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Don't worry about the video chip for now. If the RAMs are getting hot, then they are shorting the 5V supply rail which would cause the CRTC to do random things. Swapping the RAM will most likely bring the CPC back to life.

Bryce.

Hi Bryce, Thanks for your speedy reply. I suppose I was fearing a RAM issue. I think my best bet as I cannot easily diagnose which chip is defective is to remove them all and socket them. I have the sockets and I also have a donor board but probably better to go with a new replacement set from a far away place! Although it won't hurt to swap the one that seems to get really hot the quickest first? Can you recommend any suppliers of these RAM chips. Is there a newer equivalent... TMM4164AP-15???
Thanks again for your help!

There's no new equivalent. Ebay is probably the best place to find replacements.

Bryce.

So as long as a chip is labelled 4264-15 it will be compatible? Please excuse my naivety...

4164-15. There are a few other compatible parts, but the 4164 is easily found.


Bryce.

Thanks Bryce...


Before I socket all the RAM in the CPC464, can I piggy back test the RAM if I suspect a certain chip?


Pledg

For certain failures (possibly bad, but not getting hot) yes, but if the suspect chip is getting very hot it has a short inside and will "steal" the current that the piggybacked chip needs and the computer still won't boot.

Bryce.

Thanks, I'll remove them all...


Pledg

It's known that Amstrad (and other computer manufacturers of the time) had no problem using parts from the "B Bin", so it's not a bad idea to swap all of them while you have the iron heated up.

Bryce.

Progress report:
I socketed and replaced all the RAM chips and now I have gone back to a full black screen no borders with the odd flickering white horizontal interference lines. This feels like a step in the right direction from the previous state which was no video signal at all!
I think I'll re-check the input/outputs from the video chip, although I would have thought it would have booted without an issue elsewhere like the Z80 or the gate array?


Pledg

Check pins 39 and 40 on the CRTC Chip.

Bryce.

I'm reading .475v on pin 40 and .250v on pin 39

I just swapped the Z80 and that now gives me a blank grey screen with no interference?

I am getting steady oscilloscope readings from pins 6, 7, 18, 39 and 40 but nothing from pin 21 which I believe is the clock signal. So work back from there to IC125?

Okay so I'm not getting a clock signal going to look at the caps associated with the crystal X101.

Where are you measuring the clock from?

Bryce.

P.s. When I say "measure", that means with the scope unless it's a power pin/rail. Pins 39 and 40 of the CRTC should be the H and Vsync signals.

Yes I am getting the signals from pin 39 and 40 of the CRTC chip with the scope.

If you are getting signals on pins 39 and 40, then the clock is working. Which is why I asked where you are measuring the clock from.

Bryce.

Okay! Thank you, so where/what should I check next?

Well you still need to confirm that the clock is available where it should be. You still didn't say where you were measuring it from when you said it was missing?

My next check would be the 74LS153's

Bryce.

Okay so which pins do I need to check on those 4 chips?

These chips are multiplexers, that allow the address bus to be shared by both the CPU and the CRTC. The pins you need to check are pins 7 and 9 of each chip, to ensure that all are switching and none are stuck either high or low.

Bryce.

pins 7 & 9 are giving good readings on all 74LS153 chips.

They may be giving signals, but are the signals coming from the correct source? You will need to use a logic analyser to confirm that the source switches when pins 2 and 14 are enabled/disabled.

Bryce.

Thank you for your continued patience with my lack of electrical knowledge and this issue... I'm wondering whether I'll ever get it fixed???


Logic probe on pin 2 I get a high reading and nothing on pin 14? Should they be switching?

Oh, that's not good. Pin 2 should be a 1Mhz squarewave. If this is missing, then you may have a damaged Gate Array (40007). Try isolating pin 1 of the 40007 (ie: bend it a bit so that it doesn't go into the socket. If you get 1Mhz on that pin then the GA is fine, but something is pulling the clock high (some other damaged chip). If the 1Mhz is missing from pin 1 then test that there is a 16Mhz signal on pin 8 of the 40007.

We WILL get this fixed.


