Tuesday, November 24, 2015

PC Battery Redux

Commodore PC Desktops are not the only x86 computers with bios batteries I worried over recently.  Without power to the BIOS ram, Commodore PC laptops lose their hardware settings and refuse to boot up.  Fixing this problem became my next concern.



First up was my C286-LT and C386SX-LT.  These computers were, in some ways, the easiest to replace the batteries in. The battery was a 3.6V non-rechargeable AA-sized battery.  Moreover, these computers have an externally accessible battery port, which made my life much easier.




Most AAs are 1.5V, so it took awhile to get the correct ones on order.  Also, the battery that was in there had the special connector lead required for the computer board already built in.  And, importantly, the battery was coated in plastic to prevent shorting itself against the internal battery space.  Turns out that entire space where the battery goes is grounded, so this was important.  Lastly, because the battery had its own leads built in, it didn't need to fit very snugly in its place, which would become important when trying to figure out how to get a new battery in there.




The first thing I tried was soldering those wires directly to the new battery.  The solder would not hold.  So then I Dremel-tooled away some of the coating on the battery metal to see if I could get a better grip.  I ruined a battery that way, don't try it.

Eventually I came around to what you see above.  One side, for ground, hugs the batterys negative end and has a clip on which to solder the black wire.  The other is actually a clip-on that fits neatly over the one of the ends of the battery space.  Since the entire space is !!grounded!!, and I needed that end to hold the positive charge, I used some black electrical tape over the battery area, and then put the positive-end clip over the electrical tape.



The combination was enough for the snug fit and secure contact on the positive side.  I replicated this process twice, once for the 286 and once for the 386, and now, a happy BIOS.



Next up was my 486SX-LTC.

I broke it open, perused it with my magnifying glass, and to save my life could not find anything resembling a battery.   I suspect it relies on the main laptop battery for constant power, but well, time to move on.





Last up was the C325XN laptop, another 386SX 25mhz based computer.


The battery in this one was extremely inaccessible.  Five screws and an hour of painful prying was required to get the top off this damn thing.  And then, inside, I found a strange 4.8V rechargeable chain of batteries molded in plastic with custom wires velcroed between the hard drive and the floppy drive.



Replacing this one required purchasing numerous 1.2V rechargeable button-sized batteries.  Sounds easy, right?  Well, scale and dimensions aren't always mentioned in web stores.  Sometimes you order a battery that looks identical to the one you want to discover it is exactly 3 times the size and weight of the one you have.  <sigh>  Well, it only took a month, but eventually the correct batteries arrived from China.



Pictured above is the original battery chain, after unwrapping.  Below that are some spares of the new batteries from china. Those cute little nubbins on them made it possible to solder them into their own new little chain and then solder on the wire leads.  At the bottom was the final produce, wrapped snugly in electrical tape to help with any future leaking.



With all the laptops now safely remembering their bios settings, it was time to move on to the Amigas.  A few more Commodore PC desktops will be arriving next month to the collection, which I'm sure will interrupt this process, but well, a Commie-fans work is never done!



























Thursday, November 12, 2015

Rare Repair Affairs

Over the last few days I had occasion to go through a bunch of old VIC-20s from the George Page collection.

Most of them have scuffed cases, missing keys, boards covered in rust, and didn't boot at all.  I figured I would go through some of them to see if I can scrounge some working parts.  I also pulled out a few reference working VIC boards to do the testing against.  These are pictured below.



In the course of testing the various 6560 VIC-I chips (the video chip that the computer takes its name from), I made an amusing discovery.

The discovery was that, even in the exact same board, different VIC-I chips produce different tints in their basic colors.  This is something I expect from TVs and Monitors which, after all, have a Tint knob.  But from a digital component deterministically manufactured?  A shock!  I'm sure many of you olde VIC fans already knew this, but I'm still fairly new to this computer, compared to some of the other Commodores, so it was a surprise.

Below are some of the colors I observed. ++NOTE: these images were snagged off the net for illustration purposes only...








Another amusing discovery was how resilient the VIC-I chip is.  Even on the worst condition boards, where CPUs, VIAs, and ROM chips had all met their doom, not a single solitary VIC-I was defective. :)



While I was working on this, I made the sad discovery that the 6581 SID (sound) chip in my main breadbox Commodore 64 had gone silent.  In my experience, when a SID goes bad, it goes All The Way BAD.  And that's what happened to me.  A replacement was necessary.

