6128 Failed repair :(

[mrbee]

amazing thank you for taking the time to reply with all this, I will go through each one pin by pin tomorrow and report back

[SerErris]

You should also check if you have any connection between any PIN and GND or any two neighbouring PINs. Maybe you have just shorted two PINs, that would prevent the RAM to operate normally, esp if you short address PINs, that affect all RAM chips at once.

[mrbee]

I have discovered a strange continuity that I can't figure out. So I am testing every single pin of each ram chip against each other ram pin. So like beginning with the chip on the bottom right, going from pin 0 and checking for any continuity on pins on the same chip (pins next to eachother etc) and I have got to one pin in particular - pin 5 (if you count them as pin 1 being the bottom left pin and pin 8 being the bottom right, pin 9 is the top right and pin 16 is top left..

Well pin 5 and pin 12 connect to eachother, but then also they connect to these same pins on every ram chip, even on the other bank.

Looking at the trace diagram of the board, pin 5 should only connect to pin 5 of each ram chip (not touching pin 12) but I think then.. well if they arent touching, then how is every single chip showing continuity between these two pins so just trying to figure out where exactly they are bridged, worst case is that some trace wire has come away underneath the chip socket (on the chip side of the board) and touching somewhere there. so this means removing one of the sockets, but determining which one. As this board has really delicate traces, it would be a case of having even more broken traces. nightmare!

[Bryce]

They shouldn't be connected, but the trace of pin 5 passes right beside Pin 12, so you have obviously shorted them on one of the RAM chips.

Bryce.

[SerErris]

You can see it in the drawing attached.

Red is the connection for PIN5, which goes to every RAM chip and green is PIN12.

So yes, you have connected them somewhere on any RAM chip. Normally you should have the soldermask on the board to prevent this happening, but if you ripped the lines, anything can happen.

So carefully check all the connections if you scraped them off, or acidentially soldered the wrong PIN. It is very easy to mess things up, because you are need to work mirrored when looking on the bottom side (where the soldering is done).

Esp Pin5 and Pin12 are in the exact same row. You may just have mixed Upper and Lower row somewhere and therefore connected PIN 5 and Pin12.

[Bryce]

You can see it in the drawing attached.

Red is the connection for PIN5, which goes to every RAM chip and green is PIN12.

So yes, you have connected them somewhere on any RAM chip. Normally you should have the soldermask on the board to prevent this happening, but if you ripped the lines, anything can happen.

So carefully check all the connections if you scraped them off, or acidentially soldered the wrong PIN. It is very easy to mess things up, because you are need to work mirrored when looking on the bottom side (where the soldering is done).

Esp Pin5 and Pin12 are in the exact same row. You may just have mixed Upper and Lower row somewhere and therefore connected PIN 5 and Pin12.

It's impossible to mix upper and lower rows, the next chip would only have one row of holes then!

Bryce.

[SerErris]

No I mean that you confuse the upper and the lower row. Because if you turn the board over, what was up is not bottom. That then leads to confusion. So not technical, but in your mind.

[mrbee]

Ok update so far. i had found the chip that was the culprit, there was a broken trace touching the leg.
continuity is all good for the ram.

i powered on and... grey screen black border.

i connected the dandanator and... it boots to the dandanator menu! but the graphics are a bit messed up.

I then power off and turn it on in diagnostic mode.
it shows green on all the ram except number 5.
im not sure which bank this is for, so i check all of the ram chips to be sure on another cpc. all the ram is good.

still showing number 5 as no good.
so i force the banks to swap with the adapter that bryce had made previously in place of the hal chip.

running a diagnostic test then the result is that all of the ram is green.. except number 4!

im not sure what it could be or exactly what chip or what bank the diagnostic is referring to. i guess its checking the ram continuity again but am sure its all good and each ram chip is good.


anyways i noticed on the dandanator menu you can press a key to run a test on a different bank. so ive been testing this all now without the keyboard connected.

i power off. connect the dandanator. connect the two keyboard ribbons and...
the dandanator goes crazy. and boots directly to an "eeprom writer" menu which is all glitched up. and says something that looks like the word "current" in the middle.

it simply wont do anything when the keyboard is connected. if i just connect one ribbon, the dandanator menu shows. if i connect both ribbons it doesnt like it.

so am totally stumped again

[mrbee]

Alrighty! I have finally sorted the issue with the ram! One of the chips was brand new, I assumed then this was all good, as it tested ok on a previous test on another amstrad but then connecting to this one I had set it aside with all of the good chips but some reason or another it became faulty.
All ram checks out good.

I have also solved the keyboard issue! the black plastic base was slightly unclipped causing the odd pressing of random keys, i separated the membrane underneath and cleaned it. thats all good.

I have all working ram on both banks now, two had died at 04 for upper and 05 for lower.

when performing a rom test I get  rom 00 6128 basic en (caa0) and everything else is blank instead of rom07 amsdos (0f91) and in the test results I get upper rom FAILED

[mrbee]

I have tried to load the disc but i get a sort of constant motor engaging power, led is on the drive (just a slight sound coming from the drive constantly) when typing CAT etc it just says "disc drive missing" retry?
I wonder then if the 40015 rom on this is bad that controls the disc drive, as this failed in the diagnostic. I will have to look into replacing this rom I think, also just inspecting the drive now.. the belt has crumbled away! So will post again in a few days when a new belt arrives

[Bryce]

Try manually moving the head to a different point (by manually turning the motor spindle). Then do a CAT and see if the head moves to the correct track. If not, you probably have dry joints on the socket to the motor.

