Author Topic: Problem with 6128 Plus FDC  (Read 2557 times)

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Offline redbox

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Problem with 6128 Plus FDC
« on: 15:03, 18 February 14 »
My (last surviving!) 6128 Plus has a problem...

The internal 3" drive isn't working, which I assume is just a drive belt, but haven't had the chance to look properly at it yet.

So I tried to use my HxC as a B drive in the meantime (plugged into external drive port) and it doesn't work properly.  When I CAT the disc I get some data, but it's garbled and not complete.  When I try to run a file it starts to work but then I get read fails or disc missing.

I've tried 2 different cables and 2 different HxCs (SD Card and USB version) which work on other CPCs, so I know that's not the problem.

So does this mean there's a problem with the FDC controller?  Or something different...?

Offline Bryce

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Re: Problem with 6128 Plus FDC
« Reply #1 on: 15:07, 18 February 14 »
There are several parts to the disk controller circuitry. Usually it's one of the inverters that fails first. If the µPD765 or the data seperator failed you'd usually get absolutely nothing from either drive.

Some things to try:
Clean the contacts of the external floppy port.
Disconnect the internal drive completely and see if the HxC then works.

Bryce.


Offline redbox

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Re: Problem with 6128 Plus FDC
« Reply #2 on: 17:13, 19 February 14 »
There are several parts to the disk controller circuitry. Usually it's one of the inverters that fails first. If the µPD765 or the data seperator failed you'd usually get absolutely nothing from either drive.

Thanks!  So which part is the inverter?  Is it easy to source/replace?

Some things to try:
Clean the contacts of the external floppy port.
Disconnect the internal drive completely and see if the HxC then works.

Am pretty sure I tried disconnecting the internal drive, but will do it again when I get back to work.

What should I use to clean the contacts - isopropyl alcohol?  It's the Centronics type, so do you mean the pins inside the connector?

Offline Bryce

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Re: Problem with 6128 Plus FDC
« Reply #3 on: 17:59, 19 February 14 »
The gates that are most likely to cause problems on the controller are the two 74LS38 (IC105 and IC106) and the 74HC14 (IC107) all three are located in the bottom right corner of the PCB. Both parts are still easy to source. All three ICs have direct connections to the drive, so short-circuits, wrong connects etc directly hit these ICs.

Yeah, any kind of contact cleaner will do. Also check that none of the pins have bent or are missing in the connector.

Bryce.



Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #4 on: 14:38, 22 August 14 »
From time to time my CPC+ internal floppy is suddenly disabled, and if i type "cat" i get the tape message from the 464: press PLAY and....
I have also all the time an external HxC connected, and when this situation happen the HxC stops working, the LCD turn off.
Everything comes back to normal after switching the CPC+ off &on.


Any ideea what could be the problem ?


Thanks !

Offline arnoldemu

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Re: Problem with 6128 Plus FDC
« Reply #5 on: 15:04, 22 August 14 »
From time to time my CPC+ internal floppy is suddenly disabled, and if i type "cat" i get the tape message from the 464: press PLAY and....
I have also all the time an external HxC connected, and when this situation happen the HxC stops working, the LCD turn off.
Everything comes back to normal after switching the CPC+ off &on.


Any ideea what could be the problem ?


Thanks !
Does the problem happen when running a particular program/game or is it random?
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Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #6 on: 15:41, 22 August 14 »
i cant tell you.
i will check today later !

Offline Bryce

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Re: Problem with 6128 Plus FDC
« Reply #7 on: 16:52, 22 August 14 »
Are you sure that your powersupply is able to supply enough current for everything?

Bryce.

Offline CraigsBar

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Re: Problem with 6128 Plus FDC
« Reply #8 on: 16:53, 22 August 14 »
My (last surviving!) 6128 Plus has a problem...

The internal 3" drive isn't working, which I assume is just a drive belt, but haven't had the chance to look properly at it yet.

So I tried to use my HxC as a B drive in the meantime (plugged into external drive port) and it doesn't work properly.  When I CAT the disc I get some data, but it's garbled and not complete.  When I try to run a file it starts to work but then I get read fails or disc missing.

I've tried 2 different cables and 2 different HxCs (SD Card and USB version) which work on other CPCs, so I know that's not the problem.