I have a nice selection of pull-spares in my parts cabinet, so I wasn't worried.  But I decided to dig into a sealed bag of SIDs I purchased off eBay 7-8 years ago.  They were sold as a group, and most appear to come from the same manufacturing batch.  All the chips were pushed into a pin-protection mat, and the static-bag was still unopened.  I cut the bag open and began testing them.  You can still see some thermo-compound on some of them -- that's my doing; they were pristinely clean with perfectly straight pins when I opened it.



I was shocked to discover that the first chip I put in did not work correctly.  I was even MORE surprised at the WAY it did not work.  As I mentioned above, when a SID goes bad, it goes All The Way.  But this chip was not silent, but FLAWED; it did not sound right.

Moreover, as I tested the chips one after another, I discovered that the same was true of all the chips.  Each one made sound, but the wrong sounds.  Some had missing voices.  Some had loud noisy interference.  Some had broken waveform generators.  None were all the way broken, but all were flawed.  I was robbed, and robbed in a way I didn't expect.  Were these manufacturing defects I purchased?  Pulls of flawed chips from an old repair shop?  Who knows.  Watch the video below to see what I found.



So, in the end, I had to dig into my working pulls, and my beloved breadbox now has its voice back.

Tuesday, November 10, 2015

A Tour Around the Lab

While perusing the web the other day, I happened upon a beautiful panorama of Yosimite Valley and it made me wonder how those are made.  Some quick googling made it seem fairly simple at first.  Take lots of pictures, combine them into one huge panorama picture with an editor program, and then, for a video, clip the picture into frames and recombine them as a video.

In the end, it took something like half a dozen programs and tools, with perhaps 2 hours of combined processing time on my PC, to produce this tour around my home away from the rest of my home: My Commodore Lab:




Sunday, October 11, 2015

Look What I Found!

For various reasons, I've been poking my nose into corners of my Commodore Lab that I would not normally poke into.  And the stuff I've been finding has been surprising and fun.



I wish I could say they bring back a wash of fond memories, but frankly I barely even remember where some of this stuff came from.  That's OK though, surprise is a delight all its own, and it's not like I don't remember anything at all.

For one thing, in the mid 2000s, I enjoyed going to the several Commodore Expos held around North America. The ECCC in Chicago, CommVex in Vegas, and (my fav) the LUCKI Expo in Louisville were yearly excursions for my carefree slightly-younger-self.  And I met some wonderful Commodore fans at those Expos, such as Jeri Ellsworth, Jens Schönfeld, Joe Torre, Robert Bernardo, Jim Brain, Eric Kudzin, Jim Butterfield, Larry Anderson, and numerous others.


L->R: Eric Kudzin, Me, unknown gentleman.
Photo Taken from Dick Estel's photo gallery http://www.dickestel.com/commvex06.htm

Apparently, it was to one of these events that I brought a Commodore 116 and VIC-20.  And to my present delight, I actually got them signed by some of their original developers.


The first one I ran across while investigating a shallow plastic crate on top of a stack of boxed computers.   It was signed by Robert Russell, a former Commodore engineer.  Mr. Russell took over the development of the VIC-20 project from Bob Yannes, and completed the computer design, added necessary ports, and adapted the KERNEL and BASIC roms,



Barely a week later, while investigating yet another strange plastic crate, I found two of my unboxed C-116s and my Commodore 232.  One of the Commodore 116s was *also* signed, this time by Dave Haynie and Bil Herd.  Although Mr. Haynie is known more for his work on the Amigas, both him and Bil Herd were engineers on the Commodore 264 series computers, which includes the 116.


L->R: Dave Haynie, Bil Herd, Robert Russell.
Photo Taken from Dick Estel's photo gallery http://www.dickestel.com/commvex06.htm

Although my mission in pulling them out was to either hook them up or box them, it seems I can do neither with what are obviously show-pieces.  I decided therefore to create a special shelf area exclusively for "Show Pieces" in my Commodore Lab, and put it right alongside the prototype CommodoreOne, Gold C-64, LCD Keyboard, and other wall-mounted show pieces.

It looks like this:



On the shelf, I added the Commodore thermostat, a C= Typewriter, Adding Machine, the two aforementioned computers, and some watches and camera.







