Ok here's a weird one, canon 300mm f/4 fault

Cobra

Cobra

In Memoriam. TPer Emeritus
Admin
Messages
114,433
Name
The real Chris
Edit My Images
No
As per title, I have a Canon f/4 300 mm IS.
its about 5 years old.
Sometime ago, (I hardly use it TBH) I noticed a problem.
Normally when I do use it, its pretty much wide open.

However, in various shutter speeds and settings
it produces the 01 error, clean contacts.
This makes no difference whatsoever.

These are the specific results from AV.
other settings are pretty much the same too
It's OK in f4. & 4.5.
f/5.6 is erratic.
6.3 & 7.1 is ok
f/8.0 is erratic
f/10-14 inc is OK
f/16 is erratic
f/18 is 20 is OK
f/22 is erratic.

Erratic in as much as you fire one shot and get an error message.
leave for a second / or turn off / on and it'll fire again.(but just once before the error message again)

I contacted a couple of well known repairers.
One said
that it would be about £300 including a full service and 6 months warranty.
. It could be the iris Or the IS unit that is faulty.

The other said
To replace the diaphragm on your lens would be £55.58p parts and £110.00p Labour Subject to inspection and VAT

Conflicting reports, and prices obviously.
Now I have no idea how lens's "really work"
But this whole thing seems odd to me.
This is on a 7D, but has been tried on a 40D 400D & 350D with the same results.

Opinions and comments most welcome.
 
Sounds very much iris related given the different results at different apertures if the is was borked you would expect it to be consistent at all apertures.

Look at your quotes carefully sounds like the first one is fixed price do even if they find both is and iris borked that is all you will pay but the other will increase if they find additional faults.
 
My guess would be the diaphragm or feedback cable, Chris. The diaphragm unit is connected to the PCB by two ribbon cables....one for power and a second for position feedback. The feedback will, I assume, be an encoder or sorts (several parallel bits representing the motor position) and it's possible that one of the bits isn't being reported....due to electronic failure or bad contact. The errant bit is probably not used for some aperture settings and hence only shows an error at certain settings.

In lay mans terms....it's like walking down stairs with a dodgy knee. You only get the pain every alternate step.

Bob
 
Thanks guys much appreciated.
Alex, good point about the quote, I'd not thought of it like that.
Bob thanks for the idiot explanation :thumbs:
 
Canon bob's suggestion makes sense, if it is a bad contact you will likely have to replace it (the contact) as those things are fragile as you like. Do you have a lens repair shop near you? It's better if you can go in and chat with them than just sending it off as you can talk about the problem with them and get a better idea of the fault and what the cost will be. I don't really trust the fixed price ones as often the fault is fairly simple and a simple tear down, tinker and clean would fix it. It's a bit like mechanics I guess, something of a dark art to the un-initiated so lots of potential for extra charges from the unscrupulous ones.
 
Thanks for your in put Sandy :)
Unfortunately there is nothing local to me,
I have however been exchanging emails with two well known ones and basically the quotes were the
Last emails.

Bob is a very knowledgeable guy (You do still have my address to send the cheque to Bob?)
And I do trust his opinion.
 
Canon Bob said:
....it's like walking down stairs with a dodgy knee. You only get the pain every alternate step.
Click to expand...
I agree.

I don't know enough about the inner workings of this lens to comment on the specific components. But the symptoms absolutely point to one bit in a parallel data bus not working properly. So that's one broken wire in a ribbon cable, or one faulty pin in a connector, or something like that.
 
I appreciate your in put Stewart :thumbs:
 
Hmmm... it reminds me of my friend, Sotiris. His zoom stopped working, didn't want to pay for replacing cable, got one from China for $5.
Replaced it, and all is good again.
biggrin3.gif


Saved him a small fortune. If you want to ask him, try contacting him here, email at bottom of page: http://www.scvphotoideas.com/p/about-me.html

Just say, Jan sent you...
biggrin3.gif
 
Thanks Jan I appreciate the thought, :thumbs:
But no way in hell am I going anywhere near it :D
 
I use a chap that works on his own doing repairs ... I sent my 70-300mmL to him last week as it was making some very strange noises and jumping around in the viewfinder. He tried it when it arrived (just to make sure it wasn't my 7D) then stripped it down, re soldered parts of the board, serviced it and then put it back together ... £60 incl return postage.

Just do a search online for Alan Marlow if you are interested ... send him an email describing the fault and he may be able to help.
 
Nice one Mike, thanks, I'll do that :)

Edit should that be Barlow?
Marlow seems to lead me to a driving school :D

Edit scratch that found it Middlesex, yes?
 
Last edited:
PMSL Thanks Mike, and I'll be sure to mention your name :thumbs:
 
Sounds like a result Chris.
 
fracster said:
Sounds like a result Chris.
Click to expand...
Looking better than £300 thats for sure Ade. :thumbs:
I've dropped him an email, (yes Mike I did mention your name :D)
I'll post back when he replies :)
 
IIRC, in The Meaning Of Life by Douglas Adams, those bits are called Exeters - my home city.
 
You must log in or register to reply here.
Back
Top