HP 97 printhead not moving full distance

[Dave Britten]

I got the printer in my 97 up and running by borrowing the paper advance roller from an 82143A that had iffy print quality, but the 97 is still being a little bit quirky. It seems like the printhead isn't moving as far left as it ought to - when I print a program listing, the left edge is kind of ragged and unaligned, and the font looks kind of narrow. When printing short numbers (e.g. FIX DSP 0 CLX PRINTX), the printhead doesn't move the minimum required distance to advance the paper a full line when it returns to the home position.

After printing a couple program listings last night, it seemed like maybe it had warmed up a bit and was doing a proper full sweep, but it's still intermittent. Does this sound like it's just a lubrication issue? I ordered some teflon lube and silicone grease to apply to the various bars and bearings, and the main screw gear that moves the printhead. Anything else I should check?

[Chr Yoko]

I completely put mine appart recently and it is a pretty simple mechanism.

Gears cascading from the motor down to the print head screw shaft must be in good shape with their teeth still ok : this is what moves the head left-right.

There is a black plastic drum on the paper advance shaft with a groove into witch a pin is attached to the print head is sliding , make sure it is properly engaged : this is that movement that rolls the paper up after a carriage return (ie when the head is coming all the way back from the right to the left, it turns the paper shaft by the equivalent of a printing line).

Motor => Pinions/gears => Screw => Head motion L/R => Paper-Shaft rotation after the head carriage return
or
Motor rotation => Head Translation => Paper shaft rotation

[Paul Berger (Canada)]

That sounds a lot like a problem I had with one of my 97s that turned out to be a flaky PIK chip, when cold print was compressed and when the paper feed button was pressed, it would not move far enough to print the paper, but once it had been on for a while it printed normally. I was able to get a PIK that came from a 91 and it prints normally however the character set is not the same as in a 97.

That said cleaning and lubrication can be an issue especially the lead screw and support rods. If the idler gear between the motor and lead screw has not been replaced, it is likely rotten and can lead to erratic movement of the head as it falls apart.

Paul.

[Dave Britten]

(01-26-2021 02:08 PM)Paul Berger (Canada) Wrote:  That sounds a lot like a problem I had with one of my 97s that turned out to be a flaky PIK chip, when cold print was compressed and when the paper feed button was pressed, it would not move far enough to print the paper, but once it had been on for a while it printed normally. I was able to get a PIK that came from a 91 and it prints normally however the character set is not the same as in a 97.

That said cleaning and lubrication can be an issue especially the lead screw and support rods. If the idler gear between the motor and lead screw has not been replaced, it is likely rotten and can lead to erratic movement of the head as it falls apart.

Paul.

Huh, interesting. The idler gear was newly replaced last year, and all the components are properly installed and engaged, so if lubing up the moving parts doesn't help, then I suppose it might be the PIK. I wonder if there are any workarounds beside leaving the calculator on long enough to warm up, or just always setting FIX 4 mode to make the printhead move far enough to advance the paper.

[Dave Britten]

Okay, dumb story: turns out it was just voltage drop from my battery-pack-converted-to-sub-C-holder not making good contact. I reshaped the internal contacts a little to apply more spring force to the ends of the sub-C cells, and it seems to be working fine now. So add that to the list of troubleshooting steps for "skinny" 97 printouts! Still going to lube up the internals for good measure, though.

[toml_12953]

(01-26-2021 03:44 PM)Dave Britten Wrote:  Okay, dumb story: turns out it was just voltage drop from my battery-pack-converted-to-sub-C-holder not making good contact. I reshaped the internal contacts a little to apply more spring force to the ends of the sub-C cells, and it seems to be working fine now. So add that to the list of troubleshooting steps for "skinny" 97 printouts! Still going to lube up the internals for good measure, though.

Glad you got it fixed. I would've installed a tiny heater to always keep it warm!

[Dave Britten]

(01-26-2021 03:56 PM)toml_12953 Wrote:  

(01-26-2021 03:44 PM)Dave Britten Wrote:  Okay, dumb story: turns out it was just voltage drop from my battery-pack-converted-to-sub-C-holder not making good contact. I reshaped the internal contacts a little to apply more spring force to the ends of the sub-C cells, and it seems to be working fine now. So add that to the list of troubleshooting steps for "skinny" 97 printouts! Still going to lube up the internals for good measure, though.

Glad you got it fixed. I would've installed a tiny heater to always keep it warm!

Oh, it definitely crossed my mind. I've got a bunch of spare 5V 1A regulators that I'm sure could be used to produce a little heat at the cost of battery life.