Looking for (idler?) gear wheel of HP-46 printer unit
Post: #1
 Sadsilence Member Posts: 134 Joined: May 2015
Looking for (idler?) gear wheel of HP-46 printer unit
Hello all,

some time ago I was lucky to get a HP-46 desktop calculator. It is in good shape, but when turning it on there was a grinding noise from printer unit and when going through test procedure printer sometimes gave out perfect lines and sometimes total rubbish and in rare cases nothing at all.

After I excluded any electrical reason I dared to disassemble printer unit. Reasonable cause for described behavior was (unfortunately) found easily: a deterioated (idler) gear wheel as shown in picture below.

Now my question: Is there any hope to get a modern replacement for that wheel? As layman in that subjects it looks pretty special to me. Any known sources? Has anyone a forgotten printer unit of HP-46/HP-81 in a desktop drawer. Does it make sense to rebuild it with a 3D printer? Has anyone already created a model or would be willed to do it?

Any idea or hint is highly appreciated. Thanks in advance!

Werner

Attached File(s) Thumbnail(s)

06-20-2016, 10:55 AM
Post: #2
 Duane Hess Member Posts: 121 Joined: Mar 2014
RE: Looking for (idler?) gear wheel of HP-46 printer unit

The 46 printer is the same lineage as other drum/impact printers. I purchased parts to fabricate the gear myself. Last of the parts arrived last week. Haven't assembled it yet.

Basically its a small gear, large gear and a brass bushing. I intend on epoxy-ing them together to fabricate the gear.

Will post where I purchased the stuff from & the part numbers. Don't have it convenient at the moment.

Likely will be 1-2 days before providing the info.
06-20-2016, 11:19 AM
Post: #3
 Sadsilence Member Posts: 134 Joined: May 2015
RE: Looking for (idler?) gear wheel of HP-46 printer unit

Of course I will. Maybe it would be a good chance to dig into 3D printer subject, but most probably much to difficult as starting point.

(06-20-2016 10:55 AM)Duane Hess Wrote:  The 46 printer is the same lineage as other drum/impact printers. I purchased parts to fabricate the gear myself. Last of the parts arrived last week. Haven't assembled it yet.

Basically its a small gear, large gear and a brass bushing. I intend on epoxy-ing them together to fabricate the gear.

Will post where I purchased the stuff from & the part numbers. Don't have it convenient at the moment.

Likely will be 1-2 days before providing the info.

Thank you very much and a brilliant idea. I have not even come close to the idea, building it from two seperate gear wheels.
06-25-2016, 05:40 AM (This post was last modified: 06-25-2016 06:41 AM by Duane Hess.)
Post: #4
 Duane Hess Member Posts: 121 Joined: Mar 2014
RE: Looking for (idler?) gear wheel of HP-46 printer unit
You might want to look at this thread:
A forum user in that thread, Damaltor, provides a German site for the 68 tooth gear and a brass bushing. (thank God for Google translate)

The thread provides the source I used for the 68 tooth gear and brass bushing. Mixing Mod 0.4 & Mod 0.5 is not a good idea; teeth won't mesh correctly. I'm very sure the gear in your printer is modul/modulo/modulus/module/mod 0.4 (spellings vary). Further, the mod # is integrally tied to the gear diameter. A 17 tooth gear Mod 0.5 will be larger than 0.4. The Mod 0.5 gear is approx. 2.0 mm too large in diameter.

I ordered the 17 tooth gear from HPC Gears (England). You need to select "spur gears", then specify characteristics. The basic gear has a 2.0 mm bore (ZPG0.4-17), I special ordered it with a 3.0 mm bore (ZPG0.4-17-S03). However, I probably should have ordered it with a 4.0 mm bore, so both gears would fit on the bushing. http://www.hpcgears.com
part-list: http://www.hpcgears.com/pdf_c33/23.6-23.9.pdf
*** note this list will have metal and delrin (plastic) gears with & w/o hubs
---> you want delrin. I don't believe in mixing metal/plastic unless you know it will pass the test of time. Personally I'd be concerned about wear. Naturally, I'm sure, that depends on the amount of use.
** HPC has a 68 tooth gear. Pretty sure I ordered the 68 tooth from the German source, as if I remember, the German source was approx. 1/3 the cost.

