Tips on cleaning a Universal Mercury II

[kb244]

I was wondering if there was any kind of grease/lubricant/etc involved in cleaning the shutter assembly of the Mercury II. I have one that works, nice clean glass, but the shutter speeds are off in the higher range (like over a stop off).

Testing with a phototransistor at the back of the camera thru the lens with an LED flashlight in front (alkaline battery so it doesn't flicker). Which was odd to me because the Mercury seemed to have a very high reliability when it comes to their shutters.

Speed on Dial = Measured Speed (Approximate deviation)

1/1,000 = 1/196.3 (+2 1/3)
1/300 = 1/158.5 (+2/3)
1/200 = 1/99.4 (+1)
1/100 = 1/74 (+1/3)
1/60 = 1/47.5 (+1/3)
1/40 = 1/31.3 (~1/3-ish)
1/30 = 1/25 (+1/3)
1/20 = 1/15.5 (+1/3)

The diagrams here shows how to get the shutter assembly out
http://rick_oleson.tripod.com/index-210.html

As stated on the top "Generally, all the shutter needs is a bit of oil on the main spindle.", just trying to figure out from the diagram where the main 'spindle' is, and what kind of oil would be best (cuz I'm assuming it's not like WD-40).

The shutter speed itself I thought is simply a gap distance between the two discs, and they just travel as one piece when the shutter is fired. So course I'm thinking that if I can get that cleaned/oiled, maybe at least the 1/100 ~ 1/300 range would get back closer to marked speed.

Edit

It seems like I can oil the spindle by just removing the rear cover at top, and cocking the shutter and setting it to "T" to expose most of the top.

 

[kb244]

Update :

I was thinking... the shutter on the Mercury II is a rotary type in which the 1/1,000th speed is going to be a very tiny slit, and the disc probably doesn't move quite as fast as that, just the exposure of the slit does. It also seems like there is a small deviation of speed difference between measuring the top, center, or bottom portion of the frame.

Is it possible that phototransistor (from photoplug.de) being a large enough diameter is not accurately reading the shutter speed accurately above 1/60th because it's getting more light as the slit passes by a different portion of the "eye"?

Then couple minutes ago I got this email from Mr. Oleson himself :

...
Also: does your phototransistor indicate the top speeds on your Canon are slow, similarly to the Mercury? One thing that might be happening - I don't know the size of your phototransistor, but sometimes they will trigger when they first detect light at one edge, and continue until they are completely dark all the way to the other edge. This means that the width of the phototransistor itself is being added to the width of the shutter slit in your calculations, resulting in a slower speed than you are actually getting. This effect is most severe when the shutter slit is very narrow, and it tends to disappear as the slit is wider at slower speeds. In the Mercury, the slit is very narrow at 1/1000 because the disc turns fairly slowly. I have found it to be very challenging to get accurate readings with some very narrow slit settings in focal plane shutters - such as 1/1250 in a Contax rangefinder or 1/4000 in a Nikon FM2. There is a certain amount of experience and technique required. With my digital shutter tester, I have a dimmer on the light source, which I adjust so that it is just bright enough to trigger the sensor - then I move the sensor about 1/3 closer to the light source to do the actual shutter test. This compensates for the tendency of the sensor to trigger on early and shut off late during the test.
...

Edit:



I went ahead and disassembled it and for the time being I put all the parts away into my dark box.

 

[kb244]

Update:

Cleaned, greased (white lithium around the lens helical). And reassembled (without the flash contacts, because I lose one of the screws, but since I don't shoot bulbs, I put the flash contacts away for later), also lightly lubricated around the frame counter gear and other areas of friction, as well as all the spindle points (front/back of the shutter spindle, spindles on the winder and shutter speed selection).

The initial 'test' with the phototransistor seemed the same as before, however when I ran thru each speed 4 times with the phone/photoplug resting elevated so it stays in the same position between each shot.

1/1000*= 1/380, 1/380.4, 1/380, 1/380.1,
1/300 = 1/212.8, 1/215, 1/211.9, 1/212.4
1/200 = 1/144.5, 1/147.9, 1/48.3, 1/145.3
1/100 = 1/90.3, 1/90.1, 1/90.2, 1/90.0
1/60 = 1/56.2, 1/56.5, 1/56.3, 1/56.7
1/40 = 1/37.7, 1/37.5, 1/37.8, 1/37.3
1/30 = 1/27.5, 1/27.7, 1/27.7, 1/27.8
1/20 = 1/17.5, 1/17.8, 1/17.4, 1/17.6

All of the tested speeds are roughly at the edge of being a third of a stop or less from their set speed, if you treat 1/1000th as 1/500th since explained to me by a few folks (in most detail by Richard Oleson), the width of the 'eye' of the phototransistor may limit the range it can test accurately and the plug is only advertised for up to 1/500th.

* Phototransistor not advertised to be capable of over 1/500 measurement,
1/380-ish from 1/500 is roughly 1/3rd of a stop, so if 1/1,000th is being seen at best as 1/500, then this makes sense and falls in line with the rest of the speed deviations.

Basically lots of help from various folks on RFF, Rick Oleson contacting me directly, and farlymac on RFF which has a nice step by step flickr album on cleaning his up.

The cleaning and the lubing seems to have sped it up a tiny bit and has it consistent between each shot. So... guess now it's just the test roll of fresh non-expired B&W film and make a note of each frame's exposure.