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Author Topic: Sencore LC102 Display Problems  (Read 19014 times)

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Offline Johnny10Topic starter

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Sencore LC102 Display Problems
« on: September 09, 2015, 04:09:39 pm »
I originally posted this to beginner forum but I notice it should have been under repairs.
My Sencore LC102 is showing a blurred LCD Display and since I have never worked on these Boards I wonder if someone here could help?

I have the manual and block diagram for the unit but no service manual.
Wondering if the blurred image could be compensated for through potentiometer?

There are about 20 available on main board none on display board and no way to identify what they control.
I have added an image.
I checked voltages at various TP and the LCD chip all seem fine.

Posting a photo of display.
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Offline OldSchoolTechCorner

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Re: Sencore LC102 Display Problems
« Reply #1 on: September 09, 2015, 09:59:29 pm »
The LCD is bad, reasons could be due to the layers of glass start to separate and the liquid crystal material starts to bleed, or seals failing around the outside of the glass.
« Last Edit: September 09, 2015, 10:01:58 pm by OldSchoolTechCorner »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #2 on: September 10, 2015, 01:01:31 am »
Are these specialty items or can they be replaced?
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #3 on: September 10, 2015, 02:16:46 am »
Is it unusual though that both displays would be failing so consistently?  Since they're subjected to the same environmental conditions since assembly, does that make simultaneous glass failure typical?  The display on the left has to be custom due to the unique legends on the display.  Since that one is custom, odds are the one on the right is custom as well.  The manual lists Sencore part numbers for the displays - it might not hurt to drop Sencore an email asking about the parts.

Some trivia for you... I ran one of the two design labs at Sencore in the late 1970's. The company was struggling to decide whether new products should stick with the traditional LED displays or go to LCD, which was new at the time.  Sencore used to rely heavily on company field reps for sales, and all the reps attended annual or semiannual meetings at the company.  I'll never forget being asked by the president of the company to prepare prototypes of both LED and LCD displays for the sales team to "vote" on as part of one of those meetings.  During my introduction to the sales team, the president stated I was ramrodding the LCD path - "look, he even brought a prototype of an LCD to convince you".  Almost laughably, all or nearly all of the sales staff pleaded for LCD, saying that's what their customers were wanting.  I started looking for new job shortly after that sales meeting.

The LC102 was after my time.
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #4 on: September 10, 2015, 04:08:04 am »
One thing I'd check is the backplane oscillator that feeds both displays.  If that oscillator quits, the display glass is driven effectively with DC, which they don't like. 
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Offline OldSchoolTechCorner

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Re: Sencore LC102 Display Problems
« Reply #5 on: September 10, 2015, 04:20:02 am »
Quote from: klunkerbus on September 10, 2015, 04:08:04 am
One thing I'd check is the backplane oscillator that feeds both displays.  If that oscillator quits, the display glass is driven effectively with DC, which they don't like.

Agree more like the backplane oscillator definitely worth checking that the LCD backplane ac oscillator is running , as could be dc bias damage to the crystal lattice. Convert it over to a LED displays, if can't source the originals. 
« Last Edit: September 10, 2015, 04:24:40 am by OldSchoolTechCorner »
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Offline Joule Thief

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Re: Sencore LC102 Display Problems
« Reply #6 on: September 10, 2015, 04:43:03 am »
Quote from: klunkerbus on September 10, 2015, 02:16:46 am
Some trivia for you... I ran one of the two design labs at Sencore in the late 1970's. The company was struggling to decide whether new products should stick with the traditional LED displays or go to LCD, which was new at the time. 

And all that time i was saving my lunch money to buy a new FE160 analog FET multimeter.
I still use it as my primary analog meter even today.
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #7 on: September 10, 2015, 02:50:29 pm »
I have a closer shot of Display.
Thanks for all the interesting analysis. Checking the oscillator later today.
Going to be difficult to get back behind the display.
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #8 on: September 10, 2015, 10:36:08 pm »
I am getting something in the 58-59 hertz range.
Does that sound about right?
I have been looking at other backplane designs in the 40-150 hz.
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #9 on: September 11, 2015, 12:10:02 am »
Quote from: Johnny10 on September 10, 2015, 10:36:08 pm
I am getting something in the 58-59 hertz range.
Does that sound about right?
I have been looking at other backplane designs in the 40-150 hz.