The two gears together are approx. 0.5 mm thinner (assuming I can read a micrometer) than the original gear. In my case I'll have to file down the length of the bushing, so probably can use extra length to compensate. I doubt the total "teeth width" would be be an issue, but potential shimmy up/down the shaft the gears ride on would be. If nothing else a trip to the hardware store should come up with a 0.5 mm nylon washer for a spacer.
** don't forget to re-install the exceptionally thin metal washer under the "C" clip at the end of the shaft when you're done. It keeps the gear from rubbing on the clip & hence, the clip rotating and possibly popping off. (although its on tight enough, you wouldn't think so)

Even if I ordered the 17 tooth gear with a 4.0 mm bore, I'd still epoxy the two gears together. Rotating the drum doesn't take a lot of force, but the paper advance function (activated by a lever pushing on the drum gear), takes some power. At least rotating everything by hand makes you think so. I'd be concerned w/o epoxying them together eventually the 17 tooth gear would strip off the bushing. Just my guess.

Further, I plan on making sure the inside of the bushing (and smaller gear, in my case) will have a thick-(not stiff)/stay-in-place grease (not oil). Especially since there will now be a brass bearing rotating on the shaft. Too bad there was no 3.0 mm bore 68 tooth gear, at least that I could find.

When I find my notes, I'll post the measurements I made of the gear. My printer, an EP-104 (from a Canon calc), is a descendant of the EP-102 printer in the HP-46. Found some web pages describing both printers & I'm quite sure the two printers use identical gears; but would warrant you verifying your gear.

*** original post time + approx. 1 hour -- EDIT to correct typos & incorrect statement (paper advance).
06-27-2016, 08:29 AM
Post: #5
 Sadsilence Member Posts: 134 Joined: May 2015
RE: Looking for (idler?) gear wheel of HP-46 printer unit
Hello Duane,

I cannot thank you enough for your detailed explanations and all the time spended for that. Out of it I learned more about gears than 40 years before. Not the least simply from learning right english vocabulary. Coming from electronics side I have not been able to find right entry point in this secret gears thing.

From your (and dalmator's) in depth descriptions (HP-46 definitely has a 17/68 double gear with mentioned dimensions, there is a C-Clip, too) I agree with you, it is the same construction like in your printer. Will give some feedback. Likely will be a few weeks before I find time.

Last Friday I talked to a friend. She is CAD specialist and is going to create a 3D model of that double gear. Moreover she is pretty confident, that it is suitable for modern 3D printing. So maybe there is even a chance to get a one piece solution.

Thanks again and best regards,

Werner
Post: #6
 Sadsilence Member Posts: 134 Joined: May 2015
RE: Looking for (idler?) gear wheel of HP-46 printer unit
Finally there was some time for rebuilding printer gear wheel today. As one piece solution failed due to software toolbox problems I followed Duane's (and dalmator's) guideline of glueing two seperate gear wheels together.

68 teeth Mod 0.4 outer gear wheel source:
http://www.steingraeber-modelle.de/Zahnr...05868_4207

17 teeth Mod 0.4 inner gear wheel source:
http://shop.kkpmo.com/product_info.php?l...6f93f4ba4e

Drill hole: 4 mm, Gear wheel width (T) = 4 mm

Order was fulfilled within a week.

As mentioned bushing is not available from Steingraeber for an undefinite time I connected both wheels with a 4,0 x 3,2 mm brass tube, a default model making item:
http://www.modellbau-profi.de/Werkstoffe...debox=box3

Together with a drop of super glue double gear wheel is good enough to handle forces within HP-46 printer unit. At least I have not got any problems during several lenghty tests.

Prophylactically I repeated procedure with a second HP-46 unit where printer still did it's job. Even there printer noise went down considerably.

Thanks again for your great help.

07-21-2016, 08:44 PM
Post: #7
 TASP Senior Member Posts: 401 Joined: Mar 2015
RE: Looking for (idler?) gear wheel of HP-46 printer unit
Always really appreciate hearing of machines, both rare and not so rare, being saved from perdition !!

