October 2008 Archives

Last month I wrote about the acquisition and repair of an original Applied Engineering RAMWorks card. Since then, I stumbled into a good deal on a 1MB RAMWorks III and decided to upgrade.

The card is very similar to the original RAMWorks - it even uses the same RAM chips, just more of them. Also like the RAMWorks, it can support an optional daughter card to increase memory capacity - this time up to 3MB. These daughter cards are virtually impossible to find though, so it’s pretty much limited to the installed 1MB.

My RAMWorks III arrived with rows of pretty metal/ceramic RAM chips installed. Regrettably, one of the chips failed the diagnostic and had to be replaced with a plastic package chip from my spares (an extra 256Kx1 I’d purchased during the RAMWorks repair last month). Now the card passes diagnostics and I’m able to successfully create a 1024K CP/AM RAM drive.

My Platinum Apple IIe is starting to really shape up into a nice system. I added a DuoDisk not long ago, and I also have a hand-held scanner with interface card standing by that I need to try out soon.

I’ve been poking around for a Mockingboard sound card for my Apple IIe for a little while now, and the one thing I’ve learned from the experience is that despite robust third party software support, the dang things are rarer than hen’s teeth.

In recent years, GSE-Reactive apparently offered a limited run of homebrew Mockingboards, but those dried up a while back as well. Fortunately, it looks like another homebrew Mockinboard source has surfaced, this time hailing from Korea.

I scored one of these boards recently, and had the opportunity to try it out in my IIe with Electronic Art’s venerable Music Construction Set. The boards come stamped with a URL: http://cafe.naver.com/appleii. My knowledge of Korean is non-existent, so you’re pretty much on your own as far as navigating the site - but it does appear to be geared towards Apple II enthusiasts.

After installing the card in slot 5, I plugged a set of headphones into the on-board mini-jack output and loaded up one of the Music Construction Set demo tunes. The card worked wonderfully, outputting stereo six voice polyphony as per a Mockingboard Sound II.

Make no mistake, a Mockingboard isn’t exactly the pinnacle of synthy goodness, but it’s several orders of magnitude better than the clicks and sputters belched forth from any stock, non-GS Apple II.

The seller appears to be offering a stream of the cards on eBay, but not at a fixed price. I wound up paying $46 before shipping for mine - you may (or may not) be able to do better depending on demand. For a home brew, limited run card, $46 seems pretty reasonable and I’m quite happy having made the purchase.

I finally took inventory of the cards installed in the IMSAI PCS-80/15 chassis I received last month. Here is the breakdown:

• Processor Interfaces Inc. Cartridge Disk Controller (this is apparently a hard disk controller)
• IMSAI MIO Rev 2
• CCS (California Computer Systems) Model 2718A 2 Serial + 2 Parallel (two of these installed, only one routed to the back panel)
• JTM 16K RAM (two of these installed)
• Artec Electronics 32K-100 Rev 0
• CCS Model 2422 Multimode Floppy Controller
• CCS Model 2810A Z80 CPU

Looks like quite a bit of serial/parallel duplication - the IMSAI MIO and two of the CCS 2718As. Not sure if this is because one or more of the cards are squirrely; I’m just going to have to play around with them when I get a Variac.

It is really sweet that it has a Z80 CPU though, as that opens up the possibility of using a HarteTec Super I/O Controller. I also have a Vector Graphics Inc. 64K RAM board I can drop in there if need be.

Now I need to chase down documentation for these cards. Unlike the IMSAI 8080, this guy came bare. However, I can’t complain for the price!

Another cool thing to add might be the S-100 Bus Probe currently being offered on eBay as a kit or a pre-build. There’s a YouTube video of it in action (linked below):

Earlier this week I picked up another IMSAI - this time the classic 8080.

This is really a special machine in multiple ways. Not only is it in wonderful cosmetic condition (save for one minor issue I’ve since corrected - more on that in a bit), it came complete with the original documentation binder, which contains warranty cards, schematics, instructions, etc. not only for the IMSAI parts, but every third party card as well. In addition, every single sales receipt for every component in the system is tucked into the binder’s rear pocket - all dating from the late 70s from various historic shops around the Silicon Valley (The Byte Shop, Anchor Electronics, Sunnyvale Electronic, Recreational Computers, The Soldering Iron, etc.). It’s a wonderful piece of history.

The computer was purchased from Stewart Chiefet, the creator and host of The Computer Chonicles. That alone is pretty darn cool!

The minor cosmetic issue I’d mentioned earlier was that it was missing three of the blue paddle switch handles (two Address Data toggles and the Examine/Examine Next momentary contact) Amazingly enough, the Fischer-Freitas Co. - which has owned the IMSAI trademark since 1979 - still sells replacement parts for the 8080, including the paddle switch covers! While ordering the paddles, I also bought four zinc mounting screws for the top cover as those were missing as well (the top cover was just resting on top when I got it). As you can see from the photos, I’ve already installed the new paddles and screws and they are absolutely spot-on perfect. Special thanks go to Thomas “Todd” Fischer for continuing to offer replacement IMSAI 8080 parts - very much appreciated!

I haven’t powered the machine up just yet as I still need to pick up a Variac so I can slowly bring the power supply online; don’t need any unnecessary explosions.