Bryce.

Okay so bearing in mind my scope is rudimentary pin 2 is reading 40hz and pin 14 is about 4hz.

Define rudimentary. What model or type of scope are you using?

Bryce.

Its a hand held effort I'm afraid... "ETEPON"


I have it set on 2vDC and 20ms.


So pin 1 of the 4008 I'm getting 200mhz and pin 8 I'm getting 30-40mhz.

Oh dear. No, that won't be sufficient. It only has a bandwidth of 200kHz, so what it's measuring is probably just an aliased sample. You'll need something better to continue.

Bryce.

Ok so looks like I'm done for now! Any recommendations for a scope that won't bankrupt me would be appreciated.


I have a donor board so I may socket some other chips and swap them in the hope it may find the fault.


IC101, IC110, IC113, IC115, IC112, IC114 and the TC74HCUOP


If any of those stand out let me know what to check and which order may be best to swap them in...


Any checks I could do with a simple logic probe appreciated.


I could send both boards away but I'm loath to give up.


Anyway thanks for you help and patience.

I get don't get a reading with a logic probe from IC110 74LS132 and when I touch pin 2 I get blue vertical characters appearing on the blank grey screen?


Also Pin 1 of IC125 TC74HCUOP has no reading but logic probe on it gives same blue characters on grey blank screen? Pin 2 gives a high reading on the probe?


Any help?


Never give up!!!!

Would you have a 40007 or 40010 gate array chip I could purchase or know of anyone with spares available?

What kind of price range would you consider spending on a scope?

Random results from touching pins doesn't really tell anything I'm afraid.

Bryce.

I suppose around the £100 mark preferable a compact model... Is it worth trying to pick up used one?


Any checks I do on my ROM chip with a logic probe?


Also my Gate Array chip is a 70008? I can't find any other reference to this version online only 40007 and the 40010?


Thanks...

Quote from: pledg on 12:02, 11 December 19
I suppose around the £100 mark preferable a compact model... Is it worth trying to pick up used one?


Any checks I do on my ROM chip with a logic probe?


Also my Gate Array chip is a 70008? I can't find any other reference to this version online only 40007 and the 40010?


Thanks...

??? Can you post a picture of your "gate Array". A 70008 is a processor! Maybe someone put the wrong chip into the CPC?

Be very careful buying used scopes, especially modern ones. People usually sell these when something is wrong. But I'll browse the interwebs and see if I can find something in that price range.


Bryce.

For £100 the only half decent scope you'll get is the Hantek2C42. It's not great, but it's worlds ahead of what you have, you get a half decent multimeter too and Hantek are a relatively ok company for entry level scopes:

https://www.ebay.co.uk/itm/2-in-1-Hantek-Digital-Oscilloscope-Multimeter-70-40MHz-bandwidth-250MSa-s-2C42/333383533016

Bryce.

No! Please don't tell me it's as simple as that!!!!


Pease see attached PCB pic:


Thanks for the scope suggestion...

Ok, that's a 40008 - a valid Gate Array for the 464. Not a 70008 as you said earlier. It still may be faulty, but at least it's the correct chip.

Bryce.

Yes sorry earlier typo... Where can I purchase a replacement?


As I said earlier I did purchased a donor board for parts but this board has the 40010 chip which I'm sure is dead also.

Gate arrays (especially the 40010) don't die that often. I'd be suprised if both were dead unless the same person connected both machines to a 12V source or something similarly stupid.

@TotO (http://www.cpcwiki.eu/forum/index.php?action=profile;u=290) did have some GA's in stock, not sure if he still has any left though.

Bryce.

Thanks...


What is the function of IC110 the 74LS132 I get no logic probe reading from this chip at all. All the other IC chips in the row give me a reading. Every time I touch it I get blue garbled characters appearing on the screen blank grey screen as if its trying to do something.


Thinking of swapping it out with the same from donor board?

I have to check. Probably few 40007, 40008, 40010 left for repair purpose. Just PM me if really required.

Part    Description
40007   Gate-Array version 1 (20RA043) (uses a heat sink, same pinouts as 40008)  ? ? ?