Hopefully someone else can chime in.  The on-line manual I've been looking at doesn't have a good schematic capture - I was hoping the frequency would have been noted on it.   When I was inking up schematics at Sencore (yeah, some of us started before the days of desktop computers), I always tried to include obvious info like that.  I don't have a lot of experience with the glass-only type of LCDs, and as I mentioned the experience I had was long ago.  I don't remember the frequency being critical though.
« Last Edit: September 11, 2015, 01:09:14 pm by klunkerbus »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #10 on: September 11, 2015, 03:21:04 pm »
I would like to thank you guys for the help!
Hopefully someone out there can point me to a source for screen replacement. :-(

I continue to look through the schematics I have available but they are not very complete as to specifics.
Is there a Service Manual available?
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Offline Quarlo Klobrigney

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Re: Sencore LC102 Display Problems
« Reply #11 on: September 11, 2015, 03:37:26 pm »
Ignore my PM here you go! http://bama.edebris.com/manuals/sencore/lc102/

Quote from: Johnny10 on September 11, 2015, 03:21:04 pm
I would like to thank you guys for the help!
Hopefully someone out there can point me to a source for screen replacement. :-(

I continue to look through the schematics I have available but they are not very complete as to specifics.
Is there a Service Manual available?
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #12 on: September 11, 2015, 04:38:36 pm »
Quarlo - that's the same on-line manual I was looking at. It doesn't include any service info, and the schematic in the scanned capture is all hacked up. The pages would have to be printed and taped together to see if it is all there.  As Johnny10 indicated, the LC102 schematic is lacking useful descriptors and labels. 

Johnny10 - as mentioned earlier, the display on the left HAS to be a custom for Sencore.  Finding a pin compatible replacement is a very long shot. Sencore no longer builds this kind of test equipment, but there's a chance they still support these older products.  Try contacting them through the methods listed on their support | service and repair web page.  If you contact the parts specialist directly, according the manual the Sencore display part numbers are 23A86 for the 6-digit one on the left and 23A87:A for the 4-digit one on the right.  It sure doesn't hurt to try asking them.

It wouldn't likely be clean when you're done, but worst case it should be possible to read the multiplexed display data coming from the LC102 microprocessor into a new microcontroller that regenerates the display on either a character display (like 2x20 or 4x20) or to a bit mapped display.  I've seen other people doing this for older test equipment where the VFD display has faded and a replacement isn't available.  In this approach, you'd basically be replacing the LC102 display board.
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #13 on: September 11, 2015, 05:47:31 pm »
Well you are correct, the schematic in the manual is a bear to work with.
I printed out 6 sheets and pieced and taped them together. However I see there is a Block Diagram and then also a chip diagram.
I will have to print this out and piece it together. I also downloaded PDF's for the individual IC chips.
The display board has D Flip Flop, Quad Latch, Dual Timer and LCD Driver IC chips that I was able to get pin-outs for.
The fun begins!

And I am still wondering if the screen damage is environmental, age or a DC Bias issue.

I am not familiar with these LCD driver boards and support chips but I guess I have a new project.
What I have read is that DC damage is irreversible and that is a big disappointment! No matter I am going to have to find replacements.
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Offline Quarlo Klobrigney

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Re: Sencore LC102 Display Problems
« Reply #14 on: September 11, 2015, 06:23:19 pm »
Fortunately my LC102 is not experiencing the LCD symptoms in your photos. I know the schematics are all over the place. Without opening mine, is the LCD just a flat piece of glass with leads on either side or is it a module? I would think the former. If so, it will be multiplexed and not compatible to a 4x20 type with µcontroller on board.
I could have a look inside if you need me to.
The MD4332 is the LCD Driver IC. Sure enough it is for the flat glass multiplexed LCD type driver.
Have you scoped the D1, CLK, RST & T/C as well as the 5V bus for noise?

Like Elvis, Sencore has left the building. And us as well. I have several pieces of their gear. All orphaned.
« Last Edit: September 11, 2015, 06:40:23 pm by Quarlo Klobrigney »
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #15 on: September 11, 2015, 08:02:14 pm »
I want to clarify that no, you couldn't simply hook an integrated 4x20 type display onto anything currently in the LC102.

Without printing out the schematic and researching the LCD display board design, my guess is that the data from the LC102 microprocessor to the LC102 display board consists of a data bus and various strobe lines, with each strobe line used to clock the display board latches for each character, and possibly a strobe line used to latch status for all the unique labels on the display.  My point with suggesting the 4x20 or another type of integrated display is that there's no technical reason those data lines couldn't be captured by another microcontroller, with that microcontroller running the custom firmware necessary to interpret what the LC102 wants displayed, and then generating the necessary interface for a new display type.  Again, people have done this before on other old equipment. With trial and error, it shouldn't be hard to figure out what each of the strobe lines is being used for.  It's a personal decision on whether the effort is worth it. 

EDIT: Of course, if the LC102 microprocessor is already taking care of the segment-level detail for the display, or the interface to the LC102 display board is serial, converting the data to a new display would be harder, but still possible.

