Having openly disagreed with you a number of times, I have to say the position
you take, this time certainly, but actually most of the time is indicative of
style. We don't all have the same appreciation for this, and, I, for one, would
take a different position on the swap of CRT versus monitor chassis. I've had
several DEC monitors of the same model number, only to find not only that the
CRT's weren't interchangeable, but that they were entirely different
manufacture, some Italian, some Korean, some Japanese, yet still carrying the
identical part number. I doubt the DEC's the only one in this position.
Since that's not what I'm gett at at the moment, however, I'd say that you,
Tony, shouldn't take these matters quite so personally. I got jammed a while
back because I was looking for folks who actually used a complete Altair setup
as a computer.
Clearly, the folks who dominated that discussion viewed the Altair, as I now do,
as a toy, really designed and suitable only for mental-masturbation. I did find
one list member, however, who had a picture on his web site of a complete Altair
system, with CPU, FDD, HDD, and HDC boxes all integrated in a somewhat
clumsy-looking desk enclosure. Having now read what's been written, reviewed
the ad's, and considered the information in them, I have to agree, the MITS
Business System, though capable of considerable computing power, was, like
Jurassic Park, result of doing what COULD be done, with no consideration for
whether it SHOULD.
I didn't see anyting that resembled a flame directed at you, Tony, but there are
folks who see things quite differently than you, and I'd be the last to try to
guess who's right and who's wrong, or, for that matter, whether either is the
case. Were I in your position, I'd tell folks how I'd approach the problem,
maybe explaining my underlying reasoning, and leave it at that. If somebody
doesn't like what's been said, ... Tough!
What you offer is useful because it's useable. If someone else doesn't use it,
that's their choice. If they don't see that, it's not your fault.
Dick
----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, June 25, 2001 2:26 PM
Subject: Re: Good Samaritan Rule?
> >
> > There is nothing quite like thinking you are doing "a
> > good thing" and being criticized for the "way" you are
> > doing it. There's something inherently offensive about
> > it. That's why so many states have passed so-called
>
> If this is aimed at me, and I think it most certainly, is, then you might
> say so...
>
> There's something that I find offensive too. And that is being flamed for
> offering what I consider to be correct advice. Please remember that I
> give my time, knowledge, and experience freely. If people here don't want
> such advice, then tell me and I will leave. I've thought about leaving
> several times due to being flamed for things like this. And I can assure
> you that _I_ will not be the loser....
>
>
> > "good Samaritan" laws, which prevent lawsuits such as
> > malpractice actions against doctors who stop and give
> > aid to accident victims.
> >
> > Do the same rules apply to collecting and attempting to
> > fix computer equipment?
>
> Oh, for %deity's sake. Nobody is going to sue anybody, surely.
>
>
> > Today I posted some questions regarding an IBM S/23 I
> > am trying to get working (VCF 5.0 is coming up fast).
> > The 5322 unit I saved from a dumpster and found that
> > the display was badly burned and feeble. A year and a
> > half later I found someone who had a number of 5324
> > displays that he was going to pitch. I paid to have
> > one of the displays shipped from St. Loius to L.A., so
> > I could swap them. I suspected that this would work
> > because the IBM part nos. for the internal display unit
> > were identical. Today I swapped the displays, and it
> > was mostly a success. But, I think I've offended some
>
>
> OK, let me make a few points.
>
> You started by asking for methods for undoing stuck screws. I provided a
> number of such methods that have worked for me in the past (note : I have
> never needed to use a hammer or similar tool to dismantle _any_ part of a
> classic computer, but I digress). I also suggested that there might be an
> alternative method to do what you wanted to do (namely to remove the
> parts from the monitor chassis). I have learnt many times over that if
> somebody is asking how to do something, it's best to find out what the
> _real_ problem is as there may be an alternative solution that's easier,
> better, or whatever. I know some people don't like being told they're
> going about it the wrong way, but....
>
> Also, you now say that the 2 monitor chassis assemblies have the same
> part number. In this case, I think it's safe to assume they _are_
> compatible (in fact they might well be identical). So the height problem
> is certainly not an incompatability. It's most likely a fault.
>
> In the circumstances, the first thing to try when the height is too low
> is, most liklely, a tweak of the height control. To be honest, I'd
> probably have tried that too (knowing that a height controller, as
> opposed, say, to a disk controller PLL adjustment, is easy to set
> correctly). But when you find that you can't get enough height out of the
> monitor that way, then the next thing to do is not to look for more
> adjustments, but to look for the fault.
>
> The fact that the height control was sealed with silicone rubber should
> have indicated that most likely this is not a common field adjustment. In
> other words you should be able to drop any monitor chassis in place of
> any other without having to adjust things -- they would have come
> correctly set up from the factory. In which case the lack of height would
> suggest a component fault.
>
> Now, as to what I would have done differently, had it been my machine....
>
> My first thought would have been to swap the CRT only. Not the entire
> monitor. For at least 2 reasons it's a good idea to replace as small a
> part as possible.
>
> Those 2 reasons are :
>
> 1) Historical accuracy -- keep as much of the machine original as
> possible. There may have been changes in design that happened during the
> production life of the machine (I know plenty of examples where this did
> happen). You don't want to confuse people by having the 'wrong' parts fitted.
>
> 2) Lack of incompatibilites. Often seemingly identical subassemblies can
> have subtle differences. I've been caught with this too often. I prefer
> to keep with parts that I _know_ have once worked together and therefore
> can be made to work together again.