40008   Gate-Array version 2 (HSG3130) (uses a heat sink, same pinouts as 40007)  ? ? ?

40009   32K ROM; BIOS and BASIC for CPC464 (English)

40010   Gate-Array version 3 (HSG3170) (no heat sink, different pinouts than 40007 and 40008)

40015   16K ROM; AMSDOS for CPC664/CPC6128 and DDI-1 disc interface

Some more info on 40008 ? (From Grim)

Different versions of the Gate Array exist.
They basically all do the same things, but their technology and design have been improved in the latest revisions.

The first version of the Gate Array is the 40007 and was released with the CPC 464.
Some of them are mounted with a huge and ugly heat sink.

Later, the CPC 664 came out fitted with the 40008 version (and at the same time, the CPC 464 was also upgraded with this version).

This version is pinout incompatible with the 40007 (that's why the upgraded 464 of this period have two Gate Array slots on the motherboard, one for a 40007 and one for a 40008).

The CPC 6128 was released with the 40010 version (and the CPC 464 and 664 manufactured at that time were also upgraded to this version). The 40010 is pinout compatible with the previous 40008. ? ? ?

Ray

@Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225)


? Is the 40008 in the wrong socket ? ? ?



The CPC 6128 was released with the 40010 version (and the CPC 464 and 664 manufactured at that time were also upgraded to this version). The 40010 is pinout compatible with the previous 40008. ? ? ?

Ray

Taking a look at our scans of the CPC PCBs, it looks like only the first series, Z70100 MC0001A, had only a 40007 socket.


Beyond that, and previous to the 664 and 6128, 464 boards have sockets for both gate array types, and it's labeled "Amstrad 40010".


Edit:In the Gate Array page, if you check the picture of the decapped 40010, you'll see "LSI LOGIC CORP (C) 83" on the die.

Quote from: Audronic on 23:13, 11 December 19
Some more info on 40008 ? (From Grim)

Different versions of the Gate Array exist.
They basically all do the same things, but their technology and design have been improved in the latest revisions.

The first version of the Gate Array is the 40007 and was released with the CPC 464.
Some of them are mounted with a huge and ugly heat sink.

Later, the CPC 664 came out fitted with the 40008 version (and at the same time, the CPC 464 was also upgraded with this version).

This version is pinout incompatible with the 40007 (that's why the upgraded 464 of this period have two Gate Array slots on the motherboard, one for a 40007 and one for a 40008).

The CPC 6128 was released with the 40010 version (and the CPC 464 and 664 manufactured at that time were also upgraded to this version). The 40010 is pinout compatible with the previous 40008. ? ? ?

Ray

I am quite sure the 40008 has the 40007 pinout.
The only picture with a 40008 (https://www.cpcwiki.eu/imgs/9/92/CPC464_PCB_Top_%28Z70200_MC0002D%29_GA40008.jpg) on the cpcwiki would confirm this.
I never had any in my hands so I only can trust the picture  ;)

@robcfg (http://www.cpcwiki.eu/forum/index.php?action=profile;u=4) The 40007 and 40008 die picture that you posted years ago seems to be identical (ie, 2 different decapped chip, but same design on same gate array techno)
Any chance that these where both 40007 ?

Thank you all for your input into this thread.


Trust me to end up with a board with an uncommon gate array in it!


So it seems that the 40008 is the same pinout and is meant to be in the 40007 socket?


I'll carry on trying to find the fault with this board.


Thanks...

They are basically the same chip, but you can notice that on the 40008, the distribution is a bit different and the cells on the gate array are rectangular instead of square.


I think the original 40007s were getting quite hot so they were changed in order to avoid that. As far as I remember, the 40010 don't have any heatsink but not sure about the 40008.


And it's quite interesting, because at Grimware, they say that 40008 is not pin compatible with 40007:

QuoteAmstrad 40008 (CPC 664)
Later, the CPC 664 came out fitted with the 40008 version (and at the same time, the CPC 464 was also upgraded with this version). This version is pinout incompatible with the 40007 (that's why the upgraded 464 of this period have two Gate Array slots on the motherboard, one for a 40007 and one for a 40008).

