Canon T90... let's see where this goes.

Laurent

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As I said on another thread, I finally pulled the trigger on a "for parts / as-is" T90 with the "EEE/Help" error, hoping that the issue it has makes it complementary of mine.

I received it today, and it's, cosmetically speaking, close to a beater when mine is pristine (the difference being that mine has been unused for 20+ years since it's not working and I chose to move to the EOS3 at this time).
Functionally, I had the good surprise that it fires sometimes (I thing I've got a few hundred shots in a raw before the "EEE" came again), so I guess I may change my plans from using it as a donor to using "mine" (the historical one ) as a donor for the cosmetic parts. My reasoning is that there's a risk that, if I can transplant the mirror magnets on mine, I may well discover it has also the shutter issue.

Hearing the T90 firing again was a delight, but I had forgotten how noisy that thing is compared to even a Canon F1.
 

eli griggs

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I was once asked to stop taking pics of a dance performance because my F-1N ae was so loud on manual.

We were in the first row and the long walk to the office was quite the embarrassment to my date, who remained in her seat, I wasn't bothered, having been told shooting during a live performance, which i had never done before, and the woman in the office, whose two troops i had been shooting for a few years, was the one that said it would be OK, now embarrassed too.

I believe the only reason we were not told to leave was for the above connection and permissions.

Alexander Godunov, was not amused.

If the T-90 is louder than the F-1, in any issue, it must have contributed to its nickname, "The Tank"
 

Niglyn

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I am on the lookout for a scrap T90.
I want to get the faulty electromagnet out of it and see exactly what the problem is.

We all know the workaround, using a magnetised screwdriver, which works for a while,
so is it as simple as either remagnetising or demagnetising it,
or maybe demagnetising the keep?
Alas even scrappers listed on ebay for far more than they are worth, so so far,
I have not been able to get one for an autopsy.
 

Andreas Thaler

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If you manage to solve the EEE/HELP problem, i.e. presumably activate the blocking shutter magnets, we would have solved all of the lady's old age problems!

Canon T90: recommendations and notes

Based on my previous (repair) experiences with the Canon T90 with regard to preservation/problems/repair options, I would like to give a summary of the following recommendations/hints: Sticky shutter - gummed-up shutter blades: Can be permanently repaired, damper in the shutter area that has...
www.photrio.com
 

Andreas Thaler

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If you find a donor T90, you can replace the mirror magnet quite easily.

Canon T90: Replacing the mirror magnet

The mirror of one of my T90s didn't want to move. The symptom is well known: When you press the shutter button, an arrow flashes in the display and you hear a quiet ticking sound. Otherwise the camera remains still. I opened the camera and tapped the mirror magnet with a magnetized...
www.photrio.com
 
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Laurent

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koraks said:
Hey, it's pretty quiet compared to a Hasselblad!

Congrats on your T90. I hope you can get it to work reliably and have some fun with it.
Click to expand...

Thanks. I had a 500C in the past, and loved it, but I agree it was quite noisy. Different noise though, so that makes a difference. The T90 is more on the high end of the spectrum in terms of pitch.


Interesting story . I'm not sure the noise level is higher but the much higher pitch makes a difference. Also I've used a Rolleiflex and some Leicas exclusively for a few years after selling my EOS rig and putting my AE1P in mothballs for while, so that can also have changed my appreciation.

In my case the magnetised screwdriver did not do the trick. I paid 44€ for this camera, including postage, and I think it's hard to get any lower, at least nowadays in France.

I missed one that may have been an easy fix as it was reported as "does not turn on".


That would be great, except I'd still have a T90 waiting for a mirror magnet and so another tempting project...
 
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Laurent

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No news for a moment... I've been busy with the F1s, and looking for info on the T90.

I was able to remove the covers, find my way through this #`¤¨`~¤ magnet.

I tried applying 3V to the magnets and, as expected, my T90 did not release the mirror while the donor did. Diagnostic somewhat clear then.

On my T90, removing the magnet was easy, except for the screw that jumped somewhere... It took me some time but a good slap on my hand finally got it outside of the body.

On the donor camera, this has been a different story. The slotted screw did not want to turn, so the head finally got damaged and it became even harder to extract it. So I had to find a way, and this was by butchering as small saw blade to enlarge the slot, so that I could use a bigger screwdriver. After some efforts I've got it, so I could get the magnet out (well, first I only got the core, the solenoid chose to stay inside... finally got it also)

A quick test gave me food for thoughts: the two solenoid seem to have the same resistance, so the issue is not electrical. I plan to test the cores and see if they have the same magnetic force...

