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Missing Segments On A Pulsar Date Command

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Planet-LED

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Missing Segments On A Pulsar Date Command

Post25 Sep 2005, 07:46

I have a Date Command that has the same segment missing on all of the numbers. I believe that it is one of the drivers (transistor) that is faulty. I have another non working module. There appears to be two connections there. Can anyone give me some insight into getting the block from one watch and putting it onto another? Thank you,
Steve
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digibloke

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Re: Missing Segments On A Pulsar Date Command

Post26 Sep 2005, 15:06

Hi, I've also been wanting to try this on a date command with the same problem for a while now, but don't have a donor module yet.

I remember reading somewhere (perhaps on this forum, so sorry if I'm ripping off someones thread) that you can gently pop them off the dead module with a scalpel, then glue them in place on the good module using silver epoxy (conductive glue) applied with a pin (much more precise than soldering). I guess that the usual rules of having a very steady hand and watching out for static electricity apply. I'd be interested to know whether it really is this straightforward or if anyones tried it :?:
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fronzelneekburm

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Re: Missing Segments On A Pulsar Date Command

Post26 Sep 2005, 18:12

The epoxy method doesnt sound like it comes from someone who studied micro-electronics, but it may work.
The catch with using epoxy in such delicate repairs is that you'll need a very calm hand and good eyes. Try to apply the silver epoxy with the tip of a needle, train on a block of wood or plastic first. When you put a cubic object on a large drop of epoxy it will be spread all along the object, most probably conducting between areas where it really should not conduct.

So be sure to not apply too much and if two wrong pins are connected by the epoxy, then you can wait until it hardens and then cut it with a scalpel. Control results with a magnifying glass. Good luck! :wink:
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ledwatch

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Re: Missing Segments On A Pulsar Date Command

Post26 Sep 2005, 20:16

Before going to all this trouble you really need to find out whether the fault is in the transistor or the logic chip, if the chip isnt supplying the necessary 1.5volt bias to the base of the tranny then it wont switch on in the first place. To do this work you need to build a module tester with two 1.5volt batteries, this will give you 3volts to run the module. The centre point is half volts (1.5v) solder this point to a flying lead with a pin on it, now tap this on the base of the trannies one by one, whilst the module is in display mode, each trannie will then turn on, if the previously missing segments light up then you now know that the transistors are not faulty but the logic chip is (and vice versa). Hope this helps!!
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Re: Missing Segments On A Pulsar Date Command

Post26 Sep 2005, 22:20

You wrote: The centre point is half volts (1.5v) solder this point to a flying lead with a pin on it.

You lost me on that one. Where is the center point? And did you say to temporarily solder a wire to the center point?
Thanks,
Steve
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ledwatch

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Re: Missing Segments On A Pulsar Date Command

Post26 Sep 2005, 22:48

Image
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digibloke

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Re: Missing Segments On A Pulsar Date Command

Post27 Sep 2005, 02:01

Cool, and to think I was planning on going fishing next weekend. Where's my soldering iron...
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Re: Missing Segments On A Pulsar Date Command

Post27 Sep 2005, 16:39

Led Watch,

Thank you for taking the time to make that illustration. It was exactly what I needed.

Steve
Last edited by Planet-LED on 27 Sep 2005, 16:47, edited 1 time in total.
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Re: Missing Segments On A Pulsar Date Command

Post27 Sep 2005, 16:47

Along those same lines, I had a Date Command where one entire digit was very dim compared to the rest. Knowing that each digit is powered by 7 different transistors, how could an entire segment be dim?
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bruce wegmann

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Re: Missing Segments On A Pulsar Date Command

Post27 Sep 2005, 23:40

A single dim digit is caused by a failing digit driver transistor. There are a total of eleven driver transistors; seven for the segments and four for the individual digits. The digit drivers are located in pairs immediately above and below the left end of the display. In later Pulsar models these individual parts are integrated onto the clock chip itself, and are no longer accessible. If one fails to switch "on" completely, there is diminished current flow through the segments, and thus a lessened light output [all segments being equally dim]. These are as replacable as the segment drivers [transistors for the segments and digits are not interchangable, though they appear identical; probably use npn for the segments and pnp for the digits, and so switch "on" with different polarity signals]. I see far more segment failures than digits, but the repair is essentially the same, in either case.
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Re: Missing Segments On A Pulsar Date Command

Post01 Oct 2005, 21:06

Bruce,
As always, I appreciate your detailed explanation.

Thanks,
Steve
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azimuth_pl

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Re: Missing Segments On A Pulsar Date Command

Post04 Feb 2006, 21:15

I already posted this in the Pulsar topic but it will also be helpful in this post. If you don't have the time to check each segment driver then just take a look at my picture below:
Image
or read more at my website:
http://crazywatches.w.interia.pl/photo/ ... _tech.html
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bruce wegmann

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Re: Missing Segments On A Pulsar Date Command

Post06 Feb 2006, 00:42

Excellent guide to the seven-segment display; note the interesting reversal of the "C" and "D" segment driver positions. In standard engineering notation; the segment positions are referred to by letters. Here, yellow=A, purple=B, blue=C, red=D, white=E, orange=F, and green=G. Clever [parallel] connection of the colon dots to the B and C segments makes them individually addressable without adding two additional external connections. You might want to expand this map to include the four digit drivers [the two pairs of transistors immediately above and below the left edge of the display]. Thanks for a very clarifying post.
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Re: Missing Segments On A Pulsar Date Command

Post06 Feb 2006, 12:52

Thanx Bruce :)
Please give me more info on the four digit drivers as I didn't so far tinker these little fellowes.

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