6220 5Mb Winchester (microNOVA I/O)

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I spotted this rather unusual (to me anyway) Data General item pictured by an enthusiast in the USA who posted on a vintage computing forum. My curiosity got the better of me even though the seller sent me a picture of the rear of the unit that looked like it had been stored in a pond for a few years! Well I couldn’t resist and did a deal and arranged for it to be shipped over to me here in the UK. 

In the flesh it was MUCH worse than I had envisaged (so much so that the shipping box had a pool of rust in the bottom that had shaken out of the unit! I thought I had simply bought a heap of rust, that was until I managed to remove the cover; which was a challenge as every screw had corroded beyond use and had to be carefully drilled out. 

Once I had finally removed the cover I was gobsmacked to find a 8″ Winchester disk sitting inside! I sent VIP Bruce Ray a message asking him what he thought it might be and Bruce confirmed that it was an external 5Mb Winchester Disk for the MPT/100. I think I might start to play the lottery as finding an MPT/100 and it’s external disk in the space of 3 months seems incredibly lucky to me! 

This is going to be a big restoration job as this 37 year old chassis will need completely stripping, sand basting, respraying and reassembly; each mechanical and electronic component will need careful removal, cleaning, testing and reassembly. Luckily all of the electronics and important components are mounted approx. 15mm from the base of the chassis and look as though they have escaped the water!

My intention is to restore it to (as close as) museum grade as I can and then see if I can get it working and hooked up to my MPT/100.

I have decided to strip this unit down now (rather than work on other projects) as I am fed up with it belching out rust everywhere when I move it! I can then sent the chassis for sandblasting and re-painting and whilst its away I can continue work on the MV/9800 restoration.

Here are some more pictures of the unit prior to Winchester Disk (005-018352) removal. 

I disconnected the two cable assemblies from the top of the Winchester and moved them out of the way. Next came the module mounting screws which are located on the underside of the chassis. The module is de-coupled from the chassis by removing three sets of two screws (Hex Head and Philips). Once these were removed I carefully lifted the unit up using the lip on the right and the pull arm (shown next to the capacitor above) on the left carefully resting it on the chassis side so that I could remove the PCB connections before fully removing the unit and placing it on the bench.

The Chassis is not too bad to be honest and very salvageable:

DG 6220 Winchester Chassis

The PCB on the underside (005-015553) is in reasonable condition considering the environment its been subjected to. Some Integrated Circuits are showing corrosion on the legs and three transistors are the worse for wear (as shown in the pictures below):

DG 6220 Winchester PCB

On to the PSU which is positioned at the rear of the unit and is secured by three screws under the chassis and one to the rear. Once these are removed the PSU lifts away from the chassis. One point of interest is that DG provided lots of spare cable length (which was obscured by the Winchester module) looped at the rear of the PSU and  once released from the clip would have made removal of the Winchester much easier – had I known!

The PSU removal revealed more rust that will need treatment and also the IN and OUT DB25 cabling which utilises panel mount IDC ports and replacement will be relatively easy.  The RED pin connectors shown below are the IN and OUT cable connections at the Winchester end.

Disconnecting the spade connectors on the fan and power switch will allow the PSU to be completely removed from the chassis.

The final items to be removed from the chassis are the Fan and I/O cables. The Fan is held in place with three bolts and captive nuns and is easily removed. The I/O cables (In and Out) are constructed from ribbon cables and IDC DB25 and IDC PCB headers and will be relatively simple to repair/replace. The female (OUT) and male (IN) DB25 sockets are heavily corroded and will require replacement.

So I now have a fully stripped chassis that I am going to have shot blast.

The chassis as now been sandblasted and all of the rust removed. I used a local company more used to working on Formula 1 parts than old DG frames! Pro-Polishers in Oxfordshire, UK: http://www.pro-polishers.co.uk/ did a fantastic job – thanks Gary. 

The next stage was to remove some sheared bolts from the chassis, I used a 2.5mm drill bit to carefully drill through the 3mm bolts and then I used a 2nd stage 3mm tap to remove the remains of the bolts from the chassis. 

Finally I treated the chassis with a rust converter which will change any remaining rust molecules (Iron Oxide) into Ferric Tannate. You can see this solution turning the remaining rust purple. A further coat will be applied and it will then be ready to send to the paint shop for a new lick of paint. 

Lots more to follow………

 

Computer World Editorial 1982
6220 Press Cutting

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