Aligning floppy drive heads

[llopis]

I have several floppy drives (3", the regular ones that came with the 6128) that give me the dreaded "Read Fail" error. One of them does it most of the time, but in some disks I can successfully do a CAT. The other one does it all the time. This is on disks that work in other drives.


Having revised all the solder joints, replaced the belts, and lubricated the shafts and rails, I'm only left with the possibility of realigning the heads.


I've heard people talking about it, and I read over the service manual where it talks about the procedure. I have the oscilloscope to be able to check those signals, but I wanted to check how do people really align the heads. Do you follow the service manual procedure to a T? Do you use some shortcuts? Do you tackle them in the order in the manual? Any tricks for someone about to do it for their first time?


Thanks!


Edit: Related question, what is the ring and the screw through it on the step drive shaft that some of the drives have? I can't seem to figure out the purpose of that screw and why some drives don't even have it.

[deepfb]

Before dealing with the head, you may need to adjust the speed of the spindle motor. I connect the disk drive to a Kryoflux interface to do the job (I haven't found any program for the CPC that checks the RPM of the disk drive motor). I set the speed "live" while KF is reading a disk, with a non conductive screwdriver: I set it to less than 300 RPM at the beginning (~290/292), since it will speed up when reaching the centre of the disk (to almost ~308/310).


When I have done this, the fight with the head's alignment starts. In my case, it's the trial & error method xD

[deepfb]

Edit: Related question, what is the ring and the screw through it on the step drive shaft that some of the drives have? I can't seem to figure out the purpose of that screw and why some drives don't even have it.

Regarding this question, it is a limit (un tope, en castellano ) that blocks the head. You can check how it works disaligning the head, and forcing it to go backwards too much, as if the track zero was farther away to the centre of the disk than it actually is. The head will hit the block ("clack, clack!").


I found a disk drive with this block cracked, and I had to replace it so the disk drive would look for the track zero in the right place.

[GUNHED]

I haven't found any program for the CPC that checks the RPM of the disk drive motor

There is a program for that, search this forum.

[gerald]

Links to RPM / DskTest here : http://www.cpcwiki.eu/index.php/Amstrad_FDD_part#Drive_maintenance

[llopis]

Yeah, I had adjusted the rpm with that program before and nothing.


I've successfully formatted a disk with that drive and I can write and read anything from it successfully. Just not other working disks that work on other drives, that's what makes me think it's an alignment issue.


I've messed around randomly moving the little platform with the diode, but that hasn't done much.


Now I'm trying to understand the signals described in the service manual, but I must be really thick because I can't understand what signals they're measuring for the different graphs presented. Any help would be appreciated.

[gerald]

I've messed around randomly moving the little platform with the diode, but that hasn't done much.

Don't mess with that ! It's the track 0 detector 

Now I'm trying to understand the signals described in the service manual, but I must be really thick because I can't understand what signals they're measuring for the different graphs presented. Any help would be appreciated.

Forget the service manual, you need an alignment disk to follow the procedure, and these does not exist any-more.

I usually use a original CPM disk (or any other commercial disk) as reference, and RPM for moving the head.
1. You have to slightly unscrew the motor head so you can turn it a bit at a time, but not too loose.
2. turn the motor in one direction (less than a degree)
3. make the head move up-down and / or down/up to make sure the head position itself properly.
4. with the scope, probe the output of the head amplifier (I just can't remember where exactly it is ...)
5. repeat step 2-4 until you reach the maximum amplitude. If the amplitude decrease, turn the motor in the other direction.

[gerald]

4. with the scope, probe the output of the head amplifier (I just can't remember where exactly it is ...)

TP1/TP2 on the EME156
http://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/ZXSpectrum128_plus_3_service_manual/zx_spectrum_128_plus_3_service_manual_12.PNG

[deepfb]

Forget the service manual, you need an alignment disk to follow the procedure, and these does not exist any-more.

Last GUA meeting we encouraged Habi to re-create the service disk, or at least a disk image of it; it should be possible to write it using the KF hardware, isn't it?

[gerald]

Last GUA meeting we encouraged Habi to re-create the service disk, or at least a disk image of it; it should be possible to write it using the KF hardware, isn't it?

I don't think you can recreate it easily.
Tracks on figure 3 and 4 P17 of DDI1 service manual are just impossible to write with a kryoflux, or any drive.
On figure 3, the azimuth alignment burst have different azimuth, and your drive only have one.
On figure 4, the track positioning burst are not aligned with the track itself. Your disk is always aligned with itself
You need a specific drive (multiple head) for that.

[Bryce]

I set it to less than 300 RPM at the beginning (~290/292), since it will speed up when reaching the centre of the disk (to almost ~308/310).

That's hilarious. Can you explain to me how the outer edge of the disk could possibly be rotating at a different RPM than the inner part? You may have found a tear in the space-time continuum!

Bryce.

[pelrun]

Edit: Related question, what is the ring and the screw through it on the step drive shaft that some of the drives have? I can't seem to figure out the purpose of that screw and why some drives don't even have it.

It's for manually checking the head position during alignment. Much easier to wiggle it back and forth with a finger while looking at the scope to see where the signal maximum is in relation to the motor detents.

[robcfg]

That's hilarious. Can you explain to me how the outer edge of the disk could possibly be rotating at a different RPM than the inner part? You may have found a tear in the space-time continuum!