To be continued when I'm back home, and of course I'll report my findings!

BTW, the Dremel vise is very helpful!
 

eli griggs

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If I had the experience back in the 1980's with a much wider range of cameras, and, if they had interchangable lenses or versions with longer and wider optic field lenses, I would likely use the 1958 Minolta Autocord (Export) or the Canonet QL17 for performances.

The films we have today include and surpasses what I was using for dancers back in the early 1980's, so film speed is good enough to go to mainstream makers instead of the often novel speed, grainy films back then.

My M3 SS, would have been too loud in that setting too, unless in a good baffle bag.
 
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Laurent

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Some interesting developments for today...

A few days ago I was able to remove the two mirror magnets, one was very resistant to removal and I had to enlarge the screw's slot to get it.

As I reported, both have very similar resistance (66.5 ohm for one, the one which had the blinking arrow issue, 68.7 for the other. @Andreas Thaler I'd love to know if you could check on some of your T90s just to see if this is confirmed).

I soldered some small wire (way too thick but I wanted to test... some appropriate wire is on its way) on both magnets, and put the working one in my camera.

Good news, it was now able to move the mirror.
Bad news, it showed the EEE error.
VERY Good news it fired a few times when slapped on my hand.
Bad news again it stopped operating and would not even turn on... a tiny wire got broken (comes from the remote command plug, can't understand why it prevents the camera from even turning on). Resoldering it got the camera back to operationg.

Then I decided to put the battery box back in place so that I can do some more tests involving hand slapping. And of course the camera does not turn on !!!

Will see this another day.

I also plan on testing the "defective" magnet on the other camera, so that I can see if the slight resistance difference plays a role, or if some other factors are involved. Could be the "default" magnetic strength of the magnet, in which case I'd love to find a way to fix this.

I'm also wondering if removing the magnet for a few days could explain the results...
 

Niglyn

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hi, you are doing what I would like to do, if I could find a scrap T90 at a sensible price,
May I ask,
You said you got the core out of the coils. Was this core magnetised?

What exactly does the electromagnet do? It cannot work like a door closer, always energised except on release, else batteries would flatten.

I can only think that once energised, it pushes against another permanent magnet, with an opposite pole, so it repels.
This being the case, if the coils are still ok, the fault can only be the core becoming magnetised & the coil voltage cannot overcome this now permanent magnet, or the permanent magnet which the electromagnet repels, has lost it's magnetism.
 
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Laurent

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Hi, for what I understand at the moment, the core is a permanent magnet, and I suppose the current in the solenoid cancels this field for a moment, hence releasing the mirror.

An planned experiment based on one of my son's ideas would be to remove the core again, to test it using a brass "balance" (not sure of the word, a primitive scale based on equal levers) above a steel plate, and see if one magnet is stronger than the other.

At the bottom of the hole in which the magnet sits there is another piece of metal with a similar look so it could be another permanent magnet working with this one.

Finding a scrap camera is a game of patience, I missed another F1 old that went for €40. Some people don't know what they sell. At the moment, on the same site, prices range from €35 (gone in minutes) to 1250 (been there for weeks and counting). I still keep an eye on these marvels as itis becoming and addictive game to find and fix their issues.
 

Andreas Thaler

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Laurent said:
Hi, for what I understand at the moment, the core is a permanent magnet, and I suppose the current in the solenoid cancels this field for a moment, hence releasing the mirror.
Click to expand...

I see it that way too:

No current flow through the coil, no magnetic field that separates the armature from the permanent magnet.
Click to expand...

Canon T90: Replacing the mirror magnet

The mirror of one of my T90s didn't want to move. The symptom is well known: When you press the shutter button, an arrow flashes in the display and you hear a quiet ticking sound. Otherwise the camera remains still. I opened the camera and tapped the mirror magnet with a magnetized...
www.photrio.com
 
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Laurent

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Thanks!

Would you have a chance to measure the resistance of the coil on one of your T90s ? 2 ohm difference seems too low to make a big impact but who knows?

This morning I opened the camera to find nothing looked wrong. Upon closing it again, the mirror flips again, so I guess there is a wire in bad shape somewhere. I'll have to find a way of finding and fixing this.
 

Andreas Thaler

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Laurent said:
Would you have a chance to measure the resistance of the coil on one of your T90s ? 2 ohm difference seems too low to make a big impact but who knows?
Click to expand...

Unfortunately, I can't measure the magnetic switch on the mirror box of my scrap T90.

The coil wire (red arrow) is broken, so a resistance measurement on the forward and return conductors (green circle) would produce a high-resistance measurement result:

 
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Laurent

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Too bad! I tried searching on the Net but found nothing for the moment.