I'm starting to hate the 664 pcb as they have no year marking nor the GA label like the rest of the boards  :P


Ok. It seems, according to the service manuals, that the 40007 is the one that is different, so the 464 board has actually the wrong IC in the GA socket.

Hi All


a Link to 40008 etc in French this May Help ? ?


http://matthieu.benoit.free.fr/pdf/amstrad_videogate-array.pdf (http://matthieu.benoit.free.fr/pdf/amstrad_videogate-array.pdf).


It has pinouts etc.
Good luck.  Ray

I'm pretty sure that the 40008 belongs in the 40007 socket, not the 40010 socket.

Bryce.

HI All


The French link indicates that the 40008 and the 40010 are pin compatible ? ?


Ray

I have seen a working 464 with 40008 in the 40007 position. In fact the 40010 socket wasn't even installed. My assumption is that the 40008 was a slightly modified 40007 with better thermal management, released because the 40010 wasn't ready yet.


Bryce.

Probably shouldn't do this but I moved the 40008 into the 40010 socket and didn't get any video signal output at all!


I presume both sockets are wired ready to go so no other modifications are needed to be made if you socket and use the 40010 slot?


I have a 40010 from a donor board that I tried in the socket also and it also gave no activity? I have no way of checking whether this 40010 chip is actually good or not.


From my testing the crystal oscillator on my donor board is dead. I may try and swap the crystal from the board I'm currently working on to see whether the donor board will fire up with the 40010 in it?


This board had a visually blown 74LS373 chip on it which I replaced to no effect. Subsequently I discovered the crystal fault.

Before you go swapping crystals, I'll ask again, because this is important and you haven't answered it yet:
Where are you measuring the clock signal?

Bryce.

The donor board has no clock signal read from the left leg of the crystal and pin 2,3,4 of the IC125 chip.

That's exactly what I suspected. You can't measure the pins of a crystal, at least not without extremely specific hardware. If you connect a meter or scope to the pins of a crystal, the internal resistance of the meter/scope will collapse the signal and the crystal will stop oscillating, sometimes until you restart the system. Only measure the clock from the CLK pin of the CPU.

Bryce.

Quote from: Bryce on 10:16, 12 December 19
I have seen a working 464 with 40008 in the 40007 position. In fact the 40010 socket wasn't even installed. My assumption is that the 40008 was a slightly modified 40007 with better thermal management, released because the 40010 wasn't ready yet.


Bryce.

Could it be that there are some 464 boards with the gate array slots mislabelled?

According to the pinouts, there's no way a 40008 would work on a 40007 socket.


Also, if the 40008 is pin-compatible with the 40007, then the 664s couldn't work with the 40010, and both 664 boards we have scanned have a 40010...

I'm not sure what you mean about the 664. They were all 40010 boards weren't they? What has the 40008 got to do with the 664?


Bryce.

Because the 664 Service Manual mentions IC116, the gate array, as "HSG3130 or HSG3170", being them the 40008 and the 40010.


So theoretically, a 40008 shouldn't work on a 40007 socket.


That's why I think that maybe some boards have mislabelled sockets.

Or the service manual has yet another mistake to add to its long list?

Bryce.

Quote from: Audronic on 09:56, 12 December 19
The French link indicates that the 40008 and the 40010 are pin compatible ? ?

The French are wrong (who said always)  ;D   
We had this discussion a while ago : http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/gate-array-decapped!/msg124988/#msg124988
I think Grim tool the info in the scanned book.

Quote from: robcfg on 12:31, 12 December 19
Because the 664 Service Manual mentions IC116, the gate array, as "HSG3130 or HSG3170", being them the 40008 and the 40010.

According to my notes :
40007 is ULA8RA023 (bipolar)
40008 is ?
40010 37AA is HSG3170 (CMOS)
40010 36AA is HSG3130 (CMOS)

The decaped picture of the 40008 is in fact a 40007 as it's a  ULA8RA023 (bipolar). The picture is just rotated and difference between them only show artefact of passivation removal, pixel alignment and bonding wires.
The French doc refers it as a RA043 in the chapter header, but as a HSG3130 in the text (and 40007 as RA043). So I would not give any credit to this.

