Author Topic: Issue 3" drive rotation speed  (Read 1785 times)

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Offline Kris

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Issue 3" drive rotation speed
« on: 15:49, 27 April 17 »
Hello all,


I just face a strange behaviour with my 3" drive: I just change the drive belt and run "RPM" software to set up the rotation speed.
Result is that rotation is read as "600 RPM" instead of 300; the soft display in continue 600 600 300 600 600...Etc

Edit: I just try this drive into another CPC and it works perfectly (RPM gave about 300 Rpm).
It means that a component into the CPC is defective but which one ? FDC ?

Any idea about what is wrong  ?
Thank you
« Last Edit: 16:00, 27 April 17 by Kris »

Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #1 on: 16:33, 27 April 17 »
Crazy RPM readings can be caused by an intermittent 12V rail. Check for dry joints on all the connectors, especially the ones to the motor. Also make sure that you have removed all the old gunk on the two belt wheels.

Bryce.

Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #2 on: 16:41, 27 April 17 »
The drive is working perfectly onto another CPC so it does not come from the motor etc... but from the CPC itself.
Everything welding point are good on the drive side and old drive belt wheels have been fully cleaned.


I also use the same monitor and 12V from it is good and stable.

Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #3 on: 16:49, 27 April 17 »
Yes, but even moving the drive from one computer to the other can be enough to temporarily "re-join" a dry joint.

Bryce.

Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #4 on: 17:44, 27 April 17 »
To be sure, I just rework 100% of the welding point on the drive: results is the same: not OK on the original CPC but works perfectly on all the other ones.


Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #5 on: 17:46, 27 April 17 »
That's wierd. Possibly a crack in the wires from the mainboard? Or dodgy terminals in the power connector? Try spinning up the disk and see if you can get it to stop by moving the power wires.

Bryce.

Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #6 on: 18:42, 27 April 17 »
The issue is coming from the CPC : I installed a drive from another fully working 6128 and got the same result of 600-610 RPM....
VEry strange, I continue to investigate.


Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #7 on: 14:07, 30 January 18 »
Back on this issue, I still don't have any idea how to fix it....help wanted  ;)

Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #8 on: 14:23, 30 January 18 »
Send me the CPC (just PCB) if you like.

Bryce.

Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #9 on: 20:46, 30 January 18 »
Why not; let's continue on PM

Offline gerald

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Re: Issue 3" drive rotation speed
« Reply #10 on: 22:04, 30 January 18 »
Did you check the index signal from the drive to the FDC ?

Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #11 on: 15:09, 07 February 18 »
At the moment, I did not take time to check any components but I will do it this evening (I own an oscilloscope but any help would be grateful) :)


Here are what RPM soft give me as results (602 RPM - note that this drive has been correctly calibrated @300RPM - track 19 with an other CPC ).



Offline guigui37

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Re: Issue 3" drive rotation speed
« Reply #12 on: 18:54, 09 January 21 »
Hello
I have exactly the same Issue on my3” drive (still internal)... [size=78%]I am running rpm from gotek externaly... the speed is always about 600 ... and sometimes displays 300 but immediately goes back to 600... did you solved this issue ? How ?[/size]
[/size][size=78%]Thanks[/size]
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Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #13 on: 19:30, 09 January 21 »
If the RPM test is giving crazy results, it's usually just a bad solder joint.

Bryce.

Offline guigui37

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Re: Issue 3" drive rotation speed
« Reply #14 on: 21:22, 09 January 21 »
Yes totally crazy....
Do you have an idea of the location ? On the mainboard of my 6128 or on the board of the floppy drive... in a specific place ?
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Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #15 on: 23:41, 09 January 21 »
On the drive itself. Usually the connectors.

Bryce.

Offline guigui37

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Re: Issue 3" drive rotation speed
« Reply #16 on: 10:39, 10 January 21 »
Ok, i will Check....
I already saved the main board so tones of soldering are fresh...
Thanks..  ;)
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Offline guigui37

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Re: Issue 3" drive rotation speed
« Reply #17 on: 12:44, 10 January 21 »
Redone all connectors and more, no change  :'(
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Offline GUNHED

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Re: Issue 3" drive rotation speed
« Reply #18 on: 14:55, 10 January 21 »

Bonjour!


My guess would be a problem in the software. If the drive would really speed up from 300 to 600 you probably would hear it.



Hello all,


I just face a strange behaviour with my 3" drive: I just change the drive belt and run "RPM" software to set up the rotation speed.
Result is that rotation is read as "600 RPM" instead of 300; the soft display in continue 600 600 300 600 600...Etc

Edit: I just try this drive into another CPC and it works perfectly (RPM gave about 300 Rpm).
It means that a component into the CPC is defective but which one ? FDC ?

Any idea about what is wrong  ?
Thank you
http://futureos.de --> Get the revolutionary FutureOS (Recent update: 2020.12.29)
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Offline Kris

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Re: Issue 3" drive rotation speed
« Reply #19 on: 15:12, 10 January 21 »
Bonjour!


My guess would be a problem in the software. If the drive would really speed up from 300 to 600 you probably would hear it.




You're right, there is no issue with the drive itself, I tested it onto another CPC and result is about 300RPM so 3" drive is not the root cause. I do the same with another drive connected to the motherboard which gave me 600 RPM: same behaviour so the difference is coming from that motherboard, but I don't see anything that can explain the difference.


Offline Bryce

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Re: Issue 3" drive rotation speed
« Reply #20 on: 16:27, 10 January 21 »
Ok, if that's the case then one of the FDC buffers is failing. Most likely IC203 (74LS240), second most likely: IC205 (74LS08).

Bryce.
 

Offline guigui37

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Re: Issue 3" drive rotation speed
« Reply #21 on: 09:51, 12 January 21 »
Maybe I could first check the soldering of the fdd controller NEC 765A ?
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Offline GUNHED

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Re: Issue 3" drive rotation speed
« Reply #22 on: 23:18, 12 January 21 »
You're right, there is no issue with the drive itself, I tested it onto another CPC and result is about 300RPM so 3" drive is not the root cause. I do the same with another drive connected to the motherboard which gave me 600 RPM: same behaviour so the difference is coming from that motherboard, but I don't see anything that can explain the difference.
The software 'sees' the index hole twice, I don't have the source right here (or even know if it was released), but maybe you can contact the author. Could be possible to adjust some waiting loop.
Or it could be some hardware problem of course too. But I still would bet on the software side. Or not? Don't know now...  :-X
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