Help needed for a broken 6128

[Audronic]

What would the voltage be for a low signal?

Around +1 Volts (approx)
I will have a look at what you have changed (Thats a lot of unwell chips).
Good luck        Ray

[Bignumbas]

The only chips that I know were unwell are all the ram chips, I tested each one after by inserting them one at a time with 15 good chips.
IC203 I read in a post in this forum that exhibited the same symptoms I am getting but he had bad keyboard and sound chip as well which I don't appear to have.


You never know where reverse polarity is going to destroy. 

[Bignumbas]

I have ordered one of these
http://www.ebay.com.au/itm/DTL-TTL-CMOS-Digital-Logic-Pulse-Probe-Analyzer-Circuit-Tester-Pen-18V-LP-1-AU-/122013296561?hash=item1c688f27b1:g:Nb0AAOSwbYZXXS8M


What about one of these for after you desolder?

http://www.ebay.com.au/itm/IC-Tester-74-40-45-Series-lC-Logic-Gate-Tester-Digital-Detection-IC-Series-Meter-/252547403135?hash=item3accff8d7f:g:~uQAAOSw4shX38q8

[Audronic]

I have ordered one of these
http://www.ebay.com.au/itm/DTL-TTL-CMOS-Digital-Logic-Pulse-Probe-Analyzer-Circuit-Tester-Pen-18V-LP-1-AU-/122013296561?hash=item1c688f27b1:g:Nb0AAOSwbYZXXS8M


What about one of these for after you desolder?

http://www.ebay.com.au/itm/IC-Tester-74-40-45-Series-lC-Logic-Gate-Tester-Digital-Detection-IC-Series-Meter-/252547403135?hash=item3accff8d7f:g:~uQAAOSw4shX38q8

Yes both look OK.


Ray

[Bryce]

I have ordered one of these
http://www.ebay.com.au/itm/DTL-TTL-CMOS-Digital-Logic-Pulse-Probe-Analyzer-Circuit-Tester-Pen-18V-LP-1-AU-/122013296561?hash=item1c688f27b1:g:Nb0AAOSwbYZXXS8M


What about one of these for after you desolder?

http://www.ebay.com.au/itm/IC-Tester-74-40-45-Series-lC-Logic-Gate-Tester-Digital-Detection-IC-Series-Meter-/252547403135?hash=item3accff8d7f:g:~uQAAOSw4shX38q8

The first the device can be pretty useful if you don't own a scope or a logic analyser, but the IC tester is kind of a pointless toy. Most of these ICs will only cost you a few cents to replace. Buying a $36 dollar tester to test a 15 cent part doesn't add up. For $36 you can blindly swap over 100 ICs. Will you really be repairing that many computers?

Bryce.

[keropi]

for that kind of money a TL866CS programmer is a better choice - it can test 74 series logic ICs and it couples as a programmer 

[Bryce]

I didn't know the TL866CS did logic IC testing too. That's pretty cool.

Bryce.

[keropi]

yes it does ! it even has a grey'ed-ouy SRAM check option, at some point I think they wanted to implement that but it's a lost feature now 

[Bryce]

You can check SRAM on any EPROM burner by powering the IC externally, then write a patern to it and do a compare.

Bryce.

[Bignumbas]

Anybody know where i can get a 40010 chip cheap?
Ebay wants $40 from the motherland.
I have been trying to buy a cheap 6128 on ebay but no luck yet.
There is a guy in Williamstown, Melbourne who sells them on Gumtree but he refuses to sell to me because I cannot come and see it running first??!! WTF!!


I have one of those programmers, the greyed out test in the menu is for "TTL CMOS RAM test"
I found a post about using it for 74 chips so I plugged in the ones I have removed so far to test.
If you type in the 74ls chip number in select IC section it immediately brings up a test window, click start and away it goes.
I have found I had a faulty 74ls38 and a 74ls32 so far, it says they failed on unit 3.  I guess that is cct 3.
The 74hc240 was ok and the other 74ls32 and 74ls38.
Once you enter a recognized ttl or ram chip number in the select menu the test option in the menu is available after the test window is closed.

Guess I won't be buying that TTL chip checker now, that gives me $40 to spend on fixing this board. 