Bryce.

What @deepfb is trying to say is that when using KryoFlux, it seems that the tracks are written at increasingly higher rpm. So the first track reports 290 rpm and the last  one, 310 rpm.


As you said, all parts of the disk rotate at the same time. Maybe the rpm calculation is off?

[Bryce]

Obviously KyroFlux isn't calculating the speed correctly. You should always set the RPM to 300 on a CPC. It really does need to spin at that rate, both on the inside and outside. Don't compensate for a calculation error in KryoFlux. If you set it to 290, then it's turning 290 at all positions.


Bryce.

[gerald]

That's hilarious. Can you explain to me how the outer edge of the disk could possibly be rotating at a different RPM than the inner part? You may have found a tear in the space-time continuum!

Bryce.

Without the head, your're right.But with, the friction on outer track result a lower RPM than on the inner track. 
Do not forget that the RPM regulation on 3 inch drive is openloop. On 3 1/2 the regulation is closed-loop.

[TotO]

I have never seen a so big RPM gap (20) from track 0 to track 39.
Usually, it is around 1 or 2 RPM from track 0 to track 39... Used on my old program to detect and display emulators names.

[Bryce]

Without the head, your're right.But with, the friction on outer track result a lower RPM than on the inner track. 
Do not forget that the RPM regulation on 3 inch drive is openloop. On 3 1/2 the regulation is closed-loop.

If the head is causing enough friction to slow the rotation down, then you have bigger problems than the alignment that need to be fixed!!

Bryce.

[llopis]

I usually use a original CPM disk (or any other commercial disk) as reference, and RPM for moving the head.
1. You have to slightly unscrew the motor head so you can turn it a bit at a time, but not too loose.
2. turn the motor in one direction (less than a degree)
3. make the head move up-down and / or down/up to make sure the head position itself properly.
4. with the scope, probe the output of the head amplifier (I just can't remember where exactly it is ...)
5. repeat step 2-4 until you reach the maximum amplitude. If the amplitude decrease, turn the motor in the other direction.

That's fantastic. I'll give it a try for sure, although I noticed the head of one of the screws holding the motor looks like it's stripped. Let's see if I can manage to unscrew it a bit.

[Bryce]

That's fantastic. I'll give it a try for sure, although I noticed the head of one of the screws holding the motor looks like it's stripped. Let's see if I can manage to unscrew it a bit.

So someone has adjusted it before? Usually the two screws will have some red varnish on them if they have never been adjusted.

Bryce.

[deepfb]

That's hilarious. Can you explain to me how the outer edge of the disk could possibly be rotating at a different RPM than the inner part? You may have found a tear in the space-time continuum!

I must recognize I was upset with your rude reply, so once I have had the opportunity I have ran to the KF device to do some tests... just to prove I was quite wrong. I am sorry about that!

The problem is I recalled wrong the range of RPM, or I was right but I was using a disk drive with a faulty belt or motor when I noticed that range ...or perhaps it was the discs I was trying to dump at that time. I have checked some tens of discs, and the change in the speed is almost negligible -although all of them tend to accelerate in the process, if the KF readings are correct.

