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475-4 Not reading Side B - Printable Version

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475-4 Not reading Side B - Steverd - 11-17-2019

Hi Jim,

  I am test a Panasonic JU-475-4 and can not read Side - B (see attached)
Side A flux image is OK.

I need some guidance please.

I have tried index and Splice,
Index Sensor - Not required.

Max Track 86
End Track: 79 Head 1
Drive speed 360.2 RPM


Jumpers are:
EX - On (Active index)
GX - ON (Read data is enabled by Write Gate)

HM - ON (Head loading controlled by motor on signal)
DA - On (Front LED controlled by Drive select signal)
PH - ON (Dual Mode ( Positive high density)
DS2 - ON  (Drive 2)


RE: 475-4 Not reading Side B - Steverd - 11-17-2019

To help anyone in the future, I found the problem to be the GX jumper.
Once I removed that, then Side B - reads worked!

So for the Panasonic 475-4 use the above jumps, BUT remove the GX and it should work.


RE: 475-4 Not reading Side B - admin - 11-17-2019

Ah, thanks for sharing that! That is great news!


RE: 475-4 Not reading Side B - admin - 02-07-2022

As a follow-up to this, the GX jumper should NEVER be closed on the JU-475-4 or JU-475-5 disk drives.


RE: 475-4 Not reading Side B - kentsu - 10-02-2022

Hi--I have a JU-475-4 as well. I made sure that the GX jumper was not installed. Could someone please provide a longer explanation of the function of this jumper -- just for my own understanding. For starters, what is a "write gate"?

A friend installed a toggle switch across the pins of the EX jumper. Do I understand correctly that this jumper controls whether the index hole sensor is active?

If so, does closing the switch (same as installing the jumper) activate the sensor?

If Yes, then I think that means that I should have the switch in the closed position when I use Index mode in SCP. Yes?

Thanks.


RE: 475-4 Not reading Side B - admin - 10-03-2022

With the EX jumper installed the drive will still read when there is no index pulse present. You do NOT need a switch. This is a permanent jumper setting that you always use no matter if you are reading the front side or the back side of a disk.

When this jumper is not installed, the drive REQUIRES the index pulse to be present for any type of read or write to work.


RE: 475-4 Not reading Side B - kentsu - 10-09-2022

(10-03-2022, 03:27 AM)admin Wrote: With the EX jumper installed the drive will still read when there is no index pulse present.  You do NOT need a switch.  This is a permanent jumper setting that you always use no matter if you are reading the front side or the back side of a disk.

When this jumper is not installed, the drive REQUIRES the index pulse to be present for any type of read or write to work.

OH!!!! I see. I didn't understand that from what I read here on the forum. So, for most people with this drive, it's apparently a simple matter to move the factory-installed jumper on DX (or GX) to EX? Easy-peasy if so...

And just to clarify: having the EX jumper installed will not interfere with SCP reading (or writing?) in either Index or Splice modes?

Thanks.


RE: 475-4 Not reading Side B - admin - 10-10-2022

That is correct. You can just move the jumper and leave it forever. The jumper in the wrong position prevents the drive from reading when an index hole is not detected. Otherwise, the index treated as normal when it is present.


RE: 475-4 Not reading Side B - kentsu - 10-10-2022

Thanks very much for confirming!


RE: 475-4 Not reading Side B - kentsu - 10-10-2022

I am making notes for all of this in case someone asks me down the road... Do I understand correctly that the problem with having the DX/GX jumper installed is that the second side of flippy disks can't be read properly? Thanks.