2speed HP41CX,int2XMEM+ZEN, HPIL+DEVEL, HPIL+X/IO, I/R, 82143, 82163, 82162 -25,35,45,55,65,67,70,80
07-24-2016, 07:45 PM
Post: #8
 Sadsilence Member Posts: 134 Joined: May 2015
RE: Looking for (idler?) gear wheel of HP-46 printer unit
Indeed this time it was extraordinarily nice as HP-46 is a very special machine. I have parts for two more double gears here and be willed to give them away (as parts or already assembled) to anyone with similar problems. Feel free to contact me.

Have a good start into next week!
04-03-2017, 10:07 AM
Post: #9
 Duane Hess Member Posts: 121 Joined: Mar 2014
RE: Looking for (idler?) gear wheel of HP-46 printer unit
Anyone have an issue with the gear from this source:

http://www.steingraeber-modelle.de/Zahnr...05868_4207

Never assembled mine, as the gear has all the characteristics mentioned in previous posts/threads, however it is 2.5mm thick and not 3.0mm.

Likely the 0.5mm makes no difference other than a 0.5mm gap on the shaft the gear rides on. As rotation is always the same direction one would expect the gear to migrate to the left or right end of the shaft and stay there. i.e. there should be no flopping back and forth and a "spacer" should be unnecessary. The brass fitting is very close to the diameter of the shaft, so the thinner gear should not increase axial displacement forces; or insignificantly of it does. When the printer is shut off, hence slows down, I suspect the gear does not migrate towards the opposite end of the shaft. Not sure why it would make any difference if it does, as upon power-on it would move to the other end. Assuming it moves at all.

