How I Repaired a Damaged Mamiya RB67 Medium Format Digital camera

I had the Mamiya RB67 and Pentax 67 on my medium-format needed record for a few years now, however I merely couldn’t justify the value tag or bear the unlucky realization that both digicam would sit lonely and unused on a shelf. That each one modified in December 2022 once I determined to seize a non-working RB67 as a Christmas Current for my eldest brother.

Certain, you have to be pondering “Jeez, this man is extremely low-cost if he provides folks damaged Christmas presents,” however boy you’ll be improper.

Shopping for the Mamiya RB67

The Mamiya RB67 was first launched in 1970, 53 years in the past. The RB67 was manufactured till 2009-2010 when no matter left of Mamiya was offered to Section One. Contemplating how little modified in design over these a long time, that’s an unimaginable run for a posh mechanical gadget like a movie digicam, not to mention any shopper product.

It’s honest to say {that a} majority of the RB67s out there proper now have been produced within the late 70s-80s. This implies the common RB67 you’ll discover has 30-to-40-year-old mild seals! Even in the event you discover a mint instance, the possibilities of disintegrating mild seals and bellows with mild leaks are very excessive. If you would like any digicam of this classic to work seamlessly, you must put aside a while and caress the digicam again to working situation.

With this in thoughts, I merely couldn’t carry myself to drop ~$500 on any RB67 in any situation. Contemplating there are not any close by movie shops that inventory previous cameras for perusal, I took a raffle and made a suggestion on a damaged RB67 from Nationwide Digital camera Trade. I’ve bought many cameras from them previously and I personally rank them a detailed second to KEH for used digicam gear. Fortunately, they took my $150 supply, and off I went trying to find components and a service manual.

The eBay itemizing for the used, non-functional digicam. Click on to enlarge.

I took a raffle. The itemizing described a stiff focus knob, separation within the lens components, an unknown viewfinder publicity meter, and the marginally much less fascinating 220 movie again, with giant components of the outer foam seal lacking. Most of those issues would deter any sane particular person from buying this digicam.

Nevertheless, I used to be banking on a number of issues. If the main focus knob was stiff, it’s seemingly that the digicam was not used fairly often and the entrance bellows principally stayed in a closed state. Sarcastically, the exterior situation of the digicam was mint. The physique paint didn’t have any scratches or chips wherever, main me to conclude that the digicam sat for some time after the main focus knob injury occurred.

A giant deciding issue was the clear and even folds proven within the bellows within the itemizing images. No creases or injury to the corrugations have been evident. That is nice information. The froth seals have been in want of alternative anyway, so I didn’t thoughts, and many people have had success utilizing 120 movie in a 220 again.

An Preliminary Inspection of the Digital camera

With the digicam on my workbench, my preliminary inspection was not very promising. A small shard of what regarded like security glass fell out of the digicam, giant bits of froth from the mirror fell out and I seen that I couldn’t examine the movie again as a result of the darkish slide was not current. As well as, extra seals have been completely toast, because the rear of the digicam physique was devoid of all foam seals, with simply traces of adhesive left behind.

Essentially the most alarming drawback was the main focus knob being stiff. The knob was busted as anticipated, however the quantity of drive essential to rotate the knob was significantly greater than I hoped. I wanted to torque the main focus knobs on either side of the digicam to simply transfer the main focus plate mere millimeters to reveal the bellows.

At this level, I used to be actually involved that the main focus rack or pinion was broken and enamel have been mushroomed over or lacking. Nevertheless, after learning the service handbook and observing different images, there was an excellent probability that the components underneath stress have been brass. Brass is a really malleable materials, and if the digicam took a fall as this one clearly did, it’s seemingly the brass half could possibly be fastidiously massaged again into form.

Worst case, if I couldn’t discover alternative components, I might machine one thing out of brass with my lathe.

As you can have guessed, there are not any components out there for the RB67! This was a little bit of a letdown and put a damper on the restore course of, as I began in search of a second restore digicam to reap components from. Out of sheer frustration with eBay costs, I simply determined to teardown the digicam and examine the main focus mechanism earlier than I went any additional. Fortunately, the service handbook is extremely helpful and accommodates all of the diagrams and procedures on find out how to teardown, service, and alter the digicam – nearly unprecedented within the yr 2023!

The disassembly course of is simple sufficient: take away the main focus knob first, then the underside plate, the chilly shoe screws, the aspect panel leatherette, a number of screws within the aspect panel, and eventually the shaft knob collar.

Earlier than I dig into any digicam, I like to make use of tape to maintain observe of the place every screw lived on the digicam physique. It’s handy and sensible, and it doesn’t discriminate in opposition to aluminum screws like a magnetic mat.

