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General Category => Technical support - Hardware related => Topic started by: WacKEDmaN on 19:35, 09 December 20

Title: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 19:35, 09 December 20
so ive got the original 464 board completely populated now...
i only have the board.. no monitor, no keyboard, no tapedeck.. im gonna add my own digital versions with overpowered arduino and/or esp32
i will use this thread to document my progress and ask a few questions (so i dont blow it up!)


i need some clarification on the power jack... i cant find the correct information, is it "centre negative" or "centre positive"...
ive done a continuity test...between the side pin of the barrel jack socket (onboard)... and both the AY-3 (pin 3) and Z80As (pin 11) 5v pins... and they seem connected...
but everything ive read is saying the 5v jack is centre positive.. even tho im seeing different on the board...
can anyone clarify it for me please?... (or should i just give up now! LOL)


next no so much a question but my next steps...... i have a SCART to RF modulator.. with female scart in...
i found this... http://www.cpcwiki.eu/imgs/c/c1/Cpc_to_scart.png (http://www.cpcwiki.eu/imgs/c/c1/Cpc_to_scart.png)
i will be wiring the 464 board directly to the scart pins on the RF board (in reverse! female din to female scart)...

heres the current look....

(https://i.imgur.com/PjV5WlP.jpg)
Title: Re: 464 Resurrection - with only mainboard!
Post by: TotO on 19:50, 09 December 20

Center is positive for 5V and GND is outside... Just check the ground continuity with other connectors.
You can test the 74LSxx IC where the bottom left pin = GND and the top right pin = VCC. (not the RAM)
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 19:54, 09 December 20
thanks ToTO, ill wire up the scart and kick it in the guts...
hopefully theres not other issues on the board...i hope i dont have to break out the sillyscope!


it does seem a bit strange the side pin on the barrel jack socket is connected to 5v positive on the main chips.. and the one coming from the centre is neg... yet it seems swapped from the actual 5v plug... all the other barrel jack sockets ive played with are outside to side pin, and then centre to centre... this seems swapped :/
i guess theres some inverse logic going on here...

tested side pin on the barrel jack socket to bottom RIGHT pin of the 74LS132p and they are indeed ground... (i looked up the datasheet!)



im confuse! ..but ill work it out! (ahh im workin from the top of the board!.. flip it..and yes bottom left is gnd ..top right is pos!)
Title: Re: 464 Resurrection - with only mainboard!
Post by: gerald on 20:33, 09 December 20
Quote from: WacKEDmaN on 19:54, 09 December 20
thanks ToTO, ill wire up the scart and kick it in the guts...
hopefully theres not other issues on the board...i hope i dont have to break out the sillyscope!


it does seem a bit strange the side pin on the barrel jack socket is connected to 5v positive on the main chips.. and the one coming from the centre is neg... yet it seems swapped from the actual 5v plug... all the other barrel jack sockets ive played with are outside to side pin, and then centre to centre... this seems swapped :/
i guess theres some inverse logic going on here...

tested side pin on the barrel jack socket to bottom RIGHT pin of the 74LS132p and they are indeed ground... (i looked up the datasheet!)



im confuse! ..but ill work it out! (ahh im workin from the top of the board!.. flip it..and yes bottom left is gnd ..top right is pos!)
As far as I know, the plug is positive on centre pole unless you have a very rare version of a 464. :D
How do you check continuity from jack center to the IC pins ?
5V should no go straight from the plug to the ICs. You have to do a short on the tape connector, where the power switch is connected.

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 20:58, 09 December 20
oh yeah! that probably explains why im having issues!... ive got the board sitting on the bloody silver side of the cardboard shield!


now im not getting continuity on the centre to the 5v in on the 74LS chips even with the switch connector bridged :/
(i was forgetting the switch! thanks for the heads up Gerald!)


...it looks like i know enough...just to be dangerous! LOL

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 01:46, 13 December 20
hooked up scart..and powered up the board..


..and nothing.. seems to draw about 0.9Amp and there seems to be activity on the z80 buses.. (checked with oscilloscope..)
...need to checked voltages ..seems to be 4.3v on everything..