I contacted Steingraeber-modelle. They checked, the gear is 2.5mm and their supplier cannot provide a 3.0mm thick gear. The dimensions on their web page have been updated. Found a 3.0mm from KKPMO but it costs about 11.00USD. Wondered if anyone recreated this gear for any calculator using the EP-102 (HP-46/81/9805, etc.) or EP-104 (newer calcs) and noticed undo wear issues or other problems. Personally, think I'm a fuss-budget and shouldn't worry about it. Any "gear experience" folks out there? thanks! 04-03-2017, 04:36 PM (This post was last modified: 04-03-2017 04:38 PM by Sadsilence.) Post: #10  Sadsilence Member Posts: 134 Joined: May 2015 RE: Looking for (idler?) gear wheel of HP-46 printer unit Hello Duane, to my shame I have to admit, I never checked height of 68 tooth gear from Steingraeber. Indeed I had the feeling, that replacement part is not exactly as high as original one, but design forgives missing 0.25 or 0.5mm. Even orginal part has some space. After building and testing 4 units sucessfully I have never come across your feared forth and back flopping so far. As I have to disassemble my remaining HP46 unit for testing every new build gear wheel anyway, I regularly checked my first "build" and have not seen any signs of onesided deterioation so far. Unit is in now and then use for 8 months now. Most difficult part is to recalibrate whole gear wheel system for correct timing of electronical printer signals. To be absolutely on the safe side mechanically you can lenghten selfmade brass bushing to met height of original wheel. So you get your mentioned spacer. 04-03-2017, 07:42 PM Post: #11  Duane Hess Member Posts: 121 Joined: Mar 2014 RE: Looking for (idler?) gear wheel of HP-46 printer unit I am so glad you mentioned timing! Noticed the single "nub" on the drum shaft gear for the rotation sensor and where as there are 2 on the motor shaft. Is there good way to handle alignment of the two shafts? i.e. start off aiming the nub directly at the sensor, or exactly opposite? Any geometry that's describable for aligning between the drum and motor shaft? Ya leaving a bit of the brass bushing could eliminate the gap; good idea. Your comments are very helpful. thanks 04-03-2017, 08:31 PM Post: #12  Duane Hess Member Posts: 121 Joined: Mar 2014 RE: Looking for (idler?) gear wheel of HP-46 printer unit Forgot to mention with careful observation before and after disassembly, I believe the print drum is reinstalled almost exactly in its original location. Took great care using a straight edge to compare the gear "nub" with rotational position of the drum on the shaft. The top edge of the nub skimmed the bottom of the 1's row and the bottom just clears the top of the 2's. The hex set screws left marks on the shaft. A useful 2nd check for positioning the drum on the shaft. Making it handy to look down one hole to check alignment before installing and tightening the set screw in the other hole. The very small left to right shifting to ensure all the hammers covered all of the symbol's surface was a real pain. (i.e. no skew?) Unfortunately, never thought to check positioning of the motor/drum shafts relative to each other. Instead assumed the motor shaft sensor ensured correct rotation speed and the drum sensor indicated "just past the" on the drum. i.e. guessed the two sensors were sufficient for timing and did not require positioning of one shaft relative to each other. Or that is how I interpreted your comment on timing, the alignment of the drum and motor shafts relative to each other. 04-04-2017, 09:07 AM (This post was last modified: 04-04-2017 01:02 PM by Sadsilence.) Post: #13  Sadsilence Member Posts: 134 Joined: May 2015 RE: Looking for (idler?) gear wheel of HP-46 printer unit You are right. That is what I meant with timing. Thanks for clarification. My English is not good enough for such detailed instructions like your ones. I am going to add some pictures when I am at right computer. As I learnt from conversation with forum member pcip there is no general rule, how positions of wheel nubs and magnetic sensors within printer unit have to be. Any printer unit seems to be calibrated individually. So before disassemble printer take a few pictures and reinstall system afterwards in exactly the same way. Fortunately you cannot destroy unit when you accidentally or with fading memory assemble gear wheel system misaligned. Linefeed is working fine, but you do not get letters on paper at all. Nevertheless it is timeconsuming to disassemble unit again and rearrange positions of different wheels. 