I began from the damaged knob aspect and because it was in such poor form, I didn’t need to take away the leatherette protecting the knob. The round aluminum backing plate merely unscrewed from the knob face. The retaining nut was already free and the knob got here off with ease.

There are two tiny black machine screws that maintain the shaft collar to the physique. Moreover, there are two cheeky screws hidden behind the chilly shoe spring plate. To dig any additional, the underside leatherette rectangle wanted to be eliminated and the highest proper nook of the leatherette wanted to be peeled again to disclose extra screws. The aspect panel is a bit fiddly to take away as you must rotate it and pull it again for the panel to come back free.

One thing lacking from the service handbook is find out how to take away the leatherette that’s glued in every single place on the digicam. Fortunately, the identical process utilized in eradicating leatherette from modern-day cameras applies right here. You simply want to make use of reasonable warmth and skinny, but blunt pry instruments. Plastic pry instruments work effectively with low warmth, however skinny steel pry instruments are extra dependable if extra warmth is required. I used a mix of each after which painstakingly nudged my method underneath the fabric and wiggled round to take away the fabric from the decades-old adhesive.

The method is about 20x slower than with trendy cameras because the adhesive Mamiya used barely responds to warmth and leaves a horrible yellow movie behind on the panel. You will need to tread evenly right here as even square-edged plastic spudgers can tear by way of the leatherette. I can not stress sufficient: use pry instruments with rounded edges! As you may guess, the leatherette is now not out there. You possibly can in all probability minimize your personal, however I opted to not spend the time researching a period-correct leatherette materials, and go away the digicam as inventory as potential.

With the aspect panel put aside, there’s one other steel bracket that obstructs the main focus rack: the steel focus information. Eradicating three Phillips screws reveals the sorry state the information was in: bent and mangled. Being composed of sentimental stamped metal, the information was not exhausting to persuade again into form.

The Knipex Plier Wrenches are an ideal match for this job. Every jaw is parallel to the opposite, making them invaluable for easy steel work and bending operations, moreover the marketed bolt and nut removing. They’re extremely useful instruments and I like to recommend them for anybody’s instrument assortment, despite the fact that they command a premium. Talking of helpful instruments, I often print out a service handbook when disassembling a new-to-me gadget, however my floor duo was surprisingly sensible as an alternate resolution. With the ability to zoom in and simply scroll by way of a 100+ web page PDF all whereas permitting me to regulate the viewing angle was priceless. It’s too unhealthy the duo is an extremely fragile gadget, however extra on that one other time.

With these two components eliminated, the main focus rack is now in plain sight and lets you higher observe the state of the main focus mechanism. One way or the other, not one of the enamel on the metal rack have been broken. The sting of three enamel regarded barely extra used than others, however it was such an insignificant bit of damage {that a} diamond file simply cleaned them up. Extra importantly, the entire enamel have been nonetheless sq. to the profile of the rack, which is good news.

Because the rack was undamaged, this leaves the main focus rod and pinion to reveal the burden of the injury. Within the RB67, the pinion isn’t a standard separate gear. As an alternative, the pinion is broached right into a protruding profile on the stable brass focus shaft that runs the width of the physique and connects to each focus knobs. The removing of the main focus collar provides a full frontal view of the pinion, however it’s nonetheless very a lot captured by the alternative aspect of the digicam.

On shut inspection, the left face of the pinion enamel seems to be nice! It’s exhausting to attract conclusions concerning the opposing aspect of the pinion so the complete focus shaft have to be eliminated. With the intention to free the main focus shaft, each knobs have to be faraway from the digicam together with each focus collar mounts.

The undamaged focus knob required quite a lot of finesse to take away with out damaging something.

First off is the leatherette cap utilizing the identical approach as above. Behind the pores and skin are a round aluminum plate and a small brass screw. Make sure that to unscrew this screw completely sq. with the screw head because the screw provides little buy to ease within the removing course of. Apply quite a lot of drive, flip, and it ought to come out. For those who simply blindly unscrew it, you may be in for a nasty day.

Subsequent up is an 8mm brass nut, however you will want a method to stop the knob from turning whilst you loosen the nut. I opted to make use of the spherical tip round profile lens spanner wrench from SK Grimes. It’s a easy but invaluable instrument for lens restore and value its weight in gold for duties like this. Lastly, you may unscrew the knob.

These focus knobs are Bakelite, making them extremely brittle if torque is inconsistently utilized. There are additionally many casting traces on the floor of the knob, which is a bit unsettling as I don’t have a alternative knob and components are unobtanium. I made my life a bit simpler and pressed a 120w soldering iron tip in opposition to the main focus knob brass insert for a couple of minute, simply in case there was thread compound used through the authentic meeting.