CRTC chip (HD6845SP)seems to be getting warm after a few minuites.. (ram very slightly).. is it known to get warm to hot? (its not burning hot!)


seems to be working..i just cant get a picture  ::)
..i might invest in a cga/ega to vga board...the scart to RF modulator is horrible, i plugged wii into it to make sure it works..
..ok thats ordered.. should be here by the end of the year if im lucky!  :)


Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 05:48, 22 December 20
so the EGA/CGA to VGA board arrived today...
wired it up (soldered to the pins on bottom of cpc board)... this board and pinout.. https://www.octoate.de/articles/connect-cpc-to-vga-display/ (https://www.octoate.de/articles/connect-cpc-to-vga-display/)


but still no picture...

Question: does the cpc "need" anything else connected on boot? like does it look for the tape drive or keyboard? im guessing not
i cant test the the board is working (just no pic) with no speaker or keyboard! (cant hit esc/delete to beep!)... i suppose i could hook up an amp and speaker to the headphone jack.. but bit hard to make a keyboard from an arduino without the display showing!

next step is to replace the Z80... i tryed it on a bread board and it was doing weird things on the bus.. (would stop increasing the address bus after a few cycles just doing nops..should continue increasing right?)
be a few more weeks before ill get my hands on them tho with xmas and new years 
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 10:23, 22 December 20
The CPC Mainboard will run with nothing attached accept the power cord. You would need some test equipment to know whether it's running or not, so it easier to have it connected to a display at least.

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 14:13, 22 December 20
thanks Bryce
i do have an oscilloscope.. (guess i need a logic analyser)..
not sure what i should be looking at!.. i am seeing activity on both the data and address buses on all the main chips..and the logic chips seem to be all be working...


but like i said i think the z80 maybe bad..so im going to replace that first..
...another month before i get to move on!..unless someone has some ideas for me! :P
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 15:23, 22 December 20
What are you getting on pins 39 and 40 of the CRTC?

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 01:33, 23 December 20
[screwup]... this is pin 40 of the CRTC (pin 39 looks the same) with just the power connected, no jumper between pin1 and 3 on the tape connector (power switch)..power supply says no current!
when i do jumper it, it remains the same... just triggering more often ... and showing about 90mA current usage on the power supply...[/screwup]

ermagherd im dumb!.. i scoped the clock pin!..and the power supply was too close inducing the ripple onto the signal.... SMH...told ya im dangerous! LOL

... ok next attempt!... this is the real pin 40..
it seems its triggering vsync every half second or so...that doesnt sound right.. should be with every frame drawn right?..

10ms timebase..

(https://i.imgur.com/vjZFzEx.png)



here it is at 500ms timebase..


(https://i.imgur.com/cDeaK6r.png)



for pin 39 - hsync...its looking much better..
200us timebase!

(https://i.imgur.com/o1cvzOh.png)
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 03:23, 23 December 20
it also seems the CRTC is the hottest IC after having it running for about an hour..its much warmer than the 40007 gate array...
..im gonna order a CRTC chip and some z80s... cant hurt to have spares!..


also grabbed a 6pin din today..so ill rewire the EGA to VGA board to make things a little nicer..


edit.. so after some reading i find this..
Quote"The standard monitors on the Amstrad (GT6x, CTM64x, CM14 or even TV) have a 50Hz Vertical refresh rate (meaning that a VSync pulse must appear every ~20ms, 19968μs exactly) and a 15625Hz Horizontal refresh rate (an HSync pulse every 64μs). Of course they can usually tolerate some slight variations of these timings but each monitor has it's own limitations."
it seems the vsync timings are a bit off on my board?!
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 10:54, 23 December 20
If you probed properly and that's the output of pin 40, then the CRTC has an issue. The signal levels are too low too. But just to be 100% sure: What scope are you using?

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 17:06, 23 December 20
cheap hantek 6022be...


thanks Bryce.. CRTC will be socketed and replaced..aswell as the z80 replaced for good measure!
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 16:56, 14 January 21
so got the new CTRC and Z80s today..
...removed the old CTRC IC..and put a socket in..
fired it up...
and same..no sign of video.....altho all the chips seem to be getting hotter now....ill have to check on oscilloscope later...