Here is the list of cards currently installed in the machine:

• IMSAI MPU-A Rev 4
• IMSAI MIO Multiple Input/Output board
• Solid State Music Prototype Board (this currently contains a wire wrap implementation of a “Video Display VII” card according to included schematics)
• Ithaca Audio 8K Static RAM
• Thinker Toys SuperRAM 16K-A
• Solid State Music MB6A 8K RAM Board
• Solid State Music VB1-B Video Interface
• IBEX 16K EPROM Board
• Tarbell Elect MDL-1011A floppy controller
• Active Terminator No. 106B (CompuKit/Godbout)

The N8VEM booted for the first time today! I got the last couple components in from DigiKey, and was able to get it running during lunchtime.

The only thing that isn’t working is the power LED. I probably put it in backwards, and my attempt to reverse it didn’t work out. Not critical though - I can live without it. The computer itself is working great, including my freshly burned EPROM.

Now I need to start on the backplane and bus monitor boards - need to order some more parts!

(Yes, I do have a better power supply arrangement on order - this is just something I cobbled together to test with.)

Test Prototype Monitor Ready

>c
CP/M-80 VERSION 2.2C FOR THE TEST PROTOTYPE COMPUTER

A>f:
F>dir
F: PIP      COM : ASM      COM : STAT     COM : DDT      COM
F: DUMP     ASM : DUMP     COM : SUBMIT   COM : XSUB     COM
F: ED       COM : LOAD     COM : DEBLOCK  ASM : RTC      COM
F: VDE263   COM : VINST263 COM : R        COM : BBCBASIC COM
F: W        COM : WSMSGS   OVR : WSOVLY1  OVR : WSU      COM
F: WINSTALL COM : PRINT    TST : NEWRCB   ASM : WS       INS
F: MBASIC   COM : XM50LB3  HEX : XM50LB3  COM : XM       COM
F: WS       COM : BASCOM   COM : BASCOM   HLP : BASLIB   REL
F: BCLOAD       : BRUN     COM : L80      COM : UNLOAD   COM
F>mbasic
BASIC-80 Rev. 5.21
[CP/M Version]
Copyright 1977-1981 (C) by Microsoft
Created: 28-Jul-81
30776 Bytes free
Ok

I’m happy to report that the attempt to refurbish the ADM-3A’s screen went absolutely beautifully!

After watching a series of informative videos on YouTube stepping through the process, I was pretty confident that it would be a fairly easy task.

I followed the gist of instructions laid out in the video, with the exception that I didn’t preheat the lens with a work light beforehand - the CRT was small enough that it proved easy to heat up using just the gun. I also used bamboo skewers to poke underneath the lens to coax out hunks of PVA as I went, which worked out nicely.

Once the lens was removed from the CRT, I used Goo Gone to clean up any remaining PVA, and Windex with newsprint to clean up streaks and fingerprints. I applied bits of double sided foam tape around the outside of the CRT to hold the lens and keep it elevated from the CRT face, and after fitting the lens in place, sealed with packing tape around the perimeter to guard against any foreign matter entering between the lens and CRT. I then reinstalled the CRT assembly and it looks as good as the day it was made - no signs of burn in and perfect image quality.

Now I can concentrate on the lower case ROM project; I have the EPROM burned and ready, just need to wire up the shim socket. Hopefully I can get that completed later this week.

I finally took a trip down to Fry’s yesterday afternoon and picked up an adequate Compact Flash card for the CFFA - something I’ve been meaning to do for weeks now. They didn’t really have much of a selection to choose from, but I found a 2GB Kingston card for $15 which does the trick.

This morning I installed the new CF in place of the 16MB evaluation card, created a few 32MB ProDOS partitions and installed GS/OS 6.0.1 on the first. Everything went smoothly, and the machine boots up just fine. A pretty sweet setup all in all! I’d considered going with an Apple High Speed SCSI card, but this is really the superior option - it’s fast, quiet and has plenty of capacity to go around. Plus it’s pretty easy to read/write the CF cards on a modern machine for file transfer.

Yesterday afternoon I purchased a sheet of acrylic from Home Depot and cut a new monitor shield for my Neo Geo arcade machine. What an improvement that makes - it was somewhat tiresome looking through all the carved initials on the old one. I think I’m just about ready to move into the painting phase - I should order up some side art vinyl and a monitor bezel to get ready for that.

I finally picked up a modern EPROM programmer. I actually have an old Hippo programmer designed for the Atari ST, but the lack of documentation makes it tough to use (plus it can’t handle 32 pin DIPs). Anyway, Willem programmers are amazingly inexpensive on eBay - the 5.0C I picked up only came to $42 including shipping.

I spent the early hours this morning installing Windows XP on an old laptop (my desktop lacks a parallel port) along with the Willem software. My first target - a fresh 27C080 from Jameco, which arrived a couple days back along with my other N8VEM parts. Why the new 27C080? There’s an enhanced ROM on the N8VEM web site which includes Wordstar and other CP/M goodies, and I didn’t want to sacrifice my known good, pre-programmed 27C080 should something go awry with my own experimentation.

It took me a couple of tries, but in the end I got a successful, verified burn. I’ve gone ahead and installed the new ROM in the N8VEM.

The Willem burner will also come in handy when the 2716s arrive for my ADM-3A lowercase project - the 2102-1 RAMs have already arrived and are installed and waiting. Which reminds me, I need to pick up a heat gun this weekend and see about that CRT lens …