Subject: Restoration: how far should it go??

From: "peter tremewen" <[email-masked]>
Date: Sun Jun 15 17:36:44 2003

Hi all,

        Being a new comer to the hobby, I have not posted much on the forum
before. The subject however is one that has recently been brought to my
attention, and hopefully will bring about some debate.

        Here is the scenario. You've just come home from the Antique
show/Trash and treasure/garage sale. You've picked up a nice new toy,
hopefully at least a little less than the price you should have paid. (With
the blessing of the other half of course) You know it's not a worker and have
a general idea of the condition of course. You just can't wait to get it back
to the workshop. You take the cover off and......

        How much do people think is too much restoration???   Now obviously
you aren't going to spent thousands on a system that even in the distant
future will not even generate hundreds, and obviously you aren't going to
rebuild and replace every part in the item, because then it's a replica not an
antique. Obviously however a going system is more valuable than a broken one.
So to what lengths do you go to fix it?? For quite some time I have had in my
possession a fairly old system that I am told is "historically significant".
For those that know what one is it is an EDUC-8 a descrete logic
CPU/Programming trainer from the mid 70's.  There seems to be two main
opinions among computer collectors.

        Opinion 1: The collector who collects entirely for the sake of owning
the object in question and is not concerned about operating it or whether the
item works as planned. They will buy an antique for preservation and think it
is sacrilegious to do any restoration other than maybe a "spit and polish".

       Opinion 2: The collector who collects with the intention of
restoration. Who might go to extreme lengths to rebuild and restore the item
he has brought, because to him the idea of keeping something that isn't
working as planed is against God and nature.

        Without getting into protracted discusion about the theology of either
collector, I would like to hear the opinions on the list about how far a
restoration should go before it starts detracting from the value of the piece.
I know this is a complex issue, and obviously depends on allot of factors, but
surely there are SOME guide lines that should or could be followed. I am about
to start a complex restoration on the EDUC-8 and am hoping the experts on the
list will give me some ideas based on their experience with other systems.
Idealy I would love the thing to be actually working. Possibly with some
replica I/O interfacing. I must say the the system is at best in "fair to
poor" condition, and without some attention it will probably deteriate
further. I supose I could just clean it up and place it in a "display case"
but I tend to be a collector of more the second opinion than the first.
Obviously however I do not wish to "distroy" the "vintage" significance of the
unit either

                Hope to hear from you soon.....

                        Peter T.

---

From: [email-masked] (Tony Duell)
Date: Sun Jun 15 17:38:10 2003

>         How much do people think is too much restoration???   Now obviously

Well, my view is simple. The machine originally worked. I want to restore 
it to as near original condition as possible. Therefore it must work again...

I am not interested in collecting as an investment. I collect computers 
because they _are_ computers -- they're interesting (and sometimes 
complex) electronic systems that can be investigated, programmed, 
modified, etc. A non-working computer -- one that can't be made to work 
-- is of little interest to me.

> future will not even generate hundreds, and obviously you aren't going to

Actually, I might. If I had no chance of getting another one, then I'd 
_certainly_ do whatever was necessary to get it going again. Hobbies do 
not make financial sense!

> rebuild and replace every part in the item, because then it's a replica not an

I wouldn't replave unnecessary parts, and I'd replace the smallest part 
that I could (e.g. I'd change a chip, not the entire PCB). But I would 
replace as many chips as were necessary. And I'd certainly inspect and 
maybe rebuild mechanical sections (including fans!)

> antique. Obviously however a going system is more valuable than a broken one.

It's certainly more valuable for me. In that it can provide me with a 
source of interest -- programming, interfacing, etc. 

> working as planed is against God and nature.

I am definitely of that type...

> restoration should go before it starts detracting from the value of the piece.

Well, I'm not really interested in value, but I do have some ground rules 
to follow :

1) _Never_ change the basic architecture of the machine. Ripping out all 
the boards and replacing them with a PC running a simulation of the 
original machine is not a restoration

2) Do not make permanent modifications, unless unavoidable. Don't cut PCB 
traces if you can avoid it, and avoid drilling holes larger than 
screwholes. 

