Mark Hoskins' HP 97 printer idler gears

[Dave Britten]

Fellow 97 owners/ebay addicts may have noticed that Mark Hoskins is now selling metal idler gears for the HP 97 printer. Naturally, I bought one almost immediately, since my plastic gear was stripped, and I'm happy to say that I'm pleased with the results so far.

Installation is fairly simple - open the calculator, remove the printer mechanism, and pop the E clip off the idler gear shaft. Remove the old gear (if it's still present), and slide on one of the included washers, followed by the new gear, then reattach the E clip. I also added a drop of synthetic oil to the bore and teeth for good measure.

I did notice that the gear I received was an extremely tight fit on the shaft in my unit. To fix this, I used a 3/32" bit on my drill to true up the bore, using my thumb and two fingers on my other hand to firmly hold the gear in place (probably not OSHA approved, but oh well). Just run the bit slowly while working the drill in and out a little. Shouldn't take more than a minute before it's moving more freely in and out of the gear. After I did that, the gear slid in place easily, with no discernible slack. I mentioned this to Mark, in case he's able to refine the drilling and boring technique.

After reassembling everything, I printed out a 224-step program listing as a test, and it turned out perfect!

So this appears to be the ticket to getting that printhead moving properly again. Just be aware there is a possibility (for now) that you may need to tune the bore very slightly with a 3/32" drill bit depending on tolerances. If you're comfortable digging around inside these old calculators, you're probably fairly comfortable with using a simple power drill.

[Dave Frederickson]

Here's a link:
https://www.ebay.com/sch/waterhosko/m.ht...7675.l2562

[aurelio]

(05-03-2021 07:01 PM)Dave Frederickson Wrote:  Here's a link:
https://www.ebay.com/sch/waterhosko/m.ht...7675.l2562

Thank-you for the link, Dave and compliments to Mark for his production, what a pity that it's all shipped from overseas, so far away from who live in EU

[Dave Britten]

(05-03-2021 07:01 PM)Dave Frederickson Wrote:  Here's a link:
https://www.ebay.com/sch/waterhosko/m.ht...7675.l2562

Thanks Dave, wasn't sure how everybody felt about direct ebay links.

I'll be sure to report back after I've had some time to run this gear for a while.

[Dave Frederickson]

(05-03-2021 07:41 PM)Dave Britten Wrote:  

(05-03-2021 07:01 PM)Dave Frederickson Wrote:  Here's a link:
https://www.ebay.com/sch/waterhosko/m.ht...7675.l2562

Thanks Dave, wasn't sure how everybody felt about direct ebay links.

Shouldn't be an issue for parts and services. Just noticed that Mark has dropped the price of Classic AAA adapters from 2016.
https://www.hpmuseum.org/forum/thread-6339.html

Speaking of replacement parts, looks like a good time to plug Sylvain's HP Parts and Services article. No need for a link because it's right near the top of the Articles Forum under Important Threads.

Dave

[Jonas Sandstedt]

Hello,

I have read in the forum that gears that possibly can be used as idler gears for the HP-97 can be bought in the EU from GHW-Modellbauversand, see
http://www.ghw-modellbau.de/
The product that should fit is "Spur gear module 0,3 brass - 30 Z", articel number 753030. According to what I have read, the inner diameter has to be increased to fit.
I have bought some, but have not tested yet, so please note that if you buy it is at your own risk.
Luckily, they are fairly inexpensive.

best regards
Jonas

[Dave Britten]

Update on the gear: Still working great so far! And it hasn't stripped the plastic drive gear.

I've been doing some light printing here and there - calculations, an occasional program listing - and it's working nice and consistently.