04-05-2017, 12:46 AM Post: #14  Duane Hess Member Posts: 121 Joined: Mar 2014 RE: Looking for (idler?) gear wheel of HP-46 printer unit I'm too neurotic for my own good. The timing issue intrigues me. Was driving around thinking about it and at afternoon coffee. After coffee, came home & examined the printer. I get too wound up, so must go for coffee now (again). Will explain later, but I feel the motor shaft and drum shaft orientation to indicate "start" is predictable before assembly. Although, at the moment, I do not know that orientation. In short it appears 13 rotations of the motor rotates the drum once. Rotating 3 teeth on the drum moves you one row. I agree alignment is physical and not time delays calculated from rotation sensor readings. Eh, get too tense & ramble too much. After coffee, hopefully, can comment coherently. And yes, coffee usually does take hours! Just remember, there are 300-500 poorly understood chemicals in coffee. Anyone who does not think they are addictive is looney. Cheaper than presciptions and illicit drugs. But you can't go to jail for snorting a cup! (but you might end up in a padded room) 04-05-2017, 12:19 PM Post: #15  Duane Hess Member Posts: 121 Joined: Mar 2014 RE: Looking for (idler?) gear wheel of HP-46 printer unit Background: This all started over a year ago with a Canon F-20P (print only) which had a broken 17/68 gear. Visually, a previous owner must of stored it in a steam sauna, it has many issues. Upon goofing around it showed some functional ability. Borrowed the 17/68 gear from a F-10P (print & display). Saw the nub on the drum & 2 on the motor shaft. Figured they were timed speed of rotation of drum and motor. Exponentiation e(x) produced a response. The drum was obviously out of sync, but produced consistently produced the same inaccurate symbols. e(1) should produce the value of e. Upon examination noticed the 2 was off by ... some number of rows+partial row. The decimal point was off by the same number of rows + partial row; likewise with the rest of the value. Thought about loosening the gear plate & rotating the drum until aligned. Then thought why bother? The unit has so many issues, potentially from tarnished connections figured after clean up, the printer may be OK or need realignment. Assumed, at this point, the 3 nubs allowed rotational speed calculations for timing regulation. Stealing the gear from one unit to the other is all the examination I had ever done on a EP-102 or EP-104 in my life to that point. Didn't have everything needed to even try cleaning it up, so placed it on the shelf. -------------------------------------------------------------------- For various reasons started cleaning up a EP-102 from a HP-46. It is reassembled minus the 17/68 gear & mounting plate and the ribbon lift shaft. After your note about timing started thinking while driving around & at afternoon coffee. A brass collar on the motor shaft has 2 rotation sensor nubs. Kept wondering why 2? And why 120 degrees apart? Better speed control? Were their purpose speed control or something else? If 2 for speed control, why not 180 degrees apart? If the motor PCB had built-in speed control imply the collar/nubs perform another purpose? What do the nubs mean? Cleaning the printer made me aware of the ridge on the motor shaft, which physically powers the hammer striking mechanism. Pondered if the first nub indicates start of the print hammer activation. And the 2nd number indicates the print hammer has struck? i.e. hammer firing duration timing? It just bugged me. The only obvious indication of "where is the drum & when should the hammers strike?" seems to be the drum & motor sensors. Without other feedback how would printer timing circuits know the 1's row is coming under the hammers, for example? Does some geometry between the two shafts indicate "starting point?" If not geometry, do the drum/motor nubs provide a timing base? i.e. using the sensed drum rotation rate and "hammer time" of the motor shaft for hammer fire calibration? That is why I ensured orienting the drum to its exact rotation position on the shaft during reassembly. Further pondering made me feel hammer timing is not resultant of time delay calculations. Replacing the drum in its original position should assure correct operation upon full printer reassembly. Also considered whether timing requires "must be close" geometric orientation; i.e. the each shaft nub must be within a small angular boundary to its sensor. Still unsure; realized the drum nub must pass the sensor twice to time one full rotation. In terms of early 70's electronic circuit response speeds such a large rotational delay should lend itself to easily calculating hammer firing delays for the 13 rows on the drum. So, why a need to be close? Just simply get up to speed and calculate from there. Meaning reassemble and all is OK. Purchased a Canon F-10P while in Jr. High school (70's). Never disassembled it. It has a printer and display with an ON/OFF print switch like the 46. Being adolescent, I needed to try things. As I recall turning the printer switch ON consistently required (more/less) 2 drum rotations before being able to print. It has minimal print buffering but trial and error seemed to produce that result. This might imply a delay timing synchronization method; i.e. not geometric. Being naturally "tense" came home after coffee today and looked at the printer; which does not have the idler gear & mounting plate installed yet. The ridge on the motor shaft strikes a forward protrusion of hammer actuation "picks" on the back side of the printer, which in turn shove into the lever end of the print hammers. What determines when to energize the selenoids that push these picks into the path of the motor shaft ridge? Realized I never bothered to count the number of teeth on the drum nor motor shaft gears. There are 39 and 12, respectively. Feared the positional orientation method may be a hair-puller! 