Topcon Super RE - Light Meter Help

Discussion in 'Classic Manual Cameras' started by stevenenglund, Dec 5, 2017 at 7:14 PM.

  1. Can someone with a Topcon Super RE with a *VERIFIED & WORKING* light meter help me solve this problem... I'm more interested in fact than opinion.

    The question to answer: When you remove the battery from your Super RE, does your light meter change if you adjust the shutter, ISO, and or aperture?

    I purchased a Super RE and am trying the "hearing aid battery fix." But I've tried a couple different batteries now so I'm curious if my light-meter is simply broken. I turn the camera to On and nothing changes. The light meter does not move when I adjust anything. If I can verify the light meter does absolutely nothing without a battery, then I'll move on and try purchasing a Wein MRB625 1.35V Zinc-air.

    Attached is an image of what my (in viewfinder) light-meter reading looks like. I've read page 16 of the manual and know that something is is not being displayed correctly.

    topconsuperrelightmeter.jpg
     
  2. For gear lovers, here's a picture of the camera. It has an old Zeiss lens on it that I purchased two years ago at a yard sale, and haven't been able to use... until now... maybe.

    This photo was taken with a Canon 5D MK2. I'm matching shot for shot, exact same settings, with the two cameras. It's a test for the first roll of film going through my Super RE. Hopefully results are worth posting.

    _MG_5424.JPG
     
  3. I have a Super D (afaik basically ther same camera) with working meter, and I can confirm that without a battery the viewfinder looks exactly as in your drawing. The bar to the lift is simply part of the "T" element which, with a battery in place and meter ON, will show correct exposure (re. Page 16 of the manual). Changing aperture, speed or/and ISO setting without the battery does not result in any modification to the image; the "T" will only became visible when the meter is working.

    There is no real reason to go for an expensive Wein cell, which is basically a standard hearing aid battery within an adapter - at least, not before checking whether the meter works. You should be able to use an hearing aid battery with an O ring to keep it in proper place. However, it is also possible that the battery compartment is so designed as to provide contact on the battery`s circonference, in which case you should use a thin metal foil ring in lieu of the O ring. Personally, I use thre adapter sold by Jon Goodman (interslice on ebay) and would recommend it.
     
    Last edited: Dec 6, 2017 at 11:29 AM
  4. @bonsignore_ezio Thank you very much, that is just the reply I was hoping for! Concise and helpful. Also, thank you for the recommendation for Jon Goodman's products. I found his email address online and contacted him directly. I will also try to make a foil ring for the hearing aid batter that I have in there now, which is a Duracell 357 1.5V.

    Which lens do you use on your Super D?
     
  5. Glad if I was of any help. I have a Topcor 58mm 1:1.8 and a Topcor 35mm 1:2,8.
     
  6. Steven, a 357 1.5V is not a hearing aid battery, rather it's a standard alkaline button battery. Hearing aid batteries are Zinc-Air and have a nominal voltage of 1.3V, near enough to the 1.35V Mercury batteries which are no longer made. It should power the Topcon meter, but may give inaccurate readings, depending on what circuit is used. I've found that some cameras designed for Mercury batteries actually give good readings using 1.5V units. I've no specific knowledge of Topcon cameras, though.
     
  7. Which brings us to the "vexata quaestio" of replacement for Mercury batteries. First point: Steven's 357 1.5V should anyway power the meter (if the meter works), but it might, or then might not produce inaccurate readings, depending on whether or not the meter has a so-called bridge circuit. Which brings us to the second point: at least based on my experience, bridge circuits will work very well in reducing an excessive voltage (i.e., using a 1.5V instead of the prescribed 1.35V), but cannot "extract" more power from a lower voltage battery; when voltsge drops below 1.35V, functions will cease. The latter will of course apply to adapters or to Wein cells. Third point: I use Zinc-Air hearing aid batteries with the Jon Goodman's adapter for all of my cameras originally designed for 1.35V Mercury batteries, with satisfactory results - but at least this side of the pond, these batteries have a nominal voltage of 1.4V, which makes them ideal for our purposes. If voltage were 1.3V, they would be useless for us, and of course there would be no Wein cells.
     
  8. If you don't already have a manual, (Butkus link) has one. If you use it, for the sake of the cause, make a donation to support his site.
     
  9. For all of my older cameras I use the battery adapter from CRIS Camera. It uses a standard silver battery and reduces the voltage. They are not cheap but you only have to buy it once. I never have had very good success with Wein cells or hearing aid batteries. They do not last long and the voltage drops as soon as you start using them resulting in inaccurate readings. They work very well in my Nikons and Nikkormats.
     
  10. Upon further inspection, the batteries I purchased are 357 "watch/button batteries" (and according to Rick Olseon- are silver cells and even thought they are the same size as the 675, they are not a good substitute for mercury)... so it is correct that they are not hearing aid batteries. I impulse purchased them thinking they would work- alas, I probably just need to hunt down a 675 now. I will test both a shim that allows side contact, and one without. It's probably impossible to find out *officially* if my Topcon has a bridge circuit.