Bryce.

[SerErris]

when performing a rom test I get  rom 00 6128 basic en (caa0) and everything else is blank instead of rom07 amsdos (0f91) and in the test results I get upper rom FAILED

I try to interpret what you wrote as it does not make sense normally.

If you run the diagnostics ROM test, it will test the lower ROM 00 and then upper ROMS 00 to 15.

lower ROM 00 needs to read as OS 6128 EN (B360)

Upper Roms:
00 BASIC EN 1.1 (CAA0)
07 AMSDOS (0F91)

All the rest should be ---- (emtpy).

So you are saying you see in lower ROM the BASIC 1.1 ROM? And in 07 you see AMSDOS ROM?

Or is this both upper ROMs?

So if you start it without Dandanator, you are now getting to the BASIC prompt?

[mrbee]

Try manually moving the head to a different point (by manually turning the motor spindle). Then do a CAT and see if the head moves to the correct track. If not, you probably have dry joints on the socket to the motor.

Bryce.

I tried to quick edit my post but it didnt seem to save it for some reason, after further inspecting the drive I noticed some plastic falling out of it..
It wasn't plastic.. it was a rock hard and crumbling drive belt! So I have ordered some new belts but they wont arrive for a few days and see if this sorts it.
For the time being I tried to get the drive to read with an elastic band and it did try to read something, but the band is not the right size but at least it is recognizing the drive

[mrbee]

when performing a rom test I get  rom 00 6128 basic en (caa0) and everything else is blank instead of rom07 amsdos (0f91) and in the test results I get upper rom FAILED

I try to interpret what you wrote as it does not make sense normally.

If you run the diagnostics ROM test, it will test the lower ROM 00 and then upper ROMS 00 to 15.

lower ROM 00 needs to read as OS 6128 EN (B360)

Upper Roms:
00 BASIC EN 1.1 (CAA0)
07 AMSDOS (0F91)

All the rest should be ---- (emtpy).

So you are saying you see in lower ROM the BASIC 1.1 ROM? And in 07 you see AMSDOS ROM?

Or is this both upper ROMs?

So if you start it without Dandanator, you are now getting to the BASIC prompt?

sorry man. I will try to explain it better. As I was at the shop serving whilst doing this I didn't have time to word it correctly. I appreciate the time reading this though.

I run the test with the dandanator connected, i run the ram test and upper and lower ram is all good now.
running a rom test I get the results as you say with the rest blank. But at the end of the test it says the upper rom failed.
I'm not sure why it is failing.
If I boot it without dandanator it all operates fine in basic

[SerErris]

That is indeed strange, that the upper rom test fails if two of the ROMs are available (the two that should be available) and no other is installed and all the rest is correct.

I need to run it on my 6128 to see how it works, but will not be able to do it in short amount of time right now.

[mrbee]

With the rom test, does it mean that the upper rom is the chip 40015 and the lower rom is 40025?

I had replaced the 40025 (I didnt touch the 40015 chip) with a socket and put the original chip in the socket. so now the 40025 is socketed. The continuity is all good, no broken traces. If the lower failed then I would know that it was the soldering/ traces. but as this one passes fine, I wonder then why the one I haven't touched is failing.

What I mean to ask if the upper means the top rom chip (40015) and the lower is 40025. If this is the case then I wonder why 40015 is showing failed unless there is a broken trace as the data travels from lower to upper and there is a problem there.

I will check the diagram again and check each pin for continuity to see if all traces between 40025 and 40015 are good, they all seem like they are but I will triple check this.

[SerErris]

Nope,

Lower Rom and Upper 00 are both in 40025.

40025 is a 32kb ROM chip, that contians the OS (lower) and BASIC (upper 00).

40015 is AMSDOS  only and linked to upper 07.

[mrbee]

Here is a link of some images of the test 

Amstrad 6128. it works. but..yellow is missing on the monitor and the potentiometer for yellow is a duplicate of blue! - retrogaming post - Imgur

It fails the upper rom test.
I have got a new drive belt delivered today and fitted it and it loads perfectly, I am not sure why the rom is failing in the test though.

I have unearthed another problem but this is for the monitor, but will create another thread for this. The monitor is missing the yellow/green colour, turning the potentiometers on the yoke it shows that the yellow is controlling blue, and blue also controls blue, so there are two intensities of blue and only showing red and blue.

I didnt realise this before on the basic screen as the red was turned up bright enough to look yellow to me, but I am colourblind! So I only noticed then when the turtles were black lol

[SerErris]

Yes, not sure why it shows failed.

[SerErris]

You should update the diagrom to the latest version on the Dandanator which is Version 1.3

https://github.com/llopis/amstrad-diagnostics/releases

Release notes:
Amstrad Diagnostics 1.3 Latest
Fixed upper ROM detection that was failing in some cases.