...i think im in over my head  :doh:

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 06:40, 08 February 21
so ive had a bit of a look around the CRTC with a continuity tester....


seems i killed some vias ripping the old chip out and puttin the new socket in... now i gotta rip the socket out (and possably destroy more vias) and wire the bastard up!
...im thinking i might make a "floating" chip! (wires outta the board to the socket) coz fixing it with the socket in place is gonna be a PITA!


i wonder if it would be cheaper (labour wise), easier, and nicer in the long run, if i was to redesign the board to make it smaller.....
...or...
should i just stop now and send this to someone i know can fix it!? would make a nice vid for a youtube channel!:P

(llopis im looking at you!)
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 09:13, 21 May 21
YAY! i finally got some output!

i pushed down hard on the CRTC... and it booted!.. i guess i need to touch up the solder joints!


but that said... it look like there is ram issues...
i get either a gray screen with blue border, or corrupt colored pixels on screen...


im correct thinking this is the ram right?
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 10:08, 21 May 21
Yup, RAM problem.

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 13:07, 21 May 21
thanks Bryce..


...more waiting for parts...

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 05:54, 14 April 22
..im back!.. with the fix to my issues! ;D 
 

i should have it going in a few hours..then i have to make a keyboard for it! :P
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 21:52, 14 April 22
powered it up.. no boot... its pulling 700mA... which seems a bit low? (usually around 800mA on boot right)..
checked chips and they all seem to be getting about 4.3v... time to setup the oscilloscope again....

Title: Re: 464 Resurrection - with only mainboard!
Post by: robcfg on 22:06, 14 April 22
Maybe check the diodes orientation.

You should be getting 5v not 4.3, and that 0.7v difference is the same as the usual diode voltage drop.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 23:17, 14 April 22
tried the diode..no luck..(band at the top of the board right?)
i may have the transistors installed wrong.. i used the new ones that came with the board..
my shitty scope is showing 8mhz out of the xtal...(again a new 16mhz)... and it looks horrible.. it seems to be very low voltage wise too..
the clock on the z80 and gate array seems to be just under 4mhz... but its not square.. (dont think its my shitty oscilloscope)...theres no activity on the z80 bus either..
i may remove the original transistors and try them...

...i suck at desoldering/removing components.. ...the whole reason i got this board! LOL

edit:
https://pdf1.alldatasheet.com/datasheet-pdf/view/2827/MOTOROLA/2N2369.html .. hard to tell which leg is which..
it seems i may have got the collector and base around the wrong way.....check and double checked..and rechecked..and its installed right!..
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 16:32, 15 April 22
The clock signal will never be a perfect square as shown in textbooks. It will always be rounded and the lower the bandwidth of your scope, the worse the signal will look. However, it doesn't need to be a perfect square, all that matters is that it's there and passes a certain threshold on each cycle. The 4.3V is a bigger issue. You need to find out where the other 0.7V is being lost.

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 20:44, 15 April 22
thanks Bryce...
it use to be 4.3v on original board aswell..... do you think i could possibly have a bad logic chip somewhere? (i havent got a tester)
..i guess i could pull one chip at a time and see when the voltage goes up!

my scope is still the hantek6022BE...only 24Mhz bandwidth but should be plenty... the clock signal out of the gate array looks nothing like it does in Noels youtube vid... its the same at the nand gates and at the crystal (just lower voltage. i even changed that back to the original!)

...ive changed Ram, CTRC, and z80.. so really theres only the logic, AY, PIO, and ROM that could be bad..
Title: Re: 464 Resurrection - with only mainboard!
Post by: robcfg on 21:30, 15 April 22
How are you powering the board?
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 21:59, 15 April 22
powering the board with a small CV/CC power supply i use for all my micros n what not, 5v exactly at the barrel jack on the board..has voltage and current draw displays so i can see whats being used..

heres the clock on the scope.. (with "phosphor" on to sorta help..)..i see no squares!
..at pin 12 of the quad nand...

 

and here is leg of R141 (out of the opamp..to z80)..its just lower on pin 39 on the gate array..

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 22:54, 15 April 22
the CRTC pin 21 is generating a nice square-ish wave..

