Epson PF10 problems

Tony Duell ard at p850ug1.demon.co.uk
Tue Dec 27 07:20:46 CST 2005


> 
> On Monday 26 December 2005 05:01 pm, Tony Duell wrote:
> > > > > The roms in mine seem to be hand-labeled too,  I think there are
> > > > > three
> > > >
> > > > Are you talking about a PX4 or a PX8?
> > >
> > > A PX8.
> >
> > Actually, the ROMs in my PX8 have no labels at all. They have Epson part
> > numbers stamped on the package, but nothing to easily identify them as
> > the utilities and BASIC roms.
> 
> I don't think this one has BASIC in it.  There are eproms,  Portable WordStar, 

Probably not if you have wordstar. There are only 2 EPROM sockets, BASIC 
fills an EPEOM, I think wordstar would as well. 

The EPROM you really need is the utilities one. Without it, you don't 
have PIP, and therefore no way to copy files.

> and I forget what else (I'll know when I find it by looking at the labels :-)
> 
> > [PX8 wedge]
> >
> > > Yes,  there's that modem,  and I forget what else.  I'd grab it and have
> > > a look but don't recall just where it is at the moment.
> >
> > FWIW, that techncial manual I mentioned includes schematics for some of
> > the add-ons. Note that the RAMdisks are rather complicated, they have
> > their own Z80 processor and a memory control gate array
> > (similar/identical to the one in the PX8 I think).
> 
> Their own z80?  Hm.  I did download that stuff,  all of it,  but haven't read 

Yes, the RAMdisk units contain a Z80, a litle EPROM/ROM, and communicate 
with the main PX8 via a couple of I/O ports. The RAMdisk is really a 
second dedicated computer.

> it yet.  And a few other things besides.  There's a pile of interesting stuff 
> on that site...
> 
> > Digging in my junk box (again), I found the Epson accostic modem that was
> > sold for these machines. It's just a plain 300 baud unit with an RS232
> > interface, but it's nice to have the 'right' peripherals.
> 
> I can't recall what other jacks there were on the back of that unit,  just 
> that there were a bunch of them...

>From memory, a PX8 has the following connectors : 

A coaxial power connector for the charger

An 8 pin mini-DIN 'serial' port for the disk drives. It can also be used 
for a printer, but only at a cery limited selection of baud rates. It is, 
at least, at RS232 levels. Only 5 pins are wired (ground, TxD, RxD, 
handshake out, handshake in, the latter being on the pins used on the 
RS232 poer for DTR and DSR).

An 8 pin mini-DIN 'RS232' port  All pins usedm you get the normal 
hardware handshake lines.

A 3.5mm stereo jack socket (like a 'walkman' headphone socket) 'BCD' 
port. This is for a BarCoDe reader, the connections being ground, signal 
and +5V power out from the PX8. From what I can see the signal goes both 
to one channel of the ADC chip and to a pin on one of the gate arrays 
which contains logic to measure the time between transitions of the 
signal. Note there's no barcode software in the BIOS ROM

Another 3.5mm jack socket 'ADC In'. This is an analogue input to another 
channel of the ADC chip, the other connecitons being ground and a 
TTL-level trigger signal

A 3.5mm mono jack socket 'SP out' for an external loudspeaker.

A 50 pin header 'System Bus' which is essentially the unbuffered Z80 bus 
lines.

> > You can turn it off with the little switch inside the main batter
> > compartment. The machine should run from the main battery (or a 5V PSU
> > connected in place of the main battey) if there are no otehr problems.
> 
> To the battery connector?  Ok...

Connect a _reguylated 5V PSU_ (nothing else)  to the battery connector 
inside. I mentioned where to get the sockets in an earlier message, you 
can get the polarity from the technical manual or by examining the NiCd 
pack. 

I will emphasise this again because it's important. There is no regulator 
circuit between the battery and the standby supply line (maintains RAM, 
real time clock, etc when the machine is turned off) or, indeed the main 
logic supply line. Do not connect an unregulated supply here, you will 
wipe out chips throughoug the machine.


> > Do remember there are no regulators in the PX8 PSU. The power supply must
> > be close to 5V (4.8V is OK), not a random unregulated one. You may well
> > do a lot of damage with the latter.
> 
> Are you talking about going right into the battery input connector?  Or to the 
> charger input on the rear of the machine?  The "power supply" I use with it 
> is a wall wart,  I don't recall what it's rated at,  but it's labeled with 
> that dymo tape stuff as being for that machine,  came with it when I got it.

The wall-wart is an unregulated thing. Claimed to be 6V 600mA on the 
label (and in the manual), in reality it's nearer 12V off-load. This 
charges the main battery, and the machine depends on the fact that the 
the battery will clamp the voltage to 4.8V or so to limit the voltage on 
the logic supply lines. Do not, I repeat, use that PSU in place of the 
battery, do not, in fact, plug it in without as good battery in place 
(there is a proteciton zener diode, but I don't trust it!)>

I run mine from a regulated electornic workbench supply connected in 
place of the battery (and set between 4.8V and 5V). I would think the 5V 
supply from another computer would be OK (e.g. an old PC power supply), 
but I've not tried it, so don't blame me if you kill all the ICs in the 
PX8...

-tony



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