HP97 The journey begins
01-13-2019, 06:01 AM
Post: #21
 teenix Senior Member Posts: 1,379 Joined: May 2016
RE: HP97 The journey begins
Hi all,

Looks like I finally found a fork in the road.

On full reassembly, I pressed the paper advance switch and a horrible growl came out of the printer.

On inspection I found a stripped drive cog. As it has been working quite ok up to this point my first thought was I put the switch connections on wrong, but no and the home switch works fine.

I took the cog out and I just put slight pressure on a cog tooth and it broke off and is almost powdery, so it too looks like it too has deteriorated over time.

I've haven't heard this problem mentioned as yet, and I guess these are as scarce as hens teeth too.

Ahh well, must be beer o'clock...

cheers

Tony

Attached File(s) Thumbnail(s)

01-13-2019, 06:12 AM
Post: #22
 Paul Dale Senior Member Posts: 1,725 Joined: Dec 2013
RE: HP97 The journey begins
Is this the idler gear mentioned by Paul Berger earlier?

Pauli
01-13-2019, 06:51 AM
Post: #23
 teenix Senior Member Posts: 1,379 Joined: May 2016
RE: HP97 The journey begins
(01-13-2019 06:12 AM)Paul Dale Wrote:  Is this the idler gear mentioned by Paul Berger earlier?

Pauli

Hi Paul,

Yes, the one between the motor gear and the final black gear that drives the head mechanism. looks like it has crumbled after a few uses.

cheers

Tony
01-13-2019, 07:04 AM
Post: #24
 teenix Senior Member Posts: 1,379 Joined: May 2016
RE: HP97 The journey begins
(01-13-2019 06:51 AM)teenix Wrote:  Yes, the one between the motor gear and the final black gear that drives the head mechanism. looks like it has crumbled after a few uses.

Looks like some aluminium ones might be available for $US45 which seems steep 01-13-2019, 08:06 AM Post: #25  AndiGer Senior Member Posts: 380 Joined: Oct 2015 RE: HP97 The journey begins Now and then there is an offer on the idler gear made from brass on German TAS site. Me . Ships worldwide. Less than 20 Euro. Andi 01-13-2019, 02:30 PM Post: #26  rprosperi Senior Member Posts: 5,008 Joined: Dec 2013 RE: HP97 The journey begins (01-13-2019 04:58 AM)teenix Wrote: I switched to PGM mode and wrote 5 + 7 enter and put in a blank card and through it went. Presumably the program was actually "5 Enter 7 +" --Bob Prosperi 01-13-2019, 06:39 PM Post: #27  teenix Senior Member Posts: 1,379 Joined: May 2016 RE: HP97 The journey begins (01-13-2019 02:30 PM)rprosperi Wrote: (01-13-2019 04:58 AM)teenix Wrote: I switched to PGM mode and wrote 5 + 7 enter and put in a blank card and through it went. Presumably the program was actually "5 Enter 7 +" My body turns 60 this month, I think my brain is miles ahead cheers Tony 01-30-2019, 05:27 AM Post: #28  teenix Senior Member Posts: 1,379 Joined: May 2016 RE: HP97 The journey begins Hi all, I got my oscilloscope the other day and have been having a play. The attached image shows the trace from an active HP-97 display Yellow - RCD (reset cathode driver to first digit) Blue - STB (go to next digit cathode strobe) The bottom 2 are LED segments A and B of the exponent digits just after the RCD pulse. What I find confusing is the different voltages at the 3rd STB pulse. Most are at around 3V while the larger ones are at 5V and don't appear on all segments for a single digit. Has anyone played with this in the past and could offer some insight? cheers Tony Attached File(s) Thumbnail(s) 01-31-2019, 11:50 AM Post: #29  teenix Senior Member Posts: 1,379 Joined: May 2016 RE: HP97 The journey begins Hi all, I figured out the display problems. I bet no HP 97 display had this showing :-) cheers Tony Attached File(s) Thumbnail(s) 01-31-2019, 10:04 PM Post: #30  BobVA Senior Member Posts: 357 Joined: Dec 2013 RE: HP97 The journey begins (01-31-2019 11:50 AM)teenix Wrote: I bet no HP 97 display had this showing :-) I think you win that bet :-) Now, do go on... 01-31-2019, 10:15 PM Post: #31  Jlouis Senior Member Posts: 668 Joined: Nov 2014 RE: HP97 The journey begins (01-13-2019 07:04 AM)teenix Wrote: (01-13-2019 06:51 AM)teenix Wrote: Yes, the one between the motor gear and the final black gear that drives the head mechanism. looks like it has crumbled after a few uses. Looks like some aluminium ones might be available for$US45 which seems steep

Hi Teenix,

I have a spare one from that German site, it only have to be driled a little bit in the hole, if you want I can send it to you, no charges, just send me your address. It will be a pleasure and a honor for me to sent it to you.

