themselves aren't that expensive.
04-06-2018, 11:32 PM   #7
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QuoteOriginally posted by dcpropilot Quote
I am about to order....

Would you have gone with the 1.5mm thickness instead of the 2mm since it had to be grinded down?
2 mm is not OK because of physical dimensions of the pin, especially the tip of the pin. The tip must be protruded a little until thicker part of it. In case of 2 mm spur gear the protrusion of the tip is not enough and the spur gear lies on the plane of the plate of the focusing mechanism. That prevents the spur gear ro rotate freely. This is the reason why you need to grind 2 mm spur gear a little.
1.5mm gear could be OK. But I did not used them. You can buy two different as HarisF1 said.

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