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Author Topic: Memory problem? with a 6128  (Read 2389 times)

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Offline angelcaio

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Re: Memory problem? with a 6128
« Reply #25 on: 12:09, 26 July 18 »
Hi. I tried this:
If you can see a black border and grey screen the Z80, CRTC and the Gate Array are mostly OK.
To have this screen, the Z80 managed to read the ROM and configure the CTRC. If not you would only get a black screen.

However, it likely a RAM access problem.
In a 6128, you need the following to access the RAM :
- the PAL
- the Gate array (which does all the multiplexing
- the data buffers (IC114 / IC115)
- and ... the RAM

If you have a doubt on the PAL, you can remove it and close LK5/LK6 (above the PAL) and LK8 (at top of the main DRAM bank). This will put your 6128 into a 464 configuration. Since you have the RAM on socket, you better remove the second bank to be sure they will not interfere with the main one while their are not controlled anymore. The second bank is on the left side, away from the PAL
You can also test it in another 6128 if you have one.

If you have a XMEM or LowerROM board, you can also run my memory test : http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc



I checked the bridges on the top side of the plate and they are ok
But the green screen with black border is still in the boot

Can I try something else? Before doing anything, at least it started. Should I give up and give it up for lost?
Thanks.


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Offline Bryce

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Re: Memory problem? with a 6128
« Reply #26 on: 12:34, 26 July 18 »
Have you 100% confirmed that all other RAM ICs are definitely working? Without knowing this, all the jumpers in the world aren't going to get you any further.

Bryce.

Offline angelcaio

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Re: Memory problem? with a 6128
« Reply #27 on: 14:02, 26 July 18 »
Have you 100% confirmed that all other RAM ICs are definitely working? Without knowing this, all the jumpers in the world aren't going to get you any further.

Bryce.
Hi. Before replacing the ic127 the rest of ic worked. Although I can not assure that any other ic has been damaged in the operation, I think I have been careful. I have checked the continuity in the pins of the rest of ic but I do not know how to verify something else.


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Offline angelcaio

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Re: Memory problem? with a 6128
« Reply #28 on: 13:35, 28 July 18 »
Updating...
 I have taken the m4 board of my 464 and the TV adapter of a friend to see the cpc on the tv. I've loaded Gerald's ramtest.bin
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc/msg106676/#msg106676
and it's all in red! I do not think all the memory chips are wrong. I changed the first one with three new ones with the same result. I think something else has been broken but I do not know what



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Offline gerald

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Re: Memory problem? with a 6128
« Reply #29 on: 21:13, 28 July 18 »
By the way, can you see something on the screen during the test phase, or it's always black ?

By removing the previous RAM device you may have damaged some track or made short.
If you only have access to a continuity tester, check that the whole memory is properly connected.
That mean :
- Z80 (IC)data bit are going to the DRAM DIN (pin 2), for both banks.
- DRAM data out (pin 14) are going to the data latch (IC114)
- adress are going from the address mux (IC104, IC105, IC109, IC113) to the DRAM
- control signals (RAS, WE) from the GA/PAL, CAS from the PAL

6128 schematic can be found here : http://www.cpcwiki.eu/imgs/4/4a/CPC6128_Schematic.png

Offline angelcaio

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Re: Memory problem? with a 6128
« Reply #30 on: 14:03, 29 July 18 »
By the way, can you see something on the screen during the test phase, or it's always black ?

By removing the previous RAM device you may have damaged some track or made short.
If you only have access to a continuity tester, check that the whole memory is properly connected.
That mean :
- Z80 (IC)data bit are going to the DRAM DIN (pin 2), for both banks.
- DRAM data out (pin 14) are going to the data latch (IC114)
- adress are going from the address mux (IC104, IC105, IC109, IC113) to the DRAM
- control signals (RAS, WE) from the GA/PAL, CAS from the PAL

6128 schematic can be found here : http://www.cpcwiki.eu/imgs/4/4a/CPC6128_Schematic.png
Hi. All connections are ok except pin 9 of IC109 with pin 13 of RAM: (it only worked with the bank 1 but not whit bank 0). I have bridged the pins 13 of the dip0 of each bank and ....IT WORK!!!!.
Thank you very very much!!!
Really, Many thanks to all!!


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Offline gerald

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Re: Memory problem? with a 6128
« Reply #31 on: 14:48, 29 July 18 »
Great news !!!!  :)

Online VincentGR

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Re: Memory problem? with a 6128
« Reply #32 on: 19:05, 01 August 18 »
Fantastic!!!
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