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Author Topic: Sencore LC102 Display Problems  (Read 19025 times)

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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #25 on: September 21, 2015, 09:34:55 pm »
Sencore emailed me back today...

No LCD screens, No detailed schematics, no calibration Procedures
They do have power Supply for sale.
« Last Edit: January 14, 2016, 06:20:34 am by Johnny10 »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #26 on: September 27, 2015, 06:17:58 pm »
I have been putting together schematic image from 8 different shots
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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #27 on: October 20, 2015, 07:26:56 pm »
I replied on your other thread.  I've worked on these units for years and I've never seen one quite like this but I'm almost certain it's the LCDs themselves.  Sencore ran out of these LCDs quite awhile ago as well.  If you can find a replacement front board from a LC102 or possibly a LC77 you should be good to go.  If you get a LC77 you'd have to move the screens from it to your old board though.

Sencore ran out of the schematic packet years and years ago and it was never scanned in.  If anyone needs help on these units I'm happy to lend my services. 
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #28 on: October 21, 2015, 01:04:53 pm »
I have been working on other projects but the Sencore is still on my workbench.
I believe you are correct something in the LCDs the oscillator seems to be working fine at about 45Hz
With what did I say? 47% duty cycle.
Yesterday however I shorted something on the unit as I was moving around the disconnected front panel looking to hook a probe to the display driver chip. Yikes!
Now no power going anywhere.
 :palm:
I missed a unit on eBay for a ridiculous 99 dollars which would have saved about 400 dollars in time and parts.
Ahh for the love of a hobby!

As you can see I am piecing together schematics for the unit from a scanned group of pages.
No calibration instructions yet but I am still looking.
The measurements for a 1000mf Nichicon 400volt electrolytic reads 1304
For ceramic disk a 68pf reads 71-72.
Caps just out of the box.
Thanks for the help I will be working on the LCD as soon as I figure out what I shorted.
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #29 on: October 21, 2015, 02:44:00 pm »
Just noticed you gave me cal data.
Thank you very much.

I am wondering if I should change caps on this unit while I have it apart?
What would you suggest?
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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #30 on: October 21, 2015, 05:41:45 pm »
Quote from: Johnny10 on October 21, 2015, 02:44:00 pm
Just noticed you gave me cal data.
Thank you very much.

I am wondering if I should change caps on this unit while I have it apart?
What would you suggest?

The only caps I've seen fail on these are the old poly caps on the top board.  Even those were few and far between.  The only ones I'd worry about are the filter caps on the power supply board(bottom board) and I wouldn't change them unless the supplies start to look dirty.
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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #31 on: October 21, 2015, 05:48:26 pm »
Quote from: Johnny10 on October 21, 2015, 01:04:53 pm
I have been working on other projects but the Sencore is still on my workbench.
I believe you are correct something in the LCDs the oscillator seems to be working fine at about 45Hz
With what did I say? 47% duty cycle.
Yesterday however I shorted something on the unit as I was moving around the disconnected front panel looking to hook a probe to the display driver chip. Yikes!
Now no power going anywhere.
 :palm:
I missed a unit on eBay for a ridiculous 99 dollars which would have saved about 400 dollars in time and parts.
Ahh for the love of a hobby!

As you can see I am piecing together schematics for the unit from a scanned group of pages.
No calibration instructions yet but I am still looking.
The measurements for a 1000mf Nichicon 400volt electrolytic reads 1304
For ceramic disk a 68pf reads 71-72.
Caps just out of the box.
Thanks for the help I will be working on the LCD as soon as I figure out what I shorted.


Bummer, hopefully you can find what is shorting out and hopefully it's not a driver chip those would be hard to find.  I'll do some scrounging around here and see if I can find any used LCDs, no promises but we probably have a few meters laying around that had other parts cannibalized
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #32 on: October 21, 2015, 10:53:19 pm »
Didn't someone just suggest filter caps on the power board?
With a list of cap #'s

And then it disappeared or was I reading another thread?

Hey! All the information I can use ... 

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Offline crispy_tofu

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Re: Sencore LC102 Display Problems
« Reply #33 on: October 22, 2015, 03:11:14 am »
Quote from: Johnny10 on October 21, 2015, 10:53:19 pm
Didn't someone just suggest filter caps on the power board?
With a list of cap #'s
And then it disappeared or was I reading another thread?
Hey! All the information I can use ...

Hmmm... I do remember that too. We're both dreaming?!  :scared:
Maybe they were wrong or it was a different thread.  ;)
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #34 on: October 22, 2015, 01:26:44 pm »
I appreciate any scrounging around you can do.
Will get working on finding my short or actually open!

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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #35 on: October 25, 2015, 03:15:02 am »
Quote from: Johnny10 on October 22, 2015, 01:26:44 pm
I appreciate any scrounging around you can do.
Will get working on finding my short or actually open!

I have display out of an LC77 that I think will work in a LC102.  I'm going to double check the schematic on Monday and let you know
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Offline rf+tech

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Re: Sencore LC102 Display Problems
« Reply #36 on: October 25, 2015, 07:11:00 pm »
Johnny10,

The problem with your LC102 display looks similar to a problem I encountered about five years ago with a Racal RA6790/GM receiver. To my eye, the displays on my receiver appeared to be over-driven with excessive contrast, as in the first two photos attached.

The second two photos show the improvement obtained by raising the LCD backplane frequency from 100 Hz to about 1.5 kHz. This was determined experimentally by altering the time constant of the backplane RC oscillator in steps and judging the improvement.

