RetroBard wrote on 2022-02-14, 23:20:

I just won a Schneider Euro PC in an auction. It’s missing the PSU and according to the description doesn’t power on. The seller suspects the on/off switch. He’s also tested the socketed chips to be working in another Euro PC. I’m looking forward to have a try at it. I have a suitable Mean Well PSU but I’d need to make a cable for it.

Congratulation, The EuroPC is a fascinering machine. It never stops to surprise me. I have made a series of videos about it. Check it out: https://www.youtube.com/watch?v=UwCLBB64ddI&l … NwBMedT_NEkt_cC

Thanks! Have subscribed to your channel. Would need to find a suitable PSU for it.

RetroBard wrote on 2022-02-15, 13:42:

konc wrote on 2022-02-15, 11:33:

RetroBard wrote on 2022-02-14, 23:20:

I just won a Schneider Euro PC in an auction. It’s missing the PSU and according to the description doesn’t power on. The seller suspects the on/off switch. He’s also tested the socketed chips to be working in another Euro PC. I’m looking forward to have a try at it. I have a suitable Mean Well PSU but I’d need to make a cable for it.

101 times out of 100 it's battery damage and not the switch, I hope you've seen photos from the battery area and your euro pc is the exception.

Battery’s been removed. Based on the pictures, the battery damage doesn’t look at least very excessive. The resolution isn’t good enough to tell for sure. At least the traces by the battery area appear all right. One via might be a bit suspectible.

Edit: take that back. There’s definitely one eaten trace on the side of the battery where there’s only one leg.

That's a lot of damage and it's going to get worse once you start removing chips and components. It's not one trace.

RetroBard wrote on 2022-02-15, 13:51:

Here’s a closeup of the battery area. https://www.dropbox.com/s/jfnb4vsflysklyf/Photo%2015.2.2022%2C%2015.47.25.jpg?raw=1 […]
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Here’s a closeup of the battery area.

The metal tube is a quartz crystal. Perhaps that ~14MHz one..

konc wrote on 2022-02-15, 16:43:

RetroBard wrote on 2022-02-15, 13:42:

konc wrote on 2022-02-15, 11:33:

101 times out of 100 it's battery damage and not the switch, I hope you've seen photos from the battery area and your euro pc is the exception.

Battery’s been removed. Based on the pictures, the battery damage doesn’t look at least very excessive. The resolution isn’t good enough to tell for sure. At least the traces by the battery area appear all right. One via might be a bit suspectible.

Edit: take that back. There’s definitely one eaten trace on the side of the battery where there’s only one leg.

That's a lot of damage and it's going to get worse once you start removing chips and components. It's not one trace.

That’s always possible. There’s some gunk also on the legs of some IC’s. But once I get it here and manage to give it a good clean, I’ll be wiser. The thick trace that looks completely cnackered, can anyone tell me whether it’s VCC or ground?

Jo22 wrote on 2022-02-15, 17:57:

RetroBard wrote on 2022-02-15, 13:51:

Here’s a closeup of the battery area. https://www.dropbox.com/s/jfnb4vsflysklyf/Photo%2015.2.2022%2C%2015.47.25.jpg?raw=1 […]
Show full quote

Here’s a closeup of the battery area.

The metal tube is a quartz crystal. Perhaps that ~14MHz one..

The metal tube is a quartz crystal, indeed. It's not a 14.318MHz one, though but the 32.768kHz quartz for the real-time clock chip directly next to it. This tube-style case is typically only used for low-frequency quartz crystals that are "tuning-fork" shaped. Quartz crystals in the MHz range often are disk-shaped and require other cases.

mkarcher wrote on 2022-02-16, 20:46:

Jo22 wrote on 2022-02-15, 17:57:

RetroBard wrote on 2022-02-15, 13:51:

Here’s a closeup of the battery area. https://www.dropbox.com/s/jfnb4vsflysklyf/Photo%2015.2.2022%2C%2015.47.25.jpg?raw=1 […]
Show full quote

Here’s a closeup of the battery area.

The metal tube is a quartz crystal. Perhaps that ~14MHz one..

The metal tube is a quartz crystal, indeed. It's not a 14.318MHz one, though but the 32.768kHz quartz for the real-time clock chip directly next to it. This tube-style case is typically only used for low-frequency quartz crystals that are "tuning-fork" shaped. Quartz crystals in the MHz range often are disk-shaped and require other cases.

I see. You're right. 32,768 KHz is the standard frequency for quartz clocks, afaik.
I've seen them before in wristwatches from the 1990s when I was changing batteries.
I assume it simply just didn't occur to me that this was one of them, because I haven't seen them in years and thus expected such a component to be integrated into an IC.😅

By the way, is it normal/common that such oscillator crystals are, uhm, "loose"as seen in the picture ? 🤷‍♂️
I always assumed that these components are fragile and thus mechanical stability is important.
The very few of these KHz crystals that I can remember of were attached to the PCB somehow (glue, solder blob etc)?

Edit: Or is it soldered in the picture? Hm. Never mind.

Jo22 wrote on 2022-02-16, 21:03:

By the way, is it normal/common that such oscillator crystals are, uhm, "loose"as seen in the picture ? 🤷‍♂️ I always assumed th […]
Show full quote

By the way, is it normal/common that such oscillator crystals are, uhm, "loose"as seen in the picture ? 🤷‍♂️
I always assumed that these components are fragile and thus mechanical stability is important.
The very few of these KHz crystals that I can remember of were attached to the PCB somehow (glue, solder blob etc)?

Edit: Or is it soldered in the picture? Hm. Never mind.

