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300D fried, need schematic :(

Hello

I recently had the sub mirror on my 300D fail and also the motor on an EF 75-300usm lens stop working.
I repaired the sub mirror pin following the guide on the net, All went pretty smoothly except id lost a few lines of the LCD display and the amber light had stopped, i put this down to the clip on the PCB securing the ribbon cable to the back cover not closing properly (i damaged it slighty when removing first time). Camera worked fine except i had no shutter or battery and exposure info on the LCD.
So i took the rear off again and re-inserted the ribbon, more lines gone!!! Inspected the connector and thought id seen some bent contacts towards one end of the connector, tried to tease them up to see if they were bent,

alas they were not bent but were power connections of some sort and i had forgot and left the battery in (yes im a twat!) re-assembled the camera and its dead :(
if i can get a schematic i can get one of the test guys in work to have a look at it and see if theres anything obvious like a fuse or a diode has went.

Anyone know where i could get a schematic for the 300d?

also if anyone is intersted, i was using my ef75-300 usm mk3 lens one day, it was raining pretty heavy but the lens didnt get wet, worked fine then the next day when i tookt he lens out again, it had condensation on the inside and the AF had stopped working. Took it apart and fiddled about a little, located the USM motor and removed it, it was stuck solid!!! i rotated it by hand with some effort, re-assembled the lens and it works fine, pity ive no bloody body to put it on now! :(

ANy help would be greatly appreciated!!!!

regards Neil

Neil Thompson
Tue, 28 Aug 2007 08:58:28 +0000

Neil,

Am in the dark as far as a schematic is concerned. There are some online manuals but they
show only the mechanical disassembly only. Not much use when it comes to the electronics or
firmware listings.

Did you check for broken traces on that connector?

Also there are two ends wach with a connector between the rear panel display and the
camera body main PCB. Check that the other end has not been pulled ajar.

I got a 300-D that went through all sorts of hell which I fixed since I am too poor to aford
a new one. A friend gave to me one that had 9 - 10 damaged parts.
It had fellen into a brackish water lake and the case that it was in leaked.

There are two connectors that look like a highly minatureized ISA computer card edge card
connector with the two staggered row pads with traces going between the inward group.
One is the mirror and shutter mechanisn state flex where it is connected to the syscon
board. The other is the one that you are working with. These are particularly bad and
dense pitched designs. These were a rescue from not designing the the circuit in a way
that uses less connections such as using serial signaling.

Making sure that the camera is well held down onto the work bench is essential. Otherwise
you will chase the thing across the workbench and will cause other damages.

THe last problem was that the rear board that contains the status LCD and the button
board has some corrosion problems and that the connector had some dirt.
The board was removed from the rear panel and given a wash. Removed the connector with
Indum alloy solder which lowered the melting point of the solder that held it in place to
see if there was any corrosion and it looked okay. Placed the connector into an ultrasonic
cleaner and some dirt could be seen comming out of it. Then dried and resoldered it to the
board. The camera work as new. A repairman lost the clampdown for one on the main board
and a shim had to be made to replace it.

You can see what this looks like by looking at http://www.tinkerhack.com/photos ,
High rez, Projects and experiments and DSLR repair.

Where did you get your 300-D from?

Take care

Mike Kan

Michaek Kan
Wed, 29 Aug 2007 16:13:42 +0000

Cheers for the reply dude.

I bought it off a friend a few weeks ago who had never had a problem with it and is upgrading to 20d.

Ive acutally got the thing in bits infront of me right now.

Just to check i tested the fuses on the DC/DC board and the middle fuse is gone.

For reference fuses look like 0402 size SMD's. the markings on them K and P refer to the ratings, K being 1.5A and P being a 3A rating.

search results found for "fuse smd"

The middle K fuse as identified in one of the other sites i found (think it was the 300d repair adventure) is blown. Im going to get some fuse wire here to bridge the spare pads and see if it works.

ill post back in a couple of hours with a yay or ney!

Neil Thompson
Wed, 29 Aug 2007 18:14:48 +0000

Hello

just thought id update this. Replaced the fuse last night, re-assembled the camera, switched it on...............and its still dead :(

going to let one of the test guys in work loose on it and see he can come up with anything but its not easy without the schematic :(

Neil Thompson
Thu, 30 Aug 2007 07:15:18 +0000

Neil,

Do you have any test equipment?