...im going to replace the LS153s, the 244, 373, 32 and the 00, later today if i can get over to the shop..i cant get the others locally unfortunately..
Title: Re: 464 Resurrection - with only mainboard!
Post by: robcfg on 01:23, 16 April 22
How much current can your power supply give?

I think around 2 amps should be good but you'll need more if you add expansions.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 01:34, 16 April 22
Quote from: robcfg on 01:23, 16 April 22How much current can your power supply give?

I think around 2 amps should be good but you'll need more if you add expansions.

3Amp... 5 with better cooling!
i noticed all the main chips getting warm, gate array, z80, crtc, pio..are all a bit warm..
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 06:04, 16 April 22
so i changed the 4 LS153s, the 244, 273, 373, and the 00..
the last 3 LS chips will need to be ordered from somewhere...
...and same result...(i think my scope cant keep up with the clock..CRTC is puting out nice square waves.)
no activity on the bus..(low this time)

im really stumped.....
i guess i could order a new AY, and PIO...and new CRTC for good measure..
...maybe a rom burner aswell...
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 03:56, 17 April 22
seems i cant get an ay, ppi, or crtc in the country...SMH...good old parts shortage...

what should i be checking for next...? ..could it be ram/rom?..if i pull all them, it should just nop right? so i should see activity on the address bus...
or should i be checking something else on the gate array?
should i pull the rom and try to read it with an arduino?
maybe i should pull TR2 and replace it with the original?..(altho that shouldnt stop bus activity)

not sure where to go next.. some help would be appreciated..

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 00:29, 19 April 22
ordered the LS32,LS132 and LS145...should be here in a coupla weeks knowing auspost!

ive got a funny feeling its LS132 or LS32.. LS132 would make sense being part of the reset circuit..
Title: Re: 464 Resurrection - with only mainboard!
Post by: tjohnson on 02:45, 19 April 22
so you had a board a couple of years ago, now you have a different board but that doesn't work either, tbh not sure what it say.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 08:02, 19 April 22
Quote from: tjohnson on 02:45, 19 April 22so you had a board a couple of years ago, now you have a different board but that doesn't work either, tbh not sure what it say.
yup...its that bad!..ive been at this about 18months now...
..old board i purchased online cheap.. missing the gate array.. sourced one from Tot0 here.. no boot..
i was playing around with it and pushed down hard on the CRTC and got a screen..but looked like bad ram..never has it booted again!...
tryed replacing CRTC..killed the board..damaged tracks and ripped out almost every via on the CRTC :/
...so waited till these new boards where available..soldered it up.. looked good.. put chips in..nothin.. tried replacing most of the logic, the ram is also new..crtc is new..

could only be the ROM..the 8522, the AY-3, a bad CRTC..or hate to say it..bad gate array..
..i dont have a rom burner, or any rom boards like dandanator etc.. so im flying blind!... i do have sillyscope.. but its crap! wont read the 16mhz clock,  4 and 1mhz is fine..

other than replacing the logic i havent replaced yet.. im stumped where to go next...
Title: Re: 464 Resurrection - with only mainboard!
Post by: tjohnson on 10:29, 19 April 22
What are you trying to achieve?  Maybe you can send the board to Bryce to diagnose and get working.  I'm assuming the board is actual known working i.e. not a development board where there could be faults.  Tbh it would have been easier to find a working machine i would think rather than trying to build a new board.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 11:46, 19 April 22
Quote from: tjohnson on 10:29, 19 April 22What are you trying to achieve?  Maybe you can send the board to Bryce to diagnose and get working.  I'm assuming the board is actual known working i.e. not a development board where there could be faults.  Tbh it would have been easier to find a working machine i would think rather than trying to build a new board.
just trying to get a working cpc!..
this is the board ive after it was tested and faults found and fixed..
https://www.tindie.com/products/bobsbits/amstrad-cpc464-replica-pcb/

and ..im in australia..so im not really fond of sending it out of the country...i waited a month for the new board to arrive..
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 05:20, 22 April 22
so i bumped up the voltage on my power supply to 5.6v... chips now getting 4.9v.. but still no boot :(
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 12:09, 25 April 22
24MHz is definitely not enough bandwidth to measure a 16MHz square wave. I've a post here which will explain why: https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/understanding-retro-electronics/msg144677/#msg144677