With no knob on the opposing aspect, the one method you may safely take away the knob is to first place the digicam on its backside. Seize the knob, apply downward stress on the main focus shaft so the main focus pinion mates with the rack, then unscrew. This manner you don’t by accident injury any enamel.

As anticipated, the main focus rod was broken. Oddly sufficient, the enamel of the pinion gear have been unscathed. The grey marks noticed have been simply previous grease and a tiny bit of damage. There have been no indentations within the pinion enamel or stepped geometry. All enamel have been nonetheless sq. and not one of the edges have been mushroomed over, simply the rod was badly bent. That is the best-case situation.

I used to be debating machining one other rod with my lathe, however then I remembered that brass is sort of malleable and I might in all probability simply make the rod rotate true once more.

All that was wanted was the lathe, a three-jaw chuck, copper shims, a machinist arm or “magic arm” and a dial indicator. Essentially the most essential a part of this system is to scrub any traces of steel chips from all jaw enamel and use a delicate steel shim inventory on the three jaw chuck in order to not deform the brass focus rod and trigger extra injury. I select copper for the job.

This process was a chunk of cake for my Southbend 9. When it got here time to tighten the chuck with the chuck wrench, solely a small quantity of torque was utilized to the wrench, sufficient in order that the brass rod didn’t spin after my makes an attempt by hand. I’d say I rotated the wrench only a mere few levels. I’m mentioning this as a result of the half diameter is small and chuck wrenches mean you can apply quite a lot of torque on a component, sufficient to make spherical brass inventory triangular.

Observe: No energy was utilized to the lathe for this process, because the lathe was solely used for fixturing and commentary. It’s unhealthy apply to go away a chuck wrench put in in a chuck. It’s only displayed right here to exhibit the dimensions of chuck wrenches and the way a lot torque you may apply to a component.

I mounted the rod within the chuck, ensuring the pinion cleared the jaw enamel, and mounted the magic arm close by with a dial indicator immediately above the middle of the main focus rod axis.

It’s crucial that the dial indicator is adjusted perpendicular to the rod or else you aren’t going to acquire any helpful measurement from rotating the rod. I used a “0.0005in” or 5-tenth dial indicator not as a result of I used to be making an attempt to be tremendous correct, however as a result of the tip on the indicator was sufficiently small to clear the three jaw enamel and the pinion with none catastrophic interference.

As proven, the rod was extremely off-center. For those who discover, I began by measuring the rod earlier than the pinion, not between the pinion and the threaded half. That portion of the rod was deformed from my preliminary silly makes an attempt of bending the rod earlier than fully disassembling the digicam.

Since brass is so malleable, my weapon of selection was a chunk of hickory, or just a damaged claw hammer deal with. I rotated the three-jaw chuck with my left hand and watched for patterns within the dial indicator.

The dial indicator provides you an thought of change over rotation. By rotating the chuck forwards and backwards a number of instances you get an thought of the place the excessive spots and low spots are primarily based on the place the pointer on the dial stops and adjustments route. When the pointer adjustments route you could have discovered one of many extremes.

Rotating forwards and backwards helps you discover the opposite excessive and you may get an excellent ballpark of how out of around the half is by counting up the gradations on the dial face between the extremes. These gradations often symbolize thousandths of an inch. Within the case of my dial indicator, they symbolize 5 ten thousandths of an inch. Which will sound complicated, however simply consider each bigger marking as a thousandth and each shorter marking between as 5 ten thousandths or half a thousandth.

Since brass may be very delicate, it may be persuaded to bend with even the slightest little bit of drive. Rotate the chuck to one of many extremes and faucet evenly with the wooden deal with. You will notice the needle change on the dial indicator. Rotate the chuck once more and observe the dial indicator. You may even see a rise or lower within the gradations between extremes. For those who observe a lower between the extremes, you could have been hitting the right aspect of the brass rod.

Proceed to evenly faucet at that location of the acute and observe the dial indicator till you decrease the quantity of runout between the 2 extremes of measure. For those who occur to strike the improper excessive, the variety of thousandths out of spherical will enhance. Merely faucet close to the alternate excessive measurement and it is best to start to see an enchancment between your excessive measurements.

Tapping the top of the brass rod evenly with the wooden deal with a number of instances reshaped the half again right into a helpful rod. I selected to strike the brass rod between the threads and the pinion to stop any potential injury to the vital geometry.

To be clear, once I point out “tapping” I actually imply tapping. I barely utilized any substantial quantity of drive on the brass shaft. The load of the wooden deal with utilized a lot of the drive, I didn’t use any extra hand energy to strike the brass. That is the extent of caress you need to use when performing this activity. A little bit goes a great distance.