39 teeth running a 17 tooth gear which drives 68 teeth on a 12 tooth gear. The integral rotations for repeatable boundary alignment of the drum/motor sounds like "OH HECK!" Lacking other ideas decided to examine what happens upon one drum rotation: - how does one drum rotation compare to the 17 tooth gear? 39 - 17 - 17 leaves 5. So 2 rotations + a 5 "tooth rotation" arc. - 2 rotations + 5 teeth of the 17 gear causes how many tooth displacements of the 68 gear? 2 rotations = 136 tooth displacements. 5 teeth on the 17 gear produce: 2 * 68 / 17 = 20 teeth so 136 + 20 = 156 tooth displacements for both the 68 gear and driven 12 toothed motor shaft. - 156 displacements on the 12 tooth motor shaft is: 156/12 = 13 motor rotations WHEW! Feared it would be way more difficult. For whatever reason, noticed there is 6 equally spaced resting positions of the motor. i.e. turning the motor by hand you can feel six "chunks" (detents?) during its movement. Let go of the shaft and it turns to the closest of these six positions. Happened to notice two of the detents produced motor shaft nub alignment its positional sensor. Nub (on a detent), detent, nub (on a detent), detent, detent, detent. This explains the 120 degree nub separation. The mid-nub detent alignment was centered between nubs. Have no idea why these 6 locations occur. Something in the motor? The motor shaft bearings? Checked the motor shaft ridge location relative to sensor/detent alignment. At mid-nub detent the ridge appears to begin striking the forward surface of the hammer actuation picks. The 2nd nub detent reflects when the ridge just clears the pick striking surface; i.e. the hammer has fired. .... Decided the 1st detent (leading nub) has two possibile purposes. To indicate "energize needed selenoids." Or is an inhibit to signify insufficient time left to energize a selenoid and provide correct operation. The latter should mean energizing occurs after the 2nd nub detent and before the 1st nub detent returns. Learning towards geometry orientated timing and not time-delay synchronization, looked at the drum. The drum nub was (nearly) centered between the 1's and 2's row. Rotating the drum, noticed the machined surface of the hammers was very close to 1/3rd taller than the tallest symbol. Interestingly, rotating the motor one detent moves the drum 1/2 tooth of the drum. And the drum nub width (rotationally) appears almost exactly 1 tooth. Turns out 6 detents, being one motor rotation moves the drum one row (3 drum teeth). DUH! finally hit me. 13 motor rotations produces 1 drum rotation and there are 13 rows/drum. 3 teeth * 13 rows = 39, the number of teeth of the drum gear. Having a 2nd assembled 46, took off the calc top cover to check drum/nub alignment. Left the rest of the calc fully assembled. Moved metal tear bar up out of the way. Was able to flex the right black plastic shield enough to see the drum gear. Rotated the motor with needle nose pliers inserted into a hole in the left plastic shield. This verified the nub and 1's/2's row alignment, albeit a tad under 1 tooth lower on the drum than the printer I'm refurbishing. Unfortunately did not think of checking the motor shaft collar alignment before replacing the top over & storing the calc. Interesting potential that drum nub location might tolerate being + OR - one tooth position off relative to the drum. But clearly not either +/- one tooth; the machined hammer surface is not tall enough. Was in a quandary at this point. Cleared the head then wondered how was this device assembled and calibrated. The EP-101 was introduced in '68 (for Olympics). The EP-102 was introduced afterwards (year?) then replaced by the minimal/modestly refined EP-104. From memory of my Jr/Sr High school youth the EP-104 was used into mid-70's. After that calcs usually had an individual spinning plastic wheel per column. Yes, I was such a loser as to regularly scope out office equipment stores. In hindsight, during the '68-'75 era, robotic assembly of this printer was likely minimal if at all. That will be my premise. Possibly some components were resultant of mechanical assembly (a cog & gear machine), but still few parts. Should the hammer firing calibration be due to geometric synchronization, undoubtedly assembly alignment was manual. Further, to have reasonable assembly speed and "getting it right the first time" this alignment would require "eyeball it" precision. Back into a quandary again. Ashamedly, after some TV, "DOH!" hit. I have an EP-102 printer with an intact gear for a different calc in a box: - the drum nub aligned with the 1's/2's row and was also nearly 1 tooth lower relative to the drum of my refurb printer - both motor shaft nub detents were exactly aligned with the sensor - makes sense, detent locations are very precise and repeatable, hence allowing easy alignment - width of motor sensor pickup and rotational width of nubs look identical - with drum nub aligned exactly to sensor, 1st drum nub aligned to its sensor - width of drum sensor pickup and rotational width of nub looks identical The refurb printer motor shaft nubs were off just under a nub width. Both were offset the same amount and