In the Euro PC, the 32.768 kHz quartz is soldered with its thin connecting wires into the PCB, and the cylindrical can is pressed into a metal clamp that is soldered to the board and fixes the crystal to a specific positon, so that there is no mechanical stress on the wires. This is a standard mounting technique for watch crystals. When the battery in the Euro PC leaks, the metal clamp fixing the crystal in place is one of the first components that gets eaten away by corrosion, so Euro PCs with loose crystals are quite common. This is damage nevertheless and a proper restoration should fix the crystal can to the board in some way.

Oops, while the striked out statement might be true for some Euro PC PCBs, I rechecked the one I'm trying to revive right now. The watch crystal is soldered not clamp-mounted on that PCB. The high risk of the mounting getting corroded by battery leakage still applies, though.

I received the EuroPC on Friday. I opened it up and had a better look at the motherboard.

There were two traces that had rotted away from the battery goo. Others seemed to test okay with my multimeter.

I applied some vinegar to neutralize the remaining battery residue and rinsed it with IPA.
I also changed the crystal and diode.

To fix the damaged traces, I soldered a couple of bodge wires.

The EuroPC didn’t have it’s original PSU, so I made a makeshift PSU from a Mean Well that I had lying around. It was time to give it a boot.

I’d call that signs of life. I have the picture coming through CGA2Scart to my TV. I gather it doesn’t like the 80 col mode.

I need to install a coin cell battery and put it together to see if I can get a comprehensible picture out of it.

Installed a battery and was able to go and store the settings. Now when I boot it, the drive makes a seek but the memory counter stops at 128k.

RetroBard wrote on 2022-02-27, 13:54:

I’d call that signs of life. I have the picture coming through CGA2Scart to my TV. I gather it doesn’t like the 80 col mode.

The Euro-PC character ROM contains both a 8x8 pixel font used for CGA-type monitors with 200 scan lines and a 8x14 pixel font (with a hardware-synthesized 9th pixel) for use with MDA-type monitors with 350 scan lines. A TV connected using CGA2Scart is a "CGA-type monitor" in that terminology. Your photo of the 80-column mode looks like characters from both font sets are intermixed. This symptom should be independent on the 40/80 column mode though. The photo suggest that a trace to the font (E)PROM (should be clearly labelled) or a connection in the font EPROM socket is corroded and needs cleaning. As a later photo shows correct operation (in 40 col mode), I'd expect the machine to now work in 80 col mode, too.

mkarcher wrote on 2022-02-27, 17:09:

RetroBard wrote on 2022-02-27, 13:54:

I’d call that signs of life. I have the picture coming through CGA2Scart to my TV. I gather it doesn’t like the 80 col mode.

The Euro-PC character ROM contains both a 8x8 pixel font used for CGA-type monitors with 200 scan lines and a 8x14 pixel font (with a hardware-synthesized 9th pixel) for use with MDA-type monitors with 350 scan lines. A TV connected using CGA2Scart is a "CGA-type monitor" in that terminology. Your photo of the 80-column mode looks like characters from both font sets are intermixed. This symptom should be independent on the 40/80 column mode though. The photo suggest that a trace to the font (E)PROM (should be clearly labelled) or a connection in the font EPROM socket is corroded and needs cleaning. As a later photo shows correct operation (in 40 col mode), I'd expect the machine to now work in 80 col mode, too.

Now that you mention it, I can see the different font sets. I need to check the character ROM.

I probably need to try a different battery, as the EuroPC, while reseving the settings through a power cycle, doesn’t seem to hold them a longer power down. I also need to get some new RAM chips.

The 80 col mode still shows mixed character sets. I looked at the schematics and according to that the char ROM is only connected to the GPU. I’ll check the continuities between the char ROM and GPU.

Another thing is that I’ve added a CR2032 in place of the battery with diode between the + terminal and + line and - terminal connected to that leg of the resistor that shares the same trace with - terminal. The issue is that the settings survive a quick power cycle, but not something like 1 min power down. The CR2032 measures 3.28 volts.

Pin 2 of the char ROM that according to the schematic is connected to mono had one broken resistor and a broken trace next to the battery. I desoldered the three resistors that were next to the battery + terminal and will get some replacements.

I got the 80 col mode working by changing the three resistors next to the battery and fixing the broken trace between two resistor legs with a bodge.

Sorry, Jinxter for hijacking your thread. I can start a separate one.

RetroBard wrote on 2022-03-04, 16:58:

Sorry, Jinxter for hijacking your thread. I can start a separate one.

I don't think of it as my thread. 😀

One question, can you determine from the memory checkup at boot, which chip might ne faulty? The memory check in mine always stops at 128k.

RetroBard wrote on 2022-03-04, 18:37:

One question, can you determine from the memory checkup at boot, which chip might ne faulty? The memory check in mine always stops at 128k.

Half of the memory chips are for the range 0..255K, and the second half is for the range 256K..511K. If just some data bits are broken, you should get an error message, not a plain stop. I guess you have an addressing problem, and testing the range slightly above 128K overwrites the stack of the BIOS (which is located near 0). Check the address lines for continuity from the address multiplex chips to the RAM. Possibly you have further broken traces.

I got the issue with the settings not being stored. I saw a note in the service manual that JS8 should be closed when a battery is connected. I saw a reference picture where the JS8 pads had a closing blob of solder. The pads in mine were so badly corroded that the solder just wouldn’t take hold, so I added a bodge between the capacitor leg and the + terminal of the battery. That did the trick. It’s a good thing the service manual had that note.

Still need to sort out the RAM issue. For that, I’d better print the schematics on paper.

I checked the continuities between the multiplexers and RAM, and the continuities between the octal tranceiver and RAM. Both were okay. I also checked the continuities between the LS373 address latches and the multiplexers all were fine except the line 17 between U6 pin 5 and U45 pin 13.