TRS-80 Model 100 Board Replication

[Daniel]

I guess I've decided to do a board replication project starting on the
M100. At this point, I'm looking for a dead model on ebay but no one
wants to sell for less than $100 with shipping it seems. I'd pay $50 for
a 'for parts' unit.

Success will define this project if I can get some assistance. I have
designed pcb's in the past but for simple projects. This will be, by
far, my most complex effort to date. And I hope a success in this
project will lead to more restoration projects in the future.

Daniel

[Black Epyon]

Are you planning on doing a drop-in replacement "replica" using modern components, or just an emulator? There's a copy of the service manual on Internet Archive that has the schematics, and should help get you started.
https://archive.org/details/TandyM100ServiceManual/page/n81/mode/2up

[bill]

On 2/5/2023 9:32 PM, Daniel wrote:
> I guess I've decided to do a board replication project starting on the
> M100. At this point, I'm looking for a dead model on ebay but no one
> wants to sell for less than $100 with shipping it seems. I'd pay $50 for
> a 'for parts' unit.
>

Welcome to eBay. I was recently looking for a Realistic (Tandy Brand)
shortwave radio. There were about 8 of them all listed as "not working/
as is/for parts". Prices ranged from $150 to around $300. The radio
only cost about $300 when it was brand new 40 years ago. Go figure.

bill

[Daniel]

> Welcome to eBay

I know, right?

Yeah the whole retro thing has become so big since covid that people are
expecting crazy money. I hate when people outbid and item, it sells,
then the same thing goes back on the market a day later. you know the
seller is looking for more money. Anyway that happened to me on a new
old stock sony walkman.

[Daniel]

I'm planning a replica, one-for-one drop in of the board and all traces,
stencils, etc. Some dead devices are due to battery leakage and traces
will be destroyed in many areas - but many components will be okay. In
these cases the device is usually salvaged for parts only and that means
one device removed from circulation. Like the commodore, I'd like a
board replacement and there's been very little interest in the project.

I have the service manuals already and also have Birt's modern remake of
the schematics from his github.

I need to get a dead device so I can depopulate the board, remove all
solder/flux, and do a high definition scan of both sides for all three
boards.

Later, I'd like to redesign the power supply and convert it to USB-C
input and rechargable batteries, but that's way down the road.

I plan on posting my progress of this project on this thread as I go -
barring health issues. Also, I invite community members interested in
helping with design and/or documentation.

Daniel

[Walt Perko]

Hi,

Personally, for the limitations of the Model 100, I'd say go for a Model 1 board ...

As this is a replica, maybe add a VGA video OUT and USB keyboard IN and if possible a microSD card FDD or HDD to BOOT to OS and contain most if not all TRS-80 software and games.


.

[Josh Malone]

On Tuesday, February 7, 2023 at 3:25:54 AM UTC-5, Daniel wrote:

> I'm planning a replica, one-for-one drop in of the board and all traces,
> stencils, etc. Some dead devices are due to battery leakage and traces
> will be destroyed in many areas - but many components will be okay. In
> these cases the device is usually salvaged for parts only and that means
> one device removed from circulation. Like the commodore, I'd like a
> board replacement and there's been very little interest in the project.

I have a couple of "parts boards" from dead 100s, but I specifically want the unique parts on them, so I would have to depopulate them before I send you the board (for which I have no use). I'm not sure how quickly you want to get these boards, but, given a bit of time, I could provide one.

> I need to get a dead device so I can depopulate the board, remove all
> solder/flux, and do a high definition scan of both sides for all three
> boards.
>
> Later, I'd like to redesign the power supply and convert it to USB-C
> input and rechargable batteries, but that's way down the road.

I would REALLY love to see that happen. There's lots of "improvements" that I think need to be made to these machines to make a modern replica board useful. Use modern RAMs instead of the Tandy modules. Maybe make the optrom socket JEDEC standard. Definitely the power supply, as you say.

-Josh

[bill]

How about when someone says $200 OBO but then won't accept any offer
less than $199. Just had one of them, too.

bill

[Walt Perko]

Hi,

The thing about the boards is if the board itself isn't totaled, the circuit shouldn't be too difficult to repair. Maybe just a bad cap or a chip died.


.