Sunday, October 4, 2015

When Pee-Cees Leak

The next most important thing on the big white board where I keep my TO-DO list is to finally go through all my Commodore PCs and Amigas for a battery check and replacement.

You see, just like modern computers, these older PCs use batteries to maintain power on its internal clock chip.  This is why your computer remembers what time it is between reboots.  However, the older computers used Nickel-based batteries that, over time, would go bad, leak a base chemical onto the motherboard, and eat away at your computer like an acid!



Here you can see a NiCd battery leaking its evil all over the motherboard of a Commodore PC10-III.

The most obvious solution would be to clip out this bad battery and replace it with an identical one.  However, that only puts off the next leak for another decade or so.  I figured it was better to find a more permanent solution.



The solution I've been going with is to replace the NiCd battery with a Lithium ION battery holder.  This solves several problems: it makes the battery more easily replaceable in the future, Lithium batteries will last many many years longer even than the rechargeable NiCd, and best of all, Lithium batteries don't leak when they go bad; they just fade away.

In the picture above, you can see that my battery holder is two-pin, while the NiCd battery it replaced was three pin.  There were two positive-side pins.  I chose to solder the positive pin on the battery holder into the hole most removed from the rest of the motherboard, which was important, as I'll explain below.



While trying to educate myself about this problem, I learned that the NiCd batteries would push 3.6V into the clock chip when the computer was turned off.  However, when it was turned on, the power supply would push 5V back into the battery to recharge it.  Some people have said that pushing 5V at a non-rechargeable Lithium battery might actually cause it to explode or something!  To prevent this, I followed some advice I found about putting a Shotsky diode between the positive output from the Lithium battery and the motherboard.  A diode allows current to flow fairly freely one-way (out of the Lithium battery), but blocks current coming from the other direction (into the Lithium battery).

Since the original battery was two pins, with only one of them going to the clock chip, I saw this as a perfect chance to put my diode across the two old positive holes, on the underside the motherboard, after separating the short between those holes, of course.  The 3.6V from the battery would flow through the diode, and from there out to the clock clip.




Success! (Yes, this is just a gratuitous picture of the PC10-III running PC-GEOS).




So, later Commodore PC motherboards corrected the mistake of using leaky NiCd batteries by using Lithium batteries as well.  Unfortunately, they didn't use battery holders, but did something which, IMHO, was almost worse: they used an integrated battery + clock chip in a single monolithic black box.  The Lithium-Ion battery is actually underneath that black casing, enclosed in plastic.

This is wonderful for preventing damage to the motherboard from leaking NiCd batteries.  However, even the Lithium batteries run out eventually, and then what do you do?  



The answer was to carefully drill away at the block-o-plastic to expose the Positive and Negative poles of the internal battery, and then solder on a new battery holder, into which I put a new battery.

I used a very small grinding head on my Dremel tool to slowly expose the hidden pins.  I then tested the exposed metal with my multi-meter to confirm I'd really gotten the right ones.  If you look carefully, you'll see I actually had to remove a component to get to it.



This wonderful picture from Peter Wendt of Germany shows exactly how to go about this.  You can read his own account here: http://www.mcamafia.de/mcapage0/dsrework.htm

So, that's what I've been up to.  I took down every single one of my Commodore PCs, and I've been slowly taking each one apart, checking for batteries to replace, doing quick tests, taking pictures, and then shuffling them away. :)




However, as you can see here, I still have quite a few to go.... and those don't count the boxed PCs, or the PC50-III I have hooked up.

Monday, September 28, 2015

Two Things I'm Not Fixing Right Now

Sometimes I find a problem just isn't worth fixing, and sometimes the problem just isn't worth fixing by Me ... Right Now.

I recently went through two devices that were taken off the shelf for one reason or another, but both got re-shelved when I determined that my limited repair knowledge and resources were best used elsewhere.


First up was this Commodore VC-1540 disk drive.  It was just sitting lose with a pile of other stuff, so I decided to clean it up and properly box it, since it's 220V and not a drive I use every day here in the 110V U.S.

I also wanted to confirm that it actually had the original 1540 roms.  A disturbing number of 1540 disk drives were "upgraded" to 1541 roms for compatibility with the Commodore 64.


Fortunately, the roms were indeed the original 1540 roms, which give the VIC-20 both compatibility and a nice little boost in load-speed by default.  This youngster is a "true" and stock VC-1540.