So basically, we miss the 40008 die picture !

What do you mean the die picture? The one with the metal layer removed?

I see what you mean, but actually these pictures are from different chips, and I sent Sean a 40007 and a 40008.


Could it be that there's a difference in the type of packaging rather than on the chips themselves?

So on my donor board (Was going to use this for parts but thought lets check it out anyway) it has the 40010 gate array.


I get no clock signal from pin 6 of a new Z80 chip.


When I got this board it had a visibly damaged (Top damaged exposing internals) 74LS373 chip which I have replaced.


I have a good 5v throughout the board?


Any tips???

40008 where taken from this post :http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/gate-array-decapped!/msg135615/#msg135615

Quote from: robcfg on 13:27, 12 December 19I see what you mean, but actually these pictures are from different chips, and I sent Sean a 40007 and a 40008.


Could it be that there's a difference in the type of packaging rather than on the chips themselves?

The packaging would not justify a reference change.

If it was a process change, i would expect the manufacturer to change the mask to differentiate them. Here everything is identical.

Seeing no difference in the die it could be that :
- Sean decapped a second 40007 thinking it was a 40008
- We sent him a 40007 remaked as 40008 (was the 40008 bough on ebay ?)
- or just that the 40007 was done on defective process and amstrad updated the reference to 40008 for the good one. 
The only thing i can currently conclude from picture, 40008 = 40007

side note : we should continue this discussion somewhere else  :-[

Look for cracks in the copper traces and cracked solder joints first.

Bryce.

Negative can't find anything suspicious... Even lifted the socketed chips to look underneath!

Quote from: pledg on 13:42, 12 December 19
When I got this board it had a visibly damaged (Top damaged exposing internals) 74LS373 chip which I have replaced.

Some chips will literally blow apart if subjected to a high enough voltage. I know this, because I once accidentally connected a item of equipment (that has a board with 4000 series logic chips) to a 50V DC supply instead of a 13.8V DC supply (the equipment came in two different versions, one designed for use on 13.8V DC and one designed for use on a 50V DC supply and both used the same type of 5 pin DIN connector). Suffice to say, there was a bang and it was then dead. When I moved it, I heard something rattling about. Inside I found one chip had blown apart. I had to replace all the 4000 series logic chips to get it working again!

So if this CPC board has a blown apart chip, it's possible that either it was fed with the incorrect polarity, someone used an AC supply, or used a DC supply at a much higher voltage. If so, there could be other dead chips on the board.

You really need a working board to work out if your gate array chips (and other socketed chips from your "donor" board) are working or not.

Swapping chips that are suspect (and may well be faulty) into a board that you are attempting to fault find is not something that I recommend. Especially if you may loose track of what happened/happens with each chip...

Mark

Can somebody clarify this please...


If you have a 40007 board with the 40010 socket provision above. It's not just a matter of installing a socket in that 40010 position but other changes are required to the board to make that 40010 socket work?


Does that then render the 40007 socket unusable or can the board then accept the 40007 or the 40010 chip?


I did see another post on this matter but it wasn't answered.

As far as I know, there are no further changes required. If you install the socket, the board can then work with either a 40007 or a 40010 (but not both at the same time!).

Bryce.

Okay here's a little update!


Unfortunately an 8-bit Xmas was off the cards but I feel progress is being made.


I have installed a working 40007 chip to the board and immediately got a change in output. I have a corrupted colour screen mainly vertical patterns with a visible scrolling output working up from the bottom of the screen. The output colour generally changes with each reset. (see attached typical pic)


I also socketed and replaced all the 74LS153 chips.

Although I'm getting a pulse output from the RAM chips the multiplexors seem to give a high reading on the logic probe no pulsing?

The following are working (NEW):
40007
RAM
CRTC
Z80

Wondering whether the AY or ROM chip could be at fault?


In the process of reseating the Z80 but ran out of sockets so can't test this change yet!