rotational direction. One wonders if any amount of drum or motor shaft nub overlap with their pickup sensors or are abut to it, is close enough for alignment. Closeness of motor shaft nub positioning should be easy. One detent position would be way off. Drum nub/sensor pickup width should allow 1 tooth mispositioning. Consistent with variances of the 3 printers examined and machined surface height of the print hammers. Haven't tried this yet. The 17/68 gear mounting plate is held on by 3 screws. Top right, bottom right and bottom left corners of the plate. Looking from the plate side, through the plate hole revealing the motor shaft makes me feel an easy 17/68 gear alignment scenario is probable. Remove the top right and bottom left screws, loosen the lower right screw. It looks like the plate might easily rotate away from the gears without displacing either the drum or motor. Like-wise rotating back for assembly without displacement. Possibly barely wiggling of drum, mounting plate or motor shaft might allow all parts to fall together correctly. Motor detents should hold the shaft alignment. The toothed lever which flops forward against the metal portion of the drum gear to actuate a paper feed might be useful also. Aligning the drum with its sensor and pulling that lever forward should lock the drum in place. Then rotating the mounting plate back should be easy. This allows wiggling of the motor, if needed. Would take some force, but minor vertical movement of the advance lever should allow wiggling of the drum without skipping a tooth. Seems the same applies if the mount plate is free of all screws and is simply placed into position. That's what I'll guess anyways. Need to resolve some property maintenance in another town, likely taking most of a week. Will have my laptop but will not be messing with the F-20P, returning gear to F-10P or the refurbed 46 printer until I'm back. You probably don't care about my personal items. The point of mentioning it is I need way too much therapy to wait a week before trying out today's messing around and posting about it. Evidently the coffee was not strong enough! 04-06-2017, 03:29 AM Post: #16  Duane Hess Member Posts: 121 Joined: Mar 2014 RE: Looking for (idler?) gear wheel of HP-46 printer unit After reading through my last post, gee the coffee wasn't strong enough! Its hard to tell what the point is. It's the rambling of how my thoughts went throughout the day. I'm apologize for sounding to schizo. I was trying to be informative. The point was (somewhere in all that) examining the 3 printers where the drum is aimed directly at its sensor and the motor shaft sensor is directly inbetween the 2 nubs may imply "start here". Reinstalling the 17/68 gear with the above orientation should produce correct operation. Noted each printer had a minor drum to nub shift between them. Implying each printer may require individual alignment. However it's likely alignment may require repositioning of either drum & motors shafts a single tooth. Although physically accomplishing such may be tedious but eliminates trail and error to find initial alignment. Presumably after "start point" is done, printing occurs on a time delay basis, i.e. one rotation of the drum. Probably all is reset each time the drum passes its sensor. Intially trial and error was my thoughts on the F-20P but much other work was required so I didn't try it. Wasn't ready to tear into that. Well, had to get the car repaired, so haven't left town. Of course the coffee wasn't strong enough!!!!! Naturally, I can't leave things alone either. Subsequently looked at the F-20P. (with the barrowed 17/68 gear from a working F-10P) Did not remove the printer from the calc; simply removed the top cover. Removed the "housing cover" exposing the drum/motor/surrounding areas. Interestingly, the motor detents did not align with the nub/sensor but was about 12 degrees off. Noticed the drum was nearly 1/2 a row high relative to the nub. Figured this was individual alignment during manufacture because of how other components fell into place or varing component tolerances. Removed the upper right and lower left screws from the 17/68 mounting plate. Aligned motor shaft (leaving it on its detent) and the drum nub/sensor directly aligned. Its was off. So aligned the drum again. Aligned the motor shaft inbetween the two nub and held the motor as it was not on a detent. Keeping a finger on the motor and drum rotated the mounting plate back, wiggled slightly and it fell into place. (using the paper advance lever to hold the drum didn't work in this case, it actually forced the drum off nearly a whole tooth) It printed with the correct digits/special symbols exactly aligned for the function performed. Only certain functions work; the calc needs a lot of maintenance. Most functions lock it up immediately. Say, shorter is better isn't it? So much blah, blah, blah in the last one, wasn't sure where I was going; if anywhere. Well, ...., ya that's right, more coffee. 