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fleurys

compass and over-head temp display issues

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Time to use that good old forum....

 

I have a display issue with my over-head compass and temp that will sometimes be ok and others be like in the picture (kind of ghost display). Before I start to try to fix it, I was wondering if anyone here had seen and fix the issue ?   

 

IMG_1076%5B1%5D-X2.jpg

 

Cheers.

S.

Edited by fleurys

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Mine does it, but it snuck up over time and didn't really realize it was a defect. I guess I figured it was just an old display.

Sent from my SM-N950U using Tapatalk

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I dont have that issue but Id guess its similar to the digital clock on the dashboard going out due to soldering on the circuit board failing. 

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5 hours ago, TowndawgR50 said:

I dont have that issue but Id guess its similar to the digital clock on the dashboard going out due to soldering on the circuit board failing. 

 

yeah, I did repair my clock too by re-soldering the  4 "resistances", but was hoping someone would know what is defective in this electrical circuit... I'll keep my fingers crossed a few more days, then i'll try my luck if nobody can help...   and if it can help, tonight coming back from work, the display was perfect with no ghosting...  and it's a little more colder outside (-7c) versus 0c this morning.... so i'll try to see if temperature has something to do with this...

Edited by fleurys

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Does the ghosting change at all with vibration?


No.. If i start the truck and the display is good, it will stay like this until the truck is shutdown. Same thing if the ghosting is present at startup... The issue is either there or not at startup...it will not change over time when the truck is running...

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Hmm.. well I would suspect the issue is board component related rather than communication between the board and the display. I also don’t know anything about these displays whatsoever.

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Its all self contained, just like the clock. Simply connects to power and a air temp sensor in the front grill. Connector is like 6 wires.  My 2001 had a TSB for being persistently 8F too low.  I bought a new one out of a 2003 at the Junk Yard for about $8, and it fixed the low temperature display problem.

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Well, I tried to re-solder all the pins of the led display, but it did not change anything....  I will try to get a hold of someone who knows electronics and will see what he says...  I will communicate the details if the situation changes.

 

Cheers.

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So today, -14C and the display was perfect...no ghosting whatsoever...  So it DOES look like temperature has a role in this... It's getting more and more interesting as I dig deeper in this.. ! lol  in my research, I learned that these display are VFD (Vacuum fluorescent displays)... pretty cool stuff...  now the problem has just got more difficult to troubleshoot as it does not do it anymore... I guess I'll have to wait for warmer temperature..

S.

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yes..could be.... right now I am trying to understand all the components and which one could react to temperature (the colder the better the part is)... I now have a basic understanding of how the segments get lit up, but I still do not understand why other segments could be dimmed... I'm thinking the capacitor... this will be my next step... 

 

ps. I know I could just go and get a replacement part in a junkyard...but then again, where's the fun in this... besides, I have 3 R50 in the driveway.. and 2 of them suffer from this issue... learning how to fix it will eventually pay off i know...

 

S.

IMG_1083%5B1%5D-XL.jpg

IMG_1081%5B1%5D-XL.jpg

IMG_1082%5B1%5D-XL.jpg

Edited by fleurys

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no problem...keep them coming...  I had read this one though.. and a bunch of others as I am educating myself about this subject..  everything points to the capacitor (50v 33mf). A colder temperature making a capacitor have a greater capacitance is a known fix for a leaking capacitor. Right now the temperature is cold and the display is pretty much perfect. Although I can clearly see the difference between -14c and -1c today. There is a small ghosting effect today and when it was -14c, there was none.  I will bring the truck in the garage and start doing some live test at 20C with can of compressed air (turned upside down)... My goal is try to demonstrate that the capacitor is leaking by showing the ghosting disappearing when I freeze it... should be good. 

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Well..... It did not go as planned !  I tried to freeze the capacitors (and pretty much everywhere I could on the board) and was not successful at making the ghosting disappear (now that the truck is in the heated garage).  I still went ahead and replace the 50V 33mf capacitor and it did not change anything.... I think I'm gonna need a professional in electronics for this one... i'll keep everyone informed if anything changes..

S. 

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Posted (edited)

ok... After talking with a retired electronics teacher, he basically told me to forget about this...He told me that not only we do not have the circuit map for it but it would require long time and money just to troubleshoot...

So this (what I thought would be) easy fix project is transforming into a monster electronic project. Frankly I have too much on my plate and do not have the time right now to start this adventure, but I figured that this would be the perfect excuse to start learning electronics. Reading a little more about these VFD's, I learned that ghosting in a multiplexed vfd (like this one) is more likely caused by issues with the grid signal pulses. here's the official explanation here:

"

Another potential hazard in multiplexing is ghosting. This phenomena is caused by decaying grid signal pulses which are caused by stray capacitance between VFD electrodes and display drivers. If the grid timing overlaps the following grid and anode signal pulses, as shown in Fig.9(a), ghost illumination appears at un-addressed anode segments.

To overcome this problem, an inter-digit blanking time should be added between grid pulse timings as shown in Fig.9(b). Generally the inter-digit blanking time should be approximately 10 to 50usec, but this can vary depending on the delay time. Delay time occurs when high value pull down resistor type drivers are used or when the drive circuit is situated away from the VFD. We recommend that an appropriate inter-digit blanking time is utilized on the grid signal only, rather than on both grid and anode signals."

 

For those interested, this was taken from this document : https://www.noritake-elec.com/technology/general-technical-information/vfd-operation

 

 

  So for now, I am stopping this but in the near future , here's what I think will need to be done :

1) make a map of the board connections with all components

2) understand how it works in plain french (english)

3) somehow confirm the ghosting with some tool (possibly an oscilloscope of some sort)

4) insert an inter-blanking solution

 

For now I will endure the display like it is, but I am excited at the idea of starting this project eventually when time is available. 

 

Over and out ! LOL

Steve.

Edited by fleurys
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This is turning into quite the rabbit hole!

 

So it wasn't the through-hole cap. What about the two surface-mount caps on that same board?

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13 hours ago, Slartibartfast said:

This is turning into quite the rabbit hole!

 

So it wasn't the through-hole cap. What about the two surface-mount caps on that same board?

no it was not... For the other surface mount, I was not able to purchase them at the electronic store... I guess it could also be a possibility...

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