It’s simpler to make use of small faucets, rotate the chuck, observe the dial indicator, and faucet once more than blindly use one giant strike. I used to be in a position to get the rod inside 7 to eight thousandths of an inch, which is frankly not too unhealthy when contemplating how bent the shaft was initially. That is the repaired brass focus rod in opposition to the 1/4in sq. inventory utilized in my SK Grimes lens spanner. Gillette would approve.

With the shaft as straight because it’ll ever be, I shifted my consideration to the elephant within the room: the damaged focus knob. I took some measurements of each focus knobs and fired up my native CAD program. The damaged knob truly helped within the course of as I used to be in a position to take cross-sectional measurements with out having to make use of extra sophisticated measuring strategies to search out out inside wall thicknesses.

Fortunately, the unique Bakelite knobs are produced in a really simple method: a brass insert centered round help materials. If this terminology sounds acquainted to you, congratulations! That’s the answer to the damaged knob drawback: a brass insert in 3D-printed ABS. I broke away what was left of the Bakelite materials, measured the outer diameter of the brass insert, and adjusted the CAD to permit for an interference match through the last insert operation.

My little Up Mini printer did a superb job printing the knob. The primary knob got here out a bit warped, however I quickly discovered this was its method of informing me that the print mattress was in want of deep cleansing. The subsequent print got here out stellar and was close to an identical to the CAD I designed, not a straightforward feat for FDM printing.

Only a few years in the past, I started to simply accept components coming again 20 – 100 thousandths of an inch off with native printers, however this one takes the cake by way of accuracy and comfort.

To make the ultimate meeting course of simpler, I mounted my 120w soldering iron in my desk vise pointing straight up within the Z-axis route. To each stabilize and evenly warmth up the unique brass insert, I selected a small-diameter soldering iron tip with a big shoulder. I let the brass sit on the soldering iron tip for about 3 minutes to get the half good and heat. I grabbed the 3D-printed half, lined it as much as the brass insert as sq. as I might, and rapidly pressed the components collectively.

As soon as I noticed the blue extra help materials overflow from the highest of the middle of the knob, I knew the insert had efficiently handed by way of the physique of the knob. I rapidly eliminated the completed knob from the soldering iron and let the ultimate knob cool on my ESD mat. As soon as the half was cooled I eliminated the surplus ABS materials from the middle.

The ultimate consequence was nothing wanting exceptional. With some mild sanding on the perimeters, the knob felt wonderful within the hand. Selecting to print with 99% infill was seemingly overkill, however I don’t remorse the choice, because the newly shaped knob has an identical weight as the unique Bakelite knob and doesn’t deform simply even when squeezed with all my hand energy. This can be a very fascinating trait as a result of the very last thing I would like is for a knob to really feel like it would fail with continued use. Listed here are the 2 knobs aspect by aspect.

Certain the colour blue is a bit odd, however frankly, who cares, I can all the time print one a unique colour. Mort importantly, now you may too! Right here is the precise CAD of the RB67 knobs. There are two variations of the knob. One model is an identical to the Mamiya knob, with the slight taper on the grip, and the second model has a sq. profile grip. I’ve supplied the information in each .step and .stl. Get pleasure from!

RB67 Knob Authentic Obtain:

RB67 Knob Sq. Obtain:

With the knob scenario straightened out, I went forward and commenced reassembly. I did issues a bit in another way and put the 3D-printed knob on the alternative aspect of the digicam. Since that is an RB67 professional, the left-hand knob has a spotlight lock lever that torques in opposition to the within of the knob. I need to stop any untimely injury to the 3D-printed knob and let the lever torque in opposition to the unique Bakelite knob as a substitute. That is in all probability an unfounded concern, because the ABS knob is probably going extra robust and extra secure than the working Bakelite knob.

The largest problem with any reassembly is ensuring you wouldn’t have leftover screws. Fortunately, that is the place the service handbook and tape actually got here in useful.

Nicely, the digicam is all assembled and able to go, however the viewfinder wants a bit consideration. A variety of of us actually benefit from the comfort of the folding viewfinder, however everybody is aware of the chimney-style viewfinder is extra comfy and fewer fiddly.

The chimney viewfinder has a primitive built-in publicity arm that runs on an SR44 button cell battery. Out with the lil bugger and in with the clearing brokers and spare caliper battery.

Now, that’s what I name a digicam. Certain, I didn’t get the seals in time for the Christmas season, however that’s simple sufficient to use with some toothpicks, alcohol, and persistence. For now, a lonely, mistreated RB67 has been pulled off the streets and is sort of prepared for motion as soon as once more. Thanks for sticking with me this far and thanks National Camera Exchange for not disposing of such an imposing digicam!

In regards to the writer: Anthony Kouttron is the digicam fanatic, electrical engineer, and hobbyist behind the web site Salvaged Circuitry. Yow will discover extra of his work on YouTube, Twitter and Instagram. This text was additionally revealed here.