I'm studying the schematics to better understand how this board is working, checking continuity etc. for bad traces but can't find any.

Happy New Year!

I re-seated/soldered the gate array and the Z80 sockets with no effect still same garbled screen except it now has a BLACK BORDER? (see pic)


I've been swapping RAM and re-flowing sockets but no effect.


It feels so close but yet still so far! :)

I have a 6128 with a problem like yours.
Black screen was caused by the Z80 socket, it was corroded.
Now I am in the black border - grey screen and all chips are fine.
I don't have the specific 114-115 LS although I have a bunch of other LS chips  ;D

Update.


New ROM eeprom installed but no difference to main or donor boards.


Couple of questions, easy one first:


1.Can a faulty AY chip stop the 464 from starting?


2. I've been continuity testing (AGAIN) the RAM to buffers, gate array and Z80 and AY chip. My donor board has the 40010 array installed so I'm checking continuity back through the 40007 array socket via the different pin outs of the 40010 array. It all seemed fine only one dry solder. Question is interrupt pin 10 going into pin 16 on Z80. Taking this up to the 40010 array pin 32 I can't get continuity. Am I understanding this correctly or miss reading something?


Many thanks...

Quote from: pledg on 19:24, 08 January 20
1.Can a faulty AY chip stop the 464 from starting?

No, but it would make the keyboard unusable.

Quote from: pledg on 19:24, 08 January 20
2. I've been continuity testing (AGAIN) the RAM to buffers, gate array and Z80 and AY chip. My donor board has the 40010 array installed so I'm checking continuity back through the 40007 array socket via the different pin outs of the 40010 array. It all seemed fine only one dry solder. Question is interrupt pin 10 going into pin 16 on Z80. Taking this up to the 40010 array pin 32 I can't get continuity. Am I understanding this correctly or miss reading something?

What you're missing that the 40010 has a 4.7k serie resistor between pin 32 and Z80 pin 16.  ;)

Now, from the picture you posted, you should concentrate on the RAM subsystem which include
- the GA/Z80/row/column mux : IC109/IC104/IC113/IC105
- data buffers/latch : IC115 / IC114
- all the RAM device
- GA and CRTC

The fact that you have a properly set screen/border mean that the ROM is properly programming the CRTC, but crash when trying to use the stack.
If your ram are on socket, can you take a picture will all of them removed ?

Thanks for your help, I didn't have the schematic just the pin outs but I see now it goes through r144!


Also found a broken trace/ring on pin 5 of IC104 which has been successfully bridged.


Still double checking other IC's then I'll try a power up.


If that fails I'll post a pic of the RAM out of the sockets.


Thanks for your help.

Update!


So having had enough of continuity testing the RAM and IC's etc. I thought I'd take another look at IC125 which on my boards is a TC74HCU04P chip. On one of my 2 boards this chip is dead so I'm having to swap it during testing.


Part of its circuit are resisters R143, R144, R145 all of these had blown so have been replaced! The donor or 2nd board I have has exactly the same fault so I'm swapping those out too.


I believe this circuit controls the crystal clock so is fundamental to operation.


Fingers crossed for an imminent start-up but I'm not counting chickens just yet!!!!





Cheers

Any 74HCU04 IC with the same through-hole pins package are compatible.
TC is the brand and N/P are the IC package. (i.e. "D" is not compatible, because SMD)

Thanks...

.

Quote from: pledg on 19:47, 09 January 20
Update!
Part of its circuit are resisters R143, R144, R145 all of these had blown so have been replaced! The donor or 2nd board I have has exactly the same fault so I'm swapping those out too.

I have to question that statement, because it's almost impossible. How exactly were these resistors blown? Physically damaged or burnt to a crisp?If they were burnt, then every single chip on the PCB is most likely destroyed. For example: The highest normally possible voltage across R145 is 5V which would give a current of 5mA  or 25mW. But this resistor is a 1/4W resistor, so you would need at least 10 times the voltage for a prolonged period to destroy it. If there was more than 50V across this resistor at any time, then the rest of the board is fried too.The story isn't much different for R143 or R144, they would need at least 16V across them. Lower than 50, but the end effect for the board would be similar.

