7 Nov
2010
7 Nov
'10
1:28 p.m.
On 07/11/10 20:04, Tony Duell wrote:
Huh. This one has a mechanical switch. Maybe the SS drive with the mech
switch is out of a Spectrum +3 or CPC, and the DS drive is out of a
later PCW?
The DS drive shines a light at the disc if memory serves. Black for
"protected" (i.e. tab pushed in), reflected white for "unprotected".
"Hmm."
I'll try and get some scope traces later -- but first I need to find a
USB thumb-drive that's small enough for the DSO to accept...
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
I suspect, and suspected at the time, that you
areperfectly correct :-)
Well as I said, I'm bidding on another set of drives from a 9512.
Hopefully this seller is a bit more honest.
I'll be fishing the drivebelts out of the two drives once I can prove
they're shot, but I'll probably keep them for mechanical spares (read:
spindle motor).
Before we get another flamewar, I will point out that
just about every
seller I've dealt with at radio rallies has been extremely honest. If
something doesn't work, they say so. If it's missing important parts,
they say that too.
I can say the same -- I've yet to meet a dishonest seller at a radio
rally. A few traders have an over-inflated idea of the value of their
stock, but you see that *everywhere*...
I've met plenty of sellers who are happy to let
you remove covers and
have a look inside.
Seen that, too.
"Interested in that, sir? It won't power up, but it's full of mixers,
filters and other bits. Bound to be something good in there -- just let
me get my screwdriver and I'll show you!"
And I rememebr a chap with a box of assorted valves
who provided a multimeter so you could at least check if the heater was
OK.
One of these days I'm going to have to buy a couple of triodes to play
around with... "valve amplifier" is on the long-term projects list, as
is "fix that X-Y display you got half way through building". I was going
to build a few front-ends for that -- NBTV, CVBS, variable amplitude X-Y
and maybe an FPGA version of Asteroids and Battlezone.
Unfortunately I had issues with noise -- the trace on the DG7/32 shook
like a jelly in an earthquake.
Indeed.
I've got a lead on a pair of double-sided drives from a PCW9512.
They're basically the same drive design, but without the write protect
sense pin (optical sensing!), a white front panel and a slightly
different mounting cage.
Odd that the schematics in the PCW8256 manaul show an optical write
protect sensor (look at the circuitry connected to pin 42 of the ASIC). Ah, my multimeter lives on the workbench.
I haven't got a workbench, but I've appropriated the kitchen table for
DiscFerret manufacturing :)
Though it's currently taking me a day to make and debug each DF. I
really, *really* need to get that down a bit. "Solder paste stencils"
and "a tub of solder paste" are on the shopping list...
At the moment, it's a horrible
analogue thi9ng becuase I still can't find a digitial meter that I like
the look of. If I wanted a bench instrument, it would be easy (although
paying for it wouldn't be..), but a nice handheld one doesn't seem to exist.
Seems you can get a cheap junky DMM or an expensive, all singing all
dancing DMM. There doesn't seem to be much in the middle these days.
It's as if
the ASIC were oscillating internally...
It may well do this. There's probablhy an AGC circuit that cranks up the
gain if there's no signal from the head.
I asusme the head windings are continuous, and that the heads are
actually touching the disk...
But that head CT signal sounds totally wrong.