Intermittent floppy disk drive problems

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georgeo
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Intermittent floppy disk drive problems

Postby georgeo » Tue Aug 09, 2016 9:05 am

Hi everyone,

I recently purchased a Trump card clone [http://www.sellmyretro.com/offer/details/sinclair-ql-ram-expansion-and-floppy-disk-interface-10861] and a dual, 3.5" floppy-disk unit [http://www.sellmyretro.com/offer/details/dual-floppy-drive-set-for-dd-and-hd-disks-%28for-ql%2C-bbc%2C-zx-spectrum-and-more%29-10864] for my QL.

These generally work well. However, from time-to-time, I find one or both of the floppy disk drives become inaccessible. Attempting to access the drive -- e.g. 'exec flp1_c1ass' -- causes the drive motor to spin for around 10 seconds, with no read/write head noise, before reporting 'Not found' or something similar.

Removing and reinserting the diskette doesn't help, though resetting the QL (using the reset button, and without power-cycling any of the equipment) does.

I've tried re-seating the Trump card and the floppy-disk drive cable. The problem seems to occur on either of the two drive units and with different floppy disks and doesn't seem to be tied to any particular action on my part. On one occasion, it seems that a floppy disk drive became corrupted by this, though that may be unrelated.

The seller has offered to repair/ replace the Trump card, if it is a problem with this, though it doesn't look like a hardware problem from my perspective. Has anyone seen something similar to this, or have any ideas as to what might be wrong?

Thanks in advance for any help,
Georgeo.


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Re: Intermittent floppy disk drive problems

Postby RWAP » Tue Aug 09, 2016 12:20 pm

Not come across anything like this - it suggests that the problem could be down to something such as heat, or electrical noise building up on the QL.

It could be the regulator on the QL needs replacing - any other suggestions?


georgeo
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Re: Intermittent floppy disk drive problems

Postby georgeo » Tue Aug 09, 2016 12:27 pm

Thanks. Are there any other symptoms of a failing regulator? For example, I'm currently using the RF output, as my monitor only has DVI and RF inputs, and see character bleed on the initial (Choose F1/ F2) screen, plus see the signal drift necessitating a retune as the QL warms up. The screen display is also misaligned (downwards) when I load Computer 1 Forth, which has a predominantly green screen.

Thanks again,
Georgeo.


georgeo
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Re: Intermittent floppy disk drive problems

Postby georgeo » Tue Aug 09, 2016 1:03 pm

In fact, I think I can get a loan of another QL unit, so it should be straightforward to determine whether or not the fault is within the QL.


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Re: Intermittent floppy disk drive problems

Postby RWAP » Tue Aug 09, 2016 8:37 pm

Yes, borrow another QL to identify this first - but you ideally need to borrow another QL PSU as it could be the PSU itself!

From memory, the QL PSU has a large capacitor inside it which may need replacing (or at least re-soldering)


robsoft
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Re: Intermittent floppy disk drive problems

Postby robsoft » Tue Aug 09, 2016 8:47 pm

Hi Georgeo - I haven't seen anything exactly like this with mine. Are you using DD or HD disks? Is there anything that might be interfering with the Trump card - yours is unshielded and basically unprotected like mine, isn't it?

I got away from using the RF cable very quickly, I bought a QL-to-Scart cable and I use that with a reasonable, 17" type LCD TV that thankfully has all manner of inputs on the back - RF, composite, SCART, VGA and HDMI so it's pretty handy.

I did plug it into an upscaler Scart-to-HDMI type thing I got from Amazon quite cheaply, which manages to drive the monitor res but try as I might there are about 10-12 pixels down the right hand side that I can't see. So for now I've gone back to using the SCART cable without any upscale, just plugged into the telly. It's usable - it's certainly rock solid, there's no crawl and nothing alters when the screen changes colour.

But none of that really helps you with your disk problem. I didn't buy the floppy disk units (I wish I did, having them in an enclosure like that is nice, I cheated and used something else, see pic in my other thread here).

I don't suppose you can get your hands on an old floppy drive and cable can you? Though it sounds like you will have a chance to try it on another QL shortly...


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Re: Intermittent floppy disk drive problems

Postby 1024MAK » Wed Aug 10, 2016 2:53 pm

Given the reported symptoms, and that using the reset switch on the QL clears it, it is unlikely to be the floppy drives. To have the same fault on both would be very unusual.

There are seperate control lines from the disk interface to the floppy drive. As the drive is engaging, it's select line must be working. If the head does not step, the drive is not receiving the signal to step the head. This could be the QL, the disk drive interface or the ribbon cable. If the head does not step, the data returned to the computer will be from the wrong track... So this will result in an error message.

So try a different QL, try another PSU, electrically test the ribbon cable if you have a multimeter.

Mark


QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
georgeo
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Re: Intermittent floppy disk drive problems

Postby georgeo » Wed Aug 10, 2016 8:55 pm

Hi everyone,

Well, it isn't the QL, as my loan unit sees the same issues. I've also noticed that one or other of the drives sometimes doesn't work from reset. That is, each time I reset the QL there is a reasonable chance (say, 25%) that one of other of the drives doesn't work. Furthermore, it usually (though not always) seems to fail after reporting the sector stats, before displaying the file catalogue - so it is getting far enough to read something.

Based on Mark's comments, I think we're down to the PSU, the ribbon cable, or the Trump card. As I don't have access to another PSU, can anyone suggest another way of checking if it is working correctly?

Thanks again to everyone that has helped so far,
Georgeo.


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Re: Intermittent floppy disk drive problems

Postby RWAP » Wed Aug 10, 2016 10:40 pm

Speak with XorA - at least he is local (ish) - maybe a scottish QL meetup... In fact if you were planning on getting together to have a look, I could always send a quick email out to other Scottish QL users....

The other option would be to maybe send your Trump Card to someone else to try, but that doesn't help if it is a power issue!


georgeo
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Re: Intermittent floppy disk drive problems

Postby georgeo » Thu Aug 11, 2016 12:48 pm

Hi everyone,

Thanks for the various advice. I've actually made some progress in that I have found a friend with a 3.5" drive that they connect to their own QL, which they lend me over the weekend. This will allow me to test the floppy drives and ribbon cable. They're a little nervous about loaning out their PSU, so I've gone for a different approach to checking this ...

... in that it has occurred to me that we have a lab at work that is kitted out to measure power consumption of computing equipment. I've spoken with one of my colleagues who will be able to check the outputs from my QL PSU to see if they are in line with design specs from Dilwyn's site [http://www.dilwyn.me.uk/docs/hardware/qlpsu.png]. They can even replace the capacitor if things don't look quite right.

All going well, I should be able to pin down the source of the problem over the next few days, so will keep everyone informed!
Georgeo



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