So does this mean there's a problem with the FDC controller?  Or something different...?
Being overly simplistic here.... Do you have Parados installed anywhere? By default that will assume that drive b is 80 track double sided, resulting in the garbled catalogue you describe when using a 40 track disk image...
You can either set the Parados config for both drives to 40 track single sided in the Parados application (shift +cd) or fit an abba switch to swap the hxc to a.

Hope this helps. If you don't have Parados (or another patched amsdos) the I dunno, sorry.

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Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #9 on: 19:00, 22 August 14 »
ok, tested.
if i use a CF disk that cant be read, the floppy drive goes in a loop in order to try to read the disk.
Because the loop take long time, i reset the cpc+ with the keyboard combination.
I notice that in this moment, after the reset, the floppy led remains on ( brighter light ), and then i got this message.


it happents every time i use a bad cf2 disk. same pattern.
Do you guys have the same problem with the bad disks ?






Offline arnoldemu

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Re: Problem with 6128 Plus FDC
« Reply #10 on: 19:10, 22 August 14 »
ok, tested.
if i use a CF disk that cant be read, the floppy drive goes in a loop in order to try to read the disk.
Because the loop take long time, i reset the cpc+ with the keyboard combination.
I notice that in this moment, after the reset, the floppy led remains on ( brighter light ), and then i got this message.


it happents every time i use a bad cf2 disk. same pattern.
Do you guys have the same problem with the bad disks ?

When you reset the plus using the key combination then the FDC will still be active trying to read from the bad disc and performing a command. The drive light is on because the fdc is active and reading from the drive.

The amsdos rom inside the cartridge is always active on 464/6128. Before the menu comes up it tries to detect if there is a FDC or floppy disc interface and expects a specific response from the FDC.
FDC can't respond with the correct answer because it's still executing a command. So the code then says "no fdc" and it goes to normal cassette operation by default.

Another question, do you have a second drive? One which is permanently forced "ready"?

i.e. if you do CAT without a disc in drive B does it hang?

Normal operation is to report "disc missing". If you have this then this may be making the problem worse.

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Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #11 on: 19:57, 22 August 14 »
I have as drive A the internal floppy, and as drive B the HxC.
If i CAT without the disc its not hanging. i got the message disc missing. Pressing C will bring the prompter back, and i can work.


I have also a second drive with the ready signal on. What should i test ?

Offline arnoldemu

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Re: Problem with 6128 Plus FDC
« Reply #12 on: 21:21, 22 August 14 »
I have as drive A the internal floppy, and as drive B the HxC.
If i CAT without the disc its not hanging. i got the message disc missing. Pressing C will bring the prompter back, and i can work.


I have also a second drive with the ready signal on. What should i test ?
You are seeing normal operation. Do you have a reset switch attached to your Plus? I would suggest you to use this and not ctrl+shift+esc.

reset switch should reset fdc, if not best use power switch.
ctrl+shift+esc doesn't reset fdc.

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Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #13 on: 21:26, 22 August 14 »
thanks for the hint.
i feel better now :)


i don"t have a reset button yet, but it will come with the X4Mother :)




Offline TFM

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Re: Problem with 6128 Plus FDC
« Reply #14 on: 22:54, 22 August 14 »
From time to time my CPC+ internal floppy is suddenly disabled, and if i type "cat" i get the tape message from the 464: press PLAY and....
I have also all the time an external HxC connected, and when this situation happen the HxC stops working, the LCD turn off.
Everything comes back to normal after switching the CPC+ off &on.


Any ideea what could be the problem ?


Thanks !


An idea.... Is the power supply of the HxC too weak? How much Ampere does it have?

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Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #15 on: 23:08, 22 August 14 »
on 5V, 11.6 Amps.

Offline TFM

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Re: Problem with 6128 Plus FDC
« Reply #16 on: 23:22, 22 August 14 »
WoW! That is maybe ever too much (if that is possible). With 1 A you are IMHO already on the save side.  :)
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Offline robcfg

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Re: Problem with 6128 Plus FDC
« Reply #17 on: 01:12, 23 August 14 »
I had a similar problem and it was due to too many things plugged to the same power outlet. Try only plugging the computer and the hxc.

Offline radu14m

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Re: Problem with 6128 Plus FDC
« Reply #18 on: 07:08, 23 August 14 »
i supply the HxC alone  from the AT supply.
The cpc is supplyed from the original amstrad monitor.
So that there are no others things connected.