I found this at the end of the devices supported list for the programmer:


RAM test-->26
===============================================================================
standard:    6116   6164   6264     61256   62256   61512  62512  628128   628256  628512
WINBOND:  W2464  W2465  W24256   W24257A  W24512  W24010 W24020 W24040
INTEL:        6116   6264   62256  62512   628128  628256 628512
DALLAS:      DS1220  DS1225   DS1230Y  DS1245Y DS1249Y  DS1250Y DS1230W  DS1245W  DS1249W DS1250W


==================================================================================
CMOS 74/54 test -->136     (it is really 74, 54 series CMOS test the programmer, test errors can be positioned to the wrong logic gate circuits)
==================================================================================   
74HC(LS)00   74HC(LS)01   74HC(LS)02   74HC(LS)03   74HC(LS)04    74HC(LS)05   74HC(LS)06   74HC(LS)07   74HC(LS)08   74HC(LS)09    74HC(LS)10   74HC(LS)11   74HC(LS)12   74HC(LS)13   74HC(LS)14    74HC(LS)15   74HC(LS)16   74HC(LS)17   74HC(LS)18   74HC(LS)19    74HC(LS)20   74HC(LS)21   74HC(LS)22   74HC(LS)24   74HC(LS)26   74HC(LS)27   74HC(LS)28   74HC(LS)30   74HC(LS)32   74HC(LS)33    74HC(LS)34   74HC(LS)35   74HC(LS)36   74HC(LS)37   74HC(LS)38    74HC(LS)39   74HC(LS)40   74HC(LS)42   74HC(LS)43   74HC(LS)45    74HC(LS)74   74HC(LS)86   74HC(LS)93   74HC(LS)112  74HC(LS)122    74HC(LS)123  74HC(LS)125  74HC(LS)126  74HC(LS)128  74HC(LS)132    74HC(LS)133  74HC(LS)134  74HC(LS)136  74HC(LS)138  74HC(LS)139    74HC(LS)140  74HC(LS)145  74HC(LS)153  74HC(LS)155  74HC(LS)156    74HC(LS)157  74HC(LS)158  74HC(LS)160  74HC(LS)161  74HC(LS)162    74HC(LS)163  74HC(LS)164  74HC(LS)165  74HC(LS)166  74HC(LS)174    74HC(LS)175  74HC(LS)192  74HC(LS)193  74HC(LS)240  74HC(LS)241    74HC(LS)244  74HC(LS)245  74HC(LS)257  74HC(LS)258  74HC(LS)266    74HC(LS)268  74HC(LS)273  74HC(LS)367  74HC(LS)373  74HC(LS)374    74HC(LS)377  74HC(LS)378  74HC(LS)386  74HC(LS)390  74HC(LS)393    74HC(LS)563  74HC(LS)564  74HC(LS)573  74HC(LS)574  74HC(LS)576    74HC(LS)580  74HC(LS)640  74HC(LS)641  74HC(LS)642  74HC(LS)643    74HC(LS)644  74HC(LS)645   
4001  4011  4012  4013  4014 4015  4017  4018  4019  4021    4023  4025  4030  4049  4050 4051  4052  4053  4069  4070    4071  4073  4075  4077  4081 4093  40160 40161 40162 40163    40174 40175 40192 40193

[Audronic]

Anybody know where i can get a 40010 chip cheap?
Ebay wants $40 from the motherland.
I have been trying to buy a cheap 6128 on ebay but no luck yet.
There is a guy in Williamstown, Melbourne who sells them on Gumtree but he refuses to sell to me because I cannot come and see it running first??!! WTF!!

Hi Bignumbas
Yes Thats ME.
It was pickup ONLY.

Ray

There is one on Ebay finishing tonight.
http://www.ebay.com.au/itm/Amstrad-CPC6128-Retro-Computer-GT65-Monitor-Joystick-Disks-NOT-WORKING-/302151284709?hash=item46599eb7e5:g:i1QAAOSw4GVYPBXF&autorefresh=true


This is in SA Adelaide.
Good luck      Ray

[Bignumbas]

Hi Audi


I am the high bidder on that 6128 in SA.
I was born in Adelaide originally.
I see you are still trying to sell your 6128's, I gave up on them.
My daughters don't have cars, cannot believe it, over 30 and never had a car.
You can actually buy stuff from Europe cheap for Amstrads and the USA for TRS-80 stuff even with the freight costs.
So will you sell me one of your 360k drives you are offering?
I have a glut of 4164 ram at the moment.

I posted a Tandy coco 3 to Sydney I sold on ebay today.
and I changed my  ebay username to byteology on the weekend
I scored a dktronics 64k ram expansion?
I am going to expand it to 256k and set to banks 4-7 and try it on a 6128 when i get one that works. 


cheers

[Audronic]

@Bignumbas


Ok I won't bid on the SA 6128.


Which drives are you interested in 3.5" ?
Talk to a PC service place and get a Sony 920 that's the easiest to modify. There are Plenty available Second hand.


Of topic :- I just pickup a Tandy Model 1 Monitor Expansion interface, power supplies all WORKED Made up a couple of Floppy drives Goes like a bought one.


Is the Dktronics 64k the old or the new version ?


ByteOlogy  Looks good.


I think Tot0 has or had some 40010


http://www.centpourcent.net/store/p82/X-MASS_MX4_Board.html


and Email him he may be able to help.


