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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 30th Sep 2023, 12:58 pm   #181
ScottishColin
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Default Re: Commodore 8050 dual disk drive

OK - I think I'm good now.

The proper 96TPI DS/DD diskettes made a difference; I got 7 and could format (HEADER) two of them. Then, coincidence or not, replacing the 6821 with a 6520 meant I could HEADER all the rest of them.

I still get very little luck with my 48TPI DS/DD diskettes but I guess as the device is 40+ years old, I ought to feed it what it is expecting.

Using the programs here:

http://www.zimmers.net/anonftp/pub/cbm/pet/utilities/

in particular 8050diag35.d80.gz was very useful. One of them displays the speed of the drive continuously which showed me that one was a little slow and one a little fast and I could adjust them on the fly to get them to the documented 300 rotations per minute. There are other programs in that download to perform more exhaustive tests both of the drive and the diskettes and I'm now comfortable that it's working as well as it can.

Thanks to all of you. Again.

Colin.
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Old 1st Oct 2023, 6:05 pm   #182
ortek_service
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Default Re: Commodore 8050 dual disk drive

Quote:
Originally Posted by ScottishColin View Post
OK - I think I'm good now.

The proper 96TPI DS/DD diskettes made a difference; I got 7 and could format (HEADER) two of them. Then, coincidence or not, replacing the 6821 with a 6520 meant I could HEADER all the rest of them.

I still get very little luck with my 48TPI DS/DD diskettes but I guess as the device is 40+ years old, I ought to feed it what it is expecting.

>>
>>
Colin.
Good to hear you've now got this working fairly-well.
I suppose you could always try swapping the PIA's back again, to prove whether a 'digital' I/O device is actually having much affect on analogue-levels.

It may be more the case that the disks might be nearly 40years old, and may be more-likely to have degraded. However, it is probably advisable to use 96TPI, if these drives are actually 100TPI, rather than using 48TPI disks.
- Although it very-much depends on overall density of the bits on the disk / whether single or 'double' density is being used, being as there's no real distinction on the disk surface of width of the tracks and only HD ones might require different write currents.

But re-calibrating the speeds may also help - Not only in interchangeability between other drives, as if disk runs too fast then end-sector data could start to overwrite first sector.


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Originally Posted by ScottishColin View Post
Evening all.
>>
So - I've fixed the motor on drive 1 permanently spinning with the advice below.
>>
>>
I was rather confused by exactly what advice that referred to / how you actually resolved that in the end. So it would be good if you can give us a bit more info as to the cause / your fix.

TIA
Owen
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Old 1st Oct 2023, 6:20 pm   #183
SiriusHardware
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Default Re: Commodore 8050 dual disk drive

There was some faulty RAM which TonyDuell (rightly) suggested was a likely cause of the initial error flash, plus a faulty TTL chip in the motor control board preventing operation of one of the drive motors, but any further problems have been resolved by Colin himself.

That observation of 6821 vs. 6520 is quite an important observation to have made, it could save someone else a lot of hair loss at a later date. Odd the way it only affected one drive though, considering both drives operate through the same common bus and same three IEEE 488 buffers.
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Old 1st Oct 2023, 8:20 pm   #184
ortek_service
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Default Re: Commodore 8050 dual disk drive

Quote:
Originally Posted by SiriusHardware View Post
There was some faulty RAM which TonyDuell (rightly) suggested was a likely cause of the initial error flash, plus a faulty TTL chip in the motor control board preventing operation of one of the drive motors, but any further problems have been resolved by Colin himself.
>>
>>
Yes, I do recall those. But it looks you also don't know how Colin resolved the constantly-running motor problem he had.

Quote:
Originally Posted by SiriusHardware View Post
>>.
>>
That observation of 6821 vs. 6520 is quite an important observation to have made, it could save someone else a lot of hair loss at a later date. Odd the way it only affected one drive though, considering both drives operate through the same common bus and same three IEEE 488 buffers.
Well, as Colin said, it doesn't seem quite conclusive yet whether the 6821 was a problem - particularly as some disks had worked OK. And it seems he may have done some other things since (like adjusting speeds?).
So it would be good to confirm whether using a 6821 was really an issue - especially as 6520's are no doubt harder to obtain / more expensive, and Colin may have needed to borrow these from other Commodore equipment.
Although not a bad idea to try and obtain some genuine 6520's, if obtainable at reasonable cost, to keep things a bit more-original.
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Old 2nd Oct 2023, 10:39 am   #185
ScottishColin
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Default Re: Commodore 8050 dual disk drive

I had de-soldered CR26 to check something and my resoldering wasn't as good as it should have been so checking and resoldering CR26 fixed the continuous spinning.

