31 May
1998
31 May
'98
11:55 a.m.
On 29 May 98 at 0:18, Tony Duell wrote:
With the current price of fdds so low, it's hard to justify buying something
that I would rarely use.
Yeah this is pretty well documented in the Atari threads. This isn't true for
all brands however but I've never heard of any voltage conflicts. It's a 4 pin
connecter and I wasn't aware of it also having 12v available on that connecter.
Apparently most fdd brands will work 720 or 1440 but HD is not available
without a modification, I just got unlucky with the one I bought.
It's been a while since I messed with it, but IIRC thats how it was
described.
There was one on the X-circuit and another on the Y side. A voltage stabilizer
would make more sense tho. I figured there was likely a newer substitute I
could use but haven't the electronics savvy to do so. I have a son that works
for a major electronics supply company but he was unable to find one. Likely
they only deal with newer part manufacturers and I didn't pursue it with the
resellers.
lwalker(a)interlog.com
On a related
note, I have 3 Atari STs all with failed fdds. Any tips on
re-alligning these with-out the rather expensive reallign equipment ? Quite a
Depends on what you mean by 'expensive reallign equipment'. You _may be
able to do it with just a 'scope (i.e. you don't need an alignment disk),
but it's not that easy.
What you do is hook up the 'scope (in differential input mode) to the
outputs of the read amplifier (normally TP1 and TP2 or TPA and TPB, but
not always). Read a known-good disk, and move the head slightly. Find 2
points of equal amplitude drop, one on each side of the track, and set
the head midway between them.
It's better to get the right alignment disk, though
while ago I
was able to revive another one by trial and error ,fiddling with
the head placement. More blind luck than skill. I've heard that most 3 1/2 fdds
will work by reversing the P-S connecter and I picked up a 720k Mitsumi to that
Are you sure? Putting 12V where 5V should go is a bad idea, and I wasn't
aware that Atari drives had the connector backwards.
end recently
to no avail. So rather than throwing away more money I would like
to try fixing the ones I have first. I have some test equipment but
unfortunately my old Dumont tube scope died the good death. (impossible to
find neon current limiter). Any suggestions ?
Do you mean neon current limiter? I've heard of neons being used as
voltage stabilisers - in fact it was quite common. If one of those has
failed (which is not common), then you should be able to find one of a
similar voltage, or use a string of zener diodes to replace it.
ciao larry
lwalker(a)interlog.com
-tony