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 06:03, 26 April 22
yes Bryce..that was what i thought!... Nyquist says you need atleast double the bandwidth of the frequency youre trying to measure.... the clocks out of the gate array look fine so im going to assume the 16mhz clock is fine too...

got the last of the logic chips today.... and still nothing...
not even a black screen signal.....

so..thats gotta be gate array or CRTC right?!

ill order another CRTC... but...if its gate array..im guessing im screwed until the chip is reengineered....

i did notice the 3 new logic chips increased the current by almost 100mA... it pulled 1A on first boot with the new chips but dropped to 970mA shortly after...
Title: Re: 464 Resurrection - with only mainboard!
Post by: dragon on 12:48, 26 April 22
I know that sensation... You have a computer that cost cheaply and you want it work and you begin buy buy and buy pieces because nothing work and at finish you spend 10x more  money that another cost on eBay or similar.

I'n your case the 464 are the more cheaply.. Maybe os better search another and then you can swap ics?. 

But well,you have here a gate array spares.

https://www.icompplus.com/es/circuitos-integrados/12619/40010

https://www.icompplus.com/es/circuitos-integrados/32243/40007

I have not buy there... But they are in my city. I can made a order there and pickup it in person. 
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 05:14, 27 April 22
Quote from: dragon on 12:48, 26 April 22I know that sensation... You have a computer that cost cheaply and you want it work and you begin buy buy and buy pieces because nothing work and at finish you spend 10x more  money that another cost on eBay or similar.

I'n your case the 464 are the more cheaply.. Maybe os better search another and then you can swap ics?.

But well,you have here a gate array spares.

https://www.icompplus.com/es/circuitos-integrados/12619/40010

https://www.icompplus.com/es/circuitos-integrados/32243/40007

I have not buy there... But they are in my city. I can made a order there and pickup it in person.


yup its a bit like that!... but i havent really spent all that much trying to get it working (thats if you dont count the new black board!)...all the logic only cost about $20.. got the gate array from user here for like 20$ with postage..CRTC was coupla $... the original board was purchased very cheap as it was missing the gate array (and obviously had other issues!)
thanks for the links ... i'll check them out....

i finally got in contact with a local who has a complete CPC collection....so i maybe able to swap some chips over between his boards and mine to test...
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 09:46, 11 May 22
yay! finally some signs of life!
got a hold of a lower rom board with diagnostics... plug it in..fire up the cpc.. hit the reset button... and i get a screen!..albeit corrupted!

 

this is with the original ram chips... ill drop my new ones in and see what happens....

its really looking like the rom is the whole issue with my board....
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 09:48, 11 May 22
Throw the left hand switch to the other position
With the the Computer turned off
Power up and tell us what  happened
 
Keep Safe

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 10:04, 11 May 22
Quote from: Audronic on 09:48, 11 May 22Throw the left hand switch to the other position
With the the Computer turned off
Power up and tell us what  happened
 
Keep Safe

Ray

...still with the original ram...


 
i guess i need to start working on my ps2 keyboard through arduino if i wanna test some more! (or atleast workout which pins to hit to fake a keypress!)

EDIT: i tryed rebooting Noels rom and now i just get corruption cant read anything... interesting...
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 10:20, 11 May 22
well this is a bit strange....
i dropped the "new" ram chips in and just got corruption....
i removed 1 ram chip (top left)... and now i get the ram tester screen....
its saying chip 3 is bad... even tho, what im presuming is chip 0 is missing!

what is the layout for the chips on the ram tester??

 
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 10:25, 11 May 22
Can you send us a Photo of the Motherboard

Noels diag photo said " 128K ram" ????