Code Select Expand

00.1    : frev: 41724, drift: 0.125 us, tfer: 197921 B/s, rpm: 297.599
00.1    : band: 3.866 us, 5.814 us, 7.781 us
01.1    : frev: 43393, drift: 0.083 us, tfer: 206383 B/s, rpm: 297.821
01.1    : band: 3.872 us, 5.809 us, 7.730 us
02.1    : frev: 41957, drift: 0.133 us, tfer: 199557 B/s, rpm: 297.801
02.1    : band: 3.873 us, 5.802 us, 7.735 us
03.1    : frev: 40572, drift: 0.058 us, tfer: 192117 B/s, rpm: 297.951
03.1    : band: 3.871 us, 5.816 us, 7.770 us
04.1    : frev: 41099, drift: 0.058 us, tfer: 196143 B/s, rpm: 297.961
04.1    : band: 3.871 us, 5.797 us, 7.761 us
05.1    : frev: 43044, drift: 1.407 us, tfer: 205091 B/s, rpm: 297.955
05.1    : band: 3.870 us, 5.805 us, 7.788 us
06.1    : frev: 43500, drift: 0.033 us, tfer: 207129 B/s, rpm: 298.070
06.1    : band: 3.878 us, 5.806 us, 7.715 us
07.1    : frev: 43745, drift: 1.457 us, tfer: 207880 B/s, rpm: 298.019
07.1    : band: 3.870 us, 5.807 us, 7.806 us
08.1    : frev: 40859, drift: 1.390 us, tfer: 193822 B/s, rpm: 298.002
08.1    : band: 3.868 us, 5.798 us, 7.787 us
09.1    : frev: 41139, drift: 0.166 us, tfer: 194976 B/s, rpm: 298.031
09.1    : band: 3.873 us, 5.817 us, 7.744 us
10.1    : frev: 41711, drift: 0.191 us, tfer: 198865 B/s, rpm: 297.922
10.1    : band: 3.878 us, 5.813 us, 7.759 us
11.1    : frev: 41697, drift: 0.117 us, tfer: 198693 B/s, rpm: 297.951
11.1    : band: 3.878 us, 5.809 us, 7.781 us
12.1    : frev: 41465, drift: 0.100 us, tfer: 197155 B/s, rpm: 297.953
12.1    : band: 3.881 us, 5.818 us, 7.752 us
13.1    : frev: 41974, drift: 0.158 us, tfer: 200080 B/s, rpm: 298.029
13.1    : band: 3.880 us, 5.811 us, 7.733 us
14.1    : frev: 41988, drift: 0.100 us, tfer: 200080 B/s, rpm: 298.075
14.1    : band: 3.880 us, 5.815 us, 7.816 us
15.1    : frev: 41982, drift: 0.058 us, tfer: 200255 B/s, rpm: 298.041
15.1    : band: 3.879 us, 5.824 us, 7.916 us
16.1    : frev: 42367, drift: 0.050 us, tfer: 202019 B/s, rpm: 298.235
16.1    : band: 3.889 us, 5.826 us, 7.779 us
17.1    : frev: 41778, drift: 0.117 us, tfer: 198320 B/s, rpm: 298.233
17.1    : band: 3.888 us, 5.839 us, 7.734 us
18.1    : frev: 40799, drift: 0.125 us, tfer: 194013 B/s, rpm: 298.288
18.1    : band: 3.892 us, 5.839 us, 7.776 us
19.1    : frev: 40192, drift: 0.092 us, tfer: 191182 B/s, rpm: 298.381
19.1    : band: 3.888 us, 5.836 us, 7.746 us
20.1    : frev: 41098, drift: 0.125 us, tfer: 194782 B/s, rpm: 298.311
20.1    : band: 3.884 us, 5.840 us, 7.750 us
21.1    : frev: 42535, drift: 0.100 us, tfer: 202375 B/s, rpm: 298.497
21.1    : band: 3.882 us, 5.841 us, 7.799 us
22.1    : frev: 40770, drift: 0.117 us, tfer: 193822 B/s, rpm: 298.448
22.1    : band: 3.884 us, 5.851 us, 7.781 us
23.1    : frev: 40495, drift: 0.067 us, tfer: 192493 B/s, rpm: 298.495
23.1    : band: 3.881 us, 5.849 us, 7.750 us
24.1    : frev: 41115, drift: 0.100 us, tfer: 196143 B/s, rpm: 298.548
24.1    : band: 3.877 us, 5.846 us, 7.804 us
25.1    : frev: 40676, drift: 0.175 us, tfer: 194150 B/s, rpm: 298.458
25.1    : band: 3.885 us, 5.840 us, 7.760 us
26.1    : frev: 40064, drift: 0.108 us, tfer: 190811 B/s, rpm: 298.566
26.1    : band: 3.889 us, 5.850 us, 7.791 us
27.1    : frev: 40657, drift: 0.125 us, tfer: 193060 B/s, rpm: 298.650
27.1    : band: 3.887 us, 5.844 us, 7.738 us
28.1    : frev: 40884, drift: 0.125 us, tfer: 195474 B/s, rpm: 298.665
28.1    : band: 3.883 us, 5.857 us, 7.748 us
29.1    : frev: 40852, drift: 0.050 us, tfer: 194976 B/s, rpm: 298.783
29.1    : band: 3.895 us, 5.852 us, 7.761 us
30.1    : frev: 41090, drift: 0.166 us, tfer: 195558 B/s, rpm: 298.701
30.1    : band: 3.890 us, 5.865 us, 7.797 us
31.1    : frev: 38968, drift: 0.125 us, tfer: 185761 B/s, rpm: 298.873
31.1    : band: 3.888 us, 5.857 us, 8.023 us
32.1    : frev: 38940, drift: 0.092 us, tfer: 185761 B/s, rpm: 298.876
32.1    : band: 3.873 us, 5.868 us, 8.035 us
33.1    : frev: 38927, drift: 0.050 us, tfer: 185761 B/s, rpm: 298.968
33.1    : band: 3.880 us, 5.862 us, 7.646 us?
34.1    : frev: 39756, drift: 0.158 us, tfer: 189523 B/s, rpm: 299.050
34.1    : band: 3.905 us, 5.875 us, 7.819 us
35.1    : frev: 40891, drift: 0.108 us, tfer: 195142 B/s, rpm: 299.044
35.1    : band: 3.898 us, 5.862 us, 7.741 us
36.1    : frev: 43245, drift: 0.067 us, tfer: 207129 B/s, rpm: 299.164
36.1    : band: 3.893 us, 5.867 us, 7.816 us
37.1    : frev: 40802, drift: 0.058 us, tfer: 194397 B/s, rpm: 299.237
37.1    : band: 3.889 us, 5.870 us, 7.786 us
38.1    : frev: 43534, drift: 0.083 us, tfer: 208636 B/s, rpm: 299.221
38.1    : band: 3.894 us, 5.867 us, 7.771 us
39.1    : frev: 39907, drift: 0.150 us, tfer: 190441 B/s, rpm: 299.277
39.1    : band: 3.888 us, 5.857 us, 7.651 us?
40.1    : frev: 38430, drift: 0.050 us, tfer: 183507 B/s, rpm: 299.249
40.1    : band: 3.913 us, 5.713 us, 7.681 us?
41.1    : frev: 38442, drift: 0.150 us, tfer: 183678 B/s, rpm: 299.400
41.1    : band: 3.909 us, 5.782 us, 7.687 us?
42.1    : frev: 38442, drift: 0.067 us, tfer: 183678 B/s, rpm: 299.373
42.1    : band: 3.909 us, 5.739 us, 7.682 us?