[Daniel]

Josh Malone <josh....@gmail.com> writes:

> On Tuesday, February 7, 2023 at 3:25:54 AM UTC-5, Daniel wrote:
>
>> I'm planning a replica, one-for-one drop in of the board and all traces,
>> stencils, etc. Some dead devices are due to battery leakage and traces
>> will be destroyed in many areas - but many components will be okay. In
>> these cases the device is usually salvaged for parts only and that means
>> one device removed from circulation. Like the commodore, I'd like a
>> board replacement and there's been very little interest in the project.
>
> I have a couple of "parts boards" from dead 100s, but I specifically
> want the unique parts on them, so I would have to depopulate them
> before I send you the board (for which I have no use). I'm not sure
> how quickly you want to get these boards, but, given a bit of time, I
> could provide one.

That would be great. Yes I'd love them soon than later so I can get to work.

>> I need to get a dead device so I can depopulate the board, remove all
>> solder/flux, and do a high definition scan of both sides for all three
>> boards.
>>
>> Later, I'd like to redesign the power supply and convert it to USB-C
>> input and rechargable batteries, but that's way down the road.
>
> I would REALLY love to see that happen. There's lots of "improvements"
> that I think need to be made to these machines to make a modern
> replica board useful. Use modern RAMs instead of the Tandy
> modules. Maybe make the optrom socket JEDEC standard. Definitely the
> power supply, as you say.

This is where the community would need to come in. You're talking about
territory way outside my knowledge. The point of this project, for me,
is to allow for full restoration of these old devices without removing
them from circulation. Some say there are so many of them out there that
it's okay. Our community is far more niche than the commodore side of
things. If a board has extensive trace damage from leaking caps and
other issues, I'd love if a board could be replaced and the working
components populated on the new board. I know it's alot, but it's being
done all the time in other communities like the C64. Hell, you can order
a board of all revisions and a choice of colors. Some youtubers have
managed to make brand new c64's with off-the-shelf components and
homebrew replacement chips.

And creating boards that accept all the old components but modified with
improvements I'm totally open to - but it's secondary far in the future
unless the community jumps on the bandwagon.

Daniel

[Daniel]

Happy update: After a weekend with the momo-in-law, good karma cashed in
with an ebay search this evening and found a dead M100 with a cracked LCD
display for $30 with zero bids with a 'buy now' price at $39. With
shipping, a bit north of $50. It's mine now and now I just have to wait
for delivery.

https://imgur.com/jskcJUG.png

It has a dead screen and, by the looks of it, tons of battery residue on
the battery terminals. It'll likely be quite ugly inside, but we'll
see. I'm taking the thing apart anyway. Fingers crossed the traces won't
be too terribly rotted.

[David Plass]

Ah, so you're the one who bought that unit. I seriously considered buying it...but didn't give in to my obsession.

[Daniel]

David Plass <dpl...@gmail.com> writes:

> Ah, so you're the one who bought that unit. I seriously considered buying it...but didn't give in to my obsession.

Thank you so much for letting me have it. This device will be used for
science. Actually, I hope that, after the board is designed, that I may
be able to bring the device back into service if the traces aren't in
bad shape. Or maybe it could be my first transplant project.

The 100 community should have some space LCD's for sale.

[Daniel]

Okay the victim 100 came in the mail today. It is as described. Looked
like it went through some serious abuse. Some black markings on the side
as if it was exposed to a high electric load. LCD is finished. Stickers
on the bottom with serial number are almost wiped clean, figure that
out. Wherever it was from originally, it was really not loved, liked,
disliked, or even hated. This little box was treated like a mafia hit
victim.

Cracking her open and seeing the boards.

https://imgur.com/Bzek9eA.png
https://imgur.com/yhEDNnt.png
https://imgur.com/osSS0oG.png
https://imgur.com/0ev3sTB.png
https://imgur.com/u6I8CWw.png
https://imgur.com/Jvwls7M.png
https://imgur.com/8mZVQwE.png
https://imgur.com/H84Olmj.png
https://imgur.com/tBgWLYn.png

As I thought, a ton of residue. And time for deconstruction.

Anyhoo. Enjoy the images, I guess.

Daniel

[Black Epyon]

The LCD is definitely buggered, but just because the liquid crystal leaks through the layer doesn't mean you can't get a picture (at least enough to see if the rest of the board works, it's worth a shot). The rest of the board should come clean with some cleaning vinegar and a light scrubbing. I wish I took pictures of the one turbo-XT I restored (Varta splooshed everywhere, blown tantalums, etc, had to replace one of the ISA slots, the corrosion was so bad), because as far as corrosion goes, both these boards are fairly light.

