Plastic wrote, on 8/Feb/11 22:30 | Feb8:
Hi all,
During my time at Sandy, I learned microdrives (the part inside the case,
not the cartridge) were surprisingly reliable and fault-free. The only two
faults that came up on a regular basis were dirt, and damaged capstans.
The capstan, for those not in the know) is the rubber wheel on the motor
which contacts the tape. The microdrive capstan has one advantage over
capstans from tape decks. Tape deck capstans contact a metal pin when in
position. If left for a long time, the capstan rubber acquires a "dent"
which makes the tape change speed as it passed through - also, it slightly
stretches the tape. The microdrive design contacts a plastic wheel in the
cartridge, so it only touches something when a cartridge is left in.
However, some people leave a cartridge permanently in the drive when not in
use, and this can cause problems eventually.
I found a large number of QLs I repaired had migrating capstans. They
had nothing other than friction to hold them onto the metal shaft, and
they rose up in the majority. Maybe the ones that didn't had unused
microdrives! In extreme cases the capstan actually touched the top case
- I saw many like this.
The wires that enter the motherboard are just tinned stranded wire and quite
fragile. I always soldered pins on these as a first act of owning a QL -
often, soldering on the pins was quicker than trying to fit that floppy mess
of bent wire. I have tons of these pins so if anyone wants some for their
QL, I'll happily mail them at no charge.
If I had to remove microdrives, I always did this. Better than pins
though is a SIL socket strip. I cut sections off a DIL turned pin
socket. That way re-fitting is a doddle.
At Sandy, we also found that cartridges would become error prone if not spun
once in a while. I got into the practice of, once a month or two, spinning
up every cartridge through at least one full loop (about 20-30 seconds) just
to prevent print-through and to redistribute the lubricant.
You'd be amazed how often we'd get "mad microdrive" complaints and we'd ask
them to send in the computer and the problem cartridges, and they'd ALWAYS
have fingerprints, or the computer smelled of cigarettes. Smoking kills
cartridges! So does finger grease.
If you pen your case to clean anything,
.... or even 'open'. You are coming up with some brilliant mistypes,
Dave. Wasn't it you who talked about 'dinky cars'?
it's always a good idea to remove
and refit the voltage regulator. That's the small 3-pin device screwed to
the heatsink right behind the microdrives. It gets warm regulating the
voltage, but a poor connection can also create heat, so reseating the
regulator in its socket helps it stay cool. While you're at it, if you have
any PC thermal paste/crease/
.... and another good mistype (8-)#
arctic silver, replace that little plastic shim,
if there is one, with a tiny dab of that and you'll find it transfers heat
to the heatsink FAR better.
Yes indeed. I did that to *every* QL I repaired.
SOME people would get a tiny fan, hook it across
the +9v and ground pins, and have it draw that air out the slots at the
back. Nice if you can make it fit, but I don't think it makes much
difference - it moves heat, but doesn't make sure it's being generated
efficiently in the first place - just addresses the symptom.
If I ever designed a QL PCB, it would have a far better power supply (but
then, the PCB wouldn't be long and thin like that - it would be a eurocard
or double eurocard - 100x160mm or so. I would also give it a proper bus with
4 or 5 expansion sockets. Hindsight.
... and not require the wire connection 5v rail mod that Sinclair added
to issue 5 boards!
I know this is obvious to many, but not to all, so my apologies to those who
consider this obvious.
Always worth repeating good advice. You will be amazed at how many
still don't know.
Tony
--
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