Also, if any of these resistors or the 74HCU04 were non-functional, you wouldn't get that square screen you show above.

Bryce.

Yes of course you're right I think tiredness had set it by that point!


Resistors were fine...

Having checked and rechecked continuity I started looking at the RAM again! I have 16 4164 RAM modules enough for both boards.


Looking at the random readings from pin 2 and 14 with the logic probe I started pulling and swapping anything that didn't give a reading. I got to a state where all but one were giving a reading from pin 2 and 14.


I then popped in one of my salvaged original 4264 RAMs and the usually garbled screen flickered with interference and the tape drive started to play. I'd accidentally pressed the play button down whilst moving it.


I then connected up the keyboard but was getting no beep on pressing the delete key. The tape head was obviously working as it was picking up noise but without a tape.


I'm wondering whether the 4164 RAM I have is not compatible in some way?


Any thoughts...

Let me just put this out there!


The board I'm working on when I received it had a 40008 array socketed in the 40007 slot! Earlier in the post I think the outcome of this was that the pin outs are different to the 40007 and should the 40008 have been in the 40010 socket?


I've put a working 40007 into this socket.


I saw another post that offered a change in resister layout if swapping from a 40010 and 40007 arrays on a dual board! Can anyone confirm this?


When I was getting confused with resistor values earlier in the post I was looking at the CPC464 schematics that show the 40007 array pinouts.


When you have a 40010 on a board there are resistor changes to the published schematic. Particularly R144 which on CPC464 is 330ohms and on the 40010 should be 4.7k???


I'm still struggling to find a decent image of the 40010 schematic.


Could my struggles be that the board is not actually set up for running a 40007 hence the garbled screen?

My suspicion is that you damaged a track while removing the old RAM. Have you checked that all RAM pins are connected to where they should be?

Forget the Gate Array, if it the pinout wasn't correct the square frame wouldn't be appearing on the screen.

Bryce.

I'll give those a final check before throwing the towel in and shipping it off to you :picard: 

Success!!!!  :D


After probably a 30+ year sleep the AMSTRAD CPC464 lives!


Firstly a big thank you to everyone who contributed to this thread and put up with the inane ramblings of a complete electronics beginner.


I'll do a final post detailing what was changed on this board to get it up and running soon. I'm just a little loathed to go poking around in it for the moment but now it's working I can use it as a test machine to get my donor board up and running also.


I popped the case back on and all works as it should apart from 1 key the right hand shift key. How lucky was that! at least there's two of them! I'd already changed the tape drive belt and that seems to be running okay. I don't have any tapes so I'll give the audio in mod a go. Although I certainly won't be drilling a hole in the side or rear of the case!!!



Cheers


Paul.

Congtatz Paul  :)

So what was the issue?

Bryce.

Well before posting a definitive answer I would like to work back through some components I swapped out.


I suspect it had the wrong power supply put though it causing multiple failures!


Now it's working I can say I enjoyed the experience of repairing it.  :doh:


Pledg

Quote from: pledg on 13:17, 15 January 20
Well before posting a definitive answer I would like to work back through some components I swapped out.


I suspect it had the wrong power supply put though it causing multiple failures!


Now it's working I can say I enjoyed the experience of repairing it.  :doh:


Pledg

But obviously, the last thing you swapped out is what brought it back to life! So what was that?Please don't tell me you were swapping multiple parts each time. Never do that, it will only confuse the process.

Bryce.

Well the final fix that brought the system back to life was swapping RAM chips and testing the i/o signals with the logic probe. I discovered that from a newly purchased set of 8 4164 RAM chips two were faulty!

Confirmed faulty on main board:

40008 Gate Array
RAM
IC112

Confirmed faulty on donor board:
40010 Gate Array
Z80
RAM
ROM 40009
IC108 Video
IC114 (visibly blown damaged)


IC125 (can't confirm which board had the failed chip I unfortunately mixed them up!)


Replaced anyway:


C101
X101


Pledg.