    Eventually once I know that the light meter is working, I'll test the accuracy (even at 1.5V) and hopefully post results. At this point I think only firsthand experience with my Topcon will prove what works and what doesn't! If I run a 1.5V that slightly alters exposure calculations then I will just shoot accordingly.

    Thank you for your help!

    PS: Why can't there just be a magical page on the internet that lists every battery powered camera ever made, then lists it's battery types including modern substitutions and if they need side contact, and whether or not that camera has a bridge circuit and whether or not it calculates exposures wrong with a different voltage...
     
  11. Hmm... I'm working on
    that now...
    [​IMG]
     
  12. Steven, this old web page seems to have much of the info your are looking for

    http://archive.li/We5vP

    but unfortunately the links don't seem to work anymore.

    And, no, you really cannot compensate for the voltage-induce wrong readings, because the error will vary with the amount of light available (been there, done that...)
     
  13. @bonsignore_ezio Could you please do me a favor and test the light meter without a lens attached? I'd like to eliminate the meter not working because I don't have an official Topcon lens attached.

    On the other hand, good news... The photos came back great. Yes I had to meter with a 5DMk2, but the focus and exposure look great. No light leaks!
     
  14. Yes, the meter will react to light even without a lens. Of course the readings will be all over the place, but it will react.
     
  15. Thank you for checking! I can probably conclude at this point that the meter is broken, because I put in a modern 625 battery equivalent, and the meter still did not work.

    Bummer too because I really loved the feel of this camera.
     
  16. Here is a comprehensive list of camera batteries Camera Batteries - a complete chart - Photoethnography.com's Classic Camera DB along with their chemistry. There are more links at the bottom of the page.

    A bridge circuit neither raises or lowers the voltage. It measures by comparing the ratios of 2 resistances against the ratio of another 2 one of which is derived from the CDS resistance. The ratios do not change so it is a voltage independent circuit. It will work above 1.6v and below 1.3v.

    Zinc Air cells work well as a replacement for mercury cells. Their output voltage is between 1.35v and 1.4v. The Wein cell will last longer than a hearing aid cell. The Wein cell has 1 air hole and hearing aid batteries have 4

    Cris adaptors work by delivering Silver oxide cells 1.6v through a schottky diode. The drop across the diode is nominally 2v, however this varies considerably with temperature and load.
     
    Last edited: Dec 9, 2017 at 10:21 PM
  17. The meter pointer does move when you rotate the shutter speed dial (or the lens aperture) without battery or turned off. But it should also always be hidden behind the black plastic band when the meter is off. If it doesn't move, something is awry with the network of chains that move when you adjust shutter speed or aperture. If you change shutter speed quickly, there will be a bit of relative movement between the pointer and the black band.

    It's very easy to smash up the meter movement when disassembling the camera. The chains connected to the shutter speed dial and aperture feeler turn the body of the meter, working against a strong spring. If you don't put the right "holding screw" through the shutter speed dial when taking it apart, the chain will go free, and the spring will rotate the meter body too far and bend the pointer, or get it stuck in one of the stops.

    The MR-9 adapter is problematic in the RE Super. The contact in the bottom of the battery well is so large that it shorts out the 386 battery that is inserted in it, shorting the button to the outer shell. The contact needs to be reduced in diameter. I don't know how much, since I have a hoard of real mercuric oxide 625's.

    But the current alkaline 625 cells fit fine and make contact. They just don't offer accurate metering. But fine for troubleshooting.

    Probable failure points in the meter electrical circuit are the incredibly fine wires in the meter coil, and the wires that flex (twist) as the shutter goes up an down. I ruined one meter by leaving the camera is a cool humid place, it corroded the wire in the meter coil.

    Easy to test the electrical circuit, use an ohm-meter (with a low voltage) to measure resistance between the battery contact and the camera body. If it's infinite, there's an open-circuit.

    Service manual for RE Super can be found free online. You have to make or buy tools, like a ring wrench for wind lever, spanner for PC terminal, and a pointy metric screw for the "holding screw".

    The RE Super does not have a bridge circuit. Standard series connection of battery, CdS cell, and meter movement. Most famous for having a bridge circuit are Pentax cameras. Very good design Pentax used.
     
    Last edited: Dec 9, 2017 at 10:45 PM
  18. It may be something as simple that the black plastic band has hopped it's pivot, and is blocking movement of the meter pointer.
     
  19. @john_shriver Sounds like you have extensive knowledge on the meter of this camera! Now that you mention it, I am thinking the black band has hopped off track and is preventing the needle from moving. When I adjust the shuttle near 1/30 to 2, the needle and black band appear locked together and move left or right together at the same time.

    While I do like opening up things and tinkering around, I'm not sure that I am confident enough yet to tackle this project...
     

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