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I've just posted GLCD pin voltages ("emonGLCD Display Problem") and it would not hurt to check yours, but on the face of it, it does sound possible that the display itself is failing.

Thanks for the reply. At the moment they are ...

1. 8.04
2. 6.93
3. 5.74
4. 2.381
5. 1.232
6. 0.0001
7. 1.604
8. 5.57
9. 3.83
10. 1.621
11. 7.26
12. 7.96
13. 0.0001
14. 3.29
15. 3.29
16. 0.050 unsettled - possibly a clock
17. 0.041 unsettled - possibly a clock
18. 3.29
19. 3.29
20. 0.0001

I'll wait til the thing fades out completely and measure again.

It's interesting that 11 and 12 appear to be low - those are part of the voltage multiplier. It's quite unlikely that one or more of the electrolytic capacitors is going faulty, but I would not rule it out at this stage.

Yeah, you are right. I expected the screen to go dim overnight. Sods' Law meant it didn't.

Checking the voltage on 11 was 7.54 and on pin 12 8.23, so about a quarter volt higher than yesterday, and the screen looked OK.

I've not got any spare small 10uF 16v here. I think I'll get a few and try a change.

I can't believe the LCD will go faulty, it must be a problem with the capacitors.

Joy !

I replaced C12 thru C15.

Display now much better. I can now look at the screen from a wider angle without seeing dim cols of pixels. It has never been this good.

Pin 11 voltage now 8.3 (up by 1 volt)

Pin 12 voltage now 9.13 (up nearly 1.2v)

For anyone else having this problem, I gained access to the caps, by desoldering the the 2 groups of 3 connectors on the LCD, and carefully bending the LCD out. The backlight had been fixed to the LCD with hot-melt glue, and this easily snapped off, allowing the backlight to be unfolded from the PCB. Took the caps out with a solder sucker. I had soldered them too close to the PCB to allow snipping off the legs and removing each leg individually. The new caps I put in were 10uF @ 63V, physically a little larger, so the legs are now bent at 90 degrees, which as a positive means I can get at each leg individually next time I need to desolder them.

"... next time I need to desolder them" Pessimist!

That's rather surprising to find electrolytic capacitors failing after only 2½ years. Is it a particularly hot environment, by any chance?

The room oscillates between 5 & 25 degrees.

I suspect one or more of the capacitors has always been faulty because the display is now better than it ever has been.

You know how with LCDs if you tilt the screen up it usually appears dimmer and dimmer, well, now it doesn't. It is possible to look at it at the most obtuse angle, and it's still readable.

Hmmm. Spoke too soon.

Pin 11. now 6.8v
Pin12. now 7.2v

Screen pretty much blank.

Anyone got more ideas ?

The voltage multiplier circuits inside the GLCD? That would imply a replacement LCD.

But just check the voltage on those capacitors in relation to their polarity markings first.

I'm afraid of that.

This particular LCD unit is not that easy to get hold of. I'll try phoning the OpenEnergy shop after the hols, or see if I can find a different more easily sourced 128x64 pixel unit.

"This particular LCD unit is not that easy to get hold of"

Is it different from the replacement display in the shop?

http://shop.openenergymonitor.com/replacement-emonglcd-lcd-backlit-unit/

Paul

Yes. My unit is different.

Same sort of pinout arrangement - pinout pitch is the same, but my unit is bigger. 68mm wide x 49mm tall, so the two rows of pins are further apart, and the plywood cutout for the front will have a hole 17mm too wide and 6mm too tall.

I can knock up a new facsia the right size on a 3d printer, so that's not a problem, it's just that I don't know if the LCD unit is at fault, and £20 for something the wrong size, and if this is going to happen every 2 or 3 years, well ...

The information that the emonGLCD puts out, I now sort of duplicate on a small Nokia display plugged directly into a Raspberry Pi, which in turn is directly plugged into the emonTx board so really the emonGLCD is pretty redundant now, so I may just write it off.

It is just annoying. These things really should not fail.

The Nokia display looks like...

Press the button and I get rolling pages of other stats and disgnostics

As the display is not the same one, are you certain that the display requires exactly the same driver arrangement as the Electronic Assembly DOGM one that is normally used in the emonGLCD? You never mentioned this before so I think we all assumed that you were using the standard display module.

Err, well, as the display came as part of my original kit for the emonGLCD from the OpenEnergyMonitor shop. I assumed that is was the standard display. It is only now that I see that there is a replacement screen available (the EA DOGM128) that I notice there is a difference.

Looking at the emonGLCD build instructions, the pictures DO seem to match up with the display I have, which is bigger than the replacement EA DOGM128 available from the shop.

