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Discussion Starter · #1 ·
The Marelli Tester (a.k.a. Fiat-Lancia or Alfa Tester) can be a great aid for repairing Alfas, Fiats, & Lancias. I use it to diagnose suspension faults on my S which is a terrific timesaver as it literally pinpoints the problem.

But I just came across a situation where the Marelli itself needed repairing. Of course our resident BBer “Goats” was the first person I contacted to see if he’d take a stab at this; I paraphrase our email exchange.

Pinino: “I’ve got this Marelli where only lines 1 & 3 of the display are working, while lines 2 & 4 are either blank or have “| | | | “. It’s not usable in this state, as the instructions or results get truncated. For example it might indicate that a strut is misbehaving, line 3 says “rear” but without line 4 I don’t know if that’s “right” or “left”.

Goats: “send me a picture of the back of the display module”




Goats: “If you look closely at that photo, you can see the metal tabs that pull the display module down against the circuit board, and most likely a zebra connector under the metal bezel that surrounds the display glass. Look closely at the metal tabs, it seems that at least one has been disturbed from its original position – top row, center tab.  The green of the PCB insulation is missing in the spot( it appears) that the tab originally occupied (it is gold there). Someone has taken this display apart. You may be able to reseat the zebra connector or source a replacement.”

Pinino: “I put my jeweler's glasses on and saw exactly what you are suggesting about the tab (the center top is not the only one that has some of the green missing), so the scenario that someone has been there is certainly possible.”


Goats: “The module is made by Optrex and should be easy enough to get a replacement : try searching PWB-16433”

Pinino: “Are you 100% sure that it’s the display?"

Goats: "97%. Hey, you’ve got another Marelli, why don’t you just swap in that display and see if it works”.

Pinino: “Great idea, I’m a little bit slow today! [ten minutes later...] The problematic Marelli works by swapping in the other display!! Now, searching the net I found a replacement from an electronics surplus store, $21.99 + $10 shipping.



Goats: “That part no. has a 'D' after it. Look at the data sheet I sent you to see if it’s different. But that's cheap, you might take a chance at that price.”



Pinino: [2 days later] “The display module arrived and I swapped over the 2 wire + 14-wire flat cable. It’s now back in the Marelli and the Marelli is working again. Thanks for all your wonderful help.”



Goats: “Great, does the backlight work?
 

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what an incredible ressource this bb is for the most unlikely repairs you might want to do in the Alfa context.....

Thanks for documenting this and I am glad the tester was repairable!

cheers
Sig
 

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It's so good when electronic devices are designed with commonly available parts.

I imagine these testers are not so easy to come by.
 

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Discussion Starter · #4 ·
"It's so good when electronic devices are designed with commonly available parts."

You are so right about that. When I did my search for the replacement display I came upon this interesting site of an electronics experimenter, who takes a "vintage 80s" Optrex 16433 out of his junk box and creates a simple interface with a microprocessor. "ellow World" was the the display's first message.

"ello World" - Interfacing a venerable LCD
 

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14 data lines + 2 for the backlight and an Hitachi HD44780 LCD controller chip... looks like it's just a generic 4 line LCD.
If you hadn't been able to find the exact replacement display, any of the 16x4 LCDs on ebay would work - or pinch one out of an old fax machine etc.
"Modern" LCDs tend to have 16 pins - the first 14 are the same as yours, and pins 15+16 are the backlight.
 

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Discussion Starter · #6 ·
"...any of the 16x4 LCDs on ebay would work..."

I just checked ebay with that simple search—what a treasure trove of LCDs that comes up! Thank you so much for the advice. Also for pointing out that models with 16 pins have 15/16 reserved for backlight.

Although I'm not really concerned about the backlight, the new Optrex backlight is not working. Would reversing the leads (photo 3 in post #1), or using different pads of those "twin" connectors solve this? (the board didn't come with a data sheet)
 

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maybe

As I suggested earlier, try switching the leads (the 2 on the left side). Does not matter which pad you solder to. This module may have an EL backlight, in which case you would need an inverter to power it
 

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Discussion Starter · #8 · (Edited)
Under the subject "Repairing a Marelli Tester" I thought I'd add a brief post regarding the 5x4 matrix keypad.

Mine recently was acting up: the "OK" button, absolutely critical for proceeding with a test (only second to "E/C") wasn't working. Pushing it a bunch of times in a row would sometimes make it work, but that was extremely frustrating. Analyzing the situation I discovered that the entire first column of buttons wasn't working (R - 1 - 5 - FC - OK). So I took it apart to investigate. Couldn't find a single test on the internet using a multimeter to verify the keypad. So I started probing with the multimeter using intuition, setting the meter on "ohms", here is what I found "pinwise" (to get a reaction) as I pushed the keys:
Font Line Circle Pattern Number


That verified two things, that it wasn't the keyboard, and that the pin associated with the problem was wire no. 10 (the keypad uses a 10-wire ribbon connector).

Re-seating the ribbon connector did nothing; adding a little dialectic grease to the sockets also had no effect. I noticed on my bench using a 18v power supply (the Marelli Tester needs a range of 12v - 24v to operate) that key "OK" was a little better than the car's 12v. So.. um.. [head cratch] a bad solder joint? I followed pin 10 on the pcb through a series of 4 solder joints (including one resistor ), and re-flowed the joints. Verdict: the tester was saved, keypad column A alive again.

So fellow Alfa/FLT tester owners, if your keypad fails, don't toss it, there is hope.
Mobile phone Telephony Communication Device Portable communications device Font
 

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tho I understand little of this stuff, reading about it is interesting and interest is usually the first step to understanding. IOW, you guys are scary but some fear in life is wonderful. Ciao, Chris
 

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tho I understand little of this stuff, reading about it is interesting and interest is usually the first step to understanding. IOW, you guys are scary but some fear in life is wonderful. Ciao, Chris
Me, too. I had that tester set up, that Myron bought for me to maintain his 95LS. Pinino got me a 12v V6 cartridge for it and I used it a couple times on my 12v 164s. I sold tester, carrying case and all the cartridges off with my 24v tools to Joe and guys at Centerline for real money as I was getting ready to move to FL.
 
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