emulatorII-list

Kevin,

Re the 12V rail, I think I will change my statement to "some EII's did not use the power supply 12v rail, but instead connected the disk drive +12V to the power supply +13.2V rail". As you say, some have fans, some don't, and the position of the power supply varied. I don't expect anyone will update the group as to why they went to 13.2v, I pondered at one time that it might have been because +12v was too lightly loaded and unstable, so they tried to find a middle ground; who knows!

From memory, the +13.2 rail also feeds a +12V regulator on both the logic and digital cards, so 1 LM1086 may not be up to the job; I would advise you check the current load.

Because I saw the Zenith 150 as a solution to the EII's woes I purchased the few supplies (NOS, in original boxes) from the surplus electronics store I found them in; PM me if you are interested in one.

Chris

--- In emulatorII-list@yahoogroups.com, "kgslug2"  wrote:
>
> That Zenith PSU is interesting, I haven't seen any other SMPS which allow you to adjust anything other than the main (i.e. 5V) output. Unfortunately it appears to be hard to find and rather expensive - almost as much as I paid for my EII!
> 
> The Meanwell isn't particularly easy to find either and is listed as not recommended for new designs - presumably meaning soon to be discontinued.
> 
> I am now thinking about one of these:
> 
> TRACOPOWER - TXL 060-0533TI
> http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1284184
> 
> I was aware of the +13.2V weirdness and intend to use a LM1086 low dropout linear regulator to deal with this and a second one to give a nice +12V supply to this disks. This will require some changes to the cabling as mine doesn't have the separate wire for +12V. Interestingly, you say that this is a "feature" of later EIIs. Mine is a very early machine with the PSU over the digital board and a Rev 1 output board (serial number 135) and Rev 0 digital board (serial number 273). I guess the PSU and wiring harness may have been replaced at some point. My PSU also has the fan, which doesn't seem to be present on all units.
> 
> Thanks,
> Kevin
> 
> --- In emulatorII-list@yahoogroups.com, "thisoldsynth"  wrote:
> >
> > Note that I went with the Zenith ZPS 150a in Darren's EII as it has adjustable outputs. The "+15v" rail is in fact +13.2V on the EII, and this was the only way I could achieve that. 
> > 
> > Why they did this I do not know, but I do know that it feeds some chips such as the SSM's directly, AND on later units they connected 12V devices such as the disk drives to the 13.2V rail and left the +12V unused, so be careful. 
> > 
> > To fit a Zenith ZPS 150a you have to do some rework on the tray to lower the power supply as much as possible, and fit a whisper quiet fan to keep the heat away from the top panel. You also need to set it up with a dummy load, and of course adapt the cable-form.
> > 
> > Chris
> > 
> > --- In emulatorII-list@yahoogroups.com, dblondin@ wrote:
> > >
> > > Here is the one I have installed. It's a Zenith ZPS 150a. Not quite as
> > > compact as that Meanwell but it does the trick.
> > > 
> > > http://www.dblondin.com/Images/emulator_ps.jpg
> > > 
> > > Darren
> > > 
> > > > 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
> > > >> > >
> > > >> > >
> > > >> >
> > > >>
> > > >
> > > >
> > > >
> > > . The
> > >
> >
>