Problem CPC6128 Fixed Thanks to all who Contributed.

[Audronic]

Hi all

I have a small problem I was wondering if you could point me in the right direction.

I have a CPC6128 that gives me the following screens:-

Boot
Geralds Memtest Original,
Geralds Memtest NEW (wip)

The Links are in LK1 and LK2 ? I get "Isp 128K  etc" ? ?
No Basic 1.1 or Ready, or cursor ?

On my other machines with the Links as above I get "AWA 128k etc"

It has been in storage for 20 Years.

When first turned on "Nothing on screen"

I have Replaced IC 108 - CRT C with a New HD6845SP
and Fitted a Good Turned socket I have tried 2 of these.

Can you give me some help Please

Thanks.  Ray

[Audronic]

Hi All

Partial success.
Replaced the 8255.
The machine ID is now Awa.
Geralds Original RamTest now works.
Geralds Ramtest (wip) stalls ?

Still no Cursor

See photos

Ray

[Audronic]

Photo below after 5 Tries to get passed SECURITY CHECK

[SOS]

Hmmm, i'm not a hardware-guy,
but an similar (?) effect i have seen often, when i do strange things with the ROM's.
Could you connect an ROM-Board and burn 2 ROM's with an booting message (like MAXAM)?
One with an ROM-Number > 7 and one with an ROM-Number < 7?
Do you see both ROM-Booting Messages?

[llopis]

Yeah, my first guess would be a faulty BASIC ROM. Try replacing it with something else or connecting some kind of external ROM and see if that works.

[Bryce]

My experience from many, many repairs: This is usually due to a bad AMSDOS ROM, not the BASIC ROM. In the few cases where swapping the AMSDOS ROM didn't help, it turned out to be an issue with the FDC.

Bryce.

[Audronic]

Hi Bryce, Sos, llopis

Thanks I will have a look at those areas.

I have just found a problem with the /cas line on IC 119 - Ic 125. Out with the snippers.

I will have a look tomorrow  its 8:12 Pm now over here

Thanks

Ray

[Audronic]

Hi All


Is there a document that outlines the order in which the CPC6128 starts up.
as to what is tested, initialised etc. this would help with diagnosis of an unwell machine


If there is something please post a link or the name of the document


Thanks.  Ray

[Audronic]

Hi All

Update

Changed the ROM 40015 (Bryce Warned me) Did NOT fix the Problem
But I now have a Fault indicated with Geralds Ramtest (WIP).
But which chip/s ?


EDITED
 
Ray

[Audronic]

Hi All
Update Again !


Changed some Ram in 2nd bank, now Geralds RamTest (wip) has worked.
Still not Booting, No Ready - Cursor.


Ray

[SOS]

does the AMSDOS loaded correctly?
=> do you see both ROM-Messages (e.g. MAXAM on ROM9 and MAXAM on ROM 5), when connecting an external ROM-Board?

[Audronic]

@SOS 

AMSDOS does not fully load.
I have tried Dandanator,Just goes to startup screen.
I have used lower rom for the 2 RamTests by Gerald.

I plug in my Xmem-X-mas and I get as per photo Starts to boot and stops after |RPM.

Thanks for your thoughts.

This is the 8th (EIGHTH) time I have tried to send a photo Grrrr Security check Hmmmn
on the 9th time I was able to send the photo ? ? ?

Ray

[GUNHED]

Still looks like a bad ROM. Try to replace connected ROMs - one by one if possible.

[Bryce]

Still looks like a bad ROM. Try to replace connected ROMs - one by one if possible.

But it didn't start even with zero external ROMs attached. My guess is that something in the floppy circuitry is bad. Try disabling the entire floppy hardware and see if it boots.

Bryce.

[GUNHED]

But it didn't start even with zero external ROMs attached. My guess is that something in the floppy circuitry is bad. Try disabling the entire floppy hardware and see if it boots.

Bryce.

Exactly, the problem is in the ROM. Since the OS seems to work, take a look at the BASIC ROM.

[Bryce]

Possible I suppose, but unlikely. ROMs tend to break in terms of rows or columns, or bits stuck on the address or databus. Any of these failures would stop the CPC from getting as far as it does at the moment.

Bryce.

[Audronic]

Hi All


Thanks.
I will change over the 40015 FDD Rom IC 204 tomorrow and see what happens

TYPO Should read 40025 Grrrr.

Ray

[Bryce]

I thought you already changed it? At least you stated you did just above??

Hi All

Update

Changed the ROM 40015 (Bryce Warned me) Did NOT fix the Problem
But I now have a Fault indicated with Geralds Ramtest (WIP).

If the AMSDOS ROM hasn't been changed yet, then that is definitely the first thing to try.

Bryce.

[GUNHED]

Another idea, probably unlikely... can it be a weak PSU? With them this issue could happen.

[Audronic]

If the AMSDOS ROM hasn't been changed yet, then that is definitely the first thing to try.

Bryce.

Bryce sorry I made a TYPO I have removed only the 40025  (ROM-PC3) IC103

Thanks

I am about to remove the 40015 and test the motherboard without the 40015 ?




Thanks.  Ray

[Audronic]

Another idea, probably unlikely... can it be a weak PSU? With them this issue could happen.

Thanks  Have used a good known power supply (2  different Power Supplies) Both around 5.04 Volts with a 4 amp capacity.
I think the power supply is not the problem


Ray

[Audronic]

Hi All


Nearly there 40015 Removed, Powered up and got this Yeahhh


Ray

[Audronic]

Hi All


No Success back to NO Ready- NO Cursor after replacing 40015 , Now it gets hard to find the fault.


Ray

[SOS]

When you remove the AMSDOS 40015-IC and burn an AMSDOS.ROM on Slot 6 on your ROM-Board and e.g. MAXAM on Slot 5.
What happens?
Hung the ROM6 (you dont see Booting-Messages from ROM's with Number < 6?) ?
Can you access the floppy?

[Audronic]

Hi SOS


No The machine CanNot Boot to a ready or cursor.


I am working around the Floppy drive circuit at the moment.


I have found an 74HC240 that is unwell.
Am about to replace this. ( I think I have done this on an other machine ?)


I don't know about Maxam  I will have a look at what it does ?


Ray