Good luck   Ray

[Bignumbas]

I have some 920's, Panasonics and  I modded all of them for Amigas to sell, I have some 3.5's that I have put drive ready on in anticipation.
I was after 360kb 5.25", all the ones I have do not have jumpers for RDY and DC.
Although it seems you can earth pin 34. I think I read that recently.

[Audronic]

@Bignumbas


Ok looks like you are sorted for the 3.5" Drives
The 5.1/4" Drive If you short 33 to 34 that will work BUT CPM will complain after using Disckit (3).
Hope you get the 6128 In SA.


Ray

[00WReX]

That one in South Australia on ebay at the moment, is actually a worker now.

I gave the guy a tip about the Power Switch (same as I gave you Ray  ) and it came to life.

He did not re-list it or change the title, just added a couple more photos showing it booted and added a note indicating it is working.

@Bignumbas

I saw the CoCo 3 you had up on ebay,
Also notice you have a composite modded CoCo 2.
That was always one of my gripes about the CoCo 1 & 2...they only had RF from the factory.
The mod on the later PAL machines is nice & easy though, unlike the NTSC model.
Also if it is only a 16K model, the 64k upgrade is nice and easy too.

Cheers,
Shane

[TotO]

Anybody know where i can get a 40010 chip cheap? Ebay wants $40 from the motherland.

Ebay sucks... I will send you a PM.

[Audronic]

@Bignumbas


Any progress on the repairs ?
Ray

[Bignumbas]

Sorry for the slow updates, progress is like walking through knee deep mud/snow.
I bought another 6128 last week and it is working fine with the 40010 chip from the dead board and the dead is still dead with the replacement 40010 from the working board. I also swapped the HAL chips.
I received a logic probe today, just need to figure out what, where and how to test with it.
Where would you get info on logic probe testing on this system?
I also received various 74ls chips that Jaycar could supply.
I am thinking that if I desolder the 74ls chips one at a time and test them in my TL866CS programmer that would be  a way of testing.
I have already found two of the 74ls chips I replaced were not working properly with it.
I am also thinking that maybe the FDC chip is gone. I can get one cheap online.


In the meantime I have made 4 x 3.5" floppy drives compatible with the CPC and got my HXC Gotek drives working with it as well.
I got 15 3" floppy disks with the new 6128 and only 3 floppies are good on both sides and 2 on one side plus the drive belt was gone.

[Audronic]

@Bignumbas
Last - First. The floppy Disks  if you can find a Magnet from an old hard drive then erase the disks with that.
Or a Bulk erased. I have recovered a lot of disks this way.

I have link somewhere on the board as to the test i have performed on a 6128.
I will find it eventually for you this may help.

Gotcha

http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/repairs-to-a-cpc6128/

This is the same link as what you found earlier.

Good luck    Ray

Late thought.:-
I have had some Open " vias " on the 6128 mother board. Drats took a long time to find.


Ray

[Bignumbas]

I have spent the afternoon replacing the chips I bought and removing and testing the rest.
All the ls74 chips have now been tested on the right hand side of the CPU except for IC117.
40010 and HAL have been checked.
16 chips of memory have been replaced.
I also have a MC0020G board which is different from the board layout in the service manual.
http://www.cpcwiki.eu/index.php/File:CPC6128_PCB_Top_(Z70290_MC0020G).jpg


I also swapped the CPU just in case but still not booting to prompt.
I think I will order a new FDC.


I have washed all the floppy media and the ones that do not work have all been scored, you can see the circular lines in the media.
This PC had a lot of red dust from the far north so I think that was the culprit. I did try a magnet on a few, I will try them all.
It would be good if you could buy the media in sheets and make new disks from the old shells. Bit of glue an scissors 

[Bignumbas]

I have ordered a new FDC chip. I desoldered the existing one and put in a socket.
If I leave the FDC out or the 40015 out the system boots to the prompt.
I can load and run a cassette game from a tape player(Fighter Pilot - 17 blocks!).
I can remember now why I was so happy to get a DDI-1 back in the day.
The sound, screen and KB work fine.
I can change the rom chips for parados and UK 40025 and all works well.


Waiting, waiting.......

[Audronic]

@Bignumbas
Phew    Well done.

Your journey is a bit like my avatar  (A Long and windy road).

Ray

[Bignumbas]

Well my replacement FDC chip arrive.
The system works now!
Cause of the problem was reversal of 12v polarity.
So in closing the final tally is 16 ram chips, 1 x 74ls32 (ic112 or 207), 1 x 74ls38 (ic206 or 208) and one 765 FDC controller chip (ic201).
Plus about 8 hours of wailing and nashing of teeth (I'm never going to fix this syndrome).
Cost was approx AU$30.
Thanks to those who gave some input.



Now to build a multi rom attachment

[1024MAK]

Well done on getting it working again 

Mark