PC Archeology: The plasma screen is probably the best thing about Schneider PC 7640

Hi Adrian, I'm not a power supply engineer, per se, but an electronics engineer with 80's era switch mode power supply design experience. There are two potential issues I can think of when running switching supplies below their rated voltage. One is that, switch-mode supplies are "constant power" devices, so they will draw more current as input voltage is lowered. That could overheat input circuit components or blow a fuse, if running well below rating. The second issue is that these supplies typically regulate output voltage by adjusting pulse width to a step-down transformer. Lower input voltage causes the pulse-width to increase, thus increasing the peak magnetic field strength in the transformer core. There is a maximum pulse-width, which will cause the transformer core to saturate. Saturation causes the primary's impedance to drop rapidly (essentially, becoming a wire), which would then drastically increases current flow. If a current limiting measure is not implemented, this could damage components. This saturation effect would also happen if supply output is shorted. I bet that any PC power supply would have active over-current / under-voltage protection, beyond just a fuse, but can't guarantee. Keep up the amazing work!

1:02:06 "I don't think I'm gonna film that, because there's gonna be a lot of cursing..." Adrian, you are a gem! 😂

Hi Adrian, Berend here. Thanks for another great episode and happy we could contribute by donating this machine. Don’t feel bad about mispronouncing my name. Almost every American I met didn’t get it right the first time, so I am impressed you got it right at the end of the video.

'Velcro' is a portmanteau of two french words 'velours' (velvet) and 'crochet' (hook) named by the inventor.

I used a Toshiba 5100 back in the early/mid 90’s. It was a 386 but still had the orange plasma display. I worked for the railways in Sydney Australia and we wanted a PC for field work but the government procurement regulations at the time banned the purchase of laptops. To get around this problem, we got the supplier to sell us two units with bundled hardware modules and they listed them as protocol analysers. They were very capable machines in their day and were used a great deal by me and my team into the 2000’s.

The thing I hate even more than the complexity of working on laptops, is the amount of plastic clips and thin plastic brackets that are often used. Over time the plastic becomes quite brittle because of the heat and age. I always end up breaking something, then have additional work to fix that. Thank you so much for this video Adrian.

The floppy issue is probably due to the original using the READY signalling on Pin 34 rather than the IBM-PC DSKCHG signalling. READY will go low when a disk is in the drive so the system wouldn't be able to tell that the floppy is in the drive so never try to read with the PC drive in there.

I love the Adrian's Digital Basement QC Sticker. It gives me more guarantee and security to trust that floppy drive than if I had bought it new.

Hi Adrian, in The Netherlands we use the US International keyboard layout. There are keyboards with a Dutch layout, but we use it very rarely. I've seen it once in production 25 years ago.

Holding the disk platter in hand ... "Well that escalated quickly"

Love seeing Dave's lovely multimeter. Forget the expensive Fluke, Dave's meters are amazing.

Great video - it demonstrates that electronic repair on vintage equipment can sometimes be a challenge. I'm glad that plasma screens had a relatively short life-span.

I remember the Toshiba (T3100) plasmas being much brighter than any of the early LCDs that were available, and it was waaaaay waaaaay better to type on. If you were using it for business, the plasma screen offered a way to type a document or something in a hotel room that was quite a reasonable experience. I do think they have dimmed over time

I love the long videos. 💚

This is precisely why I appreciate the GRiDCASE 1500 series so damned much. They crammed top notch displays, into a portable form factor that could take a beating.

I know you said this was an unplanned deep repair… but this is the content I’ve been craving recently. I appreciate your commitment and followthrough. Thanks for all you do! I truly appreciate your information dense videos and soothing voice. I’ll totally be patronizing soon.

230V - 50Hz (used to be 220V too) also here in Greece single phase for homes but if you measure it you will see great fluctuasion from even under 190 to 250V which is really bad overall for electronics so a stabilizer is very useful especially under thunderstorms... We had a lot of Schneider PCs here and even if I respect Japan's products many times their companies design them in a really bad way for expandability-upgradeability and fill them with proprietary connectors and stuff which is really a shame and puts aside the great build quality of them. Great long video as always Adrian, keep up, JIm.

Most modern power supplies support multiple input voltages because they contain as first stage a power factor correction circuit that is implemented as a step-up converter and boosts the voltage to around 450 Volts internally regardless of the input voltage. Power factor correction is mandated by EU law for all consumer devices above 70 Wats. Since most consumer products are made to confirm to world-wide standards, they come with power factor correction and therefore support multiple input voltages as a freebee.

Hi from Germany :-) Love your videos. Everytime i'm very impressed from your work.

Excellent job as usual and very informative. TY Adrian for all that you do for us!