04-07-2017, 01:47 AM Post: #17  Mark Hardman Senior Member Posts: 525 Joined: Dec 2013 RE: Looking for (idler?) gear wheel of HP-46 printer unit I rather enjoyed (and prefer) the original Faulkneresque post. It provided us with wonderful insight into your thought process and problem solving paradigm. I'm going to need to clean and lubricate the printer in the HP-81 that I'm refurbishing. What you have posted here will be invaluable. I owe you a venti coffee. Mark Hardman Ceci n'est pas une signature. 04-09-2017, 09:25 PM Post: #18  Sadsilence Member Posts: 134 Joined: May 2015 RE: Looking for (idler?) gear wheel of HP-46 printer unit Finally found some time to look for pictures I have done when creating my last gear wheel. I am quite impressed about your thinking process. Unfortunately I cannot drink coffee any more and switched to tea one and half year ago. Maybe the reason, why I choose a pragmatic try and see tactics. Additionally I remember a HP-46 service manual (either coming from google to me or through Forum's document usb memory) which explains setting timings of printer unit electronically. Really difficult to understand and nearly impossible measuring signal forms with an oscilloscope within HP-46. It seems you need a special printer unit lab device. So I surrendered without a pratical test. Attached is a picture showing positions between drum nubs and sensors that works for my unit. It needs one explanation: Left marker (green) should be aligned with it's magnetic head. With second (red marked) gear and it's two marks picture shows a position that does not work (I forgot to take one with right position). First marker of brass gear should be in perfect alignment with second magnetic sensor, with second marker targeting away from first magnetic head. In other words brass gear has to be rotated by around 45° counterclockwise compared to picture: 04-10-2017, 04:34 PM (This post was last modified: 04-10-2017 05:05 PM by Vtile.) Post: #19  Vtile Senior Member Posts: 404 Joined: Oct 2015 RE: Looking for (idler?) gear wheel of HP-46 printer unit (04-09-2017 09:25 PM)Sadsilence Wrote: Finally found some time to look for pictures I have done when creating my last gear wheel. I am quite impressed about your thinking process. Unfortunately I cannot drink coffee any more and switched to tea one and half year ago. Maybe the reason, why I choose a pragmatic try and see tactics. Additionally I remember a HP-46 service manual (either coming from google to me or through Forum's document usb memory) which explains setting timings of printer unit electronically. Really difficult to understand and nearly impossible measuring signal forms with an oscilloscope within HP-46. It seems you need a special printer unit lab device. So I surrendered without a pratical test. Attached is a picture showing positions between drum nubs and sensors that works for my unit. It needs one explanation: Left marker (green) should be aligned with it's magnetic head. With second (red marked) gear and it's two marks picture shows a position that does not work (I forgot to take one with right position). First marker of brass gear should be in perfect alignment with second magnetic sensor, with second marker targeting away from first magnetic head. In other words brass gear has to be rotated by around 45° counterclockwise compared to picture: Why it is "nearly inpossible" to measure with Oscope? Is it impossible to measure with Digital storage oscilloscope? Or is the signal a type where you would need a logic alalyser. In these cases and if one is heavily on the restoration of these and similar units it might be worth to invest a few tens of dollars to some hobby level USB digital analyser & storage oscilloscope, which makes you look the life in different viewpoint if all you have used is analog oscilloscope without storage options (or very limited storage time). Ie. I have both Analog (well digital and analog hybrid) and USB scope (not the cheapest on the market, but low end from respective manufacturer). My USB unit can decode UART and CAN protocols on fly, really handy. I know there is atleast one really popular chinese model (Digi analyser) in hobby use with 3rd party software, unfortunately I can not recall the name of the product or the 3rd partysoftware project atm. Cost were something like25..\$50 on ebay..

Edit: I found it or atleast similar project: http://www.sigrok.org/wiki/Supported_hardware
Post: #20
 Sadsilence Member Posts: 134 Joined: May 2015
RE: Looking for (idler?) gear wheel of HP-46 printer unit
Sorry for not explaining detailed enough. It has nothing to do with oscilloscope quality at all. It is a problem of physical access. To check signals, printer unit has to be powered and connected to a sending device. When HP-46 is only available sending device you must run calculator and printer unit at least partially disassembled, a 110/220VAC transformer is smiling at you, connection line between printer and rest of calculator is short and so it is difficult to connect/hold your oscope probes to right positions in that mess of "floating" calculator parts. Generating right test patterns by initiating coincident print commands might be tricky, too. I feel calibration was done useing a special test device back in 1970s. Of course it may be much easier than I thought and I simply missed right entry point. Any additional information is highly appreciated.
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