Printer heads misalignment?

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bola_dor
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Joined: Wed Oct 02, 2019 5:32 am

Printer heads misalignment?

Post by bola_dor »

Hi,
This is from a Timex Sinclair 2040 thermal printer. Its exactly the same hardware as an Alphacom 32.
Looks like heads get misaligned from line to line.. characters get illegible. When you print an inverted space can see the broken edges
Is this a common issue? Any advice to fix this?
IMG-20210822-WA0076.jpeg
IMG-20210822-WA0072.jpeg
This is the self test that should look like 888888 and 11111 like this one:
IMG-20210822-WA0074.jpeg
Last edited by bola_dor on Mon Aug 23, 2021 7:19 pm, edited 1 time in total.
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
Moggy
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Re: Printer heads misalignment?

Post by Moggy »

This printer doesn't have "heads" as such or styli.

The paper passes under a flat plate which has a grid of points which when energised cause a thermal reaction on the paper at the required spot.
This plate doesn't have all the points needed for full paper coverage so moves ever so slightly side to side to cover all points on the paper.

The plate is gear driven and seeing as the test mode appears to be working would have thought gear drive ok, so probably something wrong with either the printer logic, a dirty edge connecter or the printer routine you are using if it is a custom one for example.

Has this just happened? is the printer new to yourself or have you been using it for some time? Is the power supply the correct one etc?
bola_dor
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Re: Printer heads misalignment?

Post by bola_dor »

Moggy wrote: Mon Aug 23, 2021 7:07 pm This printer doesn't have "heads" as such or styli.

The paper passes under a flat plate which has a grid of points which when energised cause a thermal reaction on the paper at the required spot.
This plate doesn't have all the points needed for full paper coverage so moves ever so slightly side to side to cover all points on the paper.

The plate is gear driven and seeing as the test mode appears to be working would have thought gear drive ok, so probably something wrong with either the printer logic, a dirty edge connecter or the printer routine you are using if it is a custom one for example.

Has this just happened? is the printer new to yourself or have you been using it for some time? Is the power supply the correct one etc?
Yep I know about the 16 (what I call heads) that moves covering a two character space each..
The good test that you see is from another in good working condition printer. I am sorry I didn't clarify it before.
In the other two pictures you can see the test being mesed..
My guess is that logics are OK but there is some loosening in the movement and it's about 1mm side to side in between lines..
(I will try to edit the pictures)
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
Moggy
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Re: Printer heads misalignment?

Post by Moggy »

For anyone wanting to see the internals of the Alphacom but don't want to risk taking one apart I've taken some pictures for reference.

Zoom in on the first picture to see part number of small chip. The two transistor types on the left are a normal 5v regulator to power the chips plus a TIP 100 transistor which I presume provides the "kick" for the printer heads.
Attachments
SANY0318.JPG
SANY0312.JPG
SANY0308.JPG
bola_dor
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Re: Printer heads misalignment?

Post by bola_dor »

Moggy wrote: Mon Aug 23, 2021 8:02 pm For anyone wanting to see the internals of the Alphacom but don't want to risk taking one apart I've taken some pictures for reference.

Zoom in on the first picture to see part number of small chip. The two transistor types on the left are a normal 5v regulator to power the chips plus a TIP 100 transistor which I presume provides the "kick" for the printer heads.
Nice..
AC plug is a common failure.. and it looks like yours have solved that issue for good..

Have you disassembled the moving mechanism ?
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
zx-heinz
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Re: Printer heads misalignment?

Post by zx-heinz »

@moggy: Is there a horizontal moving heat head or is there just a line of 256 heat "hooks" (one for each pixel)? Could you show a more detailed picture around the printing unit?

The first picture in https://sinclairzxworld.com/viewtopic.p ... 887#p43887 seems to prove that there are even two moving heat heads, and the second one comes to early. So the problem could be a wrong adjustment.
Moggy
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Re: Printer heads misalignment?

Post by Moggy »

zx-heinz wrote: Tue Aug 24, 2021 11:33 am @moggy: Is there a horizontal moving heat head or is there just a line of 256 heat "hooks" (one for each pixel)? Could you show a more detailed picture around the printing unit?

The first picture in https://sinclairzxworld.com/viewtopic.p ... 887#p43887 seems to prove that there are even two moving heat heads, and the second one comes to early. So the problem could be a wrong adjustment.
As I said in the first post they move slightly side to side, and yes there are two heads but they are held together as one fitting and are connected to the oscillating grey bar via the drop down fittings seen at the top of picture two, are none adjustable and move as one entity.

The grey bar oscillates side to side moving the connected heads at the same time.

A spring located at the back of the Central fitting keeps the two heads in tension and alignment and I doubt very much that there is a problem there as if they are out of alignment as you suggest the noise created by such a fault would be obvious and would require all three fittings to have broken.

I did notice some more chips as seen in picture one. there are four in total and each one is marked..

UCN 4401A-2 with a date code 8312. These as far as I understand are the driver chips for the stepper motor.

There is also a chip in the interface connector plug marked'

HD74LS 10P

In picture one there is also three ribbon connectors which may need checking for loose fitting or a break in the ribbons themselves. I would also check each line from the interface plug to the circuit board for continuity because other than a fault in the logic chips, burnt out heads, a faulty stepper motor or everything described above I cannot see a "mechanical" cause for the fault.

This is as far as I'm prepared to strip the printer as I don't want to cause any damage by my clumsiness.
Perhaps the OP could strip his/her own printer down and confirm any of the above.
Attachments
SANY0323.JPG
SANY0320.JPG
bola_dor
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Re: Printer heads misalignment?

Post by bola_dor »

I guess I will have to disassembly it again. I've opened several of these printers but never opened the "gear box"
As far as I know there are 16 printing elements placed along the printing area side o side and them moves with a lever the distance needed to print two characters wide. Those are congruent with the 16 big resistors you can partially see in that picture download/file.php?id=10137&mode=view
I am struggling with an Isue 2 rampack right now, I want to finish it first and will post news about the printer then.
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come :D
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1024MAK
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Re: Printer heads misalignment?

Post by 1024MAK »

Moggy wrote: Tue Aug 24, 2021 7:30 pm There is also a chip in the interface connector plug marked'

HD74LS 10P
A 74LS10 is a triple 3-input NAND gate.

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