Testing my midi thru box prototype pcb, for my 'midi module tower'.

Spent some time with my DOS project, trying to find a packet DOS driver for the build in Realtek 8168, without any luck.

dreamblaster wrote on 2021-08-14, 08:56:

Testing my midi thru box prototype pcb, for my 'midi module tower'.

Looks nice - what are the big indents in the PCB for since they don't match up with the box's screw posts?

This evening I've been taking a laptop's keyboard apart - on Thursday I got an NEC Versa S/33 laptop delivered and although it fired right up, the bios battery was dead and it was impossible to set any settings. External keyboard doesn't work for some reason and the laptop's Enter key wasn't working along with a bunch of other keys. So it couldn't save its BIOS settings or have the hard drive settings configured. It's got a coin cell fitted in place of the dead 3.6v lithium cell it had (not rechargeable afaik) and the electrolyte leak from the nimh bridge battery is all cleaned up.
Initially I thought I'd broken it after doing the cleanup, but it turned out that I should not have removed the weird looking TSOP chip from its oddly removable clip. That was actually the BIOS, and the plastics of the clip degraded to the point where it can't go back together, so now it's got a soldered BIOS eeprom instead of that clip socket.
Then the inverter shorted and nearly burned a hole through one of the fpc cables - thankfully that still works too.

Since there are *no parts* for this little laptop from 1994 (?), I decided to go ahead with pulling apart the keyboard. I've never taken apart a laptop's membrane keyboard before. Tracing the bad key trace and checking with the multimeter, finally found one darkened / corroded trace that passed all of the bad keys and was breaking the link:

Repaired with some copper 'slug tape' and my 20 year old conductive paint:

Then heat staked back together:

and now the laptop can auto detect its hard drive, it booted straight up into Windows 3.1 😁

Thermalwrong wrote on 2021-08-14, 13:00:

dreamblaster wrote on 2021-08-14, 08:56:

Testing my midi thru box prototype pcb, for my 'midi module tower'.

Looks nice - what are the big indents in the PCB for since they don't match up with the box's screw posts?

They originated indeed as cutouts for the box screw post.
I shrunk the pcb, but kept these, now unnecessary, ornaments..
At least in this first revision 😀

ah that makes sense 😀

Just opened up the NEC laptop's battery, I wonder if this is how it came from the factory?

PC Hoarder Patrol wrote on 2021-08-14, 08:48:

Tested, cleaned and retrobrighted a box of old (1995 - 2001) beige cd drives / writers I got the other week. Not a bad haul in the end as there was only one failure out of 9 so I ended up with 5 ATAPI (4 drives + 1 writer) and 3 SCSI (2 drives + 1 writer). Funnily enough the failure is my 2nd of this exact model in recent times - a Creative (Goldstar OEM), and dead as a doornail just like the other.

bad cd.jpg

Looks good ! To bad is it dead 🙁 Seems some of the early IDE cdroms were not built as well as the scsi ones of same speed.

Spent last night digging for old docs and drivers for some early 1990's controller cards, had some success with a few of them.

Before and after😉
The ikea pax series are good if you want to store your retro stuff....way better organized and more space.

I booted up my Packard Bell 486DX2 system for the first time since I got it from eBay. It had a failed power supply, and a failed and leaking CMOS battery. Got those replaced, it booted to BIOS setup with no issue, I was able to configure all my drives and it booted right to Windows 3.1. No games on the hard drive but lots of old productivity software, Quickbooks, Quicken, some Corel database and graphics software.

Did a test retrobrite treatment on the mouse, it seemed to work out well.

Even the floppy drive still works! Didn’t think it would based on the amount of dust I cleaned out of it.

Now will work on upgrading to MS-DOS 6.22 and WFW 3.11 getting a network card in it.

My wife who’s generally uninterested in my computer and ham radio stuff was just as excited as I was to see Windows 3.1 again, checking out solitaire and MS Works.

I finally decided to assemble the P II machine I'm planning for over a year now. I got a case recently which looked decent. It's supposed to be a Yeong Yang YY-5250. A little dirty, but nothing a shower can't help.

The case is spacious and the easy to deal with. The motherboard tray slides out through the back. The finish is a little rough, I've cut my middle finger during cleaning. But it seems the power button wire has been cut off. Whatever, I can use the reset button for the time being. The real problem is, that the 5.25" drives mounts with a proprietary drive mount which screws in from the front and I don't have it. Whatever, let's proceed without mounting the CD drive... And I can't find the Sound Blaster 16 I was planning on using for this. I must have misplaced it during moving.

At the end I decided this is not the right day for the job.

Nexxen wrote on 2021-08-14, 08:30:

I'm saving this.
Thanks for the advice!
It's impressive how it coats everything, everywhere.

Glad to help! While I'm at it, remember to take the paper towels out to the trash outside when done, don't leave them in your trash can. 😀

I have not had anything yet damaged by the bleach, but watch out for paper labels.

