Part of the Museum's 
Restoration Lab

Power
Many classics used external power adapters and the adapters often don't accompany the computer when it arrives.  Unfortunately, many manufacturers don't include the essential voltage and pin out information on the case.  This results in a bit of detective work, usually a web search for users (or best of all designers) of the computer, an old FAQ or if luck is shining an old service manual that has been scanned or typed in by a good Samaritan.  We have over the years acquired a wide variety of exotic power supplies and connections and once the requisite information is on hand we can usually rig up power pretty quickly.  This can be trickier than it sounds as some of these old beasts have very strange power requirements (such as 16.8V AC on the PC Jr.!).

In some cases the manufacturer used non-standard DIN connectors for power that are no longer available.  This requires opening the case and tapping the power directly onto the motherboard or internal connections with small test clips.  Sometimes power can still be rigged externally to the DIN connector because many DIN pins were of similar diameter.  Thus a cable can be soldered with the requisite DIN pins hanging bare at the end.  Once tested such a cable can be made semi-permanent by shaping some quick-setting molding putty around the DIN pins.

Keep in mind that many of the most interesting classics are from distant lands and can require alternate wall power, most usually 220V.  If you are based in the U.S. you'll want to keep a 220V 50Hz power transformer handy at your test bench along with a variety of foreign power connector types (Shuki being the most common).  Some of the more common connector types are commonly available in "travel kits".  Make sure however that if you get an actual power transformer that it is beefy enough to drive the computer and perhaps a monitor.  Some of the cheaper transformers sold for travel are only designed to handle small loads such as an electric shaver.  A helpful reference source is the EastWest Electronics website which features diagrams of the connectors they sell as well as a variety of transformers etc.

A few things to watch out for:  Some manufacturers would change power requirements on the same model without warning (the Atari 1200XL being a good example).  Be careful to ensure that the information you have is for the correct model (sometimes denoted by the revision of motherboard or country of origin).  If reliable information is not available a bit of snooping inside the case can usually put you in the right ballpark.  Following the board traces to certain key chips can be helpful.  Pin outs for most processors ever used in the machines are readily available on the web (even for bizarre chips like the RCA COSMAC 1802).  Once you've determined your +5V, +12V, -12V, etc. from the key chips on the board the rest falls into place pretty quickly.  Anytime you are poking around inside once of these computers be sure to take extreme precaution with static electricity discharge.  Although not as much of an issue these days, very old components were much more susceptible to being zapped by ambient static discharge.  Get a wrist grounding strap from Radio Shack and use it.  

Although not for the faint of heart, we have had success deriving the general power requirements from an investigation of the board and then experimentally applying our "best guess" voltages to a machine.  If you do this be sure to start at voltages lower than you think are needed and work your way up slowly.  If you are not careful (or are unlucky) it is likely you will fry the computer permanently.  Only consider the experimental approach if you know what you are doing and only then as a last resort! 

Video
It can be hard to know if you've got the right power because many of the classic consoles didn't have a power light.  So you'll need to get the video connected properly too and in some cases you won't know if you've got the power wrong, the video wrong or if the computer just doesn't work.  This is where the real fun begins.  A lot of the classics simply fed an RF signal out which was designed to be connected to a standard television through it's antenna input (possibly via a TV/Game switch).  Radio Shack will be able to supply you with the various 300 ohm antenna to 75 ohm coax connections you might need.  Many of today's display monitors don't even have RF inputs anymore.  In this case an old VCR can be used as a handy adapter to take RF input and convert into a  composite video (RS-170A) output on an RCA style connector which will go into today's video monitors.

When working with foreign consoles you'll need to have a PAL video display (625 lines at 50 fields per second vs. NTSC's 525 lines at 60 fields per second).  Dual mode video monitors are available but pricey.  There are some inexpensive "Dual Standard" VCRs now on the market that can convert PAL to NTSC and vice versa.  The quality of the converted video signal is fairly poor compared to professional standards converter but they'll get you by.  A few consoles (particularly French ones) features SCART connectors and some have dual mode SECAM/PAL operation.

Some consoles output monochrome composite video (RS-170) on an RCA connector.  This will hook up to a standard video monitor however you may see color fringing effects in the monochrome signal.  This is a result of your monitor trying to interpret the monochrome signal as a color one.  If your monitor has a comb filter switch this may help.  Alternatively turning down the color all the way will solve the problem. 

A few later consoles featured RGB video outputs in addition to their standard video outputs.  The pin outs for these connectors did not follow any standard convention and even if you see a 9 pin CGA-style connector don't assume it's the same.  Some of these were digital RGB signals instead of today's analog RGB signals common to VGA monitors.  Many of these computers output RGB video at scan rates slower than today's VGA monitors are designed to deal with (15 KHz - 30 KHz).  There were several monitors made that scanned a wide range of these frequencies and could deal with either digital or analog signals.  The Commodore 1084 monitor (made by Magnavox) was one of these and it handled digital, analog, composite color, s-video and monochrome with the proper cables.  

If you can't find any information on the RGB pin outs of a particular console you can do some detective work by determining the video output chip that the console used.  Many consoles used fairly standard video encoder chips and looking up the pin outs of the chip will help give you a good idea of what kind of signals are on your 'mystery connector'.  Outside of this your only options are to find a friendly engineering type with an oscilloscope to take a look at the signals.  

