emulatorII-list

An update, rather later than planned.

Over the last month or so I have been trying (and failing) to get the EII to boot. After connecting it to my HxC I was able to run the RAM diagnostic disk image and found a couple of supposedly dead RAM chips. Swapping these solved that problem, but it still wouldn't boot. A couple of days ago, my rebuilt PSU decided to start making a very loud wine, which I suspect is caused by the feedback circuit oscillating, so despite the fact that I have replaced all of the caps, power resistors and transistors, there is still a fault somewhere.

All PSU rails check OK with a multimeter, but I don't have a scope (one of those things that I keep meaning to buy) to check for ripple. If the feedback circuit is indeed oscillating, I imagine it would cause a fair bit of this!

I think it is time to give up on the PSU and look for a modern replacement. There has been a discussion on the EIII forum about this, including a link to this page: http://www.synther.org/emulator2.html. The PSU looks like a Meanwell T-60C, providing 5, 15 and -15 volts at 5, 2 and 0.5 amps respectively. Has anyone used one of these?

In the mean time, I decided to have a play with an ATX PSU – and it boots! I haven't done any further testing with this as the keyboard is currently dismantled, but it seems to prove my bad PSU theory.

Kevin


--- In emulatorII-list@yahoogroups.com, "kgslug2"  wrote:
>
> Thanks Nigel,
> 
> I'll have another play with the memory chips tomorrow. I have an HXC in my EPS16, so I'll borrow that and make up a cable to use it with the EII and give the memory test disk a try.
> 
> Kevin
> 
> --- In emulatorII-list@yahoogroups.com, Nigel Cruickshank  wrote:
> >
> > Kevin,
> > 
> > The first row of 8 memory chips on the main board (at the right side closest to the keyboard) are the ones that load the boot sequence.  Swap these 8 out for another row – the third or forth row – and see if this makes a difference.
> > 
> > My EII was hanging on boot and after swapping a row out I had a fully operational EII.  After that I ran the memory test disk (from my HXC) and located the faulty chips and replaced them.  It was a slow process but eventually I got them all and now the memory test passes without fault.
> > 
> > Let me know if this helps,
> > Nigel
> > 
> > 
> > On 12/12/2012, at 9:44 AM, kgslug2 wrote:
> > 
> > > Having fixed the PSU and the short on the output board, I was rather hoping to have a working EII. Unfortunately this was a somewhat optimistic assumption!
> > > 
> > > On power up, the LCD reads "**Emulator 2** Boot in progress", followed a few second later by "Insert Diskette". Inserting a disk gives "Software Rev 3.1", followed by "This will take a while". The disk drive clicks for about 30 seconds, but booting never finishes. It either freezes at "This will take a while" or seemingly reboots and reverts to "**Emulator 2** Boot in progress", repeating the whole process until I switch it off.
> > > 
> > > I have about 50 disks and have tried maybe 20. I have also tried both drives, with the same results. Suspecting it could be a RAM problem, I swapped the ICs from the memory upgrade board to the digital board, again with no change in the outcome. Any ideas?
> > > 
> > > Kevin
> > > 
> > >
> >
>