User5518 wrote on 2024-12-15, 20:06:

Hi everyone, […]
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Hi everyone,

First, a little story:
Today I drove over 350 km (round trip) to pick up a Siemens Nixdorf PCD 4ND. I bought it on kleinanzeigen.de, and from the pictures, it appeared to be in excellent condition. When I arrived, I was greeted by an elderly couple, and the PCD 4ND was already set up for testing on their living room table. Unfortunately, I immediately noticed a few issues:

• A red vertical stripe ran through the display.
• The floppy drive couldn’t read any disks.
• Windows 3.11 threw a “System Error” and wouldn’t boot.

The red stripe bothered me the most. However, the sellers knocked 20 Euros off the price, so I ended up taking the device with the following specs (and defects) for 80 Euros:

• 486D4 with 75 MHz
• 4 MB RAM
• 500 MB hard drive
• SoundBlaster-compatible sound card
• Active Matrix TFT display (not STN) – but with a red stripe. 😒

This evening, I sat down to address the individual problems.
When I turned the device on, this is what I saw:

The attachment 1_stripes.jpeg is no longer available

For some reason, the stripes multiplied during transportation. 🙁

So, I decided to work on the floppy drive first before attempting the display. The floppy drive (which internally is a "Citizen LR102061") luckily just had a worn-out drive belt. My replacement belt doesn’t fit perfectly, so disks aren’t always read reliably, but at least I could boot DOS form a floppy.

Now, onto the display. I disassembled it and noticed that when I gently ran a screwdriver along this part:

The attachment 2_screwdriver.jpg is no longer available

The stripes flickered.

It became clear to me that soldering something here was out of the question. So, I decided to try using hot air.
I started with 250°C and planned to slowly increase the temperature if nothing happened.

When I applied the heat gun, more stripes initially appeared, but after cooling down, they disappeared:

The attachment 3_heatgun.jpeg is no longer available

The attachment 4_repaired.jpeg is no longer available

I’m super happy!

The attachment 5_final.jpeg is no longer available

Of course, I don’t know yet if this is a permanent or just a temporary fix, but I’m very pleased that it’s working for now and that I essentially have a fully functional PCD 4ND. 😀

Has anyone else ever repaired display stripes this way and can tell me how long this solution might last?

Best regards,
User5518

That looks great 😀 Thanks for writing up the process, I've got a couple of LCDs with a similar problem that I might try this with.

Essentially you've re-melted the anisotropic conductive adhesive that connects the Chip on Film column drivers to the TFT glass contacts. It's really cool that just applying heat got them to melt in a decently uniform way.

I'm a bit surprised the glass didn't crack from the uneven heating but I guess the process was short enough (how long did you heat things anyway ?) and the mask you made helped too.

In past I have used soldering iron through teflon tape for doing this. Nowdays I would use kapton too.

Thermalwrong wrote on 2024-12-18, 00:13:

That looks great 😀 Thanks for writing up the process, I've got a couple of LCDs with a similar problem that I might try this with.

Essentially you've re-melted the anisotropic conductive adhesive that connects the Chip on Film column drivers to the TFT glass contacts. It's really cool that just applying heat got them to melt in a decently uniform way.

Thanks for your comment. I didn’t know that conductive adhesive was used there. But that explains why I didn’t need to hold the heat gun on it for long (only a few seconds).

Tiido wrote on 2024-12-18, 01:46:

I'm a bit surprised the glass didn't crack from the uneven heating but I guess the process was short enough (how long did you heat things anyway ?) and the mask you made helped too.

In past I have used soldering iron through teflon tape for doing this. Nowdays I would use kapton too.

Looks like I was really lucky. Just 3-5 seconds after I aimed the heat gun at it, I saw the stripes increase and began to flicker. Then I removed the heat gun, and the stripes disappeared (as it cooled down).

That seems like a reasonable timeframe. Was the airflow set low or toward higher setting ?

Tiido wrote on 2024-12-18, 11:24:

That seems like a reasonable timeframe. Was the airflow set low or toward higher setting ?

I used a "SMD rework station 858D" at "full speed" ( AIR: 8,5 of 8 ) :

and the nozzle had a diameter of around 1cm