Durst Printo repair advice

Hello photrio community!

This is quite a long one so sorry about that. My school darkroom has a Durst Printo dry to dry paper processor for RA-4 processing. It has been unused for ~10 years. This was because one of the motors with a heating element made a weird smell. Now me, my teacher and our janitor have been trying for a year to get an electrician to look at it but it has been unsuccessful. Today we decided to get it running to see if it really was broken, which motor made the funny smell etc. Now this was without a multimeter and no electrical experience so expectedly it went to shit.

When we got it assembled we turned it on and there was this horrible grinding noise and my teacher remembered that could be fixed with pressing on the motors. We did that but the motor 1 still wasn't turning the rollers to feed the paper. We had one replacement motor with heating so we put that on and well it exploded immediately. We took the whole thing apart and found out that processor one had the big gear upside down and a small gear broken. We replaced the small gear(same size and teeth, didn't have the half circle at the top but fit the shaft anyway). We put it back together but it still made that grinding noise and didn't roll the paper feeding rollers.
The processor gears turned great manually so I tested the motors on their own, outside of the unit, with no water putting a power cable straight to the connection(genius move). Motor 1 gear turned normally and the heater worked. Motor 2 exploded in my arms, lucky I didn't get electrocuted.

Now with my absolutely imbecile work out of the way. What could cause the grinding noise that goes away when put under pressure? If we can fix that(and either of the broken motors...) it should be good to. And yes next time when turning it on I will have an electrician with me.

That's a pretty cool processor. Did someone change gears around before you got there?

jarrupoljin said:

What could cause the grinding noise that goes away when put under pressure?

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Usually more stripped gears, or perhaps a spring-loaded axel that is supposed to push two rollers together and now doesn't because the rollers have warped? Note that on these old processors, very often the transport rollers have expanded due to corrosion of the metal axes. This pushes the rubber of the rollers outward, making them bulge. This creates additional friction and in systems where springs are used to press the rollers together, this can result in the cogs being pushed apart from each other, making them slip against each other.

So in short, inspect the machine closely, in particular the rollers.

mshchem said:

That's a pretty cool processor. Did someone change gears around before you got there?

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I have absolutely no idea why that gear was upside down and who would've done that. My teacher has been here since it was put out of use and hasn't touched it

koraks said:

Usually more stripped gears, or perhaps a spring-loaded axel that is supposed to push two rollers together and now doesn't because the rollers have warped? Note that on these old processors, very often the transport rollers have expanded due to corrosion of the metal axes. This pushes the rubber of the rollers outward, making them bulge. This creates additional friction and in systems where springs are used to press the rollers together, this can result in the cogs being pushed apart from each other, making them slip against each other.

So in short, inspect the machine closely, in particular the rollers.

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Okay that is interesting thank you. I didn't look at the rollers other than to wash them. Although I didn't notice any friction when manually turnng gears(last video), maybe it is different when using the motor.

But yeah I'll inspect all rollers, springs and gears more closely and update here! Have to try open those motors too

jarrupoljin said:

Okay that is interesting thank you. I didn't look at the rollers other than to wash them. Although I didn't notice any friction when manually turnng gears(last video), maybe it is different when using the motor.

But yeah I'll inspect all rollers, springs and gears more closely and update here! Have to try open those motors too

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If the rollers spin freely when you manually spin the gears I would find someone who can inspect the motors. You need to use the gears to spin the rollers (not the rollers to spin the gears) if the gears are good, motors could corroded.

Will a motor turn a single set of rollers?

People go nuts for these on Ebay. I have one of the little 8 inch capacity Durst machines that was designed for EP2 that I converted to RA4. Super little machine.

One issue with the Durst Printo, is the squeegee rollers, which are the last two rollers. These two are very soft and are pressed together by a pair of coiled springs, when the unit is stored the squeegee rollers need to be separated by a little plastic tab. Any kind of plastic will do, it just needs to be about 10mm wide by about 20mm long and around 2mm thick.

These two exit rollers if left together stick to each other and the whole lot gets stuck. I have a spare tank with a set of rollers that are stuck together, it is how I received them about 20 years ago as a gift. I kept that roller rack for spare parts, which fortunately I have not needed so far.

The top roller is spring loaded to press onto the bottom roller, which is driven by the gears. In the first picture you can see the coil spring and the back of the black spacer, which is directly underneath the white round thing.

the second picture shows more of the D style of spacer. I bought my Durst Printo new, only one roller rack came with the spacer, the other rack did not, so I immediately made up something and kept the exit rollers apart. The complete unit I received as a gift, was brand new never opened but about 10 years old. When I opened it the exit rollers were stuck together and still are stuck together. Durst quality control wasn't the best with these units it seemed.

When stored correctly and with the spacer on the exit rollers, the top roller is able to be turned by hand quite freely. the bottom driven roller will not move.