Code Select Expand

00.1    : frev: 39919, drift: 0.125 us, tfer: 189889 B/s, rpm: 298.734
00.1    : band: 4.028 us, 6.041 us, 8.017 us
01.1    : frev: 43716, drift: 0.067 us, tfer: 208447 B/s, rpm: 298.725
01.1    : band: 4.025 us, 6.048 us, 8.111 us
02.1    : frev: 43901, drift: 0.092 us, tfer: 209399 B/s, rpm: 298.882
02.1    : band: 4.026 us, 6.047 us, 8.098 us
03.1    : frev: 43470, drift: 0.142 us, tfer: 208068 B/s, rpm: 299.073
03.1    : band: 4.032 us, 6.052 us, 8.068 us
04.1    : frev: 40302, drift: 0.092 us, tfer: 191182 B/s, rpm: 299.138
04.1    : band: 4.031 us, 6.058 us, 8.062 us
05.1    : frev: 39728, drift: 0.125 us, tfer: 189341 B/s, rpm: 299.220
05.1    : band: 4.032 us, 6.051 us, 8.071 us
06.1    : frev: 39719, drift: 0.108 us, tfer: 189706 B/s, rpm: 299.257
06.1    : band: 4.025 us, 6.057 us, 8.063 us
07.1    : frev: 38920, drift: 0.125 us, tfer: 185411 B/s, rpm: 299.310
07.1    : band: 4.028 us, 6.052 us, 8.071 us
08.1    : frev: 38181, drift: 0.058 us, tfer: 182484 B/s, rpm: 299.425
08.1    : band: 4.030 us, 6.054 us, 8.075 us
09.1    : frev: 41030, drift: 0.083 us, tfer: 195558 B/s, rpm: 299.413
09.1    : band: 4.034 us, 6.046 us, 8.050 us
10.1    : frev: 37663, drift: 0.083 us, tfer: 179978 B/s, rpm: 299.427
10.1    : band: 4.017 us, 6.052 us, 8.039 us?
11.1    : frev: 37656, drift: 0.191 us, tfer: 179484 B/s, rpm: 299.389
11.1    : band: 4.052 us, 6.053 us, 8.036 us?
12.1    : frev: 37665, drift: 0.125 us, tfer: 179648 B/s, rpm: 299.407
12.1    : band: 4.036 us, 6.050 us, 8.083 us
13.1    : frev: 37653, drift: 0.158 us, tfer: 179648 B/s, rpm: 299.488
13.1    : band: 4.036 us, 6.048 us, 8.045 us?
14.1    : frev: 37658, drift: 0.117 us, tfer: 179978 B/s, rpm: 299.454
14.1    : band: 4.039 us, 6.043 us, 8.051 us?
15.1    : frev: 37664, drift: 0.142 us, tfer: 179978 B/s, rpm: 299.477
15.1    : band: 4.049 us, 6.038 us, 7.989 us
16.1    : frev: 37660, drift: 0.075 us, tfer: 180142 B/s, rpm: 299.459
16.1    : band: 4.027 us, 6.046 us, 8.039 us
17.1    : frev: 39421, drift: 0.117 us, tfer: 188252 B/s, rpm: 299.518
17.1    : band: 3.015 us?, 4.024 us, 6.046 us, 7.132 us?, 8.072 us
18.1    : frev: 39224, drift: 0.158 us, tfer: 187355 B/s, rpm: 299.591
18.1    : band: 4.030 us, 6.047 us, 8.089 us
19.1    : frev: 40491, drift: 0.108 us, tfer: 194480 B/s, rpm: 299.563
19.1    : band: 4.036 us, 6.044 us, 8.018 us
20.1    : frev: 44094, drift: 0.117 us, tfer: 210746 B/s, rpm: 299.591
20.1    : band: 4.029 us, 6.051 us, 8.074 us
21.1    : frev: 44074, drift: 0.175 us, tfer: 210940 B/s, rpm: 299.603
21.1    : band: 4.030 us, 6.041 us, 8.014 us?
22.1    : frev: 40274, drift: 0.092 us, tfer: 192305 B/s, rpm: 299.607
22.1    : band: 4.033 us, 6.043 us, 8.045 us
23.1    : frev: 40544, drift: 0.142 us, tfer: 194315 B/s, rpm: 299.702
23.1    : band: 4.036 us, 6.061 us, 8.108 us
24.1    : frev: 37642, drift: 0.092 us, tfer: 180142 B/s, rpm: 299.621
24.1    : band: 4.038 us, 6.047 us, 7.821 us
25.1    : frev: 37626, drift: 0.200 us, tfer: 179978 B/s, rpm: 299.668
25.1    : band: 4.041 us, 6.051 us, 7.982 us
26.1    : frev: 37629, drift: 0.100 us, tfer: 179978 B/s, rpm: 299.610
26.1    : band: 4.035 us, 6.049 us, 8.109 us
27.1    : frev: 37623, drift: 0.117 us, tfer: 179978 B/s, rpm: 299.680
27.1    : band: 4.043 us, 6.055 us, 8.156 us
28.1    : frev: 37629, drift: 0.092 us, tfer: 180142 B/s, rpm: 299.769
28.1    : band: 4.037 us, 6.050 us, 8.029 us?
29.1    : frev: 37628, drift: 0.092 us, tfer: 180142 B/s, rpm: 299.830
29.1    : band: 4.036 us, 6.051 us, 8.014 us
30.1    : frev: 37624, drift: 0.092 us, tfer: 179813 B/s, rpm: 299.823
30.1    : band: 4.034 us, 6.064 us, 8.141 us
31.1    : frev: 37615, drift: 0.158 us, tfer: 180142 B/s, rpm: 299.809
31.1    : band: 4.026 us, 6.053 us, 7.875 us
32.1    : frev: 37614, drift: 0.117 us, tfer: 180142 B/s, rpm: 299.860
32.1    : band: 4.044 us, 6.054 us, 7.938 us
33.1    : frev: 37605, drift: 0.075 us, tfer: 180142 B/s, rpm: 300.001
33.1    : band: 4.045 us, 6.062 us, 8.012 us?
34.1    : frev: 37602, drift: 0.133 us, tfer: 179484 B/s, rpm: 299.993
34.1    : band: 3.035 us?, 4.033 us, 5.013 us?, 6.056 us, 8.038 us
35.1    : frev: 37599, drift: 0.042 us, tfer: 179321 B/s, rpm: 300.043
35.1    : band: 4.041 us, 6.053 us, 7.983 us?
36.1    : frev: 37601, drift: 0.108 us, tfer: 180142 B/s, rpm: 300.055
36.1    : band: 4.043 us, 6.047 us, 7.888 us
37.1    : frev: 37579, drift: 0.100 us, tfer: 180142 B/s, rpm: 300.144
37.1    : band: 4.045 us, 6.059 us, 8.224 us
38.1    : frev: 37586, drift: 0.083 us, tfer: 180142 B/s, rpm: 300.168
38.1    : band: 4.041 us, 6.065 us, 8.093 us
39.1    : frev: 37599, drift: 0.100 us, tfer: 180142 B/s, rpm: 300.108
39.1    : band: 4.031 us, 6.067 us, 7.998 us?
40.1    : frev: 21849, drift: 836.669 us, tfer: 131024 B/s, rpm: 300.151
40.1    : band: 2.417 us, 3.459 us, 6.738 us, 10.034 us, 13.372 us?
41.1    : frev: 22321, drift: 864.229 us, tfer: 133019 B/s, rpm: 300.258
41.1    : band: 2.419 us, 3.475 us, 6.700 us, 10.038 us, 13.395 us?
42.1    : frev: 22342, drift: 926.375 us, tfer: 132615 B/s, rpm: 300.256
But the range is shorter on discs that look cleaner and/or which seem to have been used less than others. This is from one (I believe) was only used once, just to write the data on it:

Code Select Expand

00.1    : frev: 39991, drift: 0.108 us, tfer: 189889 B/s, rpm: 297.687
00.1    : band: 3.876 us, 5.828 us, 7.765 us
01.1    : frev: 39604, drift: 0.092 us, tfer: 188072 B/s, rpm: 297.781
01.1    : band: 3.883 us, 5.827 us, 7.765 us
02.1    : frev: 39668, drift: 0.075 us, tfer: 188433 B/s, rpm: 297.685
02.1    : band: 3.919 us, 5.857 us, 7.863 us
03.1    : frev: 40603, drift: 0.125 us, tfer: 192493 B/s, rpm: 297.866
03.1    : band: 3.924 us, 5.851 us, 7.876 us
04.1    : frev: 40443, drift: 0.117 us, tfer: 191369 B/s, rpm: 297.851
04.1    : band: 3.904 us, 5.851 us, 7.844 us
05.1    : frev: 41729, drift: 0.042 us, tfer: 198865 B/s, rpm: 297.893
05.1    : band: 3.881 us, 5.832 us, 7.786 us
06.1    : frev: 40751, drift: 0.083 us, tfer: 193440 B/s, rpm: 297.949
06.1    : band: 3.891 us, 5.837 us, 7.808 us
07.1    : frev: 39860, drift: 0.166 us, tfer: 189523 B/s, rpm: 297.911
07.1    : band: 3.925 us, 5.854 us, 7.860 us
08.1    : frev: 40517, drift: 0.117 us, tfer: 192493 B/s, rpm: 298.022
08.1    : band: 3.930 us, 5.853 us, 7.879 us
09.1    : frev: 41516, drift: 0.025 us, tfer: 197836 B/s, rpm: 298.022
09.1    : band: 3.929 us, 5.847 us, 7.870 us
10.1    : frev: 42257, drift: 0.075 us, tfer: 201309 B/s, rpm: 298.014
10.1    : band: 3.932 us, 5.853 us, 7.869 us
11.1    : frev: 43914, drift: 0.158 us, tfer: 209017 B/s, rpm: 298.106
11.1    : band: 3.933 us, 5.843 us, 7.878 us
12.1    : frev: 44042, drift: 0.100 us, tfer: 209782 B/s, rpm: 298.006
12.1    : band: 3.931 us, 5.842 us, 7.864 us
13.1    : frev: 43659, drift: 0.092 us, tfer: 207504 B/s, rpm: 298.105
13.1    : band: 3.934 us, 5.846 us, 7.872 us
14.1    : frev: 43513, drift: 0.100 us, tfer: 207129 B/s, rpm: 298.070
14.1    : band: 3.933 us, 5.855 us, 7.883 us
15.1    : frev: 43561, drift: 0.058 us, tfer: 207316 B/s, rpm: 298.130
15.1    : band: 3.926 us, 5.838 us, 7.856 us
16.1    : frev: 46222, drift: 0.100 us, tfer: 219838 B/s, rpm: 298.202
16.1    : band: 3.932 us, 5.838 us, 7.830 us
17.1    : frev: 46043, drift: 0.108 us, tfer: 218373 B/s, rpm: 298.148
17.1    : band: 3.931 us, 5.845 us, 7.849 us
18.1    : frev: 46025, drift: 0.142 us, tfer: 218790 B/s, rpm: 298.268
18.1    : band: 3.935 us, 5.836 us, 7.885 us
19.1    : frev: 42289, drift: 0.100 us, tfer: 201486 B/s, rpm: 298.275
19.1    : band: 3.932 us, 5.861 us, 7.871 us
20.1    : frev: 46516, drift: 0.100 us, tfer: 221324 B/s, rpm: 298.259
20.1    : band: 3.933 us, 5.848 us, 7.878 us
21.1    : frev: 44668, drift: 0.158 us, tfer: 212898 B/s, rpm: 298.331
21.1    : band: 3.932 us, 5.849 us, 7.856 us
22.1    : frev: 39425, drift: 0.183 us, tfer: 187534 B/s, rpm: 298.231
22.1    : band: 3.923 us, 5.864 us, 7.871 us
23.1    : frev: 39620, drift: 0.142 us, tfer: 188614 B/s, rpm: 298.395
23.1    : band: 3.925 us, 5.854 us, 7.877 us
24.1    : frev: 39340, drift: 0.175 us, tfer: 187177 B/s, rpm: 298.343
24.1    : band: 3.923 us, 5.856 us, 7.877 us
25.1    : frev: 39893, drift: 0.133 us, tfer: 189889 B/s, rpm: 298.335
25.1    : band: 3.925 us, 5.859 us, 7.874 us
26.1    : frev: 44277, drift: 0.083 us, tfer: 210940 B/s, rpm: 298.406
26.1    : band: 3.933 us, 5.848 us, 7.858 us
27.1    : frev: 41333, drift: 0.133 us, tfer: 196536 B/s, rpm: 298.377
27.1    : band: 3.920 us, 5.847 us, 7.863 us
28.1    : frev: 42648, drift: 0.067 us, tfer: 203634 B/s, rpm: 298.420
28.1    : band: 3.924 us, 5.842 us, 7.783 us
29.1    : frev: 42713, drift: 0.117 us, tfer: 203815 B/s, rpm: 298.478
29.1    : band: 3.924 us, 5.849 us, 7.843 us
30.1    : frev: 42627, drift: 0.100 us, tfer: 203273 B/s, rpm: 298.484
30.1    : band: 3.923 us, 5.844 us, 7.829 us
31.1    : frev: 41078, drift: 0.042 us, tfer: 196143 B/s, rpm: 298.565
31.1    : band: 3.914 us, 5.839 us, 7.877 us
32.1    : frev: 39010, drift: 0.142 us, tfer: 185761 B/s, rpm: 298.501
32.1    : band: 3.877 us, 5.846 us, 7.661 us
33.1    : frev: 39023, drift: 0.108 us, tfer: 185411 B/s, rpm: 298.664
33.1    : band: 3.889 us, 5.834 us, 7.687 us?
34.1    : frev: 38994, drift: 0.067 us, tfer: 185761 B/s, rpm: 298.676
34.1    : band: 3.858 us, 5.848 us, 7.591 us?
35.1    : frev: 38992, drift: 0.067 us, tfer: 185761 B/s, rpm: 298.694
35.1    : band: 3.868 us, 5.847 us, 7.726 us
36.1    : frev: 38990, drift: 0.175 us, tfer: 185761 B/s, rpm: 298.763
36.1    : band: 3.892 us, 5.843 us, 7.743 us
37.1    : frev: 38976, drift: 0.158 us, tfer: 185937 B/s, rpm: 298.727
37.1    : band: 3.870 us, 5.848 us, 7.859 us
38.1    : frev: 38995, drift: 0.133 us, tfer: 185411 B/s, rpm: 298.828
38.1    : band: 3.877 us, 5.837 us, 7.631 us?
39.1    : frev: 38996, drift: 0.050 us, tfer: 185937 B/s, rpm: 298.880
39.1    : band: 3.871 us, 5.848 us, 7.906 us
40.1    : frev: 22376, drift: 855.073 us, tfer: 132749 B/s, rpm: 298.861
40.1    : band: 2.351 us, 3.407 us, 6.817 us, 9.866 us, 13.307 us
41.1    : frev: 22711, drift: 907.480 us, tfer: 133834 B/s, rpm: 298.926
41.1    : band: 2.333 us, 3.428 us, 6.848 us, 10.101 us, 13.347 us?
42.1    : frev: 22579, drift: 951.712 us, tfer: 133425 B/s, rpm: 298.873

And you can check a slow down in the middle of the process when reading a faulty/dirty disk like this one:

