Fixing An Industrial C-41 Processing Machine

[Dave Colangelo]

An interesting project has just come across my bench and I thought this might be of interest to a few people here:

I was at my local lab the other day and sadly found out their C-41 machine had stopped working. They knew I was an engineer and quickly asked me "how my soldering skills were". It turns out the machine had started smoking from the "mother board" and stoped processing properly. They took me over to it and the tech pointed out where it was smoking from. I snapped a pic of the unit and went home to do some research. A lot of internet trolling and I found out that the control relays on these units had a bad habit of shorting out. Since the heater tank was located essentially on the other side of a metal wall the excess heat causes the whole board to be fairly hot when in use. Anyway with the board in the unit I could not see any part numbers on the relays and the internet was less than helpful in identifying them. The shop happens to have the board from a processor that went kaput about 10 years ago which they pulled out of storage. turns out that board had the same relay issue but there are about a dozen or so relays so some are salvageable. Step 1 is pulling the relays form the old board for salvage,

they are the slim black things on the left hand side. Thankfully once we pulled the boards from each unit we could see the part numbers on them so we can order fresh replacements but at $14 a relay they wanted to see if we could get these salvaged ones in first. The machine in question is an older Noritsu for those wondering.

More to come...

Dave

 

[Dave Colangelo]

Spend last night pulling the relays form the salvage board and it looks like we are in business. Ran out of desolder wick so there is more inbound for pulling the ones off the board they need:

Went to the lab today to grab the board that is actually being repaired while I wait on the desolder pump and wick i figured I would clean up the scoring and prep the board. It looks like the trace its self is pretty cooked and I'm going to have to rebuild it so there is foil and epoxy inbound to do so. It looks like this may all have been caused by a diode that went bad (you can see it in the upper right corner) thankfully the parts board has the diode in question so I dont need to source anything just yet.

For those wondering what this is all does. These relays control the functionality of the machine. As the film moves thorough a few different things get kicked on and off since a microprocessor cant drive a motor or heating unit these relays act as low voltage/low current activated switches which turn on high voltage/high current devices. I dont have the full schematics but the relays in question seem to control the drive motors for the film feeding as well as the thermal control units for the chemistry tanks. Ironically from what i can deduce its the ambient heat from the chemistry tanks that caused all this in the first place.

 

[webestang64]

Looks like fun! We use a Noritsu V-50 here at my lab and bought a V-50P $400 for parts.

 

[Dave Colangelo]

New desolder pump and some more wick came in today so I was able to get the toasted relays off the board and clean everything up.

This is more or less how it looked when everything came off

A little bit of cleaning once everything was out of the way

Cleanup on SSR9 and SSR10 was pretty straight forward as they had the least damage. Thankfully the pins that seems to have shorted cooked the bottom of the board but the trace connections were on top so there is hope there.

SSR8 is going to take the most work and i have some stuff inbound for that. There are two main issues. In the image above you can see a bit of the exposed trace on the top. Since that is a different trace that needs to be recoated with resin to prevent any arcing. which will be part 1 of the job. Some of the damaged area has been scrapped away and I will put some resin over it to form a new bed. Then pin 4 on SSR8 will get a new ring and the damaged trace will be repaired. Once repaired that will all get some resin then the final assembly.


Here it is about as clean as its gonna get with some light tinning applied to the connections so they are ready to solder up the replacement relays.

 

[jcdeboever]

Looks like your attacking it spot on. It should work just fine when completed. Tedious task.

 

[Dave Colangelo]

So the resin came in faster than expected and I was able to do some more work today. Im using CW 2500 resin which is the green stuff you see on PCB's that actually covers the copper traces. Todays application was on the primary burned out region as well as a little bit on the other two lower regions. This was to serve a few purposes. I wanted to provide some protection as well as cap off the burnt areas to prevent any further board degradation. Due to the fact these are 220V relays they really did a number on the board which is unfortunate. Replacing the substrate is not really an option here so I need to try and fix what I have to work with. The resin was also applied to a few areas of trace that were exposed due to the damage this will protect against potential arcing and as well as corrosion and oxidation.

The lower application was largely structural

The upper application served a few purposes. Firm up the degraded portion of the board and smooth out the area under the damaged trace. Its a bit thick here but some was wiped off in the trace path to provide a smooth area to lay the new trace as soon as the copper material arrives.

The resin has a nice 45 minute working time but the cure time is fairly long so I left it the night (and most likely the next few days) to harden up. I may have gone a bit overboard with it but the exposed traces were beginning to lift up so it required a fair amount to cover them. This resin has a 600F temp limit so all soldering will be done at 550-600 from here on out.

 

[Dave Colangelo]

So all the resin dried and the trace was looking good so a test run was in order. You can see the trace here (it looks a bit chunky looking but it was solid) continuity was checking out and we were lookin good.

Booted the machine up, and.... ....smoke again. We cycled the power off and waited a bit. I pulled the board to check for shorts or burning but could not really see any. I figured the resin may just be burning off a bit around the solder joins so we tried it again. The second time no smoke but the fix tank ran way way way over temp during the heat up stage. Back to the drawing board. Anyway after quite a bit of research and a deep internet rabbit hole I was able to identify an egregious mistake I made. Turns out scorched PCB's that have developed enough carbonization from the scaring can become conductive. So back to the bench it was. I ended up cutting out 2 of the traces that surrounded the scaring to find that some of the burn had reached under them and were causing a short even from the repair. The traces were hard jumped with wire across the board to rebuild the connection and avoid the damaged area. Headed back for a trial and installed the board,

Fired it up, and the temps are holding!

One machine saved!

And hey, maybe film will live to fight another day.

 

[jcdeboever]

Awesome!

 

[cgw]

Magic...

 

[webestang64]

Yeah Baby!

At my lab we are running about 75-150 rolls a week, just enough to keep the chemicals in check (we run control strips).

 

[RowdyRay]

Awesome job and perseverance. Sometimes hard jumps are the only way to fix it.

My dad was a TV/Radio repair man. He taught us kids many tricks like this. None of us are afraid to take something apart worth saving.

Kudos!!