Author Topic: Repairs to a CPC6128  (Read 7097 times)

0 Members and 1 Guest are viewing this topic.

Offline 1024MAK

  • Supporter
  • 464 Plus
  • *
  • Posts: 320
  • Country: gb
  • Touching the hot end of an iron will hurt!
  • Liked: 137
Re: Repairs to a CPC6128
« Reply #50 on: 11:41, 13 November 15 »
From those results (simulation of the keys) it does look like one of the AY-3-8912 I/O pins has internal circuitry damage.


Mark
Looking forward to summer in Somerset :-)

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #51 on: 11:52, 13 November 15 »
HI Mark


Thanks i think that is correct, waiting some AY-3-8912's either arriving from China or Germany  I will see who gets here first.
I will now prepare the board with a new socket and Wait.
I will also put a socket strip in the place for the Resistor network just in case I am sent AY-3-8912(A).
I also have some 9 Pin 2.2k Resistor networks coming.


Ray



Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #52 on: 02:39, 28 November 15 »

After 2 Weeks :-------


The AY-3-8912 arrived as an AY-3-8912A From China.
Put it in and it seems to work, Keyboard OK, Del Key Beeps..
Awaiting on Proper replacement AY-3--------- and for some resistor networks (2.2k) to add to the AY-3-8912A.
Its still a work in progress, i will have a look at the Floppy drive next and associated circuitry..
What an interesting Project.

Thanks to all that helped, commented.

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline 1024MAK

  • Supporter
  • 464 Plus
  • *
  • Posts: 320
  • Country: gb
  • Touching the hot end of an iron will hurt!
  • Liked: 137
Re: Repairs to a CPC6128
« Reply #53 on: 03:56, 29 November 15 »
Yay!  :)

Mark
Looking forward to summer in Somerset :-)

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #54 on: 10:26, 30 November 15 »
The Saga continues, Some Good some Not so good.

The good part is that the Floppy interface is working. Phewwww. That would be a pain to fault find
As there are no Complete Floppy drive Circuits for the Mother board. MC0020B, Z70290, 40010.


The not so good :- 1) It is looking like that the Memory Bank 1 is Unwell.
                            2) The Floppy drive does all the actions steps in and out turns the disk but won't read the disk.
                                I have not had time to look at what is wrong Yet.

I have a 3.5" drive as drive B that i have used for running some test programs, this work good.
I am able to run From Drive A, (I have borrowed another 6128) CPM 2.2 , But am unable to run CPM 2+, it look like it's trying to use some Bank 1 Memory.

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline gerald

  • Supporter
  • 6128 Plus
  • *
  • Posts: 1.287
  • Liked: 918
Re: Repairs to a CPC6128
« Reply #55 on: 11:15, 30 November 15 »
The Saga continues, Some Good some Not so good.

The good part is that the Floppy interface is working. Phewwww. That would be a pain to fault find
As there are no Complete Floppy drive Circuits for the Mother board. MC0020B, Z70290, 40010.
There is  a chance that the drive section schematic in the amendment service manual, in the 6128 cost down section. The same data separator is used.

1) It is looking like that the Memory Bank 1 is Unwell.
I've attached a memory test that covers 512k expansion RAM.
It will test the 0x4000-0x7FFF main bank and all detected expansion 16K blocks.
If the extension RAM is dead and not detected, it will only test that single block.

                           2) The Floppy drive does all the actions steps in and out turns the disk but won't read the disk.
                                I have not had time to look at what is wrong Yet.
Did you change the drive belt ?

Offline Bryce

  • The Hardware Guy.
  • Supporter
  • 6128 Plus
  • *
  • Posts: 10.290
  • Country: wf
  • It's not broken, it just hasn't been fixed yet.
    • index.php?action=treasury
  • Liked: 3521
Re: Repairs to a CPC6128
« Reply #56 on: 11:30, 30 November 15 »
You can use this program - (Run it from B: with the 3.5in drive or or run from A: using the 3.5in drive and then hotswap the drives). With option 5 you can do an RPM test to check that it's spinning at the right speed).

Bryce.

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #57 on: 11:50, 30 November 15 »


There is  a chance that the drive section schematic in the amendment service manual, in the 6128 cost down section. The same data separator is used.


Yes i found the missing links in the 646 and the Plus schematics.


I've attached a memory test that covers 512k expansion RAM.
It will test the 0x4000-0x7FFF main bank and all detected expansion 16K blocks.
If the extension RAM is dead and not detected, it will only test that single block.