Troubleshooting for the Non-Technical
Once you've got the machine powered and the video output configured properly it still may not work.  Don't lose hope!  Even if you aren't an electronics whiz, there are some things you can do to troubleshoot the problem and revive the machine.  First unplug the system and open the case (after putting on your grounding strap).  You will likely find a lot of dirt and that may be the problem.  We usually start by carefully cleaning the board and checking for damaged traces.  Be sure to check all external connections and cartridge slots for debris that may be causing a short. Look for a fuse in the power section.  If everything looks ok we move on to doing a basic trace of the power input with a voltmeter.  Many machines had internal transformers and these could be the first to go with age.  If the mainboard isn't getting power from the transformer then it's a simple matter of getting another transformer or jury-rigging an external power source.

The next step is to reseat all the socketed chips.  The old sockets used in these machines were susceptible to having their contacts oxidize.  Simply pressing down firmly on the back of the chips or giving them a sharp rap with the handle of a screwdriver can reseat an oxidized connection.  Another common problem is that over time a trace or connection on the board will form a small gap and become intermittent.  Gently flexing the board can pinpoint these problems.  Next we will pull all the socketed chips out of their sockets and reseat them.  If the machine is still DOA then you'll need to seek some more expert advice.  Frequently good advice can be found on the internet from current and former users of the machine.  Typically each of these machines had their own handful of quirky little problems that the users were well aware of.  Look for a scanned or digitized copy of the service manual or schematics for the system.  This will be invaluable to any electronics whiz that you enlist to help you.  One ideal approach is to get access to another one of the machines that is working.  One can then (very carefully) swap components until the bad part is identified.  Less ideal but still useful is to get a second non-working machine and try exchanging parts.  In some cases the processors, RAM and other components are still available from electronics distributors.  In other cases the original part may not be available however an updated but still compatible family member may be available.  If you can't get the machine to work DON'T THROW IT AWAY!!!  Seek help from an experienced engineer.  If you can't find anyone familiar with old computers, a person that repairs old stand-up video arcade games will usually have the right skills as well.

Many of these systems were manufactured with primitive plastics and case designations were applied with early screening processes.  When cleaning the system there is a significant risk of removing silk-screened type or logos from the case or keys by using too strong of a cleaner or solvent.  A solvent such as acetone may actually melt the plastic case!!!  Use a gentle and safe cleaner on the whole system and reserve the strong stuff for specific problem areas.  Test any strong solvent on the inside bottom of the case first.  We've had very good results from two specialized cleaners called Motsenbockers Lift-Off #2 and #3.  One of them is designed to remove adhesives, oil and paint.  The other removes pen marks and permanent ink.

Before basic cleaning try to remove all components from the case so that you can liberally apply liquid cleaners without risk to the electronics.  If this is not possible you will find it difficult to restore areas around recessed air vents without getting some cleaning fluid inside the case.  In our experience this is not a problem.  Keep a blow dryer handy and after cleaning thoroughly dry the inside of the computer (but be careful not to melt any components!), then let it sit for several hours before powering it on.  Drying can also be assisted by placing the computer in an oven set to bake at a very, VERY low temperature (about 120 degrees F).  If you do this, heat the oven up to a stable temperature FIRST, check that it isn't too high and only then put the computer in.  Leave the oven door cracked open a little bit and check on it often.

Sometimes the original stickers or logo plates are damaged or missing and we transfer parts from another case that is perhaps damaged elsewhere.  To relocate adhesive stickers carefully heat the area with a blow dryer until the adhesive becomes tacky and then work the sticker or emblem loose with the dull side of the Exacto blade. 

In the case of undesirable stickers (why, oh why did some people feel the need to add a "Keep on Truckin'" bumper sticker to the top of their machine?) we recommend that you heat the adhesive to remove the sticker.  Then let the case cool off and use a citrus-based solvent to remove the remaining adhesive.  These solvents are specifically designed to remove adhesives and are relatively safe.  There are other specific solvents designed to remove indelible marker and crayon.

Occasionally you will come across a mark on a case that does not yield to cleaners.  One technique that we've used on these relies on the fact that most consoles had textured plastic cases.  By working carefully with an Exacto blade the plastic can be scraped to remove the marks.  Although you are actually scraping away a very small part of the plastic case, if done carefully, this is completely hidden by the texturing in the plastic.

One all-too-common problem is keycaps broken in shipment.  Most of these machines had keycaps that were molded to the keyboard itself.  Unlike most of today's keys, they cannot simply pop off and be snapped back on.  This damage usually occurs during shipment and is a result of putting protective padding in the wrong place.  Many people make the mistake of putting most of the protective wrap on the top of the computer, however the keycaps are usually snapped off by downward force through the bottom of the case.  Be sure to put padding on both the top and the bottom. 

Once a keycap is broken it can be quite a chore to repair it.  When it breaks a spring may also pop loose and must be found (in the bottom of the box it was shipped in usually) for repair to commence.  You'll want to use Super Glue and a toothpick for the job.  The trick is gluing the keycap back on securely without having the glue travel, causing the up and down mechanism underneath the keycap to 'stick'.  You'll want to have some pieces of masking tape already torn and hanging off the edge of the table to hold the keycap in position while the glue cures (yes, even super glue should be allowed to cure for several hours).

With enough diligence most consoles can be restored to immaculate condition however there is one kind of damage for which we currently have no solution.  This is case 'yellowing' caused by excessive exposure to the sun.  Many older beige cases were susceptible to this kind of damage.  If they were in a place where direct sunlight would fall on them for a portion of every day, the case would start to slowly turn yellow.  Once a case is yellowed there is nothing that can be done to restore it.  The yellowing process is caused by ultra-violet light and computers near windows with UV-coatings definitely fared better than those next to plain windows.  If the case is a little yellowed and it is yellowed evenly, it usually isn't noticeable.  However if the case had something covering up part of it for any length of time, for instance a Post It Note, it will have a very visible "tan line" and there's nothing to be done about it.  This yellowing problem is why restored computers in a museum's hands must be kept away from direct sunlight at all costs.