New Zealand Vintage Computer Forums

This machine came to me without a monitor cable. Amazingly I could buy one new over the Internet for $18??? That's right, a genuine new QX-10 monitor cable! Amazing! I was expecting to have to wire one up.

Anyway, I did the big switch on tonight. Fans wirred, drives spun, keyboard lights flashed momentarily. Then on the screen appeared the words "INSERT DISKETTE".

It works!!

I had to take the monitor casing off to adjust the vertical hold but it seems the basic electronics and the screen are AOK.

Now I just need to get a disk image onto a floppy and I can see what state the drives are in. They certainly spin up OK so I'm hopeful.

I'll post progress notes. Might not get around to it for a few days though.

I'm happy!

Ok, I've made some CP/M disks and have ascertained the disk drives work.

That's the good news.

The bad news is after about an hour of use the power started to flicker on and off very quickly and erratically. Some problem in the PSU I think.

So, the machine is now in the queue for a repair project. Oh well, it happens with these old machines. Could be a short just starting, a cap or power transistor starting to go or something as simple as a loose wire?

I would recap it first. Use good quality low ESR caps from the likes of element14, not the cheapies from Jaycar - they'll get a hard life in a switch-mode PSU. You don't have to go silly on the caps, the mid range Panasonic 105deg low ESR ones (can't remember what range) are fine.

http://nz.element14.com/aluminium-electrolytic

If the thing is still running the switching transistor or FET is probably fine, but I wouldn't run it until you've recapped.

Yeah if it's getting unstable get on top of it before something bad happens and waxes the thing.

Glad to see it's gone to a good home

Hmm...this might be trickier than first thought. Rather than duplicate the latest update, if you're interested you can read what I posted on the Vintage Computer Forums here:
http://www.vintage-computer.com/vcforum ... post253839

Now it's a matter of waiting for the replacement part to arrive.

The replacement part seemed to do the job. I haven't tested it extensively but the QX-10 now appears to be working and stable.

I'm happy

Ok, I've now tested this a little more and the original issue is still present. I must have zapped the power switch IC when I was testing the PSU, so I've repaired that but not the original fault. I suspect it's a cap going out of tolerance once fully warm and causing a short. Not an easy thing to diagnose!

Anyway, I've added it to my collection pages even though it's still technically in sick bay.
http://www.classic-computers.org.nz/col ... n-qx10.htm

If you suspect dodgy capacitors you could try getting hold of an ESR meter. We fix quite a few larger LCD monitors at work and come across a few who's capacitors show no physical signs of fault but fail when tested with an ESR meter. I'm looking at building one following this guys schematic; http://ludens.cl/Electron/esr/esr.html You can also find them on EBay at a reasonable or not so reasonable price.