Faulty DDI-1 (Zaxon)

[Audronic]

Note to Zaxon (Piotr Bugaj)

I have just obtained an Amstrad CPC 464.(At Last)
And have just installed the DDI-1 Clone that you sold me.
I have a problem with the DDI-1 ( I have a technical background )


If i put the ABBA switch in the Normal Position (A)
and The PARADOS/AMSdos switch in the AMSdos Position

I have 2 Floppies 3.5" both Sony MPF920's
one as drive 0 (Zaxon)and the other as drive 1 (mine)

Then both drives perform OK

I Leave the 2 Disks in the Drives.

BUT if i put the ABBA Switch in the Other position (B)
and leave the PARADOS/AMSdos switch in the AMSdos Position

Drive A performs OK, BUT Drive B Has "Read Fails"

I have turned off the power to Both Computer and drives between each test.
(and tested that the Floppy disks are OK)

If i then put the PARADOS/AMSdos to PARADOS position (ABBA in Normal Position)
Then Drive A is OK But Drive B has a garbled Directory (CAT)

If I the put the ABBA Switch in the Other position (B)

Both Drives are Faulty.

I have noticed that the light is permanently on for Drive (1) B
regardless of the ABBA switch position,
Yes I have made up 2 other 34 Pin test leads and the problem stays.

I have also tried the above with a HXC unit and the same results.

My thoughts are that it has something to do with the ABBA Switching
I have had a look at the wiring, and the wiring to the 74LS38 Looks OK.

I can do repairs or Modifications to the DDI-1 if needed.

Can you help Please.

Thanks Ray.

[TFM]

Which formats do your discs have? Amsdos doesn't read anything else than data, system or ibm format.

[Audronic]

@TFM
Thanks for the info on Amsdos.
That disks are formatted as 40 Track Single Sided Data on a 3,5" Disc.
That same as if it was on a 3" disc.
The problem is not the discs but the Abba switch Odd behaviour.


Thanks   Ray

[TFM]

Well, you could ask Bryce or TotO or Gerald to take a look at the schematics. They are really good in hardware. I mean it may be a general problem.


Anybody here with similar problems?

[gerald]

I have noticed that the light is permanently on for Drive (1) B
regardless of the ABBA switch position,

Can you check that the ABBA switch is properly soldered ? If the light is always on on B drive it could be that its select signal is grounded.

[Audronic]

gerald

Thanks for the thoughts about the ABBA Switch, I will check it out.
I am at the point of adding a pullup to the output of the line that feeds the B drive (2.2K---1K)
as i am not sure about the loading of the 2 Sony 920 Floppy drives.
I have changed the 74LS38 to a 7400 (as per DDI-1 schematic suggestion) in the top right hand corner.
I cannot post the part of the schematic (sorry)
Thanks   Ray

[Audronic]

Have Pulled the 74ls38 from U8 and replaced it with a 7400 with all the legs plugged in.
Works OK as A and B (as Previously)
Throw the Parados switch and have the same problems as per previous discussions.


So Now we have 2 separate Fault conditions. Drats


I will have a look at it late Sunday.


Thanks     Ray

[Audronic]

Hi All

I had a Look at it on Sunday 3 and a Half Years ago and at that time i was unable to fix it   BUT today.

Give a dog a Bone and he wont give up.

The Dreaded Zaxon DDI-1 2014 version has had a fault for a long time.
I just purchased an other one of these and it also had the same Problem.

Read Previous notes Please.

I have modified the way that drive 0 (Zero) is selected and it works.

If others have these units they can be FIXXED.
See photos

Thanks Ray

[LambdaMikel]

Nice job, well done! Well, I never used it long enough to even run into that problem. And I don't own another one; you got my last one.
DDI3 works well with 2 drives - but it is intereseting that the ZAXDrive also has some issue with the 2nd drive, which requires soldering to fix... seems to be a Zaxon thing 

[angelcaio]

Hi, Audronic.
I'm reading your interesting post and I too have problems with my DFI-1 clone from zaxon: in order to write to B:, I need an unprotected drive on A:.
I have no knowledge of electronics. Could you put a photo indicating the changes to be made on the board of the DFI-1 clone?
Thank you very much in advance

[Audronic]

@angelcaio 

Sorry no longer have the hardware

Keep Safe

Ray

[angelcaio]

@angelcaio

Sorry no longer have the hardware

Keep Safe

Ray

Okay.  Anyway thanks, Ray for the reply