BBC Master compact disk issues

[jay_oldstuff]

Hi all i am on a bit of a retro computer kick right now and have just successfully resurrected a couple of acorn a3000's. I now have turned my attention to a BBC master compact, it seems to be fully working but only has a 3.5" floppy disk drive and all my BBC software is on 5.25" So with a bit of research on the web I made up a 25 pin din to IDC cable and connected that from my master compact to a Teac SSDD 80 column disk drive with external psu, now with the computer and drive powered up and a disk in the drive, press shift brake and the drive seems to initialize the LED on the drive lights and the disk spins but all I get is Disk error 50 at :0/000000
I have tried three disk drives and many disks and always get the same error.
Unfortunately my model B is very sick at the moment (Psu took out a good proportion of the logic ic's when it blew ) so I have no way of testing if the disks or drives function otherwise but they did work when put away in storage.

Jay

[cmjones01]

Disc error 50 implies to me that the Master Compact is using ADFS and therefore expecting a double-density disc. Are your 5.25" floppies formatted ADFS double density? Relatively few were - they were mostly single-density DFS.

Assuming your Master Compact has a DFS ROM installed, try holding down shift-D-Break to force it to use DFS instead of ADFS. That might help.

If you don't know whether it's got a DFS ROM, *ROMS should reveal all!

Chris

[jay_oldstuff]

Many thanks for that Chris. I tried *ROMS and I have no DFS ROM installed only a ADFS ROM, there should however be a DFS ROM in my dead model B Hopefully still in working order.
I'm out for the night but hopefully will have time for a play tomorrow.

Jay

[cmjones01]

You'll need a different DFS ROM for the Compact, almost certainly. The one from your Model B is unlikely to do the trick. The Master Compact uses a 1772 disc controller chip, and most model Bs used an 8271 or 1770 which was mapped at a different address from the Master one. The DFS for the Master series is also supposed to support *CONFIGURE, I think. There's a handy reference to what works with what here:
http://mdfs.net/System/ROMs/Filing/Disk/Acorn/versions
and even more handily, you can download the ROM images from
http://mdfs.net/System/ROMs/Filing/Disk/Acorn/

The BeebEm emulator in Master 128 mode uses DFS 2.24, so I'd probably start with that one.

If you don't have an EPROM programmer I can soon burn you an EPROM and post it to you, but it would take a few days to come from Poland...

Chris

[jay_oldstuff]

Once again thanks for that Chris, it looks like any DFS ROM after version 2.10 should be ok to run with either a 1770 or a 1772, not sure what my old model B has in it to be honest, I
Know it started out as tape only and had the disk drive IC's fitted at a later date, I have a bill for this work from 1986.
I will download the rom image when I'm home, I do have an EPROM burner, must be 10years since I used it last but will have a go if the ROM from the B is on no use.

Jay

[cmjones01]

Even if your model B has a 1770 disc controller, which it may do if it was upgraded in 1986, it'll be mapped at a different address to the one in the Master so it won't work as far as I know, but it's always worth a try!

Chris

[jay_oldstuff]

I had a look anyway but it's only DFS version 2.10, on an up note some time ago I bought the remnants of a long closed down 80's computer repair business, I've just been up to my stores and have a number of old EPROMs I can wipe and use. Also while there I found one tube of ROMs labels master compact will see what's on them when I'm home😄.

[jay_oldstuff]

Well not looking good. I’ve tried the three EPROMs with master compact on the tube. One is a word processor called word-wise, one seems to me a comms package to be used with a modem, and the other appears blank. oh well. still I’ve found a number of 27C128 EPROMs. Unfortunately, I cant find ether my UV eraser or my EPROM programmer.
Chris if it would not be too much trouble would you be able to burn the required image to an EPROM for me. I will of course cover all costs.

Jay

[cmjones01]

OK, consider it done! I burned a 27128 this morning with DFS2.24. PM me your address and I'll post it to you.

Cheers
Chris

[jay_oldstuff]

Thats fantastic Chris Pm sent

Jay

[jay_oldstuff]

The DFS ROM from Chris arrived today and I've just installed it. And we have a partial success, I can now access the 5.25" floppy but it looks like ether the drive is bad or my disks have deteriorated over time. I got 1 disk out of about 200 to run once, on the second attempt it failed. the disks at least try to load. I have some other BBC disks that where stored separate and are in there original plastic boxes which I'm going to try. I will also go over the drive, I did clean the head when I first started this project but will have another look and also have a look at the alignment procedure for the drive. once I have the drive proved to be working correctly my plan is to combine it with a 3.5" drive so I have the best of both worlds in one unit.
I had a look through my junk and uncovered this nice case which will take both drives. it originally contained a double height DAT drive so should have plenty of power for the two disk drives.