Code Select Expand

00.1    : frev: 39046, drift: 0.175 us, tfer: 186821 B/s, rpm: 299.951
00.1    : band: 3.969 us, 5.972 us, 7.967 us
01.1    : frev: 39491, drift: 0.150 us, tfer: 188976 B/s, rpm: 299.924
01.1    : band: 3.989 us, 5.974 us, 7.972 us
02.1    : frev: 38070, drift: 0.083 us, tfer: 182315 B/s, rpm: 299.905
02.1    : band: 3.936 us, 5.944 us, 7.855 us
03.1    : frev: 38087, drift: 0.117 us, tfer: 182484 B/s, rpm: 300.072
03.1    : band: 3.934 us, 5.940 us, 7.851 us
04.1    : frev: 37998, drift: 0.100 us, tfer: 181977 B/s, rpm: 300.050
04.1    : band: 3.935 us, 5.942 us, 7.854 us
05.1    : frev: 38881, drift: 0.100 us, tfer: 186113 B/s, rpm: 300.049
05.1    : band: 3.932 us, 5.941 us, 7.855 us
06.1    : frev: 39005, drift: 0.100 us, tfer: 186821 B/s, rpm: 300.247
06.1    : band: 3.931 us, 5.945 us, 7.863 us
07.1    : frev: 38975, drift: 2.098 us, tfer: 186821 B/s, rpm: 300.204
07.1    : band: 3.932 us, 5.945 us, 7.848 us
08.1    : frev: 38732, drift: 0.250 us, tfer: 185586 B/s, rpm: 300.268
08.1    : band: 3.950 us, 5.959 us, 7.870 us
09.1    : frev: 38060, drift: 0.150 us, tfer: 182484 B/s, rpm: 300.181
09.1    : band: 3.981 us, 5.979 us, 7.912 us?
10.1    : frev: 38072, drift: 0.158 us, tfer: 182484 B/s, rpm: 300.213
10.1    : band: 4.008 us, 5.972 us, 7.980 us?
11.1    : frev: 38068, drift: 0.117 us, tfer: 182484 B/s, rpm: 300.234
11.1    : band: 3.985 us, 5.975 us, 7.914 us?
12.1    : frev: 38075, drift: 0.100 us, tfer: 182484 B/s, rpm: 300.191
12.1    : band: 3.984 us, 5.974 us, 8.017 us
13.1    : frev: 38068, drift: 0.142 us, tfer: 182484 B/s, rpm: 300.326
13.1    : band: 3.975 us, 5.973 us, 7.887 us?
14.1    : frev: 38078, drift: 0.125 us, tfer: 182315 B/s, rpm: 300.238
14.1    : band: 3.990 us, 5.974 us, 7.931 us?
15.1    : frev: 38075, drift: 0.150 us, tfer: 182315 B/s, rpm: 300.410
15.1    : band: 3.978 us, 5.973 us, 7.977 us
16.1    : frev: 38079, drift: 0.108 us, tfer: 182654 B/s, rpm: 300.463
16.1    : band: 3.960 us, 5.971 us, 8.127 us
17.1    : frev: 38068, drift: 0.067 us, tfer: 182315 B/s, rpm: 300.351
17.1    : band: 3.969 us, 5.976 us, 7.869 us?
18.1    : frev: 38068, drift: 0.108 us, tfer: 182484 B/s, rpm: 300.424
18.1    : band: 3.994 us, 5.971 us, 7.916 us
19.1    : frev: 38067, drift: 0.108 us, tfer: 182484 B/s, rpm: 300.188
19.1    : band: 3.966 us, 5.975 us, 7.902 us
20.1    : frev: 38066, drift: 2.647 us, tfer: 182146 B/s, rpm: 299.767
20.1    : band: 3.976 us, 5.972 us, 7.971 us
21.1    : frev: 38059, drift: 0.142 us, tfer: 181977 B/s, rpm: 299.473
21.1    : band: 3.946 us, 5.977 us, 7.811 us?