Ray

Edited Removed NO FDC
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 10:48, 11 May 22
464 Ram Location

Bit 

0 IC 120
1 IC119
2 IC 118
3 IC 117
4 IC 121
5 IC 122
6 IC 123
7 IC 124
-================-
121.   117

122.   118

123    119

124    120
-================-

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 10:52, 11 May 22
yes i thought the 128kB was a bit strange aswell...theres a pic of the board on page 1...
thanks for the ram location.. i ended up working it out after testing one chip through all the sockets..

i havent been able to get back to that diag screen (Noels)..

i keep getting corruption.... UNLESS i remove chip 3 (top left ram chip)...then i get the ram tester screen...
ive tryed that chip in other slots and it is green... no matter what ram chip i use in slot 3 just causes corruption (they are all showing green in other slots)

i tried taking one ram chip and running it through all slots on its own... some slots would make the colors change (eg purple instead of green)..one would show a few green lines in the correct area but none of the numbers or other lines show...
....thats probably CRTC correct?

edit: heres a pic of the tester with no ram... is that dotted line between 0 and 1 supposed to be there?!
 

edit2: heres the current setup....
 
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 13:36, 11 May 22
Quote from: WacKEDmaN on 10:52, 11 May 22i keep getting corruption.... UNLESS i remove chip 3 (top left ram chip)...then i get the ram tester screen...
ive tryed that chip in other slots and it is green... no matter what ram chip i use in slot 3 just causes corruption (they are all showing green in other slots)

Ok I would check the "Chip 3 Soldering for Perhaps shorts to ? " and have a good look at Pins 2 and 14

Good luck

Ray 

Title: Re: 464 Resurrection - with only mainboard!
Post by: eto on 14:02, 11 May 22
Quote from: WacKEDmaN on 10:52, 11 May 22i keep getting corruption.... UNLESS i remove chip 3 (top left ram chip)...then i get the ram tester screen...
ive tryed that chip in other slots and it is green... no matter what ram chip i use in slot 3 just causes corruption (they are all showing green in other slots)
so most likely not the ram chips. and since all ram chips fail in that socket, it might be the socket. or the lines to the socket.

did you check for shorts/continuity for all pins on that socket?

edit: sorry, just recognised Audronic already said that.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 10:31, 12 May 22
checked all the ram pins for shorts... seems fine...
 
pin 2 on each socket has continuity to an individual pin on the CRTC...
pin 14 on each socket has continuity to an individual pin on the gate array... (ill admit i didnt check to see they where going to the correct pins..but it 'should' be ok)

all ram pins except 2 and 14 are connected across all sockets....

...so im guessing...bad CRTC..or ....(plz no!)..gate array :(
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 10:51, 12 May 22
Ok 
Last thoughts :-
Change 
IC115 75LS244
And /Or
IC114 74LS373

Keep Safe

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 11:40, 12 May 22
Quote from: Audronic on 10:51, 12 May 22Ok
Last thoughts :-
Change
IC115 75LS244
And /Or
IC114 74LS373

Keep Safe

Ray
:o :o :o :o :o :o :o :o :o :o :o

holy crap!..

big THANK YOU to everyone who had some input!

swapped out the brand new 244 for the original one....
 
 

then i switched it off...flipped the on/off switch on the lower rom board... power back up and.... nothing... i hit the reset button and then got this.....
 

....it seems there maybe still an issue tho... if i remove the lower rom board, and power up the CPC it does not boot (not even black screen/sync).... it only seems to boot the original rom when i hit the reset button with the rom board switch set to off...

edit: seems i need to hit the reset on the lower rom board every boot....its not booting on its own...

Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 13:00, 12 May 22
Ok Thats good progress

Perhaps the Rom on the motherboard is unwell

? does the Other Diag work (Geralds) Left switch in the other position

Nearly there

Keep Safe

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 13:15, 12 May 22
Do you have an other 40009 Rom to try ?

Can you temporarily add to the New Mother board a reset switch ?