>
> My second thought would be to look for faults when tweaking an adjustment
> doesn't have the desired effect.
>
> IMHO classic computers are repaired by very different procedures now to
> how they were repaired when in current production. For one thing, there's
> no source now of known-good FRUs for most classic computers. Even
> New-In-Box parts can have failed in storage. Therefore, it's necessary to
> do a lot more tests and a lot less module-swapping. But since this is a
> hobby for most of us, we don't count the time we spend looking for the
> fault. The time doesn't matter, the cost of parts might. It's cheaper to
> replace a small component rather than an FRU, too.
>
> For this reason I often ignore much of what is printed in the official
> service manual for a classic computer. I will make use of the 'reference
> data' -- the schematics, pinouts, voltage charts, waveforms, source
> listings and so on. But I almost always ignore the fault-finding charts.
> I work from the schematics, making measurements, checking waveforms, and
> figuring out what is really going on.
>
>
> > of you because I have, in effect, performed surgery
> > with a sledgehammer. Yet, this is the best I can do.
>
> There is an attidude here that I find hard to accept.
>
> I have no problem with the fact that you are probably relatively
> inexperienced in fixing monitors (or analogue stuff, or...). Everybody
> has to start out somewhere. I can remember making a lot of mistakes when
> I was starting out.
>
> The thing is, I was prepared to learn from my mistakes, from my problems,
> and so on. I don't consider that learning should stop just when you leave
> school (or university, or...). I want to stop learning the day that I
> die, and not before.
>
> There are many things (related to computers, electronics, engineering) I
> don't know. And many things I've learnt due to working with classic
> computers. My attidude if I come up against something that I don't know
> (like 'How does the vertical deflection system of a monitor work', or
> 'How do I write a device driver') is to go away and learn about it. Read
> books, experiment, ask questions, etc. And then I have got a solution if
> I ever come against the same problem in the future.
>
> Repairing and using classic computers is a hobby for most of us here. A
> hobby is something we do because we want to do it, it's fun. This doesn't
> mean that everything I do related to classic computers has to be
> enjoyable. But equally, if I found that everything was unenjoyable then
> I'd find some other hobby. But I consider learning to be an integral part
> of this hobby.
>
> OK, so you have a monitor that's not working right, how do you learn
> about it?
>
> Well, I am going to assume that the manufacturer never provided a
> schematic or component level repair manual.
>
> But a mono monitor is like the last few stages of a monochrome TV. So we
> look at books on repairing TVs. (There's a good reason why I have 30 years
> of tha annual 'Radio and Television Servicing' books on the shelf). We
> look at circuit diagrams for TVs. We look at the monitor and try to
> identify the main components -- at least the ICs. If the numbers are
> unreadable, then we trace enough pins to make a sensible guess as to what
> the chip must be (this is something that, I will admit, comes with
> expeirence). We try to find circuits in TV repair books that use similar
> components. And then try to match up the other parts -- the resistors and
> capacitors round the chip. Most likely they'll not tbe the same value,
> but the arrangement -- the circuit topology -- is often very similar.
> There are only so many ways you can use a particular chip.
>
> For example I had a problem with a Hitachi colour monitor on my DEC
> Rainbow. It was badged DEC VR241, but it was certainly a Hitachi chassis.
> The vertical output stage was part of a ceramic hybrid module. A look at
> some early 1980s Hitachi TV schematics producted one using a hybrid with
> almost identical circuitry from what I could deduce about the one in my
> monitor. Needless to say that schematic was a great help.
>
> > Although I'm an engineer, I'm an ME and my electronics
>
> If 'ME' = Mechanical Engineer, then I am even more suprised by the use of
> a hammer. I've never used a hammer for any mechanical engineering that I
> can remember.
>
> > background is mostly directed to digital stuff. (So
> > I'm not a "doctor" which perhaps destroys the "Good
>
> I'm not an engineer at all. I am also not a 'doctor' in this sense.
>
> > Samaritan analogy.) I don't have anything close to an
> > electronics lab (nor do I know anyone local that does)
>
> You don't need an electronics lab. FWIW, the tools I most often need to
> fix computers (including test gear) will all fit into one normal-sized
> 'holdall' bag. In fact I take them along to HP calculator club meetings.
> [That, BTW, is more than can be said for my 'mechanical' toolkit which is
> most definitely not portable]
>
> But, more important that tools or test equipment, IMHO, is the ability to
> think about what you are doing and to stop and think if there's a better
> way to do it. Nobody is going to flame you for making a mistake.
>
> > and, aside from an EPROM burner, my most sophisticated
> > equipment is a voltage meter.
>
> I've debugged several computers to component level using nothing more than
> an analogue VOM (multimeter) and a bit of experience. Test equipment is not
> a magic box that will find the faults for you.
>
> I keep on about experience. Yes, some of us have been working on such
> machines for rather a long time. And _all_ of us (if we are honest) will
> admit to making mistakes. Sometimes very silly mistakes. But experience
> comes from mistakes, provided you are prepared to realise that you have
> made a mistake and what uyou did wrong.
>
>
> > Should I simply not even try to do anything, lest I
> > risk criticism for doing it wrong?
>
> No, please carry on. The only way to learn is by doing things. And keep on
> asking questions -- that's another good way to learn. But bear in mind
> that if you ask for advice it may not be what you want to hear. It may
> help you in the end, though
>
> -tony
>
>
Received on Mon Jun 25 2001 - 16:54:49 BST