« Last Edit: September 11, 2015, 08:14:08 pm by klunkerbus »
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Offline Quarlo Klobrigney

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Re: Sencore LC102 Display Problems
« Reply #16 on: September 11, 2015, 08:22:13 pm »
I understand now that a module is not what you said, The data is serial in daisy chained shift-register parallel out and could be easily done with an AVR in the Megaxx9 series which support direct glass LCD output and by remapping with code, and subbing another glass LCD.

There are however glass only LCD's still available on places like eBay. It's just a matter of looking at the LCD and determining a part number/series, if in fact it is defective.

If it is all done, and can't be found, I would replace the LCD with an OLED display and µController.

Quote from: klunkerbus on September 11, 2015, 08:02:14 pm
I want to clarify that no, you couldn't simply hook an integrated 4x20 type display onto anything currently in the LC102.

EDIT: Of course, if the LC102 microprocessor is already taking care of the segment-level detail for the display, or the interface to the LC102 display board is serial, converting the data to a new display would be harder, but still possible.
« Last Edit: September 11, 2015, 08:30:25 pm by Quarlo Klobrigney »
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #17 on: September 11, 2015, 09:08:37 pm »
The problem in finding replacement glass, assuming Sencore has in fact stopped supporting the old gear, is in the display annunciators that were very likely unique to Sencore. Before I left Sencore, I do know we were always defining custom LCDs for any new product - it was just cheaper and easier to come up with a professional-looking front panel that way, as compared to a generic numeric display complemented with some sort of backlit annunciators.  I don't remember the tooling cost being that bad for the custom displays, at least not when that would have been spread across a production buy of say 500 displays.

The 6-digit display on the left includes WAIT, OPEN, SHORT, pF, uH, uA, (M-ohm), uF, mH, mA, (K-ohm), RINGS, V, %, (ohm) GOOD, and BAD.  I doubt that can be found in any off-the-shelf replacement.  The 4-digit display on the right at least only has VOLTS. 
« Last Edit: September 11, 2015, 09:18:42 pm by klunkerbus »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #18 on: September 11, 2015, 09:53:41 pm »
I will work on the unit this weekend, maybe!!

Mine is open so I will take some photos.
This morning I unscrewed the front to expose the Display Board.
Very few IC chips and about 5 capacitors.
Will post photos tomorrow.
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Offline Quarlo Klobrigney

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Re: Sencore LC102 Display Problems
« Reply #19 on: September 11, 2015, 09:54:46 pm »
I have lost myself in .... what was I just talking about
oh yeah, I just looked and the unit that I have for a backup is the LC101.
Brain fart. No wonder the designators you mentioned didn't sound right.
Also that you worked for Sencore. Too bad they went a different direction.
I use a different older LED Sencore as a daily driver. I was going to get to the 101 because the calibration is off so I stored it away and lost myself. What a dope. My apologies for my earning the asshat award.

EDIT: I also know now why I stored it away...I can't find a service manual for it. I am slipping.
« Last Edit: September 11, 2015, 10:02:12 pm by Quarlo Klobrigney »
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Offline klunkerbus

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Re: Sencore LC102 Display Problems
« Reply #20 on: September 12, 2015, 01:30:54 am »
Johnny10, good luck on whatever you hope to accomplish with the LC102 this weekend.

Quarlo, I can't speak for Johnny10, but no apologies needed on my account. I think our dialogue helped explain to Johnny10 what he's working with. 
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #21 on: September 19, 2015, 08:00:20 pm »
Waiting for a new LCD Panel to test the display board. Decided to add some pics while waiting they should be here Monday.
Tested voltage and signal at the LCD Driver chip.
This is Signal going to Data Pin on LCD.
One concern the duty cycle for LCD states should be exactly 50%. However I am getting about 45% on calculation.

Still wondering what happened to display LCD crystals.
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #22 on: September 19, 2015, 08:26:55 pm »
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #23 on: September 19, 2015, 10:56:52 pm »
I have been following the datasheet for another driver chip based on an earlier attempt by someone with a broken LCD but the information on his LCD driver was different.
Just started reading about this chip and now I need to look at completely different pins.
The true/complimentary pin has me a bit confused.
I purchased a few 4 digit LCD crystal displays just to experiment with.
For custom characters I am thinking a separate chip decoding various characters for uF, pF, MF and the Good/Bad, etc.
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Offline Johnny10Topic starter

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Re: Sencore LC102 Display Problems
« Reply #24 on: September 20, 2015, 05:42:17 pm »
After finding the correct Pin-out for the LCD Driver Chip I am adding screen shots of the  T/C Pin and ClK Pin.
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