As I mentioned, my janky 2-pin external PSU works, I had 3 of the POS systems running, now all 6. 4 Windows 10, one windows 7, and one Android 4.3.

Took a while to get out of the custom app on Android, but managed it using a USB keyboard, created a new user, but it's a pretty crippled version of Jelly Bean. Now I have to figure out how to access it from the console or dev app and try to get a couple of apps in there to unlock some features so I can rewrite the OS with a full version with on-screen navs, since there's only a power button. I did get on WiFi, however.

I wouldn't have got that far if the custom app password hadn't been "1234".

Now they will all be set aside as I continue the Wall Of Computing project and try to get more cases up, and more motherboards sorted on the shelf, and more sorted for removal, in one way or another.

No idea when, but There Will Be Giveaways. I have a lot of OEM sound cards and video cards, for example.

Luvly 20km ride over hill and down dale on one of my motorbicycles.

Life is great......

Thermalwrong wrote on 2021-08-14, 16:30:

ah that makes sense 😀

Just opened up the NEC laptop's battery, I wonder if this is how it came from the factory?

Wow that's one hell of a recell job there.

Woke up.

I think.......

Weekends are the best days for retro computer activity. 😀

Intel486dx33 wrote on 2021-08-15, 21:37:

Weekends are the best days for retro computer activity. 😀

It is Monday you silly fellow.....

Well nearly midday Monday.

I didn't just have one laptop that had a bad keyboard. I bought a Toshiba Tecra 730CDT recently to get hold of a Toshiba DeskStation V - both were horribly rusted and corroded, but both mostly work.

The dock likes powering off after a few minutes of use, I'm still wondering where to start diagnostics, could it be heat since the fan by the PSU doesn't appear to be doing anything, or maybe capacitors somewhere, either on the board or hte integrated power supply?
I've so far dismantled it, put it back together and removed the pins in the dock's lock so it can be put between regular and emergency eject mode without a key.

The Tecra 730CDT was so badly corroded that I had to fully dismantle it and carefully remove the electrolyte corrosion from the magnesium frame. It's been working but the keyboard's Up key and maybe some others weren't working. A replacement keyboard would cost £30 and I'm not interested in paying that, especially having fixed one keyboard, so I've worked to fix this one too.

These '90s laptops have nice big keyboard frames that use plastic stakes (sometimes screws) to hold in the membrane to the keyboard's backplate.
I pulled the keyboard apart, this time using the soldering iron at 200C on each of these pegs so that they could deform without breaking, for later use.
Took apart the keyboard and started following the traces on both sides but doing it just by eye is more work than it's worth. I taped it to the desk to get it flat then took a picture of both sides and drew a layer over the top with lines to visualise it. Nothing wrong with the bottom side:

The topside is much more complex to follow - notice those little black traces connecting each pad, each one is about a 10k resistor. Following it, the discolouration was visible from my picture, one of the top traces at the upper edge of the keyboard has discoloured and the connection has gone from 20 ohms to 60k ohms:

I tried using the conductive paint again, but it didn't do much good. I found a better way this time - the self adhesive copper tape is sticky on one side and conductive on the other. Stick the conductive tape over the part that needs replacing and a few mm longer, fold over the ends so the conductive side is touching the membrane trace at each end. That bridges the connection and provides a trace that's held in place, but maybe a fresh conductive ink pen would be better.

Then put Kapton / polyamide tape over the top which keeps it connected. Then I put some extra Kapton tape over the copper just in case it could short on anything.

Tested it one last time and the up key now works, no random key presses so it's all melted back together, again using the soldering iron to press on them but with a bigger round tip to squish it nicely:

Yay! now the Tecra 730CDT is back to 100% working. I've got quite a full set now - Tecra 730CDT, Tecra 740CDT and Tecra 750CDT 😁

How do you repair a keyboard when is the flex cable the one which got broken (in your case the green flex portion which goes to the mobo)? These get broken with age when the manufacturer didn't a good job accomodating them.

I haven't done significant repairs on those yet 😀 I have got a couple of keyboards working by cutting off maybe 1mm of the end of the connector where those were frayed or damaged beyond conducting well.

Beyond that, since it would need to be multiple traces it'd be hard to do by hand, I was thinking maybe a vinyl cutter could work. Or you could get a regular FPC cable if it's a standard width / pin count and bond that together with the broken keyboard cable end. That would be very tough if the cable zig-zags around though.

hyoenmadan wrote on 2021-08-16, 00:03:

How do you repair a keyboard when is the flex cable the one which got broken (in your case the green flex portion which goes to the mobo)? These get broken with age when the manufacturer didn't a good job accomodating them.

So one way is to stick a bit of thin plastic to the backside as a splint, and if the contact side is covered by a laquer, scratch that off eitehr side of the break, and paint across with conducting paint, defogger repair paint or similar. You may need to mask one line at a time with tape if it's fiddly and wait until paint is very hard dry each line before taping over it. Then when you are done, tape over the top to protect.