[GreenKeys] Rubber Renue

Fri Jun 17 01:45:11 EDT 2016

Hi, everyone,

So, the platen on my wonderful 33-ASR has been giving me troubles for a while now.  It won’t grip the paper reliably to properly advance when the LINEFEED is received.  The paper just slips, and the printing ends up running over the top of the previous line, or it only spaces part way, and then overlaps the previous line.  Not good for clean copy.

The platen had almost a glaze about it…kind of shiny looking, and just didn’t have much complexion anymore.  I didn’t know what to do.

So, some time ago, I posted my frustration here, and someone suggested using DOT Brake Fluid (not the silicone kind, but the old-fashioned stuff).   I tried it, and low and behold, it worked.  But…only for a little while, and then the same issue started occurring again – after a few weeks, the symptom returned.  Another dose of brake fluid helped a little, but it seemed to have diminishing returns.

I had read something on the Golf Ball Typewriter mailing list (e.g., IBM Selectric) that someone had used a product called Rubber Renue to resurrect the platen and power roller in an old Selectric typewriter.   I did some research, and although the product itself is rather scary, it seemed that a lot of people found that it did a good job of restoring rubber in a way that was fairly long-lasting.

So, I ordered up a bottle of the stuff.    When it arrived, it came with no real instructions on how to use it, but a whole bunch of information about how dangerous it was, and a slew of warnings about no letting it touch skin, not to inhale any vapors, and that it some ingredients are of concern for causing cancer.   Kind of scary.  I pulled up the Material Safety Data Sheet for the product, and these concerns, along with others, were all verified.   So, after having it around for a few weeks, a few nights ago I decided to give it a try on the platen for the 33-ASR.   I decided I would treat the platen in place rather than trying to remove it.  It would have probably been more thorough to remove the platen, but it involves taking apart some of the linefeed mechanism, and that’s something I just wasn’t willing to fuss with.   I’m pretty good with electronic stuff, but intricate mechanical stuff like this I’m not so good at.  

I followed all of the safety instructions.  I had two layers of nitrile surgical gloves, a long sleeve shirt, a respirator, safety glasses, and also opened up all of the doors and windows in the building to provide good flow-through airflow, and had the HVAC system running in “FAN” mode to further move air around.   I also opened the bottle of fluid outdoors, put a small amount of the fluid on a small piece of clean cloth outdoors, then closed the bottle leaving it outdoors.  I took the cloth inside, wiped down the platen while rotating it around to get even coverage across the entirety of the platen, and also wiped down the roller underneath the platen.   The instructions I found online (on the company’s website) then said that the fluid should be allowed to completely evaporate before the treated item is used.   I took the piece of cloth and wrapped it in aluminum foil, then placed it in a plastic bag and sealed it, and took it outdoors.  This, and the foil safety seal on the bottle will be taken to the local hazardous waste facility for disposal.     I then left the building opened up overnight and came back the next morning to check it out.  Even after evaporating overnight, and the building all opened up, there was still a detectable odor of solvent in the air, probably coming from the platen itself.

I left the building opened up  as I investigated the platen.  I didn’t have the respirator on, but figured that after this much time, the concentration was  small enough to not be of much concern, and with good airflow through the building due to a fairly decent breeze outside, I wasn’t worried much about any possibility of problems from the fumes.    The platen was indeed different.  The shiny sheen was gone.  It also felt more like rubber…it had some flex to it, but wasn’t mushy or sticky in any way.   It had a complexion again…that kind of grippy feeling that good rubber platens should have…grippy, but not too grippy that paper would stick to it.   I wiped the platen down with a clean piece of cotton cloth (which will also go to hazardous waste for disposal), and a slight blackish-brown residue came off, but not much at all.   I threaded in the roll of paper, and a paper tape with a bunch of test texts on it, turned the machine to LOCAL mode, and started the paper tape reader.  Linefeed performance was flawless.   I then put it in ONLINE mode, and had it connected up to the HP 2000/Access Timeshared BASIC emulation running under SimH.  I logged in and started a long BASIC program listing.  Perfect linefeed performance…the paper advanced perfectly each time.  No more signs of the paper slipping.    The back side of the paper had no sign of any kind of residue from the treatment, and there was absolutely no sign of the paper sticking to the platen.   I had limited time in the morning, so I powered down the TTY, and closed up the building and headed off to work.  I got home and did some more testing, and all was good.  There was a slight solvent smell in the building, but I left it opened up through the evening, and by the time I closed the building up as nightfall approached, that odor had dissipated.

So…although it isn’t a long-term report, I’m really very happy with the results.  Now it will remain to be seen if the treatment is temporary, or holds up over time.     This evening I treated the platen for an old Diablo Hy-Type II printing data terminal.  This time, the platen was removed from the device, and I did the treatment outdoors to avoid the fumes in the building.   The platen was pretty hopeless before the treatment..it had a hard texture with a lot of shine/gloss, and even some shallow cracks in the surface.  It was hopeless for advancing paper.  After the treatment, I think it’s going to be restored to usability.  It’ll air out overnight, and I’ll give it a try tomorrow evening or over the weekend.   If the results of the 33ASR platen are any indication, I think that this platen will be usable again.  It seems to be much better after the treatment, but it needs to evaporate completely before I re-install it and try out the terminal.

All in all, good stuff, at least so far.   If you do end up using it, I strongly suggest following all of the safety rules and respect the stuff.  Don’t let kids or animals anywhere near this stuff.  It is quite nasty.   But, it does seem to do a good job, and if used safely and cautiously, I think that it can rescue platens and rollers in old equipment like this that is either difficult to replace, or expensive to rebuild.

Good will to all,

-Rick

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Rick Bensene

The Old Calculator Museum

http://oldcalculatormuseum.com

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