I bought some last year, but lack of time and my not so good health are not letting me repair my 97

Just let me know.

JL.
01-31-2019, 11:08 PM
Post: #32
 teenix Senior Member Posts: 1,379 Joined: May 2016
RE: HP97 The journey begins

Hi Teenix,

I have a spare one from that German site, it only have to be driled a little bit in the hole, if you want I can send it to you, no charges, just send me your address. It will be a pleasure and a honor for me to sent it to you.

I bought some last year, but lack of time and my not so good health are not letting me repair my 97

Just let me know.

JL.
[/quote]

PM sent

cheers

Tony
02-08-2019, 04:12 PM
Post: #33
 wallyt Junior Member Posts: 38 Joined: Feb 2018
RE: HP97 The journey begins
I, too, am beginning my new project to restore an HP97 and will need that little gear as well. Can anyone supply a source. Thanks.
02-11-2019, 12:47 AM
Post: #34
 teenix Senior Member Posts: 1,379 Joined: May 2016
RE: HP97 The journey begins
(02-08-2019 04:12 PM)wallyt Wrote:  I, too, am beginning my new project to restore an HP97 and will need that little gear as well. Can anyone supply a source. Thanks.

Try AndiGer on this forum.

cheers

Tony
02-11-2019, 01:33 AM
Post: #35
 rprosperi Senior Member Posts: 5,008 Joined: Dec 2013
RE: HP97 The journey begins
If you can't find them anywhere else, they are also available on TAS, but they are ridiculously overpriced (like most items from this seller) at $30.00/ea. and this should probably only be considered as a last resort. https://www.ebay.com/itm/Hewlett-Packard...4105337402 The only good news is they include a 90-day warranty (!?) and shipping is free, but I suppose after charging$30 for a \$5-10 item, seller can afford to cover shipping.

--Bob Prosperi
02-13-2019, 04:14 PM (This post was last modified: 02-13-2019 04:15 PM by wallyt.)
Post: #36
 wallyt Junior Member Posts: 38 Joined: Feb 2018
RE: HP97 The journey begins
I messaged Andi about the gear. I did find a place at PIC Design that has a similar gear, stock number G46-30. It would require some modification but it should do the job. I am still waiting for a quote from them. That fellow on TAS is WAY over the top with his price, but he does have them available. It looks like what he did was use the G46-30 with modifications. Thanks!
02-19-2019, 04:09 AM
Post: #37
 Dreato Junior Member Posts: 37 Joined: Mar 2015
RE: HP97 The journey begins
I've done 4 HP97 refurbs. All required card reader rebuild (O rings and shaft coupler), Printer rebuild (new idler gear and O rings for paper advance). 3 of the 4 also required replacing some Tantalum capacitors. I usually think of these as extremely long lived, especially compared to normal electrolytics, but for these calculators this was not the case. Two of the tanatalums actually broke apart when I wiggled them. I made a charger transformer from a 10VAC wall wart and a custom plug. I also changed the current limiting resistor, since I used NiMH cells in the rebuilt battery pack, and I believe they're sensitive to overcharging. I changed R3 from 8.2 ohms to 47 ohms. This reduces the charging current to ~ 100 mA.

Regards,

Dave
02-20-2019, 05:48 AM
Post: #38
 wallyt Junior Member Posts: 38 Joined: Feb 2018
RE: HP97 The journey begins
Regarding the O-rings for the printer, were these similar to what one uses in the card reader?
02-20-2019, 06:29 PM
Post: #39
 Dreato Junior Member Posts: 37 Joined: Mar 2015
RE: HP97 The journey begins
Yes, O rings similar to the card reader repair, but bigger ones. This requires significant disassembly of the printer, where there are lots of springs and clips to lose!

After diasassembly and removal of the drive axle assembly, scrape off the old drive wheel material, and clip off the plastic spline on which the old drove wheels were molded. Sand this smooth, and place the new O rings on the drive axle where the splines were located. Once the O rings are perdendicular to the shaft, I place a micro drop of isocyanate glue to keep the O rings from moving during use. Don't get the glue on the drive surface of the O rings.

There's an exploded diagram of the printer in the HP 97 service manual. Careful with those small parts.

Regards,

Dave
02-20-2019, 07:19 PM
Post: #40
 Hans-Peter Member Posts: 94 Joined: Dec 2013
RE: HP97 The journey begins
My patient works fine with this method.