3) Use components as close to the original as possible. Personally, I 
don't care about date codes, and I might well use a 74LS00 to replace a 
7400 if that's all I had. 

4) Don't fake things. Others will moan about this, but I object to the 
practice of hiding modern capacitors inside the empty shells of old ones 
to preserve the appearance of the machine. Such practices might well 
confuse restorers in the future!. NEVER fake IC numbers (as in changing 
that 74LS00 number to 7400, or worse changing a GAL16V8 to PAL16L8). This 
will cause problems

5) Document what you've done. Certainly in a separate log book (yes, I 
know it can get lost, but it's better than having no docs at all). Maybe 
on a label stuck to the chassis if the mod is non-obvious and could be a 
problem later.

> Obviously however I do not wish to "distroy" the "vintage" significance of the

Well, I've done the above sort of thing to machines where the total known 
number cna be counted on the fingers of both hands (and sometimes on the 
fingers of one hand) -- in unary. Maybe I did ruin the vintage 
significance of these machines, but to be honest, a working machine has 
much more significance to me (and to the owners of the machines I did 
this sort of thing for) in that we can now see what the machines were 
like to use, to program, etc.

-tony

---

From: Jesse Kempf <[email-masked]>
Date: Sun Jun 15 17:39:20 2003

On Sat, 14 Jun 2003 21:13:55 +1000
"peter tremewen" <[email-masked]> wrote:

>         How much do people think is too much restoration???   >Now obviously you aren't going to spent thousands on a system that even
>in the distant future will not even generate hundreds, and obviously >you aren't going to rebuild and replace every part in the item, because >then it's a replica not an antique.

Really? I have an H740 power supply sitting inside the chassis of a PDP-11/05 that wants to argue with you. As it is, half the +5V regulator has been removed, and is going to have to be replaced. It's not going to cost that much, but still, I fie you to call that a "replica". The important part isn't "Oooh! Shiny old collectible!", it's "watch me make the binkenlights do foo after I toggle this program in on the front panel." There's a PDP-11/45 that my friend and mentor essentially rebuilt. New power supply, grafted-on LTC, etc. Yeah, you can argue that replacing a power subsystem is somehow devaluing the system in some way. The system will be worthless, though, if you use a period power supply. When linear supplies fail, they can do interesting things, like toast your logic. What is the point of having a pristine, unmolested logic board of burnt-out chips?
A different friend of mine recently acquired a PDP-10. The KL-10 sucks down 10KW, 2 for the CPU, 8 for the power supplies. I submit that his modifying the beast to run off of just over 2KW, with switching power supplies, is in no way degrading the worth of the machine. The same with his using modern memory to replace the damaged-beyond-repair memory cabinets. A PDP-10 is a rare enough beast that anything necessary to get it running, including hooking it up to life support, is a fair modification.
Falseness or legerdemain, however, is idiotic. Buying the shell of a PDP-11 and throwing a PC in running simh and an interface layer in is pointless. Or repairing a PDP-8 by reimplementing everything in FPGAs. At that point, it ceases to be the original machine anymore.
Every DEC machine prior to the Middle VAXen came with its own print set. I hold that the power supply is expendable. It's probably dangerous to the rest of the machine, and should be disposed of. Earlier machines *tend* to have simpler power systems (I have a pair of VAX 6000s should anyone want to argue the point), so it isn't completely infeasible to build your own power supply. The more important part is the processor. Except in extreme circumstances, I don't believe you should modify the processor. If the print sets no longer describe the processor logic, then you've created a new implementation of whatever the hell it was that you had. It then ceases to be the old machine, and is some sort of weird hybrid. You're pretty much on your own then if something goes wrong.
-Jesse

---

From: Ethan Dicks <[email-masked]>
Date: Sun Jun 15 17:39:30 2003

--- Jesse Kempf <[email-masked]> wrote:
> A different friend of mine recently acquired a PDP-10. The KL-10 sucks
> down 10KW, 2 for the CPU, 8 for the power supplies. I submit that his
> modifying the beast to run off of just over 2KW, with switching power
> supplies, is in no way degrading the worth of the machine.