22.1    : frev: 38070, drift: 0.083 us, tfer: 181809 B/s, rpm: 299.057
22.1    : band: 3.963 us, 5.976 us, 7.962 us
23.1    : frev: 38066, drift: 0.083 us, tfer: 181473 B/s, rpm: 298.680
23.1    : band: 3.963 us, 5.973 us, 7.922 us
24.1    : frev: 38073, drift: 0.083 us, tfer: 180805 B/s, rpm: 298.097
24.1    : band: 2.689 us?, 3.265 us?, 4.082 us, 5.954 us, 7.161 us
25.1    : frev: 35348, drift: 47.363 us, tfer: 174234 B/s, rpm: 298.118
25.1    : band: 3.357 us, 4.756 us, 5.955 us, 6.992 us, 13.187 us?
26.1    : frev: 35549, drift: 29.125 us, tfer: 175009 B/s, rpm: 298.108
26.1    : band: 3.403 us, 4.981 us, 5.962 us, 6.932 us, 13.145 us?
27.1    : frev: 38063, drift: 0.191 us, tfer: 181306 B/s, rpm: 298.137
27.1    : band: 2.316 us?, 3.273 us?, 4.190 us, 5.876 us, 6.854 us
28.1    : frev: 38079, drift: 0.166 us, tfer: 181473 B/s, rpm: 298.646
28.1    : band: 3.953 us, 5.973 us, 7.725 us?
29.1    : frev: 38069, drift: 0.142 us, tfer: 181809 B/s, rpm: 299.165
29.1    : band: 3.963 us, 5.967 us, 7.939 us
30.1    : frev: 38079, drift: 0.067 us, tfer: 182146 B/s, rpm: 299.781
30.1    : band: 3.968 us, 5.968 us, 8.076 us
31.1    : frev: 38074, drift: 0.125 us, tfer: 182484 B/s, rpm: 300.375
31.1    : band: 3.967 us, 5.969 us, 7.805 us
32.1    : frev: 38078, drift: 1.923 us, tfer: 182654 B/s, rpm: 300.569
32.1    : band: 3.960 us, 5.970 us, 8.140 us
33.1    : frev: 38069, drift: 0.100 us, tfer: 182654 B/s, rpm: 300.791
33.1    : band: 3.504 us, 3.978 us, 5.969 us, 7.855 us?
34.1    : frev: 38069, drift: 0.092 us, tfer: 182146 B/s, rpm: 300.663
34.1    : band: 3.943 us, 5.976 us, 8.049 us
35.1    : frev: 38070, drift: 0.117 us, tfer: 182654 B/s, rpm: 300.737
35.1    : band: 3.965 us, 5.973 us, 7.834 us?
36.1    : frev: 38071, drift: 0.117 us, tfer: 182824 B/s, rpm: 300.704
36.1    : band: 3.953 us, 5.974 us, 7.911 us
37.1    : frev: 38057, drift: 0.067 us, tfer: 182654 B/s, rpm: 300.708
37.1    : band: 3.977 us, 4.963 us?, 5.978 us, 6.795 us?, 8.045 us
38.1    : frev: 38066, drift: 0.117 us, tfer: 182824 B/s, rpm: 300.869
38.1    : band: 3.974 us, 5.974 us, 7.986 us
39.1    : frev: 39738, drift: 0.108 us, tfer: 190626 B/s, rpm: 300.869
39.1    : band: 3.894 us, 5.875 us, 7.802 us
40.1    : frev: 22419, drift: 879.245 us, tfer: 133697 B/s, rpm: 300.920
40.1    : band: 2.432 us, 3.506 us, 6.816 us, 10.003 us, 13.433 us?
41.1    : frev: 22861, drift: 1033.336 us, tfer: 135495 B/s, rpm: 300.882
41.1    : band: 2.400 us, 3.484 us, 6.841 us, 10.374 us, 13.518 us
42.1    : frev: 22634, drift: 995.546 us, tfer: 134659 B/s, rpm: 300.780