The drive worked great as well, of course; the only problem I found was that, at some point in the past, the fuse-mount was cracked.  It was dangling loosely when I examined it.  I considered replacing the fuse mount, but there was still enough thread to secure it with a thin nut, and replacing would have meant tearing off the rubber insulation and/or desoldering the wires from the power supply.  Clearly I decided that this was good enough for now.

It's still a lovely drive, and since I know I won't be seeing it for awhile, I enjoyed giving it some consideration.







Next up was the Commodore 128D/81, which was originally taken down just for retr0brighting.  The entire lower half of the case was a pastel burnt orange, as were several keys.  You can still see that those keys could use some more work, but the rest of the case came out beautifully.

The problem is the same as it was when I first got it.  Neither the computer inside, nor the motherboard of the internal "1563" 3.5" disk drive, would boot properly.



I immediately dismissed the idea of repairing the computer at this time.  Here is a photo of the motherboard taken by the previous owner.

The MMU, video circuitry, and especially the all-important Z-80 processor board are a jumbled and hacked Mess.  Some day I may lay out a working C128 motherboard and start swapping out the chips from this thing to make sure that, circuitry aside, at least the chips are OK.  For now, however, there is no way I'm touching this thing.  Nope Nope Nope!

However, the 1563 drive struck me as an easy task.  It was only last month that I brought its direct descendant, the 1581, back from the dead.  During that fix I made sure I had every chip on the 1581 motherboard, so I was flush with parts.  NO Problem, Right?


At first it was simple.  I swapped out the CPU, no effect.  Then the 74ls241 (which was the bad chip on my 1581), to no effect.  I then went after the 8520 CIA chip.

Whoa nelly! See that little blue wire running from the 8520 to another point on the board?  That was the tip of the iceberg.  The 8520 on this board had several pins "clipped" and then re-soldered to the socket in *different pins locations* using more little blue wire.  In other words, that 8520 was going Nowhere without carefully diagramming how the schematic was being altered, and then de-soldering everything.  To try another 8520, I'd have to more-or-less ruin it by bending up pins and reproducing the hack job hidden underneath that innocent-looking little 40 pin chip.

It was a jungle under there! And I was too terrified to mess with it.


So, whether I'm waiting for knowledge or just courage, I put the lid back on this bad boy and sent it back into the sunset.  Some day though .. some day...

Saturday, September 19, 2015

Matshushita's Revenge

I just finished swapping out the capacitors on the disk drive devices in a Commodore 720-D.  Since this is the 7th and 8th time I've done this particular process, I figured it would be useful to share some of the lessons and pitfalls I learned.



First off, this post is for anyone who has one of the following disk drives or computers:
Commodore SFD-1001 Disk Drive
Commodore 8250LP Disk Drive
Commodore 8296D Computer
Commodore 720D Computer
Commodore 256-80-D Computer
Any computer or disk drive with Matshushita 1MB DSDD 5.25" disk drives mechanisms.

If you own one of the above, you *must* change the capacitors in it, and soon.  The capacitors in them *will* leak, and they will damage the drive motherboard.  The damage gets worse over time, so the sooner the better.  If the above doesn't scare you, consider this: of the 8 drives I've checked, all 8 have had at least one leaking capacitor with some amount of drive board damage.

Here's a picture of what I'm talking about:


You can see the leak damage in the bottom left and the upper right.

So, to replace the capacitors, you will need the following:

  1. Soldering iron and solder
  2. Solder wick
  3. Alcohol and Q-tips for cleaning
  4. Small phillips-head screwdriver
  5. Flux pen
  6. Pen-razor
  7. One (1) 33uf 25V capacitor  (5mm tall or so)
  8. One (1) 47uf 10V capacitor  (5mm tall or so)
  9. Two (2) 4.7uf 25V capacitors (5-7mm tall)
  10. Two (2) 22uf 10V capacitors (5-7mm tall)
  11. Multi-meter with continuity checker



The first step is to remove the screws to the round magnetic wheel thing.  These screws can be very difficult to start, but slide right out once they are turning.  Just don't strip them trying to get them started.  Put some muscle in it!


Now lift off the magnetic wheel and set it aside.  You'll also want to remember to pull out the "spacers", otherwise they will just fall off and slide around.  Some drives will have two of them.  Some only one "fatter" one.