--Kyle

[Daniel]

I pulled the board out yesterday and did some serious scrubbing with the
vinegar. The solder-side of the board is more-or-less clean
now. Denatured alcohol is banned in my state of California. The hardware
stores don't carry 99% alcohol on the shelves. So I bought 91% from the
drug store. So stupid.

My soldering iron, it turns out, isn't staying hot enough to melt
solder for very long. I am asking Mr. Carlson's Lab on youtube to fix it
and feature it on his channel.

Meantime I have to get another iron to do the work, and looking for a
solder vacuum that won't break the bank. Alot of the joints are really
hard to melt due to the caked on flux. Pain in the ass how hard it is to
depopulate this board.

This device sat through a high heat environment - enough to make the
plastic on the molex connectors discolored while the male ends are
prestine white. The edges were cracked or broken off and dry making them
difficult to separate without destroying them. Chunks of resistor and
disc capacitors started flaking off during normal handling. It is tough
to imagine that the chips on this device survived the abuse. I'll have
to research how to test the non-memory chips before I decide what to do
with them.

If things go well with this project, I'd like to repopulate these
components on a newly minted set of boards. Of course, I have the hurdle
of desoldering them from their pcb jail.

Even though it's been frustrating at this point, I'm still having a
great time.

Daniel

[Daniel]

Project is on hold until I can get a cheap soldering iron that'll always
just work. Meanwhile I am shopping for a solder vacuum to make
depopulating easier. Right now, it's a big pain in the ass to get the
solder out with a gimpy soldering iron.

I think I found the vacuum on amazon - just a bit bulky. I need a few
days.

Daniel

[Black Epyon]

Reflow some fresh solder onto the old joints, it makes it much easier.

I use a Gaogie S-993A desoldering gun. I got it for $150CDN back in 2019 (and well worth what I paid), but they've jumped in price considerably. You might be able to get one for around $200 CDN. They've got a Preciva 929D-V on Amazon for about $30CDN, which is more like the traditional solder pump, but at least it's got the iron built in. Pick up a bit of desoldering wick if you haven't already. There's also several cheap soldering irons on Amazon with digital thermostats, but I haven't tried any of them.

For the surface mount chips, you WILL need a hot air re-work station. The 858D comes under many Chinese brand names, but they run around $60-80 CDN, and is exactly what you need. As with anything bought from China, be sure to open them up first and verify that the person assembling it at the factory did his soldering properly, and fix if necessary. Annoying, I know, but this is the price you pay when you're on a budget.

--Kyle

[Daniel]

A little update on the project. Some unexpected car issues led to major
spending that effectively put an end to my pursuits until payday. My
budget was completely blown.

The board is sitting in the closet until I can order that solder
vacuum from amazon. Found one for just north of US $100 that seems to
have the features I desire. My budget was effectively blown for a few
months but this tool will be a necessity at this point. No cigars
until May/June. I'm hoping this will free all the components from their
pcb jails unharmed. Fingers crossed the chips come out nice and clean
for easy re-use. At this point, it has taken north of five hours to
remove a handful of components and frankly, what an epic waste of time
that turned out to be. I need proper tools if this continues.

Of the things on my list to obtain is a sheet of soft foam that I can
cut down for safe chip storage.

Meanwhile, I started going over the service manual this evening and
listing the chips on a clean spreadsheet. I am hoping to find modern
off-the-shelf equivalents for all of them. This pursuit will likely
spawn mod projects in the future - optimistic that this will lay good
groundwork. Some ideas I've received would make the M100 into a
completely different machine. My purpose now is to simply replicate the
boards with a growing desire to restore this dummy device once done.

Layer two: The service manual is a low quality scan of a low quality
manual. So, I will be replicating the service manual to a clean PDF with
clear diagrams and selectable text. No one wants to do it, so I will.
<major work>

Layer three: website. The idea is inspired by the activities devoted to
the C64. I'm going to create a large image map of the main board such
that a mouse hover over the components will show a small popup of the item
info. I will have to study how to do image maps, since it's been forever
since i've seen one. The site will be written in basic html with, at
most, early javascript. The idea is to have the page loadable on retro
systems and textmode browsers for as much readability as possible.

