Midwest Scientific 6800, SS-50, PSU help!

[ncherry]

Well these definitely suffer from the bad connections that plague the ss-50 connectors. I often have to reseat the cards, deoxit spray, etc
Its time I fired this machine back up, I never did get Flex running.
I have a video microscope to take a close look. Let me get back to you with some images.

The pins were never designed to have 10’s of connect disconnect cycles, but I think the previous owner of the board was building and testing cards for Chicago based “Elektra” ss50/30 ram and floppy cards.

Also notable is the reverse numbering of the MSI pins vs the swtp convention.

I have not had any problems with the modern tin coated connections from mouser/amp - I built a 6800 Corsham tech system that has been pretty bomb proof.

Where do the SS30 boards plug in on your MWS? All I see are SS50s.

And not to steal you away from here but for Flex drop by:
List-Subscribe: <mailto:fufu-subscribe@flexusergroup.com>

I'm also working on my Corsham boards. Bought a bunch and then some from Frederic at https://peripheraltech.com/.

Herb and I are working on something for VCF East.

PS: Did you post the complete ROM dump? - Ah, yes you did. I grabbed them. We have a few other ROM images such as Humbug.

How much RAM do you have in the box? And do you know where it is (addressing)?

Thanks

 

[fdiskitup]

1, It still works !
2, massive capacitor this thing is like a coke can.

 

[fdiskitup]

Some pictures of the pins
They are golden in color, but definitely brass underneath. Perhaps some evidence of gold plating at the root of the pins where its a lighter yellow.

 

[fdiskitup]

Where do the SS30 boards plug in on your MWS? All I see are SS50s.

And not to steal you away from here but for Flex drop by:
List-Subscribe: <mailto:fufu-subscribe@flexusergroup.com>

I'm also working on my Corsham boards. Bought a bunch and then some from Frederic at https://peripheraltech.com/.

Herb and I are working on something for VCF East.

PS: Did you post the complete ROM dump? - Ah, yes you did. I grabbed them. We have a few other ROM images such as Humbug.

How much RAM do you have in the box? And do you know where it is (addressing)?

Thanks

1, there is a daughter board/ riser that plugs into the ss50 backplane. This board has 8 ss30 pin rows and all the bus decode logic chips on it. The ss50 backplane has no logic chips at all, just pins and traces, and power connection.

2, thanks for the flex link, I’ll drop by.

3, that frederic is a nice guy, let me know how you get on building the boards, ive done 2 corsham systems now for 6800 and 6809 with the arduino floppy emulator. Bobs corsham website might not be there forever, so Ive coppied most of the roms, disk images, etc.
Also, i built the the floppy disk controller and rtc from frederic. I built a couple of the model68 soundcards from bobs github.

4, I had a phase of collecting monitor roms, assist09, swtbug, smartbug, humbug. Peter stark seems to have been quite active on the front. Lots of articles in microcomputing magazine (p116, dec 1981).

5, for the MWS i have 64k in the box on a dram ram card 4 banks of 16k(?) 56kb useable. 0000 to DFFF, The monitor roms all sit at the top of memory. E000:E800:F000:F800

 

[ncherry]

Peripheral Technology​

1, there is a daughter board/ riser that plugs into the ss50 backplane. This board has 8 ss30 pin rows and all the bus decode logic chips on it. The ss50 backplane has no logic chips at all, just pins and traces, and power connection.

2, thanks for the flex link, I’ll drop by.

3, that frederic is a nice guy, let me know how you get on building the boards, ive done 2 corsham systems now for 6800 and 6809 with the arduino floppy emulator. Bobs corsham website might not be there forever, so Ive coppied most of the roms, disk images, etc.
Also, i built the the floppy disk controller and rtc from frederic. I built a couple of the model68 soundcards from bobs github.

4, I had a phase of collecting monitor roms, assist09, swtbug, smartbug, humbug. Peter stark seems to have been quite active on the front. Lots of articles in microcomputing magazine (p116, dec 1981).