The next thing I usually do is de-solder the power-cable in the upper-left.  You can see the four pins of this wire in the picture above, being pointed at by the soldering iron.  Apply some flux and solder wick, and they will dry up.  When removing them, you'll want to carefully rock them back and forth a bit until they come out.


Now remove the remaining four screws on the board.  These are a BITCH.  They will start difficult, get easy for a few turns, then go difficult again.  They are harder to strip than the "wheel" screws, but still trouble.  Just make sure you push down hard and GO SLOW when working on them.  Remember that the longer screw went in the upper-left area.


Now you'll want to carefully lift the motherboard up from the LEFT side ONLY.  Underneath the right-side area is a little ribbon cable that can be damaged if you yank it out, and once it is yanked out or torn, it is impossible to get back in.  This is also why I don't just de-solder the ribbon cable; you don't have to remove it to do your work if you are careful.

The board may be "sticky" at first when trying to lift it.  Just keep rocking it around and lifting up on it at various angles and it will eventually come up.  Remember not to pull up on that right side though!  Below is a picture of the board lifted up, so you can see the little ribbon cable we are protecting:


You can see it just above the right-middle of the white wheel paper stuff.  Sometimes you will have lots of slack.  Sometimes you will have very little.  Just feel your way to how much you can move the board around without disturbing that cable.



The first time I did this, I made myself a little drawing showing the six capacitors I was replacing, what their values were, and which pin was ground.  This is because, unlike resisters, capacitors are polar, and it is important to put the correct pin in the correct hole.  In my drawing, I show each capacitor is a V shape that points to its value, and where one of the V legs has the traditional ground symbol.

You can also see that I documented the colors of the wires in the power-cable we removed, so that I would put it back in correctly.  It turned out that that was not really a problem, but well, safer than sorry, right?




Here are the actual locations of the six capacitors you will be desoldering.  No special tricks here.  I just apply some flux and soak it away with the solder wick.

The only problem I ever had was with a through-hole trace that was so badly corroded and covered with black gunk that I had to scrape it off with my pen razor a little bit in order to get any solder lifted off.  Also the metal trace was no longer secured to the board, so I had to treat it with kid gloves.  It sucks when that happens.


After desoldering the capacitors and setting them aside, I typically take a magnifying glass and a bright light and look at the through-hole traces where the new capacitors will go in.  Acid damage from the bad capacitors will often leave a black gunk on top of the metal, making it impossible to get a good solder connection to it.  When I see this gunk, I use the tip of a pen-razor to scrap the gunk off as best I can.  Make very light tiny scrapes around the edges of the through-hole.  It doesn't take any pressure at all to remove the gunk, and if you scrape *across* the trace, you might accidentally pull it away from the board, so I recommend scraping in a circle, very lightly.  Obviously, if you can see all the metal around the hole, this is unnecessary.


At this point you can start cleaning off the places where the capacitors were removed with some alcohol solution and q-tips.  You'll need several q-tips because of all the black gunk you'll lift, as well as any flux left from desoldering.


Once everything is cleaned, you can use your multi-meter to start checking to make sure the acid damage from the bad capacitors did not eat clean-through any traces.  If any traces were damaged, you'll have to repair them with wire.  None of mine have been quite that bad, but I have heard of ones that were, so be prepared.



Now you can put the new capacitors in.  As I mentioned above, capacitors are polar.  The side of the capacitor with the white stripe is "ground" and should match with the hole that is in the white-half of the circle in the above picture.  You can also consult my little diagram for the same information.

 
It should also be mentioned that this board lives in a very tight space.  If you purchased capacitors that are taller than the things around them, you'll need to bend them down.  I made this mistake in one of my early re-caps.  The capacitor was too tall, so the board sat a few millimeters higher than normal, which caused the board to scrape against the magnetic wheel once it was put back on, preventing the drive from turning.



Once the new capacitors are in, you can put everything back together.  Don't forget to re-solder the power-cable we removed in an early step!

Also, make sure the screws are very tight.  Yes, the 4 screws for the motherboard will be almost as painful going back in as they were coming out.  Again, go slowly and firmly.

When you are done, the only thing that should move around is that magnetic wheel, and it should spin freely.  In fact, you might want to give it a spin with your finger as a final step.  If it scrapes against the board, it means you need to lower that board (or raise the wheel) until it does not.

Now your drive is good for another 10 years (or more?)!