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SFD1001 Question

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Hugo Holden

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I decided to open up my SFD1001 drive for inspection.

The casing had previously been damaged and a very amateurish repair attempted, that looked like a 5 year old had done it, but that might be generous.

There were some brass ferrules glued in with soft glue where some of the plastic had cracked away on two of the case retaining screw areas and an assortment of the wrong size & length case screws.

I can fix this properly by machining some metal inserts to go in the area where the plastic was damaged.

At least the drive works, so I am lucky there, but it shows signs it has been worked on by somebody, which I always loathe, especially if it was the same person who botched the case repairs.

In any event, this drive has what looks like an original factory mod, where one of the IC's (possibly a RRIOT) has been replaced with a sub board containing a ROM. See attached photo.

Is anybody aware of this particular modification and the reasons for it ?
 

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That allowed using a different 6530 chip by placing the rom externally.

The chip you have is "
  • 6530-047 Marked as 901885-04 and used in the CBM 8050/8250 disk drive DOS 2.7"
 
The sticker on that rom lists as Dos 2.7 for the SFD-1001. So that allowed the 8050/8250 6530 chip to be used instead of a dedicated rom version of the 6530.
(6530 chips have a mask rom from the factory.)
 
dabone said:
The sticker on that rom lists as Dos 2.7 for the SFD-1001. So that allowed the 8050/8250 6530 chip to be used instead of a dedicated rom version of the 6530.
(6530 chips have a mask rom from the factory.)
Click to expand...
I'm still not sure 100% what is going on here.

Does this mean that the chip there marked 901885-04 is a 6530 IC, where the ROM part of it is completely ignored, and instead the external added 2716 ROM is used ? Which would mean that if this particular 6530 failed , I could put any 6530 in its place, because the mask ROM contents in it are not used at all and only the 2716 ROM content used ?

........but I just read from the data sheet that when the user orders the 6530 part, there are various chip select options they can specify as part of the mask option:

The chip-select pins can also be PB5 and PB6. Whether the pins are used as chip-selects or peripheral I/O pins is a mask option and must be specified when ordering the part.

That would mean that the only 6530's that would work to replace the one in my unit would have to have the same chip select setup. How do you know what that is from the numbering system on the 6530 variants ?

This remark was on Rudd's site (thanks Rudd):

I noticed that the 8250LP and SFD-1001 have a little PCB on the place of the 6530. On this PCB you will find a 6530, an EPROM and a 74LS04. The reason for this PCB was that Commodore needed to update the ROM for one or another reason. And probably it was cheaper to create this PCB than producing new 6530's.
Anyway, the CS input of the EPROM has been connected to /RS0 of the original socket. The /RS0 input of the original 6530 has been connected to +5V. This only confirmed that my idea how /RS0 should be used was correct.
One gate of the 74LS14 is used to invert PHI2 and the result is used to control the OE input of the EPROM. This construction is needed because there are two 6502s on the main board. Each 6502 has its own address bus but both 6502s share the same data bus. This is made possible because the second 6502 runs on the inverted clock of the first one. The inverted PHI2 on the OE input makes sure that the EPROM only outputs its data when the right 6502 is in command.

And, it appears that Ruud's solution is good because it uses the easier to get 6532 rather than the harder to get 6530. Currently I can only see one 6530 on ebay and it is over $100.

Monotech appear to sell a replacement:

monotech.fwscart.com

6530 RRIOT Replacement kit for CBM IEEE Drives

If you have diagnosed your CBM IEEE drive and discovered the 6530 is faulty, you can use this to replace it. I also carry other parts used in these drives including 2114 SRAM, and 6502 and 6504 CPUs. This does not come assembled . You must solder it together. The photos only show the completed...
monotech.fwscart.com monotech.fwscart.com

Also I notice the marking on the 2716 ROM as 251257-02A. Possibly it was a very late version of the 2.7 DOS because looking at Wikipedia, the 6530 RRIOT that is last on the list has this number: (probably it would be sensible if I dumped the contents of my ROM , just in case there is something different about it)
  • 6530-050 Marked as 251256-02 and used in the CBM 8250LP disk drive DOS 2.7
 
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Hugo Holden said:
Does this mean that the chip there marked 901885-04 is a 6530 IC, where the ROM part of it is completely ignored, and instead the external added 2716 ROM is used ?
Click to expand...
Yes, it does.