Thanks for Memory tester

Did you change the drive belt ?

Yes the belt has been changed the disk spins. But no Read.




Thanks     Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #58 on: 11:55, 30 November 15 »

HI Bryce


I am unable to see the link ?


Thanks   Ray

You can use this program - (Run it from B: with the 3.5in drive or or run from A: using the 3.5in drive and then hotswap the drives). With option 5 you can do an RPM test to check that it's spinning at the right speed).

Bryce.
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #59 on: 12:13, 30 November 15 »
Hmmmnnnn.


Unwell
How do I interpret the Photo Please


Ray
« Last Edit: 12:15, 30 November 15 by Audronic »
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline gerald

  • Supporter
  • 6128 Plus
  • *
  • Posts: 1.287
  • Liked: 918
Re: Repairs to a CPC6128
« Reply #60 on: 12:38, 30 November 15 »
Hmmmnnnn.


Unwell
How do I interpret the Photo Please


Ray
Simple answer is : change the 2nd bank RAM  ;)

Long answer is :
The test failed to detect the 2nd bank properly. The detection is done by writing a signature byte in each of the possible bank and read it back.
The signature is written from the highest possible bank in 512k down to the 1st block of the 1st bank.
The "84 87 84 87 84 87 84 87 84 ....." is the signature readback.
Expected value for a 128k is  "80 81 82 83 80 81 82 83 ...."
A 512k expanded signature is "80 81 82 83 84 85 86 87 ..... 9C 9D 9E 9F"

Unfortunately, this test is only reporting error at byte level and cannot tell which device is OK and which is not.

Offline Bryce

  • The Hardware Guy.
  • Supporter
  • 6128 Plus
  • *
  • Posts: 10.290
  • Country: wf
  • It's not broken, it just hasn't been fixed yet.
    • index.php?action=treasury
  • Liked: 3521
Re: Repairs to a CPC6128
« Reply #61 on: 13:47, 30 November 15 »
HI Bryce

I am unable to see the link ?

Thanks   Ray

Oops, link disappeared: DskTest v0.1.47b (release?)

Bryce.

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #62 on: 00:55, 01 December 15 »
@gerald


"" Simple answer is : change the 2nd bank RAM ;) ""
Damn I thought that the program would be able to repair faulty RAM  :laugh:
Ok Thanks for the explanation.
Out with the SideCutters and away I go.


Ray

Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #63 on: 00:57, 01 December 15 »
@Bryce


Thanks for the Link.
Yes it works if i put on my 3D Glasses.  >:(


Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline pacomix

  • CPC6128
  • ****
  • Posts: 158
  • Liked: 73
Re: Repairs to a CPC6128
« Reply #64 on: 21:33, 21 August 17 »
Hi! I would like to know what happened afterwards. Did you finish fixing this computer?


Enviado desde mi iPhone utilizando Tapatalk

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #65 on: 02:50, 22 August 17 »
@pacomix


Thanks for the reminder.
Yes the 2nd Bank of ram was changed and it works well now.


I must remember to say Project Finished .


Thanks


 Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

Offline llopis

  • CPC664
  • ***
  • Posts: 81
  • Country: es
    • Games from Within
  • Liked: 18
Re: Repairs to a CPC6128
« Reply #66 on: 17:00, 24 June 18 »

Sorry for the thread necromancy, but I'm very curious how you generated your RAM signal tables.When you say Pulse for Din and Pulse for Dout, are you driving those signals somehow? If so, how? When I use a logic probe all I can tell is low, high, or changes between the two.


I've been wondering about isolating some of the chips and try to check their logic behavior, but I haven't figured out how yet (short of removing them from the PCB and setting up a test rig on a breadboard).

Online Audronic

  • 6128 Plus
  • ******
  • Posts: 1.000
  • Country: au
  • I know RST3 . I now know a little More.
  • Liked: 204
Re: Repairs to a CPC6128
« Reply #67 on: 02:14, 25 June 18 »

I'm very curious how you generated your RAM signal tables.


The signals are generated by the Computer after power up


When you say Pulse for Din and Pulse for Dout, are you driving those signals somehow? 


 ###  No I just read them after turning on the computer


If so, how? When I use a logic probe all I can tell is low, high, or changes between the two.


###  I just used an OLD logic probe with 3 lights  LO,   HI,  and Pulsing (activity)


###  Thats all i used Nothing special.


Good Luck
Ray

Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.