I obtained a 6128 with no screen and manage to plug in 12v with the wrong polarity due to some misinformation, damn :(
The ram was getting hot and it was booting to the gray screen of death so I replaced all the ram.
It now boots to some ROM copyright info, blue screen and yellow writing as it should but no command prompt appears. :(
There is no BASIC 1.1 written on screen, no "Ready" prompt and no flashing cursor.
It seems to me that I may have fried the AMSDOS rom a bit.
Anybody got any suggestions as to what needs replacing?
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
Can you Post a Photo of the Screen ?
What state do you live in, there may be someone near you who can help ?
Ray
Quote from: Bignumbas on 08:27, 01 November 16
I obtained a 6128 with no screen and manage to plug in 12v with the wrong polarity due to some misinformation, damn :(
The ram was getting hot and it was booting to the gray screen of death so I replaced all the ram.
It now boots to some ROM copyright info, blue screen and yellow writing as it should but no command prompt appears. :(
There is no BASIC 1.1 written on screen, no "Ready" prompt and no flashing cursor.
It seems to me that I may have fried the AMSDOS rom a bit.
Anybody got any suggestions as to what needs replacing?
Yup, you've probably fried AmsDOS. Luckily it can be replaced with a suitably programmed standard 16K EPROM. So get yourself an EPROM and swap it out. You may however discover that you have sound/keyboard issues after you've fixed the boot problems.
Bryce.
To be sure nothing else than amsdos is broken, simply remove your amsdos ROM and boot the CPC, it should behave like a 464: type [run"] then if it asks you "press play then any key" you win! Just replace a new amsdos or even better, parados :-)
Soory I posted this reply to the email I was sent, evidently that goes nowhere :doh:
Hi Ray
I live in Bundaberg, QLD
Photo of the screen?
This is what I am getting
http://www.cpcwiki.eu/forum/index.php?action=dlattach;topic=11251.0;attach=16717;image
If I touch pin 3 on the Zilog FDC I get an error message about line 3190 and then a ready prompt, but every command I type after that gets a bad syntax error.
This topic is the closest I have found to my problem
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/repairs-to-a-cpc6128/10/
cheers
Mark
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
Bundaberg is a bit far from Victoria for me to pop over and have a look.
Others may like to chip (sic) in if they are local. ?
That looks very similar to my problems (The Link).
It would be very unusual for the same fault ?
Anyway put your Finger/probe/CRO near IC 201 and re Boot ?
Read the link stuff as I had a good time fixing 2 Similar faulty units.
Good luck
Ray
Well i am going in boots and all now.I have ordered some Eproms, 32k and 16k chips and I am going to put in Parados and as this is a French system am going to burn the UK basic as well.I found you can get the key decals online now so I will change the french keys to english. Never got the hang of an azerty keyboard, I used to work on french language windows PC's.I have also ordered a 74hc240 for ic203 as well.When I look at where the reverse polarity goes its basically the whole board.I scored a 3.5 " drive that I can turn on ready so I will be putting in an abba switch plus I want to try out my Gotek drive on the 6128 when I get all this together.I have ordered a new drive belt for the 3" drive but do not have any discs, yet.
I am also looking at a dual rom setup as well.
On an off topic note I will be burning some Amiga 500 3.1 kickstarts as well, just waiting on chipsand I have a Sega mastersystem game cartridge I will be putting in an eprom to play with.
I had a 464 back in 1985 with a DD1 drive & colour monitor, those were the days! ;D
Did you just randomly choose IC203 to replace or have you reason to believe that it is fried? If you were really lucky, the ROM took the hit and shorted before anything else had a chance to die, but unfortunately this is only rarely the case. I have repaired CPCs that had the same fate and had to swap almost 70% of the ICs. The most sensitive ICs on the board are the RAM, the AY and the CRTC. The TTLs may have all survived.
Bryce.
Well my only guide I could find is this post http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/repairs-to-a-cpc6128/.Replacing all the ram brought me halfway back to a live CPC.I find the schematic in the Amstrad service manual a little lacking in detail. It misses out some detail and ic's
Do you really live in Wallis Futuna Bryce?I lived in Vanuatu for 15 years.
:D No, I live in Germany, but I like to choose some obscure little Islands flag just for fun. I change it on occassions.
Vanuatu?? Wow, that's remote, what were you doing out there? Did you have a CPC there!?? :o
Define "halfway back to a live CPC", what's it doing now?
Bryce.
Quote from: Bignumbas on 08:27, 01 November 16
I obtained a 6128 with no screen and manage to plug in 12v with the wrong polarity due to some misinformation, damn :(
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936), did you plug a 12V supply into the 5V input? Is that what you think you did? Only all the logic, the CPU, memory etc are all supplied by the +5V rail.
Mark
No I had reverse polarity on the 12 volt supply. I am using an old ide external power supply that had a 4 pin plug with 12v and 5v.When I initially plugged it in it seem to short out the power supply. :doh:
The when I reversed it back and powered on there was only the grey screen and all the ram chips were getting hot.
Then you effectively put -7V on the 5V rail. Most chips won't have been happy with this.
Bryce.
I have noticed this Bryce. Just trying to pick my way through the dead ones.
Quote from: Bryce on 09:11, 07 November 16
Then you effectively put -7V on the 5V rail. Most chips won't have been happy with this.
Bryce.
I this the circuit ?
Ray
Where did you find that? Is it in the Service manual?
