Centris 650 Upgrades

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phipli

Active Tinkerer
Sep 23, 2021
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I picked up a Centris 650 a few weeks back and have been making a few upgrades. So far I have done the following :

  • Upgraded the RAM to 104MB
  • Added an AudioMedia II sound card
  • Added the missing Reset / Interrupt buttons
  • Added a Stage II Rocket
  • Fitted a tray loading CD bezel
  • Fitted a 600i CD drive
  • Added 512k of VRAM (2x 256k)
  • Modified the logic board so that the computer reports as a Quadra 800
Luckily the C650 is the variant with the full 68040 (25MHz), 8MB onboard RAM and built in AAUI Ethernet.

Still planned is to add a speed switchable overclock (33 and 40MHz most likely, possibly also 25MHz), and a larger SCSI (spinning rust) hard disk. Additionally, there are three missing chassis screws that I need to replace.

There are ROM mods to enable the C650 to address 128MB SIMMs, which I'm not sure if I will do or not as even 104MB of RAM is excessive. I'm more likely to solder in a ROM slot just for ROM hacking reasons.

Further useful suggestions for modifications are welcome. What should I put in the third Nubus slot?
 

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Transferring data to a new internal disk... externally.

Handy bodge when you don't have many external SCSI enclosures ;)
 

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eric said:
Are you using something like this? I didnt know these existed and looks very handy!

Click to expand...
Yeah, that sort of thing. There are loads cheap on eBay :)

www.ebay.co.uk

12V/5V 2A USB to IDE/SATA Power Supply Adapter Hard Drive/HDD/CD-ROM AC DC MU | eBay UK

Rated output current: 2A. 1 IDE Power Adapter. Output short circuit protection. Output DC head: 4 holes. Output ripple & noise: 100mVp-p. Full load high temperature burn, 100% aging test. Output cable length 0.5 m (can be customized).
www.ebay.co.uk
 
Kai Robinson said:
Oooh, whats the 50-pin to 25-pin adapter??
Click to expand...
I can't remember where I got it, but I also have one with a male IDC connector so I can plug a ribbon cable into it.

I also made my own centronics to IDC adapter so I could make my own enclosure ;)
 

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The Centronics adapter probably makes more sense as not everybody has Zip drive system->system SCSI leads knocking about :)
 
@phipli do you have the development files? (not the gerber, than the schematic and PCB design - in KiCad or so?)
Would be great to extend with a Centronics female connector to be able to connect the bus-terminator too. Then it is really a "boxless enclosure".
 
fehervaria said:
@phipli do you have the development files? (not the gerber, than the schematic and PCB design - in KiCad or so?)
Would be great to extend with a Centronics female connector to be able to connect the bus-terminator too. Then it is really a "boxless enclosure".
Click to expand...
PCB? :)

The solution is wonderfully more simple than you're expecting. SCSI++

www.ebay.co.uk

5-Pack Centronics 50-Pin IDC Type Female CN50 Crimp Connector for Ribbon Cable | eBay UK

5-pieces of CN50 female Connector. Centronics 50 Pin Female. 50-Pin IDC Ribbon Crimp type Connector. 2.54mm IDC Pin Pitch. CablesOnline Part Number: FC-204-5.
www.ebay.co.uk

www.ebay.co.uk

10x 6/8/10/12/14-50Pin IDC Socket Plug Ribbon Cable Connector 2.54mm Pitch WD | eBay

Insulation resistance: Minimum 500MΩ. Pin Material: Brass. Insulation material: PBT UL94V-0. Pressure: 500VAC / min.
www.ebay.co.uk

www.ebay.co.uk

RIBBON CABLE, 50WAY, RS 105-5124, 10 METRE REEL (APPROX) 7429502927999 | eBay

Find many great new & used options and get the best deals for RIBBON CABLE, 50WAY, RS 105-5124, 10 METRE REEL (APPROX) at the best online prices at eBay! Free delivery for many products!
www.ebay.co.uk

I haven't verified the parts, just to warn you, but you get the idea ;)
 
@fehervaria @Kai Robinson

The PCB isn't my design, so I don't have the design files, but it is entirely an adapter, not even any passives. It wouldn't take long to draw one up from the pinouts of the two connectors.

Most of my drives have an integrated terminator, so I just use that.
 
I have one Quasimodo from 1987 - but that has no bus-termination possibility either.
Create a bullet proven 50 -> 25 pinout is no problem
 

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Kai Robinson said:
Oooh, whats the 50-pin to 25-pin adapter??
Click to expand...
There are a few of these lovely things out there. Here is one that I got for my BlueSCSI. It's made by Stephen Arsenault and is titled the "Over Easy II", here's a link to their github: https://github.com/Stephen-Arsenault/OverEasy

It has a 50 pin SCSI (female) port with a 25 pin DB-25 SCSI (male) port. So it can help to connect things like a BlueSCSI to an external DB-25 SCSI port. Although since it's a solder-it-yoruself kit, you can swap out the DB-25 connector to a female one if that suits your needs.
 
Mac84 said:
There are a few of these lovely things out there. Here is one that I got for my BlueSCSI. It's made by Stephen Arsenault and is titled the "Over Easy II", here's a link to their github: https://github.com/Stephen-Arsenault/OverEasy

It has a 50 pin SCSI (female) port with a 25 pin DB-25 SCSI (male) port. So it can help to connect things like a BlueSCSI to an external DB-25 SCSI port. Although since it's a solder-it-yoruself kit, you can swap out the DB-25 connector to a female one if that suits your needs.
Click to expand...

I bought two from amigakit in the end - pricey, but they work well and provide term power :)
 
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