Jay

[jay_oldstuff]

Ok well I braved the mess under the stairs and dug out the other software I have this is all original boxed software kept at a pretty constant temperature unlike the other box of disks that was up in the attic with my beeb's. Some disks are loading but the majority are not. I'm also not getting any colour output from my RGB to scart cable, it worked fine on my old model B but that was with an old CRT TV something for which I have no space for on my desk.

Jay

[cmjones01]

Great! I'd glad the ROM made a difference. I've found that 5.25" discs are fairly robust, so I'd expect many of them to be OK. However, there are a few more things to check. Is the drive you're using the one which the discs were originally written with? If not, there may be an alignment problem. I have found that a tweak on the stepper motor alignment often helps.

There's also the 40/80 track issue. BBC discs were unusual in that they tended to be a random mixture of 40 track and 80 track. I note your drive is 80 track - what symptoms do you see/hear when a disc doesn't work? Do you get a whirring motor then 'Disc fault 18' (sector not found) which implies a poorly disc or misaligned drive, or do you get a terrible clatter-clatter-clatter sound as the head hunts backwards and forwards, which would imply to me that the disc is 40 track and the drive is 80?

In any case, DFS discs have the catalogue on the first track so *. should work even if nothing else does.

Chris

[jay_oldstuff]

Right, thanks again Chris. No this is not
The original drive that most of the Beeb disks where used with I do have the original drive somewhere in the attic but sadly it's faulty. This is one I picked up years ago as a bare drive. It has been modded with a switch to select 40 or 80 track operation.

Jay

[Station X]

Have you tried formatting, writing to and reading from a disk which is no longer needed?

[jay_oldstuff]

I have just tried formatting a couple of old PC double density disks on the Beeb and both failed to format with disk write error. both these disks worked fine in my old 386 PC and running disk doctor on them showed them to be error free. I also tried formatting one of the old BBC disks on the PC (old ICL branded with a date written on the label of 1984) it formatted as a 360K double density disk OK but disk doctor showed a few bad sectors.

So it does look like I may well have drive issues,

Jay

[cmjones01]

Try formatting the discs a couple of times. It's not unusual for a disc formatted one way (double density, for example) to take a bit of effort to reformat a different way (single density, for example). I had exactly this trouble last week reformatting some old PC 360k discs to use with Beeb DFS. The factory-preformatted ones were particularly difficult and one needed three goes, but it worked eventually. I think bulk-erasing them first would help, but I haven't got a bulk eraser!

Chris

[julie_m]

It never hurts to give the heads a good clean. And make sure the head assembly is travelling freely (if you have the right manuals, you should be able to write a program just to seek the heads repeatedly from track 0 to 39 or 79 and back to 0 again by means of OSWORD calls; I remember playing with this stuff years ago. I had an old, uncased full-height drive for awhile that was good to watch) -- clean off and replace any dried-out grease.

I made a bulk eraser from a big old transformer, by removing the secondary winding (which was shot .....) and rearranging the laminations, with just all the E's facing the same way.

[jay_oldstuff]

Right we have a working system. first I dug out an old IBM double height drive I think from my original IBM PC (removed when I fitted the PC's massive 10MB hard disk). Now this drive has no drive select jumpers being hard wired as DS1 however when hooked up to the beeb and trying *form80 and selecting drive as 1 and the disk formatted with no problems. Im not going to be using this drive with the BBC but it did prove the only issue is with the old drive, ive cleaned the heads and they are spotless but the grease in the drive seems to resemble that that we find in a 70's bsr record deck I'e sticky.
A quick venture up into the attic again and we have another drive again a Teac and again 40/80 switchable. this drive was intended to be powered from the beebs PSU but I striped it from the case temporally fitted it to the case I am using.
Ive now tried about 30 disks and the majority read ok, I have a number of game disks that are recorded 40 track one side and 80 track the other and these have confirmed the 40/80 switching on the drive is working. just need to fit it in the larger case now together with a 3.5" drive and I'm sorted.

Jay

[cmjones01]

Great! I'm glad to hear it. Sticky grease could well make a difference to the accuracy of the head positioning in a drive, so that could explain the problems. At least you've found a drive that works. The Teac ones are reliable in my experience - they were the expensive choice back in the day, and the ones I've had have still worked well today.

Enjoy the machine!
Chris