6 Nov
2010
6 Nov
'10
1:03 p.m.
On 05/11/10 22:53, Tony Duell wrote:
As it happens, yes. The scheamtics of at least the single-head drive
appear in other Amstrad service manuals too.
I have scheamtics that might be related. The main
ASIC seems to be an
M51017Ap in both cases.
Yep. I think I might have the same schematics. Amstrad PCW 8256/8512
Service Manual? I an't see why it would do that. According to
the schematic, the LED is
driven by pin 44 of the ASIC, have you stuck a 'scope o nther to see if
the half-brightness is actually a square wave?
Not yet, no. If getting the power lines backwads does do
damage, is it psosigle that
the otehr drive was damaged before you got it?
I'd go with "probable". They were sold to me as "spares or repair, no
idea if they even work." I haven't checked the centre tap. I've just
found a test/adjustment
procedure in the Amstrad manual which suggests that the ASIC tries to
float the head in relation to ground, but that the absolute voltage over
the head is zero unless it's in use. That might explain the strange
measurements.
The scehamtic of the double-head drive gives the pin votlages for the
ASIC. It owuld appear those are the votlages you'd get if the drive is
powered, but not conencted to a controller (all inputs pulled high). May
be worth checking the ones around the read section.
Anything on TP1,2 on the drive PCB? Those are the
differential outputs of
the read amplifier, used for head alignment.
Nope, nothing on either. - Heads. Dirty, out of alignment or otherwise
completely pooched.
Well, clean the heads!. Check the DC resistance (should be very low
between the 4 wires going
to a head).
On the to-do list (it's a bit late to be getting out the DMM at this
time of day!) Good point.
Do you have
the schemciats?
I have the PCW8256/8512 service manual, the 8256-only service manual and
the 9512 service manual as PDFs, which include the drive schematics.