Sorry, perhaps I confused things when I put that last photo up of the small Nokia display I have on the Raspberry Pi which shows the same sort of information

This is a photo of my emonGLCD display (when it is behaving correctly)

All the LCD's included in emonglcd kits have always been the same type and this is the same as the replacment emonglcd we sell via the shop. Your report of display stopping working are very strange. I've had an emonglcd running continously since 2010 and I'm sure Jeelabs have had displays running for even longer with no issues

Thanks for the reply.

Looking at the replacement LCD in the shop, there's a picture that shows the dimensions of the EA DOGM128. This shows the width of the display unit as 55mm, and the display area as 47.99 mm wide whereas my unit is about 68mm & 61mm respectively - a lot bigger, which was why I was wondering if this is a different unit.

It is good to know people have been running these things a lot longer than me without problems.

The display does recover if left powered off for 24hrs or so, byt then fades out over the next 3 or 4 days. I find it difficult to believe that it is the LCD electronics - charge pump or whatever;

Maybe I have another faulty electrolytic in there - it is just possible some of my stock could be over (Gulp!) 30yrs old by now. I'll buy some new ones of known provenance and replace C13 thru C16 again.

You shouldn't have mentioned the 30-year old electrolytics. Unfortunately, they're not like a good wine, more like a bad wine with a bad cork - they go off and dry out over time. Did you try reforming the replacements, before you installed them? That might have shown whether they were good or not. So I do recommend replacing with new.

Yep. I've spent most of the morning researching the load life of electrolytics. I've got trays and trays of these things. No idea of the age of them, and no, I didn't reform them. It didn't occur to me.

New ones on order.

OK. Well that didn't work.

Replaced C13 thru C16 with new 10uF 50v caps, and the display was good to start with. 48hrs later it was readable with some vertical banding, but now about 72 hrs later the display is dim again.

Way back, I said check the voltage on those capacitors in relation to their polarity markings. Did you actually do that check?

Yes. They are in the right way.

I have a PCB v1.4, so C13 & C14 are in the wrong way with respect to the PCB legend.

So reading the voltages along the 8 pins of the electrolytics leading away from the RFM board I currently have...

1.603, 5.29, 3.69, 1.62, 7.09, 1.62, 0, 7.81

The important pins for the charge pump voltage multiplier are 7 - 12. C13 & C14 are actually on pins 9 - 11. Pin 12 is the output, "contrast", and should be about 12 V (mine reads 11 V).

The GLCD numbers the pins 20 less than the display itself. Here's my table for the DOGM 128-6.

Display is used "upside down", PCB pins 1 - 20 map to display pins 21 - 40:

Display Pin   GLCD PCB Pin      Symbol Level Function
    21            1             V0      -    LC Drive
    22	          2             V1      -    LC Drive
    23            3   		V2      -    LC Drive
    24            4   		V3      -    LC Drive
    25            5   		V4      -    LC Drive
    26            6   		VSS     L    Power Supply 0V (GND)
    27            7   		CAP2N   -    Voltage Converter
    28            8   		CAP2P   -    Voltage Converter
    29            9   		CAP1P   -    Voltage Converter
    30            10  		CAP1N   -    Voltage Converter
    31            11  		CAP3P   -    Voltage Converter
    32            12  		VOUT    -    Voltage Output about +12V
    33            13  		VSS     L    Power Supply 0V (GND)
    34            14  		VDD2    H    Power Supply Booster
    35            15  		VDD     H    Power Supply +1.8..3,3V
    36            16  		SI    H / L  Serial Data In
    37            17  		SCL   H / L  Serial Clock
    38            18  		A0    H / L  L= Command, H= Data
    39            19  		RST     L    Reset (active low)
    40            20  		CS1B    L    Chip Select (active low)

You probably need to look at that in conjunction with the GLCD circuit diagram and the display data sheet.

I'm running out of ideas. Your display fails because the pin 12 (32) voltage is too low. But short of the voltage multiplier running out of steam, I can't figure out why. I do note that the data sheet shows non-polarised capacitors; and the other point is, Glyn said that all the displays have always been the same type, but if yours has different dimensions to the 'standard' one, I'm beginning to wonder how 'same type' it is. But then it worked for some considerable time. I don't think that you noticed that it faded overnight is particularly significant, because from what you've measured, it only takes a small change in the voltage to make the difference between OK and not. I think the voltage had probably been falling slowly for a while. Is it a thermal problem - does ambient temperature affect it?

As a footnote to all this - I gave up trying to work out why the charge pump stopped working.

I checked the datasheets for the ST7565 - there are several different ones; I checked the code libraries, I checked the schematics, I even dusted off my old 'scope.

I realised I was wasting too much time on it all, so in the end I admitted defeat and slapped a DC-DC converter in.

Time to move on.