CompuServe did this in period (well prior to 1994 when they started
using Systems Concepts machines to replace DEC machines that were
getting harder and harder to keep running).

I would argue that this particular change is "reasonable", even from
a historical perspective.  I'm sure that the strictest purists would
still frown on it, though.  Personally, I want hardware I can *use*
and am willing to make compromises to keep them so.

-ethan

---

From: Philip Pemberton <[email-masked]>
Date: Sun Jun 15 17:40:09 2003

In message <[email-masked]>

> working as planed is against God and nature.
That's me in a nutshell.
I collect microcomputers, especially microcomputers that were designed and
built by British companies - Jupiter Cantab, Sinclair, Acorn, etc. If it's
British-made and it's about the size of (or smaller than) a Sinclair ZX
Spectrum +2A, then I want it.
My Jupiter Ace, BTW, is almost repaired. I've got the 16K RAM Pack, manual
and demo tape for it. The only thing missing is the power supply. If I can't
locate an original PSU, I'll build a one-amp linear regulated 9V PSU with a
"crowbar" overvoltage protection circuit. Yes, I'm paranoid enough to add a
crowbar...

> restoration should go before it starts detracting from the value of the piece.
I try and replace as little as possible. If a chip has failed and I've got
both a replacement chip and a replacement board, I'll fit a socket and use
the chip. If I need to, I will repair damaged tracks on the board.
I insist on keeping a log of every repair done to a machine. In this way, if
the machine fails again in future and (shock horror) I can't identify the
dead component, I've got my notes to help troubleshoot the board.

> list will give me some ideas based on their experience with other systems.
If you need to remove a failed DIL-packaged IC, use a craft knife or hacksaw
blade to cut the pins off. Then desolder the pins and clean out the holes
with a solder-sucker. NEVER use desolder wick on through-hole boards - it
eats pads and tracks for breakfast.

> I supose I could just clean it up and place it in a "display case"
I guess you're in the majority then. Most of the people here insist that the
machine must work properly. In the words of Tony Duell:

ARD> Well, my view is simple. The machine originally worked. I want to restore 
ARD> it to as near original condition as possible. Therefore it must work again...

IOW, it left the factory in an operational state. Ergo, it must be restored
to the extent that it works properly.

Later.
-- 
Phil.
[email-masked]
http://www.philpem.dsl.pipex.com/

---

From: peter tremewen <[email-masked]>
Date: Sun Jun 15 17:40:19 2003

Hi Phil,

        Thanks for the feedback. There has been about the same feedback from
most collectors, Get the thing working. There is certainly a wide gap
between collectors of opinion one and opinion two. Most computer collectors
however seem to be closer to opinion two than opinion one. As long as there
is no attempt to hide the "Repair/restoration" most people seem to think
it's O.K. to do whatever is necessary to get the system going. Writing a
"log" or recording all repairs seems to be a common idea. I suppose if it's
recorded anyone further researching the system/part has a fair chance to see
what has been done to restore it.

        I have to agree with you on the long term affects of "Solder Wick".
I hate the stuff, having seen what it can do to boards in long service in
the telecommunications industry. It's not always possible to clean the flux
residues thoroughly off a board after using "Solderwick". I have a Denon
SC-7000 desoldering gun that I use for all such repairs. I use "No clean"
solder for all repairs, and if necessary further clean the joint with IPA.
Perhaps a bit over the top, but at least I know nothing "I" have done will
cause further deterioration to the system. When I have access to one I use
Industrial PCB washers, and dryers after all work has been done. I have
cleaned up more than one dusty crappy looking mother board or plug in card
after a bit of work, and have them looking sparkly new.

                Peter T.

---

From: [email-masked] (Tony Duell)
Date: Sun Jun 15 17:41:30 2003

> "crowbar" overvoltage protection circuit. Yes, I'm paranoid enough to add a

Fairly pointless. The only thing that 9V supply feeds is a 7085 
regulator. If that fails, then the 9V will cook the chips anyway.