Why this works is unclear, but my best guess has to do with an excessive number of operational hours. The segments may have been flexed to the point where their "hinge" has weakened and now they flip too easily. Increasing the backplane frequency to a point where the segments are less responsive makes the display look near normal. One thing I did not think to check at the time was the duty cycle of the backplane drive, prior to altering the frequency.

If anyone has some insider info, or a better theory, I would certainly like to know more.

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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #37 on: October 26, 2015, 02:49:40 am »
Now that is very interesting!
That does look like my display and that is giving me the idea to check on the schematic the backplane frequency by design and the current frequency.
They may have changed also.
I believe it was 45 hz  the research I have done says the duty cycle must be 50% to eliminate DC riding on the AC.
My device is accurate to the specs I calculated from the resistors at the PWM.


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Offline crispy_tofu

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Re: Sencore LC102 Display Problems
« Reply #38 on: October 26, 2015, 02:54:01 am »
Fantastic!!  :-+
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #39 on: October 28, 2015, 03:17:19 pm »
Sencoretech, any luck with LC 77 LCD  matchup?
My Power supply is messed up. I get 12V power to the TR15 input transistor than no turn of gate to continue for creation of 5 volt and 18 volt.
Printing out and pasting together schematic now.
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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #40 on: October 29, 2015, 01:15:30 pm »
Quote from: Johnny10 on October 28, 2015, 03:17:19 pm
Sencoretech, any luck with LC 77 LCD  matchup?
My Power supply is messed up. I get 12V power to the TR15 input transistor than no turn of gate to continue for creation of 5 volt and 18 volt.
Printing out and pasting together schematic now.

Yes, the LC77 front should work on the LC102.  THe LC77 is missing the stop testing LED so you'd have an extra plug that wouldn't connect.  One thing to note is about 1/2 way through making LC102s we had to change display driver chips and thus we had to rev the firmware.  So if you have a "newer" unit you'd out of luck with a LC77 display.

As far as power to the display you should have 5 volts coming in on plug 1 pin 3 (display board side).  Then another 5V on plug 5 pin 2, but that's just for the stop testing light I believe.  That should be it for voltages.
« Last Edit: October 29, 2015, 01:21:31 pm by Sencoretech »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #41 on: October 29, 2015, 01:35:57 pm »
Looks like I have the MD4332BE Display Driver chips
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #42 on: October 29, 2015, 01:40:38 pm »
I am not sure about serial numbers.
Unit has stickers saying Run 12
220 P102-3
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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #43 on: October 29, 2015, 03:25:59 pm »
Quote from: Johnny10 on October 29, 2015, 01:40:38 pm
I am not sure about serial numbers.
Unit has stickers saying Run 12
220 P102-3

Run 12 is the second production run, so yes you have an older LC102 with the same driver chips.  I believe I have a working LC102 that I can try this display board in.  I'd rather not sell you this w/o being 100% sure it'd work.  Let me give it a try and I'll get back to you. 
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Offline Sencoretech

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Re: Sencore LC102 Display Problems
« Reply #44 on: October 30, 2015, 03:39:10 pm »
Quote from: Johnny10 on October 29, 2015, 01:35:57 pm
Looks like I have the MD4332BE Display Driver chips

Johnny10,
I couldn't find a working LC102 to test the board in.  I do believe it'll work but I can't be 100% sure.  The driver chips and LCDs match the LC102 and if need you could transfer them over to your display board.  I did test it in a LC77 and the board does function. 
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #45 on: December 19, 2015, 04:15:46 am »
Somewhere along the way I shorted out the TR15 Transistor MTP3055 after replacing that I now have a display only showing Volts image.
There is data on Pin 1 of the 4332 driver but nothing on Pin 2 from the MCU.
If I cool the area around the processor and some latch chips. I get a jumbled display.



Volts.image
« Last Edit: December 22, 2015, 07:55:28 pm by Johnny10 »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #46 on: December 19, 2015, 09:18:18 pm »
Pin 1 of 4332 display driver

« Last Edit: December 22, 2015, 07:42:19 pm by Johnny10 »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #47 on: December 22, 2015, 07:58:05 pm »
Jumbled Display
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #48 on: December 30, 2015, 05:17:47 pm »
I ordered a new 80C39 MCU chip just waiting for it to arrive.
Seems there was a voltage and frequency from the 7556 timing chip going to display driver but only a .380 volt signal on the Data pin coming from I think pin 15 on the ribbon.

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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #49 on: January 13, 2016, 11:18:20 pm »
OK, New micro-controller came in and guess what?
No work!
Well I should have known 11 mhz version and this chip has 6mhz clock.
Not from same manufacturer original is intel my replacement chip is Phillips.
Not sure on date code DSD8801V5 YS
I did question the guys at Micro-controller EEV BLOG FORUM they thought would not be a problem.
Will say when I asked a couple of months ago a kind forum member said so many improvements and added instructions it would be a difficult match.
What maybe should have tipped me off is after I ordered chip I did some research and it said "added instructions".
But too late.
Well nonetheless I got the unit working again I now have full display, I can enter data from front panel, all test point voltages are match and I lowered ripple  from 100mV to about 9mV... one more problem left.
When I try and zero leads. I always get a short on the open test.
Which also causes Capacitor Value test to display "short"

Anyone know how this unit tests for the short condition?






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