Regarding the victim device I obtained for this project, the PCB seems
in good enough shape for re-use. The system certainly saw a ton of abuse
including a high heat environment. Some resistors and few of the disc
capacitors literally fell to pieces after some gentle handling. I had
the board on a silicon mat while melting a solder joint. When I lifted
it to flip it around, half the disc of a cap was sitting on the
mat. Literally flaked off like it was a dead leaf. It may necessitate a
completely new stock of electrical components on a rebuild project. I
will NEVER sell that device after all the work it will demand. I may
also retro-brite the case and give it UV blocking clear coat to prevent
future discoloration.

That's all for now,

Daniel

[Daniel]

Project update: Solder sucker on order. I will continue my project once
the thing is in my hands.

[Daniel]

Project update: Solder sucker received. Problem is massive atmospheric
river with heavy rain, flooding, and high winds have made power
intermittent. Waiting for power to be restored consistently before I get
back on the ball.

Daniel

[Daniel]

I'm well underway on depopulating the board. It's slow going. Needing to
melt new solder on the old, then using the solder vacuum to clean the
joint. Sometimes needing to do it two or three times to completely clean
it out. So far so good. The weather has been nasty here in California,
nasty for us at least. Many power outages and intense wind/rain
storms. Some tornado warnings north of us. Drought is more-or-less over
for most of the state finally.

I will continue with the desoldering job and get it as clean as
possible.

Then I'll move onto high quality scans of both sides before beginning
the replication.

I will dump everything on github so the community can assist, if
possible.

Daniel

[Bob Campbell]

I had no idea anyone was still interested in these. I just trashed a Model
100 a few days ago. A whopping 32k of storage, black vinyl case and power
supply.

It worked, but the screen would fade out after a few minutes. I had not
powered it on for around 10 years.

I can’t imagine using these for anything these days. But good luck with
your project.

[Walt Perko]

Hi,

It's so sad to see somebody trash vintage computers when the chips can be so hard to find to repair another computer.


.

[Bob Campbell]

Walt Perko <r4r...@gmail.com> wrote:
> Hi,
>
> It's so sad to see somebody trash vintage computers when the chips can be
> so hard to find to repair another computer.
>

Well, let’s not overdramatize. It’s just a crappy, 40 year old computer.
I’m not throwing away food in front of starving people. I’m not laughing
manically while lighting cigars off of a $100 bill in front of homeless
people.

[Walt Perko]

Hi,

A lot of old chips are not manufactured anymore. We need to save them. It took me two years to find the last part to build a reproduction DAZZLER board. They quit making half the chips on that board back in the 1980s ... today I have the last chip that was in an obscure collections of chips.

The chips on all these old machines need to be recycled for repairing other old computers ... even Model 100s ... I have a working Model 100 ... I keep it under a plastic cover to keep dust out when I'm not playing with it. Yeah, it's not a great machine compared to my Altair 8800c or my IMSAI-JAIR or my IMSAI Z-1 or my Sol-20 that I'm slowly repairing and have to make my own cabinet for it as I only got lucky to get the main board and S-100 backplane. But all these machines use old out of date chips and they all have a lot of chips in common.


.

[bill]

On 4/5/2023 1:25 AM, Walt Perko wrote:
> Hi,
>
> A lot of old chips are not manufactured anymore. We need to save them. It took me two years to find the last part to build a reproduction DAZZLER board. They quit making half the chips on that board back in the 1980s ... today I have the last chip that was in an obscure collections of chips.
>
> The chips on all these old machines need to be recycled for repairing other old computers ... even Model 100s ... I have a working Model 100 ... I keep it under a plastic cover to keep dust out when I'm not playing with it. Yeah, it's not a great machine compared to my Altair 8800c or my IMSAI-JAIR or my IMSAI Z-1 or my Sol-20 that I'm slowly repairing and have to make my own cabinet for it as I only got lucky to get the main board and S-100 backplane. But all these machines use old out of date chips and they all have a lot of chips in common.
>
>

And yet, when people offer these old systems for sale they have no value
at all.

bill

[Daniel]

Project update: It's been a tough six months. Health issues abound,
intense work schedule and family stuff has kept my hobbies in a rut. I'm
getting back into this replication project soon. Just wanted to keep
everyone updated.

Solder sucker is still in the closet in the box it came in. It didn't
even see the light of day so far. I hope the thing does the job I hope
it does.

Need to see if my soldering station is still on the spectrum.

D