I plan on putting the supposedly defective magnet on the donor camera, to check what happens. I'll post results obviously.


Would be nice to be able to re-wind these magnets!
 

Andreas Thaler

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Laurent said:
Too bad! I tried searching on the Net but found nothing for the moment.

I plan on putting the supposedly defective magnet on the donor camera, to check what happens. I'll post results obviously.


Would be nice to be able to re-wind these magnets!
Click to expand...

I still have three T90s with affixed red dots (i.e. corpses

I use one of them to remove the magnetic switch under the mirror and measure the coil.

I'll report tomorrow
 
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Laurent

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Well, some interesting findings... the "defective" magnet I removed from my historical T90 works flawlessly in the other camera!

So clearly 2 Ohm make no difference.

Since I see no gooey stuff that would block the mirror mechanism, I assume something else change the situation, and I can't see what except if having the cameras without this magnet for a few days helped de-magnetise some other parts?

So the current status is I now have two T90s with the EEE/HELP issue, except of two different issues on the two cameras.

I tried blowing some hot air (maybe I could get a job as a minister if I practice this enough?) in one of the cameras with a hair dryer for no result.

It may happen that, while I'm home alone tomorrow, somebody may try putting one in the oven for a moment and see if this works or is urban legend. Slapping the cameras do not help, but it did so there is clearly some extra force needed...
 

Andreas Thaler

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Andreas Thaler said:
I still have three T90s with affixed red dots (i.e. corpses

I use one of them to remove the magnetic switch under the mirror and measure the coil.

I'll report tomorrow
Click to expand...

Measuring the coil on the magnetic switch under the mirror box on my Canon T90 gives ~65 ohms.

Measuring conditions:
  • The magnetic switch is measured when installed.
  • I use measuring needle tips that pierce the insulation of the supply conductor (orange) and return conductor (black).
  • To create a closed measuring circuit, I cut the leading conductor.
  • The approx. 2 cm cable length each from the two measuring points at the start and end of the coil winding should not add any relevant resistance value.




@Laurent

Is this value plausible for you?
 
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koraks

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Laurent said:
66.5 ohm for one, the one which had the blinking arrow issue, 68.7 for the other.
Click to expand...

That would constitute less than 5% difference in magnetic field strength, assuming that the measurement is actually reliable. Differences n contact resistance at the measurement points could explain the entire difference easily. I don't think the difference in resistance is a factor in the problem.

The direction of demagnetization of either of the permanent magnets involved seems more promising to me.
 
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Laurent

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Thanks!, yes this seems plausible and in line with my own measurements!


I agree, I just wanted to make sure. The fact that both magnets work now proves it even more clearly.

At the moment I'm stuck at the "EEE" error, but at least I learned something.

The oven test was unsuccessful (except it gave me the opportunity to confirm my oven is crap, I needed to set it to 100 Celsius to get 55 and let the T90s a moment there. Then I removed the cameras and tried and the maximum of 250 which gives 150! I knew it was crap but now I know how much crap it is!

Even with how much I Ioved the T90, I'm much more attracted to fully mechanical cameras, at least I have the intellectual tools to understand every part of them, even if the whole is complex.
 
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Laurent

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I received two T90s I bought for parts, with melted front panel and battery packs.



My plan is to use these as guinea pigs to practice before I try to dissect the two other ones to access the shutters.

I think this shows the "oven" treatment should be well done (I'd assume the camera was treated with a hot gun). the cameras as so altered that it's impossible to insert the batteries holder.

Today I started an autopsy on one of these just to see, and also started storing small parts in little pouches for future use.

I collected many parts for future use, and could see that the camera's front panel is also melted on the inside. I could recover the DOF preview button as it is made in two screwed parts. The LED cover itself is half melted...

Apart from that the inside looks clean



I removed the top cover to check the status and again it looks fine. I also made a picture for future reference as I plan on unsoldering the wires to access the shutter.



Of course I removed the battery holder as it's dead, and took the opportunity to try to hook the camera to another camera's pack for a quick check. Believe it or not, the camera turns on, the display seems OK and the shutter operates (then I get the "EEE / HELP" error). The mode button also works, as does the drive/self-timer button.

I had no opportunity to shoot an image, as I already needed 3 hands to do everything at once.

I noticed there's a third wire in the battery holder, it seems to short something when the battery is removed. I suppose this resets the camera, as when I just lose the precarious contact with the external battery the camera does not turn off immediately, but the display fades slowly...

To be continued... there is still another melted camera to open, and I need to devise a way to hook the camera to a proper power supply...
 
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