Pentax ES II - timing capacitors

Petrs · 11-07-2021, 10:52 AM

Hi to all,

I wanted to ask if anyone happen to know what are the capacitance values of the 2 timing capacitors on the motherboard of the Pentax ES II (or ES). I would like to replace them with newer ones, because the camera has a problem with the shutter speeds in automatic mode. Pentax itself writes in the service manual that nothing is repaired on the board, it changes completely. Of course, this worked in times when new ones could be found. Replacing the capacitors would be simple and cost a few cents, while I would rule out one of the possible causes of the fault. Unfortunately, no information or value is given on the capacitor package.Thanks for your advice.

Petrs

**Bob 256** · 11-07-2021, 01:13 PM

Unless you can come by a schematic for the camera, it's hard to determine their value. You might unsolder the existing and measure, then check to see how close a replacement gets the timing. Typically, a higher value will increase timing interval so you might be able to get there by trial and error. Usually, these capacitors are good for 10 years or more - are you sure they are the issue?

Ultimately, you might end up sending the camera in if the timing is seriously off.

Petrs · 11-08-2021, 01:40 AM

Thanks Bob for your answer and valuable consideration. The camera produces dark, underexposed images. So the automatic sets shorter times than optimal, or rather than the exposure meter shows (it shows correctly compared to my other functional cameras). So if a higher capacity gives a longer time, and if I assume that the capacity of capacitors usually increases with age, then this should probably not be the cause of my problem. If film / foil capacitors are used there, they should not age at all. Capacitors are manufactured in certain standard values, so I will try to unsolder it and measure the value. Then I can try to replace it with a capacitor with the next higher value. We'll see if it helps.

Not a Number · 11-09-2021, 09:13 AM

The ES service manual is used for the adjustments as per the ES II parts list. For automatic exposure times it says to first adjust the mechanical exposure then using then using the exclusive shutter speed testing unit ESST-1A and Light Value Correction Unit (calibrated light source) PA16-C/31-C adjust the time with variable resistors VR5 (slow) and VR8 (fast) on the O-T1 print pattern assembly. It also mentions there is a minimum time interval between shutter releases (not to test consecutive releases one right after the other).

According to the Camera Craftsman repair article there are three capacitors:

C1 - as soon as timing capacitor (Ct) reaches the reference voltage stored stored across C1 the transistor-switching system shuts off the current flowing through the electromagnet. The shutter variables and the memory circuit just determine how long it takes for Ct to reach the reference charge.

C3 - hooks in parallel with the coil of the electromagnet and appears to be a shock absorber.

Ct - memory capacitor - you can't see the memory capacitor unless you destroy the memory switch assembly. The capacitor sits within the memory-switch assembly sealed in epoxy.

So the capacitors you'd need to replace are C1 and Ct. To replace Ct you'd have to replace the memory-switch assembly.

ES Service Manual, parts list and article can be downloaded from:
https://learncamerarepair.com/product.php?product=824

Last edited by Not a Number; 11-09-2021 at 09:41 AM.

11-07-2021, 10:52 AM	#1
Petrs New Member Join Date: Nov 2021 Posts: 2	Pentax ES II - timing capacitors Hi to all, I wanted to ask if anyone happen to know what are the capacitance values of the 2 timing capacitors on the motherboard of the Pentax ES II (or ES). I would like to replace them with newer ones, because the camera has a problem with the shutter speeds in automatic mode. Pentax itself writes in the service manual that nothing is repaired on the board, it changes completely. Of course, this worked in times when new ones could be found. Replacing the capacitors would be simple and cost a few cents, while I would rule out one of the possible causes of the fault. Unfortunately, no information or value is given on the capacitor package.Thanks for your advice. Petrs

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
A question about ES/ES II/Spotmatic F	Jason 407	Film SLRs and Compact Film Cameras	7	07-18-2020 10:43 PM
Do flash capacitors discharge over time?	JoseFF	Pentax K-30 & K-50	14	06-05-2016 10:03 AM
ES vs. ES II	Stevopedia	Film SLRs and Compact Film Cameras	24	07-12-2009 05:49 PM
Pentax ES and ES II ads from the 70s	Nesster	Film SLRs and Compact Film Cameras	6	03-15-2009 06:25 PM

11-07-2021, 01:13 PM	#2
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,378	Unless you can come by a schematic for the camera, it's hard to determine their value. You might unsolder the existing and measure, then check to see how close a replacement gets the timing. Typically, a higher value will increase timing interval so you might be able to get there by trial and error. Usually, these capacitors are good for 10 years or more - are you sure they are the issue? Ultimately, you might end up sending the camera in if the timing is seriously off.

11-08-2021, 01:40 AM	#3
Petrs New Member Join Date: Nov 2021 Posts: 2 Original Poster	Thanks Bob for your answer and valuable consideration. The camera produces dark, underexposed images. So the automatic sets shorter times than optimal, or rather than the exposure meter shows (it shows correctly compared to my other functional cameras). So if a higher capacity gives a longer time, and if I assume that the capacity of capacitors usually increases with age, then this should probably not be the cause of my problem. If film / foil capacitors are used there, they should not age at all. Capacitors are manufactured in certain standard values, so I will try to unsolder it and measure the value. Then I can try to replace it with a capacitor with the next higher value. We'll see if it helps.

11-09-2021, 09:13 AM	#4
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	The ES service manual is used for the adjustments as per the ES II parts list. For automatic exposure times it says to first adjust the mechanical exposure then using then using the exclusive shutter speed testing unit ESST-1A and Light Value Correction Unit (calibrated light source) PA16-C/31-C adjust the time with variable resistors VR5 (slow) and VR8 (fast) on the O-T1 print pattern assembly. It also mentions there is a minimum time interval between shutter releases (not to test consecutive releases one right after the other). According to the Camera Craftsman repair article there are three capacitors: C1 - as soon as timing capacitor (Ct) reaches the reference voltage stored stored across C1 the transistor-switching system shuts off the current flowing through the electromagnet. The shutter variables and the memory circuit just determine how long it takes for Ct to reach the reference charge. C3 - hooks in parallel with the coil of the electromagnet and appears to be a shock absorber. Ct - memory capacitor - you can't see the memory capacitor unless you destroy the memory switch assembly. The capacitor sits within the memory-switch assembly sealed in epoxy. So the capacitors you'd need to replace are C1 and Ct. To replace Ct you'd have to replace the memory-switch assembly. ES Service Manual, parts list and article can be downloaded from: https://learncamerarepair.com/product.php?product=824 Last edited by Not a Number; 11-09-2021 at 09:41 AM.