Hugo Holden said:
Which would mean that if this particular 6530 failed , I could put any 6530 in its place, because the mask ROM contents in it are not used at all and only the 2716 ROM content used ?
Click to expand...
No. Commodore did produce various brands of the 6530, some made after specifications of customers. The ones that triggered my research were the ones of the KIM. These are not interchangeable but only because of the ROM. But they cannot be used in your 1001 with the extra PCB and vice versa.

Hugo Holden said:
This remark was on Rudd's site (thanks Rudd):
Click to expand...
Ruud !!! You are not the only one making this mistake (no offense taken) but I just wonder why?

Hugo Holden said:
Currently I can only see one 6530 on ebay and it is over $100.
Click to expand...
Is it the correct one and is it working? That are the two big questions. For $100 you can build several replacements.

Hugo Holden said:
Monotech appear to sell a replacement:
Click to expand...
$20 for a PCB and 6532 is reasonable IMHO.
 
Sorry, yes Ruud, not Rudd! I think it is because I know a Rudd and I'm so used to typing it, it just happens typing without thinking.
 
In the meantime I turned my attention to the damaged plastic housing of my SFD1001 drive.

The top cover, for each of the retaining 4 screws, has a long cylindrical channel with a taper, which leads to a blind end with a hole in it. Each one of these four architectures has a hole for a screw thread in the other half of the case., that passes to a brass threaded inset in the bottom plastic cover, so as to hold the two case halves together, like a clam shell. The photo attached on the left shows the blind end of one of the undamaged fittings.

In the case of my unit two of the blind end hole areas had been snapped off.

So I planed the rough ends down with a milling tool and prepared two brass inserts, on my mini-Lathe to make up for the missing and damaged plastic.

The holes in the plastic that these brass inserts fit into fit into are tapered. And I cut a pair of surface grooves into the insert. I pressed them in with a good coating or 24 Hr epoxy resin. This way the brass inserts cannot pull out of the resin and because of the taper in the hole, the glue cannot easily pull out of the tapered cylindrical hole. (see attached picture before I pressed these inserts into the case).
 

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jafir said:
Are the housings the same as a 1541?
Click to expand...
I don't think they are exactly the same. I would have to check, they are definitely different at the rear top because of the IEEE-488 connector, but the rest might be similar.

I thought these was something off about the housing on mine because the top and bottom had slightly different shades of mild of yellowing. It could be possible that the bottom is the same as the 1541.
 
I have finished the SFD1001 housing restoration.

I treated in the usual way I restore yellowed computer plastic. I am not a fan of chemical oxidation of the surface. I prefer to protect it from future degradation.

I have re-named the method now......."The Molecular Fusion Technique" because it has a better Sci-Fi ring to it. If it is called "Painting" people get the wrong idea and pre-judge the results.

I have attached some photos. You can see the new color compared to the plastic color inside the housing, the outer housing surface was a shade or two yellower than the inner surface and in this instance, the color of the two housing halves did not match, with one being yellower than the other, they were obviously once from two different disk drive units. Now they exactly match.

The method works (only with one product I know of) because of the highly volatile solvent and the short time frame drying Lacquer. Not so slow drying that it melts the surface texture, not too fast setting that it doesn't react enough with the plastic surface. The product here is Dupli-color spray, number DTS56, which is just a tad off white and looks almost identical to the white on PET computers.