The original PSU is unregulated (just transformer, bridge rectifier, 
smoothing cap). There's little point in regulating it -- the 7805 will 
stand up to 35V on the input IIRC (it may well go into thermal shutdown 
if you give it excessive voltage, but it shouldn't short). No sensible 
fault in a simple unregulated linear PSU will make the output go up by a 
factor of 4 or so.

If you want to add a crowbar, put one set to trip at a little over 5V 
across the 5V line on the Ace's PCB...

> the chip. If I need to, I will repair damaged tracks on the board.

Me too. And I also regard sockets as a sensible modification. But I only 
ever used turned-pin (machined pin) sockets now. Yes, they're expensive, 
but so is my time in tracing bad connections.

> eats pads and tracks for breakfast.

The only use I've found to solderwick is to clean up the pads on an 
SMD-based board when replacing a component there. I never use it on 
through-hole boards.

-tony

---

From: [email-masked] (Tony Duell)
Date: Sun Jun 15 17:41:50 2003

> Really? I have an H740 power supply sitting inside the chassis of a
> PDP-11/05 that wants to argue with you. As it is, half the +5V regulator
> has been removed, and is going to have to be replaced. It's not going to
> cost that much, but still, I fie you to call that a "replica". The

I see no problem in rebuilding a PSU, but I'd want to keep to the 
original design if at all possible...

> important part isn't "Oooh! Shiny old collectible!", it's "watch me make
> the binkenlights do foo after I toggle this program in on the front
> panel." There's a PDP-11/45 that my friend and mentor essentially rebuilt.
> New power supply, grafted-on LTC, etc. Yeah, you can argue that replacing
> a power subsystem is somehow devaluing the system in some way. The system

Yes, actually I would claim that. The PSU _is_ part of the computer.

> will be worthless, though, if you use a period power supply. When linear

Why? My 11/45 (early version ,too) is still running on the original PSUs. All
I've had to do is rebuild one -15V brick...

> supplies fail, they can do interesting things , like toast your logic.

FWIW the 11/45 PSUs (and AFAIK all PDP11 PSUs) have switch-mode 
regulators, at least for the +5 and -15V lines. YEs, they can fail, and 
yes, in theory they can put overvoltage onto the logic, but DEC put 
crowbars everywhere. 

I've had mainns-side SMPSUs fail too, and put nasty HV spikes on 
the output (an open-circuit or high ESR output capacitor will do that!), 
and I've had regulation circuits fail in modern SMPSUs...

Perhaps it's just me, but I've had a lot more problems with relatively 
modern 'commodity' PSUs that with the units in 1970s minicomputers. And 
at least the latter come with printsets so I have a hope of fixing them.

> What is the point of having a pristine, unmolested logic board of
> burnt-out chips? A different friend of mine recently acquired a PDP-10

That's why you alwys check PSUs on dummy load after installing the 
machine or workign on the PSU. And why you check the crowbar (NOT by 
triggering it! -- with a dummy load, put a lamp in series with the SCR 
anode and then twaek up the PSU output to ensure it will trip -- assuming 
the PSU can be turned up that high). In fact I'd probably replace the 
crowbar components with new, tested, parts in any really rare machine. 

-tony

---

From: [email-masked] (Tony Duell)
Date: Sun Jun 15 17:42:00 2003

> it's O.K. to do whatever is necessary to get the system going. Writing a

Thsi is of course entirely up to you, as it's your machine. But it really 
saddens me to see a classic computer that could run again but which is 
never given the chance. Incidentally, I was reading a book on clock 
repair (another of my interests...) which makes much the same comment -- 
many clock enthusiasts are saddened by non-working clocks that could be 
got to run again.

> what has been done to restore it.

Yes. There are several purposes in keeping the log. The first is so that 
any future collector/restorer knows what's been done, what is not 
original, and so on. The second is so that _you_ know what's been done 
when you have to fix the machine next time, and you find it no longer 
agrees with the service manual. If the service manual is loose sheets in 
a ring binder or some other form of binding where you can add pages, then 
I think it's reasonable to add pages documenting the modicifications (or 
to copy a page, then make ammendments to it, and keep _both_ the original 
and the updated on in the binder).

-tony