[Bryce]

Sorry, my comments were not meant to be rude, so I'm sorry if I upset you. It was just humour because it sounded like you were claiming something that would break the laws of physics. I also wanted to point out to other users that you should always set the RPM to as close to 300 as possible and not compensate for readings from other devices. It is also important to remember that all of the methods used to report the RPM are approximations, so there will always be some slight difference between what the software reports and the real RPM's.

The only way to accurately measure the rotation would be to measure the pulses coming from the index hole sensor with a frequency counter or oscilloscope.

Bryce.

[llopis]

TP1/TP2 on the EME156
http://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/ZXSpectrum128_plus_3_service_manual/zx_spectrum_128_plus_3_service_manual_12.PNG

It looks like that's the EME156V: http://www.cpcwiki.eu/index.php/File:EME-156V_Bottom.jpg
The one I'm working on is the regular EME156: http://www.cpcwiki.eu/index.php/File:EME-156_Bottom.jpg
Would you happen to know how to identify the amplifier output in that board? The IC is different and there are no test points marked.
Thanks!

[llopis]

So someone has adjusted it before? Usually the two screws will have some red varnish on them if they have never been adjusted.

I don't know. Clearly someone has *tried*, but whether they succeeded in adjusting it or not, I don't know. They both have some slight green varnish, but it's hard to tell if they've moved (I've unscrewed the top one myself).


Any thoughts on how to unscrew that bottom screw? I tried with the different screwdrivers I have and no good.

[Bryce]

Yup, someone's been there before you. There's a few tricks you can try. Use the best fitting screwdriver you can find, but put a dab of super glue on the tip of the screwdriver before you start. Push the tip for 10 to 20 seconds into the head of the screw before you start turning it and continue pushing while you turn it. Don't turn it smoothly, try to give it sudden jerks. And definitely don't re-use the screw when you get it out.

Bryce.

[gerald]

It looks like that's the EME156V: http://www.cpcwiki.eu/index.php/File:EME-156V_Bottom.jpg
The one I'm working on is the regular EME156: http://www.cpcwiki.eu/index.php/File:EME-156_Bottom.jpg
Would you happen to know how to identify the amplifier output in that board? The IC is different and there are no test points marked.
Thanks!

That's definitively the EME156, no the 156V.
But there are at least 2 different version of the EME156, ME56PB31 PCB and ME56PB41 PCB.
The ME56PB31 uses the M51017AP controller (as do EME155 and EME150A), the ME56PB41 uses the M52813FP controller.
EME156V and EME157V use a M52819FP

But all this does not change where to look  .
It's always on TP1 or TP2. BTW TP3 is ground.

On EME150A to EME156, these grouped together on a connector (only mounted on EME150A)
On other, tests point all over on the PCB