Various things

From: Mark <mark_k_at_iname.com>
Date: Sat Sep 5 18:27:26 1998

Hi,

A reply to a previous post and some other things...


On Sat, 29 Aug 1998 Tony Duell wrote (Re: MAC ATTACK):
>The normal sets in the UK are of 2 forms - either integral handle/blade
>(just like a normal screwdriver) or a set of 1/4" hex insert bits and a
>handle. In neither case will they fit into a classic Mac, alas. The
>problem with the insert bit type is that the bit holder is too large to
>fit into the Mac.

CPC plc sell a "Macintosh Computer Case Screwdriver" for 1.19 pounds (+VAT).
The order code is TL01544. They also sell a more or less identical one (Ideal
brand) for over 5 pounds.



Repair of switchmode PSU from SyDOS 44e external drive case
-----------------------------------------------------------
I am trying to repair the PSU from an old SyQuest external drive case. The PSU
is made by Skynet, model SNP-9533-2. It has +5V and +12V outputs, both rated at
2A.

The fault is a short between the +5V and ground lines. This showed up as a
twitching of the cooling fan, as the unit repeatedly shut down and started up
again. Thanks to the sci.electronics.repair FAQ, I have found the faulty
component. A schottky rectifier has gone short circuit. There are two identical
rectifiers in parallel. The other one is okay.

So, I need to find a replacement for the broken rectifier, which is marked as
follows:
        31DQ
         04
         3F
According to the data sheet available from www.irf.com, the specs are:
   I Rectangular waveform 3.3A
    F(AV)
   V 40V
    RRM
   I _at_ tp=5us sine 470A
    FSM
   V _at_ 3Apk, T = 25C 0.55V
    F J
   T -40 to 125 C
    J

Will it be okay to use any diode of higher rating than the original? Can anyone
recommend a suitable replacement, or does someone have a spare 31DQ04 diode?



Mac SCSI cable
--------------
I have a Mac SCSI cable, which has 50 way Centronics type connectors on both
ends. On one end there is a small "extension", the body of which is about 2cm
deep. It has a male Centronics connector on one end, female on the other. The
Apple logo is moulded into it, and the Apple part # is 590-0304-A. What is the
purpose of this?

When it is in the SCSI cable, I cannot boot (my non-Apple computer) without
having the external MO drive turned on. Without this thing,it works fine. Maybe
something to do with TERMPWR?



Wangtek tape streamers
----------------------
I was lucky enough to find Wangtek 5525ES and 5150ES SCSI tape streamers the
other week, along with a couple of Adaptec PC SCSI controller cards. One of
these, assuming that they work okay, should finally allow me to read (if not
make use of) my Amiga UNIX tape.

Did the Wangtek streamers normally come with any PC driver software, or is this
not necessary?



Hitachi CD-ROMs
---------------
I have some old external Hitachi CD-ROMs (model CDR-1503S, I think). These have
37-way D connectors on the back, and they came with a couple of 37-way D
cables. It looks like you can daisy-chain two or three of these to one PC.

The Hitachi web site was unhelpful. Does anyone know anything about these? Do
they need a special interface card, or do they plug into the 5.25" drive port
on the back of my PC (which is a 37-way D connector)? Does anyone have suitable
drivers? It would be a shame to get rid of them, since they seem to work; at
least, after powering on I can eject and insert discs.



Sinclair Oxford 300 calculator
------------------------------
I bought one of these the other week. Is this the same Sinclair as produced the
ZX80, ZX81 etc.? A quick description:
Unit is powered by 9V PP3 type battery, has an 8 digit red flourescent display.
A minimal range of scientific funtions; (arc)sin, cos, tan, ln, e^x, square
root and reciprocal. There is a switch on the back to choose between degree and
radian modes. Calculation of (for example) the sine of a number takes about two
seconds. Unless I haven't figured out how to use it properly, the answers it
gives are rather inaccurate; for example:
        square root of 2 = 1.4139192
        e = 2.6108 (obtained by entering 1 and using e^x function)
It may be faulty; repeatedly pressing the 0 button causes the number entered to
be variously 22000000, 22220000 or 20000000. (Though I just tried this again,
and it seems okay now.)


-- Mark
Received on Sat Sep 05 1998 - 18:27:26 BST