It chemically bonds with the surface and fuses to it everywhere at the molecular level, rather than creating a separate surface coating that can flake off or crack. Also, it is thin enough that it does not obscure the surface architecture or and surface patterning of the original plastic. If the surface is deeply scratched afterwards as a test, and under magnification, there is no separation of the surface coat as it is fused chemically with the plastic. The coat is also light occlusive to a good extent, helping to reduce degradation of the plastic with more aging. I think this is a far superior restoration method than Retrobright in terms of long term plastic preservation and the results are cosmetically perfect, but of course this method is not suited to labelled keycaps. But not everybody might agree. The thing is; there is only the one product that I know of which works properly for this application and if other products are tried, I'm sure disaster awaits.

I have attached some photos. It took about 1 hour to prepare it with detailed masking and it is wise to wash the plastic surface with dish wash detergent first to make sure there are no surface films. It only takes a few minutes to apply the fine spray and it is ready in a few hrs to handle. As usual, most of the work is in the preparation.
 

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djg said:
Web search for dupli-color DTS56 didn't return anything promising. Do you have a link to what you used?
Click to expand...


Oops........not a wonder that you could not find web references to it, the correct number is actually DST56 which has Glacial White/Tudor White on its label.

www.sparesbox.com.au

Dupli-Color Automotive Aerosol Spray Paint Glacial White 150g DST56 | Sparesbox

Shop For Dupli-Color Automotive Aerosol Spray Paint Glacial White 150g DST56 at Sparesbox Australia. $9.90 flat shipping Australia wide on all orders.
www.sparesbox.com.au www.sparesbox.com.au

The naming "glacial white", suggesting a white from a Glacier, is nothing like the actual color of this product."Tudor White" is probably more appropriate.

This product is a perfect match for the PET's slightly off white. It would also be great for restoration work on the PET computer housing too.
 
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Ruud said:
Just in case of a 6530 failure, here is a possible 6530 replacement.
Click to expand...
And here's one that's currently available. I repaired my SFD1001 with this exact part. Just be careful when purchasing 6532 chips on eBay. There's at least one seller who guarantees functional chips, yet would not make good on it when one of the parts refused to work in that adapter (fortunately the second one of the pair I bought did).

IEEE "L" RRIOT Daugherboard

corei64.com corei64.com
 
shirsch said:
And here's one that's currently available. I repaired my SFD1001 with this exact part. Just be careful when purchasing 6532 chips on eBay. There's at least one seller who guarantees functional chips, yet would not make good on it when one of the parts refused to work in that adapter (fortunately the second one of the pair I bought did).

IEEE "L" RRIOT Daugherboard

corei64.com corei64.com
Click to expand...

I found some 6532's (not on ebay) from Commodore drives, so I'm going to try them out on the original daughter board in my SFD unit. If they work I will post the results and where to get them.

Monotec in NZ also supply their board with 6530 & programmed ROM too ready to go, I got one of those to try as well. Can never have too many spare parts right, hedging the bets and covering all bases.
 
The ignore the IC type number typos in the above post

I have some interesting news to report.

I found some well priced 6530, and was about to share the location of these, 901869-01 IC's for Commodore drives which I though might have made a suitable replacement for a 901885-04 on this original Commodore adapter board in my SFD unit. Was that a reasonable choice ? Or did I get this wrong ?

(I won't say who the seller is, as likely they are victims and it is not their fault)

I fitted the 901869-01 IC to my SFD1001. Not only did it not work, it heated up violently.

Close inspection of it shows its surface has a matte finish and the makings on it have been applied with a laser, rather than ink. I am certain it is a fake and has no internal similarity to a real 6530.

Fortunately this does not appear to have damaged my drive in any way. But, it reminds to be ever vigilant, looking for fakes and that I probably should have bought an obvious vintage IC (my usual policy) and not been sucked in by the fraudsters, so to this extent I blame myself.

I will now try the Monotech adapter that uses the 6532.
 
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