Monthly Archives: August 2014

Wireless Fidelity

I did this last night but ran out of time to write anything. So, have yesterday’s news today.

Compaq, back open

I popped the top off the computer because I’d installed the router inside a while back to give Wi-Fi access to the machine- the reception was hampered by the antennas being inside the Faraday cage. This caused (reason unknown) the DMZ light to blink. Removing the lid made it stop.

I’d removed the antennas from an old Dell laptop that was scrap, each little green bar has a cellphone and a Wi-Fi antenna in, the Wi-Fi ones being a diversity pair.

Found a nice ground plane for one to sit on, and secured the cables.

antenna at rear

Took apart the original antennas, with strange, large coaxial screw terminals.

old antenna

Lopped the groundplane off.

groundplane gone

Stripped back the dielectric and soldered the cores together. Yes, yes, yes. I know. But I don’t have much else in the way of options.

soldered core

Replaced the missing dielectric with something similar. Black vinyl tape. That’ll work.

new dielectric

Soldered together the waveguide.

waveguide

Finished off with heat-shrink. I remembered to put some on this side. The other one, I did not remember.

heat shrink

Took the other antenna and mounted it on top of the case on the opposite corner. The little silvered pads between the red sticky foam are made from a conductive metal weave, and connects the antenna to the metal it’s on, providing a better groundplane for decent broadcast. Range is win!

sticky foam antenna

Screwed it all together, lots of wiring inside now that’s a bit untidy (project for another day).

wire spaghetti

Running a wireless scan with the case all back together is promising. The DMZ light no longer blinks and the signal reception is significantly improved. Those results are from neighboring houses. I was lucky to pick up my own Wi-Fi inside this house before.

results

Net result? Success.

Sounds good

The Compaq Portable 386 (previous post) I have did not arrive here with much installed. I have added a modem and a Sound Blaster Pro clone- one thing I’d always wanted to do was add some speakers to accompany the soundcard.

Broke down a couple old laptops today and scavenged some parts.

Loudspekers

Some very compact speakers from an old Dell. They are quite long travel- checked that they don’t pass out further than the edge of the plastic either.

Dime

Found an object that was round and the same size as the speaker aperture. A dime. Traced around it onto double-sided foam tape.

foam tape

Carefully chopped out the holes in the tape and attached them to provide an airtight seal. This does improve the sound.

All attached down

Stuck them to the vent grille. Perfect fit, there’s about 1/16″ clearance between the speaker cases and the cards. Connected up to an old CD-ROM audio cable and put that onto the amplified header on the sound card.

i see you

Very subtle mod. From the outside you have to look carefully to see them.

windows

Then, start up the main PC, find an audio track, convert it to a 22,500 Hz 8-bit .WAV file, chop that up into floppy disc size pieces, transfer piecemeal (6 chunks), reassemble with MS-DOS copy (copy file1 /b + file2 /b + file3 /b …. destination.zip) then unzip the entire thing (9.2 Megabytes, unzip took about 4 minutes) and play the wave file in Media Player!

I did put some audio but it’s from a copyright protected piece of music, so I can’t publish it. However, it now sounds like any modern laptop. Not bad. It’s even properly in stereo.

Another portable – Compaq 386

I appear to have lost the early photographs, but this machine came to me with the TRS-80 and Compaq Portable, along with a few other laptops and a very, very dead IBM “Convertible”.

Starting out in tradition with a horrible picture- it’s a portable machine. It’s not a laptop by any means, and doesn’t have a battery, so it needs to be plugged in at all times to work. It’s basically just a regular 386 in a very (for the time) small case. Power supply under the solid metal cover, disk drives under the perforated cover.

Compaq in bits

It, the same as the others, had been stored in a very humid location. I had plugged it in outside and it went BANG, let out a cloud of smoke and didn’t do much else.
I closed it up and stuck it out to the front of the street for the trash, went inside and concentrated on the “more interesting” computers.

The day passed and I had mentioned to friends about the equipment, and I was coerced into bringing the poor little 386 in and working on it.
I went outside, wiped most the rain off it with my hand, shook some of the ants off and proceeded to take it apart on the tailgate of my truck to make sure it wasn’t full of critters before bringing it inside.

Once I was sure it wasn’t infested with anything, it came in and was stripped down. (Picture above).

386 motherboard

With the motherboard removed, it was fairly easy to spot the failure. More tantalum caps. Replaced those with some spare regular electrolytics. You can see just how humid it is here, the plating on most of the shielding has gone bad.

Electrocap

With those changed… powered it up and HURRAH. It is alive!

Compaq alive

The thing needed a particular disk to boot each time, as the CMOS battery was bad. No “Press key to enter setup” jazz, this is all done by booting up into a program and setting the thing before rebooting into the OS.
The original battery, a square effort, rated 3.3V, negative top pip- next to the hacked together variant using a laser sight battery ($1.99 for 2!) which was plugged in and has duly been keeping the CMOS and clock alive.

cmos battery

Fitted a 6Gb IDE hard disk, with the cap set to 2Gb, and then written with a low-level formatter to Type 42, the largest the drive controller will address. 570 Megabytes! More than enough, and the new drive is incredibly fast compared to the old one. The keyboard wire is fairly standard but has gone really nasty due to old and damp.

keyboard wire

Recently I was encouraged to put up a dialup BBS. The Portable I was picked initially but refused to run the software (95% PC Compatible!) so the 386 was brought in to save the day. Had some difficulties with the Hayes 1200B SmartModem because nowhere has any documentation for the variant. Spent an afternoon working out the various registers and what changed with each DIP switch setting.

dip switches modem

After a lot of messing about, I got it switched to CCITT signaling and COM2. It worked but the BBS software refused to recognize the driver configuration.

back off

Apart it came again. I was reminded on the Vintage Computer Forums that the Portable 386 has jumper settings inside for various COM port settings. The white box behind the computer is the add-on unit, which clips to the back and provides two full-length 16-bit ISA headers to add various cards. I have the modem and a SoundBlaster Pro clone (incidentally my very first sound card I owned back in about 1994) in there.

instructions

Luckily the instructions inside are still intact. The computer has 2 UARTs, only one of which shows up if they are both enabled because it directs the interrupt to the internal socket that is used for an internal dialup modem (top right).

shields down

I don’t have one, so I set up the configuration differently.. ISA slot expansion modem COM1, internal async COM2, Modem COM disabled. Note the add-on RAM (1Mb) and additional 80387-20 Math Co-Pro chip. CPU and Co-Pro both run at 20MHz.

pliers

You don’t get to change jumpers much these days on computers. I’d forgotten. Luckily, we get some good results.

BBS booted

BBS software operational! You can see that more vertical lines have ceased to function. I’m not sure if it’s the transistors in the driver chips failing or if the insulation on the ribbon cables is giving out. It a gas-plasma display, basically the same as modern-day plasma TV’s, just it can do only orange.

BBS operational

Final piece de resistance- the Portable I and 386, the I running IRC and the 386 actually at that point dialed in to from New York. It’s running Citadel, when I have it switched on. I need to get a separate phone line for it really. I might pull the screen out again and test the ribbon cables- I need to get my sharp test leads for that though.

Fun times.

Well, because

Set up a bit of BASIC code to read the serial data off the P3 terminal server under my desk. The TRS-80 L2 ROM BASIC interpreter is not exactly fast… it kinda manages to do a little bit of if/then at 300 baud. Mostly.

TRS80
OK, so it doesn’t all fit on the screen at once.

More retro page

…so I tried LPRINT which sends to the printer instead of the screen, but the code for that is even slower:

Print-a-day

Fun times 😉