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 13:25, 12 May 22
no i dont have another ROM to try as yet... a local friend has a 1.1 ROM for me..just need to get my hands on it...
yes Geralds diag loads and shows this....
 


 i jumpered the keyboard connector with a wire to hit some keys to load up some tests...(on Noels)
"CANT ACCESS SYSTEM LOWER ROM" on the ROM test...
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 15:22, 12 May 22
Quote from: WacKEDmaN on 13:25, 12 May 22i jumpered the keyboard connector with a wire to hit some keys to load up some tests...(on Noels)
"CANT ACCESS SYSTEM LOWER ROM" on the ROM test...
Ok This is normal thats what mine does its not a Problem with the motherboard

I have used a 1.1 Rom that works OK

If you are stuck I can send you a 40009 Revision 2 (Rays version)
That I use with the USIFAc II

Keep Safe

Ray

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 15:33, 12 May 22
Quote from: Audronic on 15:22, 12 May 22
Quote from: WacKEDmaN on 13:25, 12 May 22i jumpered the keyboard connector with a wire to hit some keys to load up some tests...(on Noels)
"CANT ACCESS SYSTEM LOWER ROM" on the ROM test...
Ok This is normal thats what mine does its not a Problem with the motherboard

I have used a 1.1 Rom that works OK

If you are stuck I can send you a 40009 Revision 2 (Rays version)
That I use with the USIFAc II

Keep Safe

Ray



thank you Ray.. i should be good for the 1.1 ROM in the next couple of days...but will keep you in mind...

reguarding reset button pins... 
just jumper !BUSRESET to gnd right?... or do i want !RESET?

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 15:57, 12 May 22
ok... jumpered pins 2 and 40 on the edge connector without the lower rom board connected.. and it booted....

i also changed the the new 74LS132 for the original as its part of the reset circuit....no luck..

could the diode around the wrong ways (or bad) be causing it not to trigger the reset? (possibly even the capacitor?)

EDIT: working on the big screen too!
 
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 02:10, 13 May 22
The Reset Button (Momentary)
Reset Button - CPCWiki

https://www.cpcwiki.eu/index.php/Reset_Button


? Which Diode - Capacitor ?
If you are referring to the Power up reset circuit ?
In Next reply
? are you able to Boot without the Lower rom Board ?
If not then press the (New) Reset button and let go

Keep Safe

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: Audronic on 02:18, 13 May 22
Reset Circuit

Ray
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 02:43, 13 May 22
Quote from: Audronic on 02:10, 13 May 22The Reset Button (Momentary)
Reset Button - CPCWiki

https://www.cpcwiki.eu/index.php/Reset_Button

? are you able to Boot without the Lower rom Board ?
If not then press the (New) Reset button and let go

Keep Safe

Ray

yes i found that page after asking the question!..
i removed the lower rom board... powered up the cpc (no boot)...jumpered pins 2 and 40 (/BUSRESET to gnd) on the edge connector for a moment and it boots...
easier to just leave the lower rom board connected and use its reset button than jumpering or wireing up a dedicated reset button...

i can get away with using it atm....but it would be nice to have the power on reset circuit working......
ive been scanning over the reset circuit..and im thinking the diode (there is only one! and the electrolytic cap next to it) is installed incorrectly or its bad! i will try a new one soon..(replaced the 74LS132 with the original with same no boot on power-on results)
might have to break out the scope again and see what happening on the reset lines and LS132

edit: another reason im thinking the diode is the voltage drop on the chips...
ive got my CC/CV power supply turned up to 5.7V to get 4.8v on the chips.. if i go any lower, the CRTC starts acting up and the screen bounces..

or...could it be...(wait for it!) what im using for a power switch... a cheap ass dupont cable!.. that has hardly any wire inside!..maybe it cant supply enough current...i thought i felt it getting a little warm too!!
thats first test!!
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 18:50, 13 May 22
..fixed!... my dumb ass had the diode around the wrong way  :picard2: :picard:
the voltages seem a little low...i dropped CC/CV psu to 5.1v, and im reading 4.5v on the logic chips.. and noticed it rebooted itself after a few mins.. so i bumped up the psu to 5.25v and now im seein a more healthy 4.7v at the logic chips..

the gate array sure does get toasty without a heatsink... i gotta get one on it asap..ive only got a square one thats gonna hang over.. will get something better down the track..

now to sort out my keyboard implementation, so i can at least get some basic happening!..

i think i might have to grab a USIFAc II that thing looks really sweet!...
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 01:32, 14 May 22
;D
..and still going...
 