That part of the circuit switches the 12V supply on as soon as the 5V rail is ready. If you put 12V backwards on to that circuit, the 5V rail is sharing the same ground circuit, so the 12V will flow into the 5V rail in the wrong direction. However, those transistors will never switch on because the 5V rail is now effectively seeing -7V.
The delay on power up is done here:
[attach=2]
R101 and C135 form an RC delay. C135 is (relatively) slowly charged through R101. When the correct voltage is achieved it will trigger IC117 which triggers a reset several milliseconds after power has been applied. This ensures that all ICs are up and running and all started at exactly the same time.
Bryce.
Quote from: Bryce on 12:17, 08 November 16
Where did you find that? Is it in the Service manual?
Bryce.
Hi Bryce
It is in the :- Amstrad Amendment Service Manual.PDF On Page 20 ( CPC6128 Chassis Schematic Diagram )Thanks for the explanation of the Power up Delay (Reset)Ray
Thanks for that missing info Bryce.I have just received some parts from china on the slow boat.I have put in sockets for both the roms.I have replaced the ls74chip above the FDC at the end of the board.When I put in the 40025 System Rom alone the system boots to the ready prompt but asks for a cassette when a DIR command is given, Whew! I have burnt a UK rom to replace the FR one and it works so I now have a QWERTY KB.If I put in the DOS 40015 ROM it does not get to the ready prompt.I am going to burn your Dual dos rom tonight Bryce and try that.I have some Winbond 256k roms to play with now.Things are looking better :)
Well its good news and bad news.Looks like I have a 464 for the moment. CAT command responds insert cassette.Keyboard works fine as a Qwerty with my new UK 6128 40025 rom.When I plug in the Amsdos rom 40015 and type |DISC I get Unknown command.Looks like this rom is not being seen by the system.Has anybody got a suggestion as to why?
So is that with the original AMSDOS ROM or have you burnt a new one ?
I see you have burnt a 40025 ROM, but not clear about the 40015.
Cheers,
Shane
@Bignumbas
I have just burned the Parados file to a 27c128 to replace the 40015 in the DDI-1 and this works for my 464, I know that you want to put it into a 6128.
The zip contains Amsdos.v0.5 and Parados 1.2 Modified 40-40 Track
Ray
I have both he original roms, 40051(french) and 40015[size=78%].[/size][/size]I have made a 40025 (English) and it works. Inserted by itself with no 40015 I get the READY prompt and I can type qwerty but it wants a cassette inserted on the CAT command.The original 40015 when it is installed with the 40025/40051 stops the boot process just before the prompt, so there is no READY prompt. [size=78%][/size]I have experimented with making the 40015 and when it is correct ( I think) I get the same problem as with the original 40015 rom. [size=78%][/size]When I make one and it is not correct I get the READY prompt but it does not recognize the disk commands and says to insert a cassette just like there is no recognized 40015.[size=78%]Clear as mud now? :doh:
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
Have a look at pin 20 On the 40015 rom it should be LOW to enable the rom.??
This comes from the 40007/10
Good Luck Ray
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
Any Progress ?
Ray
A little progress, I have replaced Q302, Q303, IC203, IC207 & IC212 plus the entire 16 ram chips.
I have also put sockets in for the two rom chips 40015 and 40025.
I tested IC206 and IC208 pin voltages and they were both radically different to each other so I ordered them and am waiting again.
Maybe when I get them it will work.
The keyboard works and the system boots to the ready prompt without the 40015 plugged in.
I have no digital test equipment so that makes it harder, I am left with part replacement.
I bought a mix of stuff on ebay the other day for $74 because I spotted a Dktronics 64k expansion module in among the stuff, I have ordered some 41256 chips for that.
Plus it had an Amstrad game tape so i might try loading that to see if the system works on cassette.
I also had to replace the drive belt but I have no 3" disks as yet but I do have an HXCusb Gotek ready for when I get the 40015 to be recognized.
What would the voltage be for a low signal?
Quote from: Bignumbas on 23:49, 01 December 16
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
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. :doh:
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
Quote from: Bignumbas on 01:34, 02 December 16
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 (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 (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
Quote from: Bignumbas on 01:34, 02 December 16
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 (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 (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.
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 8)
I didn't know the TL866CS did logic IC testing too. That's pretty cool.
Bryce.
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 :laugh:
You can check SRAM on any EPROM burner by powering the IC externally, then write a patern to it and do a compare.
Bryce.
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. :doh:
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
Quote from: Bignumbas on 05:20, 05 December 16
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 BignumbasYes 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 (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
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
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
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
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.
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
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
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 (http://www.cpcwiki.eu/forum/profile/?u=1936)
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
Quote from: Bignumbas on 05:20, 05 December 16
Anybody know where i can get a 40010 chip cheap? Ebay wants $40 from the motherland.
Ebay sucks... I will send you a PM.
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
Any progress on the repairs ?
Ray
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.
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
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/ (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
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 ;D
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.......
@Bignumbas (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1936)
Phew Well done.
Your journey is a bit like my avatar (A Long and windy road).
Ray
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.
:D
Now to build a multi rom attachment
Well done on getting it working again :D
Mark
Congratulations. For a reversed 12V you actually came out ok. I've seen CPCs that had a lot more damage from the same mistake.
Bryce.
Well done Mark.
The advantage of the forum is that there was a lot of good Info in their thread especially this for me :-
Helpful hint from "tjjq44"
"" To be sure nothing else than amsdos is broken, simply remove your amsdos ROM and boot the CPC,
it should behave like a 464: type [run"] then if it asks you "press play then any key" you win! Just replace a new amsdos or even better, parados :-) ""
Also thanks to all the people that contributed.
Ray