Hey, I would like to know, has anyone ever replicated any of the old Commodore B128 computers (the ones utilizing the 6509 processors)?
Yes, I found multiple replications for the Commodore Pet.
Even here, I saw the Micro-PET (http://www.6502.org/users/andre/petindex/boards.html)
I suppose, I could also use another alternative https://www.glensstuff.com/pet2001/pet2001.htm , follow closely the overall design and modify the architecture as to implement the quirky bank switching of the mos 6509 processor.
My goal, was to achieve software compatibility for the B128.

Yeah, originally, I was lucky enough to acquire at B128-80 (CBM 710). http://www.zimmers.net/cbmpics/cb4s.html
As stated from the seller from eBay, "all it needs, are replacement rom chips." Turns out, computer booted up, without doing a memory check. When I did a simple test to print text, it displayed gibberish. And the built-in display eventual died after being on for a few minutes. Eventually, I discovered a number of ICs suffered the fate of corrosion from numerous pins due to age.

Having discovered, that a number of local Computer repair shops, would not touch a vintage 8-bit computer, I took the journey of learning on how to de-solder and re-solder components. Unfortunately, alone the way, I’ve learned on what not to do. Eventually, learned the proper way to solder. However, the in mist of the activity, apparently, I reached the point of, no recover , since some where down the line, I got short between +5v line and a ground. (While looking through magnifying glass, I couldn't find any obvious signs of any solder beads, touching any adjacent points.)

When, since it is really extremely rare to come across spare mother board for the CBMII series, I am wondering if anyone ever attempted to reproducing PCB board, based upon existing schematics? http://www.zimmers.net/anonftp/pub/cbm/ ... index.html

Though, I’m really not sure, if there was an attempt by Ruud Baltissen, to design a new CBM-II using modern ICs like CPLDs and may be even FPGAs. But I can’t seem to find anywhere if he was successful or not.
I sure would hate, being a newbie, to attempt this effort from scratch.

Thoughts??

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It's not what you're asking for, vmarcus but I notice Jim Brain built Fake6509 which is, I gather, a workalike board to replace the 6509 - see
MOS 6509 look-alikes?
which links to the Nu6509 repo.

For backgrounders on the CBM-II line, see
https://www.floodgap.com/retrobits/ckb/secret/b128.html
http://www.6502.org/users/sjgray/comput ... index.html

Hey,
thank for your response.
However, this is just a opposite of what I was looking for.
Basically, I have a fully functional 6509 cpu, but the issue is with main mother board.
If I'm not mistaken, the Fake6509 is replacement of the extremely rare to 6509 cpu for a mother board missing that cpu.

Hey, I like to give thanks to all who responded.

Well, like me reintroduce myself. Basically, I am career programmer for the past 29 years, primarily in Cobol and IBM mainframe assembler. So, I’m pretty much been a purely software guy, now attempting to dive into the world of digital electronics. Though, my introductory experience was a C64, of which I then ventured with C128.
Been decades ago, when I first learned to comprehend the differences in little endian vs big endian, between 6502 and z/architecture.

Yeah, I recall back when I was teenager, in the mid-eighties, of those ads from Protecto Enterprises for B128, been wondering what was the deal. http://www.6502.org/users/sjgray/comput ... tecto2.jpg


Though, after seeing Michal Pleban's demo, where he reversed engineered one of those 8088 adapter boards and had written all the necessary "glue" (in software) in bridging the interrupt calls for keyboard and screen I/O, I was pretty much impress, he was able to run MS Dos on this machine. Seemed an incredible miracle in my book. https://www.youtube.com/watch?v=u4O8dIvz3WI

I suppose, that sparked my curiosity.

Nice to have you with us, vmarcus

C64 to IBM mainframe sounds like an interesting journey...

-- Jeff

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I think I'd go with replacing all the capacitors, as BDD suggests - it's a relatively mechanical operation, and it stands some chance of fixing the problem.

Did you try sending it to Edward Shockley? He is pretty much the last B-Series repairman in the US and will repair for free for price of shipping (if no ICs are required).

https://www.insectria.org/b128/forsale.html

Well,
as a status update, alone way of my journey, I also got a hold of B128 – model CBM 610. This one had a with a 220-v power supply.
Being here in the US, I decided to replace the power supply on my own.

Lucky, I was able learned from others. Basically, I gutted out the original power supply circuit board and replace it with a MeanWell model PT-65B. Then I had to supply the 60Hhz timer feed, as required for the Video. Finally, taking the easier way out, I got pair of adjustable 555 timer module. Using a oscilloscope, I turned the variable resistors to desire frequency. Using one of the two +5v leads (at 5.5a) from power supply, I supplied the power as it, the timer module. Assuming, the module would pull in power as needed, would out burning out one of the modules. So, to remedy the situation, I limited the current with a 0.5 amp fuse, using the other module.

Well, while I was at it, since I had available +12v, I decided plug in the SBC Arm board that I had, into the mix.

So, now there are 2 video outputs from the same box, for this demonstration. I figure, I'll need fans at this point, but I'll need to first resolve issue some keys on not working on the original Keyboard. Yeah, some reason, the available ram in bank 3, is significantly reduced. Ugh, more hardware issues.

Ah, nothing like comparing an actual machine to the Vice (Commodore) emulator. A

I really need to get around to troubleshooting my B128 sometime...power comes on, but nothing happens. Of course, I have no peripherals for it anyway...

Hey,
it appears I must be one of the luckiest guys, on the planet.

As with my original CBM 710 (B128) mother board, I just knew I toasted this thing. So, luck would have it, I just happen to come across a CBM 710 mother board, that someone was selling on eBay. Apparently, there was issue with the PLA chip, but luckily, I swapped in the one from my original board. Even thing worked out. Surprisingly, this one worked out better than the origin. Looks like this one had some nice work done. They, replaced the original rom chips with a daughter board with one containing three 64k-bit HN4827G4G EEProm chips. They also, soldered in IC Sockets for banks 3 & 4. For a 40-year-old board, this one appears almost like pristine condition, compared to the original board. Originally, upon several attempts at cleaning the contacts for the keyboard port, I thought my keyboard some shotty keys. But when I plugged in the keyboard this time, all keys seem to work.
Next, I would like to follow up with the following:

1. Fix/recondition monitor, which seems to dim out, go totally black within 5 minutes.

a. Still not something, I’ll attempt without some serious instructions.
b. Saw a YouTube video, where a guy used a screw driver with a dangling alligator clip to discharge the CRT Yoke. I’m still like hanging, dude was the other end of the wire, attached to a ground? Serious, concerns about discharging residue high voltage charges.
c. While looking at the CRT Schematics http://www.zimmers.net/anonftp/pub/cbm/ ... matics.pdf, my only clue is to follow only the +12v supply line, replacing capacitors along the way.

2. Construct an external (composite) monitor interface.

a. Looking at CN10, not sure if this is technically inline 6 pin molex connector?
b. But basically, I’m assuming I just to replicate the comp video line, like that from the CBM 610 model.

3. Replace power supply with an ATX supply.

a. I already have an ATX PSU that would fit in this area. And I have ATX power break out board.
b. My challenge, is replicating the 60Hz line, and addressing the difference in current (i.e. +5v - 15a to 4a)