OT? Apple Stylewriter problems (longish)

From: Mark Tapley <mtapley_at_swri.edu>
Date: Tue Jan 15 14:32:29 2002

Tothwolf wrote:

>Did you try flexing this cable while checking its resistance? I've
>replaced a few similar cables in other printers that had intermittent
>breaks in the conductors when they were flexed a certain way.

will try it. The cable was near-zero resistance,in a write-head position
about halfway across the page, so I don't think that's it. Also the missing
line of pixels is all the way across the page, so it's not an intermittent
open over the range of motion across the page.

>Good luck with the glue, super glue and glue designed for polystyrene
>plastics does not bond ABS plastics very well.

Yeah, I know. I was being a bit facetious about the "good as new".

>A cheap transistor checker? A multimeter can sometimes be used, but it
>helps to have the pinout and specs for the transistor on hand.

Hm. Replacing all of them only runs about $4.50. But Tony suggested a
1st-order test with my VOM (see below).

>A dull knife hit with the same
>rubber hammer on the glued seams can also work,

This brick seems to have no glue. On the "wall" side (with the plug blades
sticking out), it has three *deep* holes with what look like black painted
metal or hard plastic beads at the bottom. Those act like bolts that are
holding it together. I felt the label, no screw heads obvious under it, but
I'll peel it up and check again. It's not right anyway, output is nowhere
near the 9V it claims :-( .

> 4) What am I likely to find toasted in there?

>take an ohmmeter and see what the primary and secondary winding
>resistances are.

OK, will try it if/when I get the thing open.

>....simply replace the whole brick.

What's a good source for ancient Mac parts at bargain prices?

>Of course, if you own a coil winding
>machine and have the proper wire on hand,

Um..... What's a good source for ancient Mac parts at bargain prices?

--------

Matt London suggested:

>OTOH, Araldite (an epoxy) works a treat in my experience

If everything else starts working but the cover pieces won't stay together,
I'll try it.

----------

Tony Duell said:

>How many dots is this printhead? 25 connections could be 24 dots + common
>or sowething like that. I would have suspected 1 driver transistor per
>dot, though, and 9 dots seems very small for a modern-ish inkjet printer.

Either 8 or 9. I think 8, but don't have any good evidence for that other
than the row of 9 (what look like) driver transistors, of which one is
slightly offset. 8 pixels would just about square with the width of the
missing row vs. the distance between rows when I try to print a solid black
block, but 9 might work too.

The printer is 1991-93 era (about?) and was 1st generation ink-jet for
Apple. I guessed 8 pixels based on the number of big wide traces coming
across the ribbon cable and on the theory that it takes one big wide trace
per pixel. Do they do some wizardry in the print head where one driver
drives 3 pixels, but serially, or some such?

>There's no easy way of telling. At least not without seeing the machine,
>which is kind of difficult :-)

I have a digital camera which produces .jpeg file pictures, about
450kbytes/picture. I could let you see images of many parts of it, if you
can decode jpegs.

Alternately, I have the shipping carton for it, so it becomes a matter of
whether I'll pay more for 2-way shipping to London or for the parts I fry
trying to debug the thing....

>Is this AC or DC? In other words is the wall-wart just a transformer, or
>does it contain a rectifier and smoothing cap as well?

I made both measurements DC. I never thought to check AC before breaking
it, as the label said DC output. I also never thought to check AC after
breaking it. I did try the DC measurement backward, after it broke, and it
definitely had (about) a 0.2 V DC level on it, same sense as the correct
output had been before.

>Once you get inside, it's easy to check/replace <the fuse>.

I'll look forward to it. Is it easy to identify?

>Could well be. Those sound like printhead drivers. I'd be inclined to
>trace all the connections from the printhead ribbon cable connector to
>see where they end up, though.

:-) Uh oh. Tony is trying to educate me, I'll bet. What was it Huck Finn
said about Aunt Polly? <sigh> OK, I'll give it a shot.

>Read that as 2SB1243 -- which is not in 'Towers International Transistor
>Selector'. Can you check that number, please. In fact, please post all
>markings on the original transistors.

I thought I did, unless there are more markings on the side against the PC
board? I'll look again.

>A good first check is to desolder them and then use the ohmmeter function
>(on an analogue VOM) or diode test function (on a DMM) to check that the
>base-emitter junction and base-collector junction test as diodes. And
>that the 'resistance' between the collector and emitter is very high both
>ways round.

I knowed it, he's a-tryin' to eddicate me! :-)
OK, I'll dig out the soldering iron.

>To find out which pin in base, which is collector, etc, you either have
>to look the transistor up in a databook ('Towers International Transistor
>Selector' is a well-known one in the UK that most hardware hackers have
>on their bench) or trace out enough of the surrouding circuitry to work
>out at least which pin is the base.

I think I get to cheat. I remember seeing "E", "C", and "B" markings on the
PCB.

----------

Pete Turnbull said:

>Yes, it's a PNP power trannie, in an ATV package, which is a bit like a
>TO220 but without the metal tab. It has a beveled edge on the front top,
>instead of a metal tab on the back.

This sounds familiar.

>Pin order is ECB (opposite of the common TO220).

That is what I remember from the board, though I'll check.

>Near equivalent 2SD1864.

Thanks! I'll comparison-shop for them both.

--------

All within 24 hours. Is this a *great* list to be on or what?
Will work on collecting info tonight, responses tomorrow. Thanks very much!
                                                - Mark
Received on Tue Jan 15 2002 - 14:32:29 GMT

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