Colin.

Quote:
Originally Posted by ortek_service View Post
Quote:
Originally Posted by ScottishColin View Post
OK - I think I'm good now.

The proper 96TPI DS/DD diskettes made a difference; I got 7 and could format (HEADER) two of them. Then, coincidence or not, replacing the 6821 with a 6520 meant I could HEADER all the rest of them.

I still get very little luck with my 48TPI DS/DD diskettes but I guess as the device is 40+ years old, I ought to feed it what it is expecting.

>>
>>
Colin.
Good to hear you've now got this working fairly-well.
I suppose you could always try swapping the PIA's back again, to prove whether a 'digital' I/O device is actually having much affect on analogue-levels.

It may be more the case that the disks might be nearly 40years old, and may be more-likely to have degraded. However, it is probably advisable to use 96TPI, if these drives are actually 100TPI, rather than using 48TPI disks.
- Although it very-much depends on overall density of the bits on the disk / whether single or 'double' density is being used, being as there's no real distinction on the disk surface of width of the tracks and only HD ones might require different write currents.

But re-calibrating the speeds may also help - Not only in interchangeability between other drives, as if disk runs too fast then end-sector data could start to overwrite first sector.


Quote:
Originally Posted by ScottishColin View Post
Evening all.
>>
So - I've fixed the motor on drive 1 permanently spinning with the advice below.
>>
>>
I was rather confused by exactly what advice that referred to / how you actually resolved that in the end. So it would be good if you can give us a bit more info as to the cause / your fix.

TIA
Owen
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Old 2nd Oct 2023, 10:59 am   #186
ScottishColin
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Default Re: Commodore 8050 dual disk drive

I'm not convinced re 6821 vs 6520 (and I have ordered a couple of spare 6520s - not the cheapest devices as you say). I will do further checking by swapping components. It's certainly true to say it got better with a 6520, but I (probably like you) would like to absolutely know.

Adjusting speeds was done after swapping in the 6520. That's another thing to try with the 6821 back in again. It's a neat BASIC program that shows the speed continuously and the drives allow adjustment while they are running/powered on so you see the effect of any change immediately.

When I get the time, I'll post back.

Colin.

Quote:
Originally Posted by ortek_service View Post
Quote:
Originally Posted by SiriusHardware View Post
There was some faulty RAM which TonyDuell (rightly) suggested was a likely cause of the initial error flash, plus a faulty TTL chip in the motor control board preventing operation of one of the drive motors, but any further problems have been resolved by Colin himself.
>>
>>
Yes, I do recall those. But it looks you also don't know how Colin resolved the constantly-running motor problem he had.

Quote:
Originally Posted by SiriusHardware View Post
>>.
>>
That observation of 6821 vs. 6520 is quite an important observation to have made, it could save someone else a lot of hair loss at a later date. Odd the way it only affected one drive though, considering both drives operate through the same common bus and same three IEEE 488 buffers.
Well, as Colin said, it doesn't seem quite conclusive yet whether the 6821 was a problem - particularly as some disks had worked OK. And it seems he may have done some other things since (like adjusting speeds?).
So it would be good to confirm whether using a 6821 was really an issue - especially as 6520's are no doubt harder to obtain / more expensive, and Colin may have needed to borrow these from other Commodore equipment.
Although not a bad idea to try and obtain some genuine 6520's, if obtainable at reasonable cost, to keep things a bit more-original.
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Old 2nd Oct 2023, 11:24 am   #187
SiriusHardware
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Default Re: Commodore 8050 dual disk drive

Quote:
It's a neat BASIC program that shows the speed continuously and the drives allow adjustment while they are running/powered on so you see the effect of any change immediately.
That's another thing I love about these, the fantastic community resources that they seem to have built up around them. If there's a bit of PET hardware or software that you can imagine the need for, someone has probably already made it by now.
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Old 3rd Oct 2023, 12:15 am   #188
ortek_service
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Default Re: Commodore 8050 dual disk drive

Thanks, Colin, for letting us know the constant-spinning was actually due to an an accidentally-introduced fault (always a risk of breaking something else, when trying to fix things as I'm sure many of us have found!), rather than it being an original problem with this.

And we'll look forward to hearing whether it really does seem to be crucial that a 6520 is used, rather than a 6821 alternative, for it to work reliably.
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