I have used a home made surface mount probing jig to do much of the trouble shooting on the
kind of circuits that cameras are made from.

Did you make sure that all the connectors are in and doors are closed?

Use a good land lens to check that the ribbon connectors have not developed cracks in the
flex board and connector traces.

Make sure that the extra fine staggered pad ISA style connector are properly seated.
The status LCD above the image could display hierogliphics and the syscon processor could
get very hot.

It is possible to powerup a partly assembled camera. The screen should power up without
the rear panel though many of the controls are there.

Make sure that the circuit that has the blown fuse is not powering a short circuit.

To test to see that all connector pads actualy have continuity with some components on the
board. You can use a small audio amplifier like the AUX inpit of a stereo in series with a
100K Ohm resister to stroke the connector to check that it is connected to something one the
board. there will be a buzz for each commector pad that you stroke. Pads that do not
connect to anything will not make a sound. The resistor prevents Electrostaic discharge
( ESD ) that would damage the semiconductor components. Do not connet the camera with the
power on durring the audio probe tests.

Take care and good luck More Later.

Mike Kan

Michael Kan
Fri, 31 Aug 2007 18:36:33 +0000

Hi thanks for the info.

All i have at home here is a multimeter ive been testing for continuity throughout the boards and havent been able to find much other than a blown fuse. Its next to impossible for me to trace with it being a multilayer board! Ive just been going round the power areas and around the connector pins i touched, testing everything.

In work we manufacuter a lot of different boards and assemblies. I know one of the test guys (im more mechanical than electronic) has a lot of experience fault finding and repairing mobile phones and LCD screens and has access to scopes etc, im going get him too have a look at it as hes going to know what he's looking for a lot more than i would lol.

thanks for the help :) hopefully ill get it sorted

Neil Thompson
Sat, 01 Sep 2007 13:20:42 +0000

Neil,

Chances that special extender cables and or fixtures would be needed to create enough
space between the various boards to provide access to the test points while the whole of the
camera is powered up.

Other and smaller board test fixtures would excercise each board for functionality.

This is where one would need each of the board charactorostics if not its full schematic.

Each powered test fixture would send have a small control panel with buttons, meters and
lights that one could pace the board for what it that it was meant for.

For example, the mechanism state board would have a command issuing buttons that would
cause a shutter release action, Dummy loads that would sinulate the mirror fliper and
shutter cocking motor, rotary state switch, Leading and trailing shutter electromagnets and
state leaf switches. This powered board tester would allow one to see that the board is
functioning properly dispite being out of the camera.

Failure of the board would need a " Fox Hound " kind of audio tester to passively test
the board for suspected broken traces which mine found that were caused by the ham fisted
service technician.

You would have to find what caused the fuse to blow in the first place.
That means to check what it was connected into the first place.

It is quite possible that the ribbon cable that runs from the main board to the rear
button panel and status display has been misaligned and caused a tempoary short.

The connector that is between the mirror board is similar to the high density fine pitch
connector can also suspect to a " Dead camera " if certain traces are broken.

The " Fox Hound " is a sound tool that you would place its input at one known part of a
circuit and then with the active thinly insulated probe with a 1 KHz about a volt P-P
around the board to " See " listen to find out where the other end is.
This sensitive audio signal tracer could be made from inexpensive audio tape player.
The signal generator could be made from an inexpensive 555 timer oscillator chip.

I found on mine that the signal detction would stop mysteriously as it apporaches the
flex board connector. Closer visual inspection realixed my fears that the traces were broken
by some past abuse. The hair thin traces were fixed.

Have you seen the pictures in the link in a previous post on this thread?

There shows how the traces were fixed and thus the camera work as new.

So one would greately benefit in having some kind of surface probing fixture like the
one that is pictured. it is not possible to connect clip leads to the surface mount
components. It consists of a group of spring loaded meedles on arms.
Leads from this afford to be used with clips.

Mine is home made.

Take care

Mike Kan

Michael Kan
Sat, 01 Sep 2007 17:52:36 +0000

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