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Minolta RP-101, RP-405, RP-407 and RP-1824 Microfilm Reader Printers

 A brief technical perspective

by Evis Beaton –

In the 1970’s Minolta Camera Company manufactured a series of “electrostatic-liquid” microfilm reader printers. This product line used a liquid petroleum based distillate mixed with pigmentation (ink) and a 500 ft. roll of electrostatic paper available in 8.5” and 11” widths. The machines would accept a roll of paper at the back of the unit that would feed up to an initial load roller actuated by an electro-mechanical friction clutch. These system all had a rotating multi cam switch mechanism which activated and deactivated the various functions of paper feed, cut, transport, vacuum, exposure stop, and synchronization of mirrors.

These systems all had tanks to hold up to three quarts of “Liquid Toner”.  After loading microfilm onto the machine and lining up an image, you would hit the print button for the magic to begin.

Initially, the paper feed roller kicked into play and began to feed paper off the continuous roll, when the leading edge of the paper activated (according to the selected paper length) the paper cut switch located in the paper feed path, the cutter solenoid would trigger the cutting the paper instantly and that paper continued to feed into the High Voltage charging area. This electrostatic paper was coated on one side (the exposure side) with a material that would accept and hold a charge that could be discharged when exposed to light.  The paper was feed to the top of the system and to the exposure bed via suction transport belts. These were belts maybe 3” wide with many holes throughout, there were 4 of these belts side by side and a large vacuum motor above the belt system that created enough suction to keep the paper glued to the belts during the 8-15 second exposure pause (yes a long wait time for a copy!).

The image that was on the microfiche screen was projected onto the unexposed paper by means of a moving mirror system that used several mirrors to switch from view mode to print mode, exposing the paper (the front screen went dark during this process) then coming back to view position once the exposure was made. After exposure, the suction belts transported the paper to the image processing area were metal rollers fed the paper through a bath of liquid toner where the toner would magnetically be attracted to the unexposed areas of the paper (the latent image) thus adhering to those areas and finally being squeegeed by two sets of rollers before exiting the top front of the unit. The paper exited damp and had to be placed to the side to dry for some seconds. The copy quality was good if the microfilm resolution was good, not that good with bad film, especially positive film like 35mm newspaper film. For the time, it was what was available and most users just got used to the idea of the liquid reader printer. Many customers complained to their technicians about the smell the liquid toner gave off as well as the ink solution they got on their hands as they handled the freshly printed paper.

Needless to say, the liberal use of so many micro switches along with relays and motors made for temperamental functionality which was the source of many service calls. The liquid toner began to degrade once poured into the machine so whether a customer used the machine or not, the toner was getting weaker by the day. Minolta sold a lot of liquid toner in those days. I know that liquid toner and electrostatic paper supplies were a profit center, as were service contracts and non-contract service calls in our market. I was trained on the operation, repair and maintenance of these liquid systems at the Mino-Micrographics Cypress, CA facility as well as the Rolling Meadows, IL Minolta training center.

The entry level unit was the RP-101 (RP stands for Reader-Printer) which was a rather small table top unit, metal framed but with plastic exterior panels. The RP-101 was for microfiche only, with no roll film carrier attachments.

The RP-405 was the most popular unit, a more robust mechanical system offering choice of letter or legal size copies and offered a standard Fiche Carrier with optional motorized roll film carriers for open spool film as well as 3M Type Cartridges.

The RP-407 was the “engineering” model because it accepted both 8.5” and 11” wide rolls allowing the user to make an 11x17” print which was popular with public libraries, county recorders and engineering applications.

Minolta later released and “E” version of each of these units (RP-101DLE, RP-405E and RP-407E). The “E” designated the “Auto Exposure” feature that was added to the system so that a user could theoretically put the unit in “Auto Exposure” mode and not waste prints trying to adjust the image quality. It was an improvement and did save the consumer money in wasted supplies but was not always reliable because the CDS Cells (Cadmium Sulfide) used to generate the exposure setting sat behind a partially reflective mirror that had to stay clean in order for the cells to receive the light from the image and make the exposure adjustment accurately. The system had problems with 35mm positive newspaper film since there are many pictures vs. text that media and the extra light from the pictures threw the system off. Technicians generally asked users to take the unit off auto exposure and to use manual exposure in when using 35mm newspaper film.

These systems were sold in the U.S. and worldwide until the early 1980’s when Minolta released their dry “micro-toning” system for microfilm reader printers which was already in use with their photo copier line.

The RP-1824 was a strange one-off unit that bridged the gap between the “liquid” and “dry micro-toning” technologies. The 1824 was an engineering reader printer that printed as large as… you guessed it, 18x24”. It was an “electrostatic dry” technology which incorporated much of the systems found in the liquid machines such as electrostatic paper, high voltage charging, paper roll cutter and exposure times that were even longer since the image was being projected on a huge piece of paper. I remember it could take 15-20 seconds for a paper to expose, and then it would pass to the developer unit where dry electrostatic toner was attracted to the paper by way of a magnetic roller. The paper was then pressed between a steel roller squeegee system that essentially smashed the toner into the paper causing it to permanently adhere. This system was very temperamental! Copy quality problems because of bad toner, bad paper and inconsistent HV charging was common, the paper cutter system was prone to malfunction and it was generally a nightmare of a machine and a source of constant service calls and technician frustration.

Please feel free to contact me regarding Micrographic solutions or for technical support on these or other Micrographic Systems. Evis Beaton

Evis Beaton is the Sales and Marketing Manager for and has over 25 years of experience in the Microfilm Industry working as a field service technician, technical specialist and service manager for Minolta’s then largest microfilm dealer in the USA. Evis has an ASEET (Electronic Engineering Technology) and a Bachelor’s degree in Business Management with an emphasis on e-commerce organizations.

 © Evis Beaton All Rights Reserved

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