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 19:03, 18 May 22
my arduino mega to cpc keyboard attempt failed!...
ordered an attiny2313..should be here next week..already have a LS138.. will make my own board and mount it on the bottom of the cpc board so it cant be seen/looks neater..i have the cpc board up on feet so there should be enough clearance..

also found the perfect heatsink for the gate array, on an old dead boost/buck converter!

i also changed the links so the boot screen reads "Amstrad" instead of "AWA" (my original CPC was AWA, but i toasted the PPI soldering up a joystick while it was plugged in and running (i was young and dumb!..oh wait im still dumb! LOL), when i got it back from repair the manufacturer had changed to Amstrad)

i was going through my collection of junk and found the only thing left of my original CPC system from back in the day....
the 3 meter long printer cable!.. with edge connector to centronics connector! (parents said that cable almost cost more than the dot matrix printer they got me aswell)...anyone want it?!
 

..and i also cleaned up my workbench..  ;D
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 10:59, 19 May 22
I thought you had a 40010 GA on your board? It doesn't get hot enough to ever need a heatsink.

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: Devlin on 11:13, 19 May 22
Quote from: Bryce on 10:59, 19 May 22I thought you had a 40010 GA on your board? It doesn't get hot enough to ever need a heatsink.

Bryce.
Looking back through the pictures, it is a 40007, unless the part has since been replaced
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 23:00, 19 May 22
yes its 40007...as this is a 270100 board (1983) with only the 40007 slot..
it was getting veryyy toasty!.. so hot i could hardly keep my finger on it for too long...the heatsink now gets quite warm... but its doing its thing wicking the heat away from the chips core..
my original z80 (84) gets very hot aswell... swapped it with one from the 90s and its much cooler... i have a small heatsink on the CRTC aswell as it was quite warm too (neither as much as the gate array!)
Title: Re: 464 Resurrection - with only mainboard!
Post by: Bryce on 10:00, 20 May 22
Quote from: WacKEDmaN on 23:00, 19 May 22yes its 40007...as this is a 270100 board (1983) with only the 40007 slot..
it was getting veryyy toasty!.. so hot i could hardly keep my finger on it for too long...the heatsink now gets quite warm... but its doing its thing wicking the heat away from the chips core..
my original z80 (84) gets very hot aswell... swapped it with one from the 90s and its much cooler... i have a small heatsink on the CRTC aswell as it was quite warm too (neither as much as the gate array!)
Strange. Why did someone clone the older design, rather than cloning the improved 40010 design?

Bryce.
Title: Re: 464 Resurrection - with only mainboard!
Post by: TotO on 10:31, 20 May 22
Quote from: Bryce on 10:00, 20 May 22Strange. Why did someone clone the older design, rather than cloning the improved 40010 design?
May be because, since the "covid confinement", a lot of peoples started to be interrested to reuse their old 1980/1990 micro-computer, without thinking that many things was known and done between 2000 and 2020 to keep them alive and attractive.
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 10:49, 20 May 22
Quote from: Bryce on 10:00, 20 May 22Strange. Why did someone clone the older design, rather than cloning the improved 40010 design?

Bryce.


i thought the same too...but im glad it was done... iirc it was just a project to see if it could be done, and there is a 6128 version is currently being worked on..
Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 22:27, 20 May 22
seems i still have some issues with the 74LS244. (IC115)..
sometimes it wont boot.. if i push on the chip into the socket it will boot....or sometimes it shows up like memory corruption.. it reboots itself at random times aswell, with me no where near it...
ive tried resoldering the pins...but had the same issue...

...im guessing the solder hasnt flowed through the hole to make nice contact with the top side of the board...i may have to replace the socket (maybe with machined pins)

Title: Re: 464 Resurrection - with only mainboard!
Post by: WacKEDmaN on 02:44, 22 May 22
i seem to have sorted the 74LS244 issue, just by lifting the chip slightly from the socket... if i push it all the way in i get the reboots/corruption.. its a little strange..but works!

i also did some more work on my ps2 arduino to cpc keyboard.. i got one key working (just testing).. but i sometimes get other characters (from another row that isnt even connected!).. so im guessing my implementation is too slow... i may try writing directly to the arduinos port registers, should speed things up a ton...but really im just screwing around until i get the attiny2313 to do the conversion..
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