5, for the MWS i have 64k in the box on a dram ram card 4 banks of 16k(?) 56kb useable. 0000 to DFFF, The monitor roms all sit at the top of memory. E000:E800:F000:F800

More info:

These are Deramp's videos. He managed to get an Altair 680 to boot from a serial port.
He was working with a 6800 and Flex (different memory locations) but the principle is the same. I haven't tried it yet but I am setting up one of Peripheral Technology's PT68-1 (basically a 6800 SWTPC) for doing just that. I think the second video is the serial boot but the first has some details that might clarify a few things. I also listen at 2x speed.

Flex Diskless Disk Operating System for the Altair 680 35 min

Flex Diskless Disk Operating System for the SWTPC 6800 Microcomputer by Deramp 17 min

Love Frederic's stuff. I recall reading 68 Micro magazine and drooling over the PT69-5. I now have a PT69-5A built, and a blank. Added to the rest of my weird collection of PT68K-1, PT68K-2 and other boards I've yet to build. I have various forms of Flex, RT68MX and OS9/OSK running on these.

 

[hjohnson]

Some pictures of the pins
They are golden in color, but definitely brass underneath. Perhaps some evidence of gold plating at the root of the pins where its a lighter yellow.

Good photos of the pins, thanks. Can you photograph the sockets on the SS-50 cards? Show any wear?

The thing is, many people report that TNIG gold on copper (nickel layer) will wear quickly and in the long term will corrode through. This is gold on brass/bronze, may be thick/hard or thin/soft gold. There's still old-stock Molex gold/brass parts out there, I'd like to know if they are worth the effort to obtain. But in your case they would be replacement parts! - regards Herb

 

[fdiskitup]

You can see some darker paches further into the connector, possibly some gold flake bits. But after 40 years they still look ok.

 

[hjohnson]

Enhanced closeups of your photos, show the features you describe. Seems to me the pins have sharp points, poorly cut rather than blunted. Those could act as scrapers deeper into the connectors, where the point of the pin makes forceful contact against the spring of the connector. Meanwhile, repeated removal on the SS-50 connector at the front of the bus, seems to have worn down the finish on the pins as in photo 4925. There's also evidence of small flakes which could be scraped gold. These photos and your descriptions are very informative, thank you! - regards Herb

 

[djones]

Since its a GIMIX cpu card, I think I could use GMXBUG-09 or HUMBUG. I have some 2816 EEPROM chips that migh be pin compatible with the existing UV erasable EPROM chips. Perhaps I can sneak a mini basic in.

I didnt try the ELEKTRA cpu boad with the now working SS-30 serial / baud rate generator, do you think I should disable the baud rate generator on the ELEKTRA cpu card, it cant be good to have 2 baud rate generators in the same system ?

Based on the disassembly from Daver2 I’ve been doing alot of trial and error stuff with FLEXBUG, but I’m still just enjoying noodling arround and trying to figure out the SS-50 vs SS-50c IO space etc. Theres a lot of reading to do and I get sidetracked into kilobaud and 68 magazine articles.

What I really need to do is to get the dual 8” floppy unit connected and give it a Flex boot disk. But to make a flex disk I may need to connect the 8” to my IBM to put an image on the disk…

I'm looking for a replacement Elektra MPU 8/9 processor card if you know where I might find one. Mine is corroded and currently working for now after some repair.
thanks

 

[fdiskitup]

I'm looking for a replacement Elektra MPU 8/9 processor card if you know where I might find one. Mine is corroded and currently working for now after some repair.
thanks

Corsham 6800/6809 Reproduction

Frederick at peripheral technology should have what you need to get back up and running. At least until you find an old board

 

[djones]

Corsham 6800/6809 Reproduction

Frederick at peripheral technology should have what you need to get back up and running. At least until you find an old board

Yes, I've seen that. Thanks for tour reply.